DevTools: roll CodeMirror to v4.0.3

Source/devtools/front_end/cm/codemirror.js

-// CodeMirror is the only global var we claim
-window.CodeMirror = (function() {
+// This is CodeMirror (http://codemirror.net), a code editor
+// implemented in JavaScript on top of the browser's DOM.
+//
+// You can find some technical background for some of the code below
+// at http://marijnhaverbeke.nl/blog/#cm-internals .
+
+(function(mod) {
+  if (typeof exports == "object" && typeof module == "object") // CommonJS
+    module.exports = mod();
+  else if (typeof define == "function" && define.amd) // AMD
+    return define([], mod);
+  else // Plain browser env
+    this.CodeMirror = mod();
+})(function() {
   "use strict";
 
   // BROWSER SNIFFING
 
-  // Crude, but necessary to handle a number of hard-to-feature-detect
-  // bugs and behavior differences.
+  // Kludges for bugs and behavior differences that can't be feature
+  // detected are enabled based on userAgent etc sniffing.
+
   var gecko = /gecko\/\d/i.test(navigator.userAgent);
-  // IE11 currently doesn't count as 'ie', since it has almost none of
-  // the same bugs as earlier versions. Use ie_gt10 to handle
-  // incompatibilities in that version.
-  var old_ie = /MSIE \d/.test(navigator.userAgent);
-  var ie_lt8 = old_ie && (document.documentMode == null || document.documentMode < 8);
-  var ie_lt9 = old_ie && (document.documentMode == null || document.documentMode < 9);
-  var ie_gt10 = /Trident\/([7-9]|\d{2,})\./.test(navigator.userAgent);
-  var ie = old_ie || ie_gt10;
+  // ie_uptoN means Internet Explorer version N or lower
+  var ie_upto10 = /MSIE \d/.test(navigator.userAgent);
+  var ie_upto7 = ie_upto10 && (document.documentMode == null || document.documentMode < 8);
+  var ie_upto8 = ie_upto10 && (document.documentMode == null || document.documentMode < 9);
+  var ie_upto9 = ie_upto10 && (document.documentMode == null || document.documentMode < 10);
+  var ie_11up = /Trident\/([7-9]|\d{2,})\./.test(navigator.userAgent);
+  var ie = ie_upto10 || ie_11up;
   var webkit = /WebKit\//.test(navigator.userAgent);
   var qtwebkit = webkit && /Qt\/\d+\.\d+/.test(navigator.userAgent);
   var chrome = /Chrome\//.test(navigator.userAgent);
-  var opera = /Opera\//.test(navigator.userAgent);
+  var presto = /Opera\//.test(navigator.userAgent);
   var safari = /Apple Computer/.test(navigator.vendor);
   var khtml = /KHTML\//.test(navigator.userAgent);
   var mac_geLion = /Mac OS X 1\d\D([7-9]|\d\d)\D/.test(navigator.userAgent);
   var mac_geMountainLion = /Mac OS X 1\d\D([8-9]|\d\d)\D/.test(navigator.userAgent);
   var phantom = /PhantomJS/.test(navigator.userAgent);
 
   var ios = /AppleWebKit/.test(navigator.userAgent) && /Mobile\/\w+/.test(navigator.userAgent);
   // This is woefully incomplete. Suggestions for alternative methods welcome.
   var mobile = ios || /Android|webOS|BlackBerry|Opera Mini|Opera Mobi|IEMobile/i.test(navigator.userAgent);
   var mac = ios || /Mac/.test(navigator.platform);
   var windows = /win/i.test(navigator.platform);
 
-  var opera_version = opera && navigator.userAgent.match(/Version\/(\d*\.\d*)/);
-  if (opera_version) opera_version = Number(opera_version[1]);
-  if (opera_version && opera_version >= 15) { opera = false; webkit = true; }
+  var presto_version = presto && navigator.userAgent.match(/Version\/(\d*\.\d*)/);
+  if (presto_version) presto_version = Number(presto_version[1]);
+  if (presto_version && presto_version >= 15) { presto = false; webkit = true; }
   // Some browsers use the wrong event properties to signal cmd/ctrl on OS X
-  var flipCtrlCmd = mac && (qtwebkit || opera && (opera_version == null || opera_version < 12.11));
-  var captureMiddleClick = gecko || (old_ie && !ie_lt9);
+  var flipCtrlCmd = mac && (qtwebkit || presto && (presto_version == null || presto_version < 12.11));
+  var captureRightClick = gecko || (ie && !ie_upto8);
 
-  // Optimize some code when these features are not used
+  // Optimize some code when these features are not used.
   var sawReadOnlySpans = false, sawCollapsedSpans = false;
 
-  // CONSTRUCTOR
+  // EDITOR CONSTRUCTOR
+
+  // A CodeMirror instance represents an editor. This is the object
+  // that user code is usually dealing with.
 
   function CodeMirror(place, options) {
     if (!(this instanceof CodeMirror)) return new CodeMirror(place, options);
 
     this.options = options = options || {};
     // Determine effective options based on given values and defaults.
-    for (var opt in defaults) if (!options.hasOwnProperty(opt) && defaults.hasOwnProperty(opt))
+    for (var opt in defaults) if (!options.hasOwnProperty(opt))
       options[opt] = defaults[opt];
     setGuttersForLineNumbers(options);
 
-    var docStart = typeof options.value == "string" ? 0 : options.value.first;
-    var display = this.display = makeDisplay(place, docStart);
+    var doc = options.value;
+    if (typeof doc == "string") doc = new Doc(doc, options.mode);
+    this.doc = doc;
+
+    var display = this.display = new Display(place, doc);
     display.wrapper.CodeMirror = this;
     updateGutters(this);
-    if (options.autofocus && !mobile) focusInput(this);
-
-    this.state = {keyMaps: [],
-                  overlays: [],
-                  modeGen: 0,
-                  overwrite: false, focused: false,
-                  suppressEdits: false,
-                  pasteIncoming: false, cutIncoming: false,
-                  draggingText: false,
-                  highlight: new Delayed()};
-
     themeChanged(this);
     if (options.lineWrapping)
       this.display.wrapper.className += " CodeMirror-wrap";
+    if (options.autofocus && !mobile) focusInput(this);
 
-    var doc = options.value;
-    if (typeof doc == "string") doc = new Doc(options.value, options.mode);
-    operation(this, attachDoc)(this, doc);
+    this.state = {
+      keyMaps: [],  // stores maps added by addKeyMap
+      overlays: [], // highlighting overlays, as added by addOverlay
+      modeGen: 0,   // bumped when mode/overlay changes, used to invalidate highlighting info
+      overwrite: false, focused: false,
+      suppressEdits: false, // used to disable editing during key handlers when in readOnly mode
+      pasteIncoming: false, cutIncoming: false, // help recognize paste/cut edits in readInput
+      draggingText: false,
+      highlight: new Delayed() // stores highlight worker timeout
+    };
 
     // Override magic textarea content restore that IE sometimes does
     // on our hidden textarea on reload
-    if (old_ie) setTimeout(bind(resetInput, this, true), 20);
+    if (ie_upto10) setTimeout(bind(resetInput, this, true), 20);
 
     registerEventHandlers(this);
-    // IE throws unspecified error in certain cases, when
-    // trying to access activeElement before onload
-    var hasFocus; try { hasFocus = (document.activeElement == display.input); } catch(e) { }
-    if (hasFocus || (options.autofocus && !mobile)) setTimeout(bind(onFocus, this), 20);
-    else onBlur(this);
 
-    operation(this, function() {
-      for (var opt in optionHandlers)
-        if (optionHandlers.propertyIsEnumerable(opt))
-          optionHandlers[opt](this, options[opt], Init);
-      for (var i = 0; i < initHooks.length; ++i) initHooks[i](this);
-    })();
+    var cm = this;
+    runInOp(this, function() {
+      cm.curOp.forceUpdate = true;
+      attachDoc(cm, doc);
+
+      if ((options.autofocus && !mobile) || activeElt() == display.input)
+        setTimeout(bind(onFocus, cm), 20);
+      else
+        onBlur(cm);
+
+      for (var opt in optionHandlers) if (optionHandlers.hasOwnProperty(opt))
+        optionHandlers[opt](cm, options[opt], Init);
+      for (var i = 0; i < initHooks.length; ++i) initHooks[i](cm);
+    });
   }
 
   // DISPLAY CONSTRUCTOR
 
-  function makeDisplay(place, docStart) {
-    var d = {};
+  // The display handles the DOM integration, both for input reading
+  // and content drawing. It holds references to DOM nodes and
+  // display-related state.
 
-    var input = d.input = elt("textarea", null, null, "position: absolute; padding: 0; width: 1px; height: 1em; outline: none; font-size: 4px;");
+  function Display(place, doc) {
+    var d = this;
+
+    // The semihidden textarea that is focused when the editor is
+    // focused, and receives input.
+    var input = d.input = elt("textarea", null, null, "position: absolute; padding: 0; width: 1px; height: 1em; outline: none");
+    // The textarea is kept positioned near the cursor to prevent the
+    // fact that it'll be scrolled into view on input from scrolling
+    // our fake cursor out of view. On webkit, when wrap=off, paste is
+    // very slow. So make the area wide instead.
     if (webkit) input.style.width = "1000px";
     else input.setAttribute("wrap", "off");
-    // if border: 0; -- iOS fails to open keyboard (issue #1287)
+    // If border: 0; -- iOS fails to open keyboard (issue #1287)
     if (ios) input.style.border = "1px solid black";
     input.setAttribute("autocorrect", "off"); input.setAttribute("autocapitalize", "off"); input.setAttribute("spellcheck", "false");
 
     // Wraps and hides input textarea
     d.inputDiv = elt("div", [input], null, "overflow: hidden; position: relative; width: 3px; height: 0px;");
-    // The actual fake scrollbars.
-    d.scrollbarH = elt("div", [elt("div", null, null, "height: 1px")], "CodeMirror-hscrollbar");
-    d.scrollbarV = elt("div", [elt("div", null, null, "width: 1px")], "CodeMirror-vscrollbar");
+    // The fake scrollbar elements.
+    d.scrollbarH = elt("div", [elt("div", null, null, "height: 100%; min-height: 1px")], "CodeMirror-hscrollbar");
+    d.scrollbarV = elt("div", [elt("div", null, null, "min-width: 1px")], "CodeMirror-vscrollbar");
+    // Covers bottom-right square when both scrollbars are present.
     d.scrollbarFiller = elt("div", null, "CodeMirror-scrollbar-filler");
+    // Covers bottom of gutter when coverGutterNextToScrollbar is on
+    // and h scrollbar is present.
     d.gutterFiller = elt("div", null, "CodeMirror-gutter-filler");
-    // DIVs containing the selection and the actual code
+    // Will contain the actual code, positioned to cover the viewport.
     d.lineDiv = elt("div", null, "CodeMirror-code");
+    // Elements are added to these to represent selection and cursors.
     d.selectionDiv = elt("div", null, null, "position: relative; z-index: 1");
-    // Blinky cursor, and element used to ensure cursor fits at the end of a line
-    d.cursor = elt("div", "\u00a0", "CodeMirror-cursor");
-    // Secondary cursor, shown when on a 'jump' in bi-directional text
-    d.otherCursor = elt("div", "\u00a0", "CodeMirror-cursor CodeMirror-secondarycursor");
-    // Used to measure text size
+    d.cursorDiv = elt("div", null, "CodeMirror-cursors");
+    // A visibility: hidden element used to find the size of things.
     d.measure = elt("div", null, "CodeMirror-measure");
+    // When lines outside of the viewport are measured, they are drawn in this.
+    d.lineMeasure = elt("div", null, "CodeMirror-measure");
     // Wraps everything that needs to exist inside the vertically-padded coordinate system
-    d.lineSpace = elt("div", [d.measure, d.selectionDiv, d.lineDiv, d.cursor, d.otherCursor],
-                         null, "position: relative; outline: none");
-    // Moved around its parent to cover visible view
+    d.lineSpace = elt("div", [d.measure, d.lineMeasure, d.selectionDiv, d.cursorDiv, d.lineDiv],
+                      null, "position: relative; outline: none");
+    // Moved around its parent to cover visible view.
     d.mover = elt("div", [elt("div", [d.lineSpace], "CodeMirror-lines")], null, "position: relative");
-    // Set to the height of the text, causes scrolling
+    // Set to the height of the document, allowing scrolling.
     d.sizer = elt("div", [d.mover], "CodeMirror-sizer");
-    // D is needed because behavior of elts with overflow: auto and padding is inconsistent across browsers
+    // Behavior of elts with overflow: auto and padding is
+    // inconsistent across browsers. This is used to ensure the
+    // scrollable area is big enough.
     d.heightForcer = elt("div", null, null, "position: absolute; height: " + scrollerCutOff + "px; width: 1px;");
-    // Will contain the gutters, if any
+    // Will contain the gutters, if any.
     d.gutters = elt("div", null, "CodeMirror-gutters");
     d.lineGutter = null;
-    // Provides scrolling
+    // Actual scrollable element.
     d.scroller = elt("div", [d.sizer, d.heightForcer, d.gutters], "CodeMirror-scroll");
     d.scroller.setAttribute("tabIndex", "-1");
     // The element in which the editor lives.
     d.wrapper = elt("div", [d.inputDiv, d.scrollbarH, d.scrollbarV,
                             d.scrollbarFiller, d.gutterFiller, d.scroller], "CodeMirror");
-    // Work around IE7 z-index bug
-    if (ie_lt8) { d.gutters.style.zIndex = -1; d.scroller.style.paddingRight = 0; }
-    if (place.appendChild) place.appendChild(d.wrapper); else place(d.wrapper);
 
+    // Work around IE7 z-index bug (not perfect, hence IE7 not really being supported)
+    if (ie_upto7) { d.gutters.style.zIndex = -1; d.scroller.style.paddingRight = 0; }
     // Needed to hide big blue blinking cursor on Mobile Safari
     if (ios) input.style.width = "0px";
     if (!webkit) d.scroller.draggable = true;
     // Needed to handle Tab key in KHTML
     if (khtml) { d.inputDiv.style.height = "1px"; d.inputDiv.style.position = "absolute"; }
     // Need to set a minimum width to see the scrollbar on IE7 (but must not set it on IE8).
-    else if (ie_lt8) d.scrollbarH.style.minWidth = d.scrollbarV.style.minWidth = "18px";
+    if (ie_upto7) d.scrollbarH.style.minHeight = d.scrollbarV.style.minWidth = "18px";
 
-    // Current visible range (may be bigger than the view window).
-    d.viewOffset = d.lastSizeC = 0;
-    d.showingFrom = d.showingTo = docStart;
+    if (place.appendChild) place.appendChild(d.wrapper);
+    else place(d.wrapper);
+
+    // Current rendered range (may be bigger than the view window).
+    d.viewFrom = d.viewTo = doc.first;
+    // Information about the rendered lines.
+    d.view = [];
+    // Holds info about a single rendered line when it was rendered
+    // for measurement, while not in view.
+    d.externalMeasured = null;
+    // Empty space (in pixels) above the view
+    d.viewOffset = 0;
+    d.lastSizeC = 0;
+    d.updateLineNumbers = null;
 
     // Used to only resize the line number gutter when necessary (when
     // the amount of lines crosses a boundary that makes its width change)
     d.lineNumWidth = d.lineNumInnerWidth = d.lineNumChars = null;
     // See readInput and resetInput
     d.prevInput = "";
-    // Set to true when a non-horizontal-scrolling widget is added. As
-    // an optimization, widget aligning is skipped when d is false.
+    // Set to true when a non-horizontal-scrolling line widget is
+    // added. As an optimization, line widget aligning is skipped when
+    // this is false.
     d.alignWidgets = false;
-    // Flag that indicates whether we currently expect input to appear
-    // (after some event like 'keypress' or 'input') and are polling
-    // intensively.
+    // Flag that indicates whether we expect input to appear real soon
+    // now (after some event like 'keypress' or 'input') and are
+    // polling intensively.
     d.pollingFast = false;
     // Self-resetting timeout for the poller
     d.poll = new Delayed();
 
-    d.cachedCharWidth = d.cachedTextHeight = null;
-    d.measureLineCache = [];
-    d.measureLineCachePos = 0;
+    d.cachedCharWidth = d.cachedTextHeight = d.cachedPaddingH = null;
 
     // Tracks when resetInput has punted to just putting a short
-    // string instead of the (large) selection.
+    // string into the textarea instead of the full selection.
     d.inaccurateSelection = false;
 
     // Tracks the maximum line length so that the horizontal scrollbar
     // can be kept static when scrolling.
     d.maxLine = null;
     d.maxLineLength = 0;
     d.maxLineChanged = false;
 
     // Used for measuring wheel scrolling granularity
     d.wheelDX = d.wheelDY = d.wheelStartX = d.wheelStartY = null;
 
-    return d;
+    // True when shift is held down.
+    d.shift = false;
   }
 
   // STATE UPDATES
 
   // Used to get the editor into a consistent state again when options change.
 
   function loadMode(cm) {
     cm.doc.mode = CodeMirror.getMode(cm.options, cm.doc.modeOption);
     resetModeState(cm);
   }
 
   function resetModeState(cm) {
     cm.doc.iter(function(line) {
       if (line.stateAfter) line.stateAfter = null;
       if (line.styles) line.styles = null;
     });
     cm.doc.frontier = cm.doc.first;
     startWorker(cm, 100);
     cm.state.modeGen++;
     if (cm.curOp) regChange(cm);
   }
 
   function wrappingChanged(cm) {
     if (cm.options.lineWrapping) {
       cm.display.wrapper.className += " CodeMirror-wrap";
       cm.display.sizer.style.minWidth = "";
     } else {
       cm.display.wrapper.className = cm.display.wrapper.className.replace(" CodeMirror-wrap", "");
-      computeMaxLength(cm);
+      findMaxLine(cm);
     }
     estimateLineHeights(cm);
     regChange(cm);
     clearCaches(cm);
     setTimeout(function(){updateScrollbars(cm);}, 100);
   }
 
+  // Returns a function that estimates the height of a line, to use as
+  // first approximation until the line becomes visible (and is thus
+  // properly measurable).
   function estimateHeight(cm) {
     var th = textHeight(cm.display), wrapping = cm.options.lineWrapping;
     var perLine = wrapping && Math.max(5, cm.display.scroller.clientWidth / charWidth(cm.display) - 3);
     return function(line) {
-      if (lineIsHidden(cm.doc, line))
-        return 0;
-      else if (wrapping)
-        return (Math.ceil(line.text.length / perLine) || 1) * th;
+      if (lineIsHidden(cm.doc, line)) return 0;
+
+      var widgetsHeight = 0;
+      if (line.widgets) for (var i = 0; i < line.widgets.length; i++) {
+        if (line.widgets[i].height) widgetsHeight += line.widgets[i].height;
+      }
+
+      if (wrapping)
+        return widgetsHeight + (Math.ceil(line.text.length / perLine) || 1) * th;
       else
-        return th;
+        return widgetsHeight + th;
     };
   }
 
   function estimateLineHeights(cm) {
     var doc = cm.doc, est = estimateHeight(cm);
     doc.iter(function(line) {
       var estHeight = est(line);
       if (estHeight != line.height) updateLineHeight(line, estHeight);
     });
   }
 
   function keyMapChanged(cm) {
     var map = keyMap[cm.options.keyMap], style = map.style;
     cm.display.wrapper.className = cm.display.wrapper.className.replace(/\s*cm-keymap-\S+/g, "") +
       (style ? " cm-keymap-" + style : "");
   }
 
   function themeChanged(cm) {
     cm.display.wrapper.className = cm.display.wrapper.className.replace(/\s*cm-s-\S+/g, "") +
       cm.options.theme.replace(/(^|\s)\s*/g, " cm-s-");
     clearCaches(cm);
   }
 
   function guttersChanged(cm) {
     updateGutters(cm);
     regChange(cm);
     setTimeout(function(){alignHorizontally(cm);}, 20);
   }
 
+  // Rebuild the gutter elements, ensure the margin to the left of the
+  // code matches their width.
   function updateGutters(cm) {
     var gutters = cm.display.gutters, specs = cm.options.gutters;
     removeChildren(gutters);
     for (var i = 0; i < specs.length; ++i) {
       var gutterClass = specs[i];
       var gElt = gutters.appendChild(elt("div", null, "CodeMirror-gutter " + gutterClass));
       if (gutterClass == "CodeMirror-linenumbers") {
         cm.display.lineGutter = gElt;
         gElt.style.width = (cm.display.lineNumWidth || 1) + "px";
       }
     }
     gutters.style.display = i ? "" : "none";
+    var width = gutters.offsetWidth;
+    cm.display.sizer.style.marginLeft = width + "px";
+    if (i) cm.display.scrollbarH.style.left = cm.options.fixedGutter ? width + "px" : 0;
   }
 
-  function lineLength(doc, line) {
+  // Compute the character length of a line, taking into account
+  // collapsed ranges (see markText) that might hide parts, and join
+  // other lines onto it.
+  function lineLength(line) {
     if (line.height == 0) return 0;
     var len = line.text.length, merged, cur = line;
     while (merged = collapsedSpanAtStart(cur)) {
-      var found = merged.find();
-      cur = getLine(doc, found.from.line);
+      var found = merged.find(0, true);
+      cur = found.from.line;
       len += found.from.ch - found.to.ch;
     }
     cur = line;
     while (merged = collapsedSpanAtEnd(cur)) {
-      var found = merged.find();
+      var found = merged.find(0, true);
       len -= cur.text.length - found.from.ch;
-      cur = getLine(doc, found.to.line);
+      cur = found.to.line;
       len += cur.text.length - found.to.ch;
     }
     return len;
   }
 
-  function computeMaxLength(cm) {
+  // Find the longest line in the document.
+  function findMaxLine(cm) {
     var d = cm.display, doc = cm.doc;
     d.maxLine = getLine(doc, doc.first);
-    d.maxLineLength = lineLength(doc, d.maxLine);
+    d.maxLineLength = lineLength(d.maxLine);
     d.maxLineChanged = true;
     doc.iter(function(line) {
-      var len = lineLength(doc, line);
+      var len = lineLength(line);
       if (len > d.maxLineLength) {
         d.maxLineLength = len;
         d.maxLine = line;
       }
     });
   }
 
   // Make sure the gutters options contains the element
   // "CodeMirror-linenumbers" when the lineNumbers option is true.
   function setGuttersForLineNumbers(options) {
     var found = indexOf(options.gutters, "CodeMirror-linenumbers");
     if (found == -1 && options.lineNumbers) {
       options.gutters = options.gutters.concat(["CodeMirror-linenumbers"]);
     } else if (found > -1 && !options.lineNumbers) {
       options.gutters = options.gutters.slice(0);
       options.gutters.splice(found, 1);
     }
   }
 
   // SCROLLBARS
 
+  // Prepare DOM reads needed to update the scrollbars. Done in one
+  // shot to minimize update/measure roundtrips.
+  function measureForScrollbars(cm) {
+    var scroll = cm.display.scroller;
+    return {
+      clientHeight: scroll.clientHeight,
+      barHeight: cm.display.scrollbarV.clientHeight,
+      scrollWidth: scroll.scrollWidth, clientWidth: scroll.clientWidth,
+      barWidth: cm.display.scrollbarH.clientWidth,
+      docHeight: Math.round(cm.doc.height + paddingVert(cm.display))
+    };
+  }
+
   // Re-synchronize the fake scrollbars with the actual size of the
-  // content. Optionally force a scrollTop.
-  function updateScrollbars(cm) {
-    var d = cm.display, docHeight = cm.doc.height;
-    var totalHeight = docHeight + paddingVert(d);
-    d.sizer.style.minHeight = d.heightForcer.style.top = totalHeight + "px";
-    d.gutters.style.height = Math.max(totalHeight, d.scroller.clientHeight - scrollerCutOff) + "px";
-    var scrollHeight = Math.max(totalHeight, d.scroller.scrollHeight);
-    var needsH = d.scroller.scrollWidth > (d.scroller.clientWidth + 1);
-    var needsV = scrollHeight > (d.scroller.clientHeight + 1);
+  // content.
+  function updateScrollbars(cm, measure) {
+    if (!measure) measure = measureForScrollbars(cm);
+    var d = cm.display;
+    var scrollHeight = measure.docHeight + scrollerCutOff;
+    var needsH = measure.scrollWidth > measure.clientWidth;
+    var needsV = scrollHeight > measure.clientHeight;
     if (needsV) {
       d.scrollbarV.style.display = "block";
       d.scrollbarV.style.bottom = needsH ? scrollbarWidth(d.measure) + "px" : "0";
       // A bug in IE8 can cause this value to be negative, so guard it.
       d.scrollbarV.firstChild.style.height =
-        Math.max(0, scrollHeight - d.scroller.clientHeight + d.scrollbarV.clientHeight) + "px";
+        Math.max(0, scrollHeight - measure.clientHeight + (measure.barHeight || d.scrollbarV.clientHeight)) + "px";
     } else {
       d.scrollbarV.style.display = "";
       d.scrollbarV.firstChild.style.height = "0";
     }
     if (needsH) {
       d.scrollbarH.style.display = "block";
       d.scrollbarH.style.right = needsV ? scrollbarWidth(d.measure) + "px" : "0";
       d.scrollbarH.firstChild.style.width =
-        (d.scroller.scrollWidth - d.scroller.clientWidth + d.scrollbarH.clientWidth) + "px";
+        (measure.scrollWidth - measure.clientWidth + (measure.barWidth || d.scrollbarH.clientWidth)) + "px";
     } else {
       d.scrollbarH.style.display = "";
       d.scrollbarH.firstChild.style.width = "0";
     }
     if (needsH && needsV) {
       d.scrollbarFiller.style.display = "block";
       d.scrollbarFiller.style.height = d.scrollbarFiller.style.width = scrollbarWidth(d.measure) + "px";
     } else d.scrollbarFiller.style.display = "";
     if (needsH && cm.options.coverGutterNextToScrollbar && cm.options.fixedGutter) {
       d.gutterFiller.style.display = "block";
       d.gutterFiller.style.height = scrollbarWidth(d.measure) + "px";
       d.gutterFiller.style.width = d.gutters.offsetWidth + "px";
     } else d.gutterFiller.style.display = "";
 
     if (mac_geLion && scrollbarWidth(d.measure) === 0) {
       d.scrollbarV.style.minWidth = d.scrollbarH.style.minHeight = mac_geMountainLion ? "18px" : "12px";
-      d.scrollbarV.style.pointerEvents = d.scrollbarH.style.pointerEvents = "none";
+      var barMouseDown = function(e) {
+        if (e_target(e) != d.scrollbarV && e_target(e) != d.scrollbarH)
+          operation(cm, onMouseDown)(e);
+      };
+      on(d.scrollbarV, "mousedown", barMouseDown);
+      on(d.scrollbarH, "mousedown", barMouseDown);
     }
   }
 
+  // Compute the lines that are visible in a given viewport (defaults
+  // the the current scroll position). viewPort may contain top,
+  // height, and ensure (see op.scrollToPos) properties.
   function visibleLines(display, doc, viewPort) {
-    var top = display.scroller.scrollTop, height = display.wrapper.clientHeight;
-    if (typeof viewPort == "number") top = viewPort;
-    else if (viewPort) {top = viewPort.top; height = viewPort.bottom - viewPort.top;}
+    var top = viewPort && viewPort.top != null ? viewPort.top : display.scroller.scrollTop;
     top = Math.floor(top - paddingTop(display));
-    var bottom = Math.ceil(top + height);
-    return {from: lineAtHeight(doc, top), to: lineAtHeight(doc, bottom)};
+    var bottom = viewPort && viewPort.bottom != null ? viewPort.bottom : top + display.wrapper.clientHeight;
+
+    var from = lineAtHeight(doc, top), to = lineAtHeight(doc, bottom);
+    // Ensure is a {from: {line, ch}, to: {line, ch}} object, and
+    // forces those lines into the viewport (if possible).
+    if (viewPort && viewPort.ensure) {
+      var ensureFrom = viewPort.ensure.from.line, ensureTo = viewPort.ensure.to.line;
+      if (ensureFrom < from)
+        return {from: ensureFrom,
+                to: lineAtHeight(doc, heightAtLine(getLine(doc, ensureFrom)) + display.wrapper.clientHeight)};
+      if (Math.min(ensureTo, doc.lastLine()) >= to)
+        return {from: lineAtHeight(doc, heightAtLine(getLine(doc, ensureTo)) - display.wrapper.clientHeight),
+                to: ensureTo};
+    }
+    return {from: from, to: to};
   }
 
   // LINE NUMBERS
 
+  // Re-align line numbers and gutter marks to compensate for
+  // horizontal scrolling.
   function alignHorizontally(cm) {
-    var display = cm.display;
+    var display = cm.display, view = display.view;
     if (!display.alignWidgets && (!display.gutters.firstChild || !cm.options.fixedGutter)) return;
     var comp = compensateForHScroll(display) - display.scroller.scrollLeft + cm.doc.scrollLeft;
-    var gutterW = display.gutters.offsetWidth, l = comp + "px";
-    for (var n = display.lineDiv.firstChild; n; n = n.nextSibling) if (n.alignable) {
-      for (var i = 0, a = n.alignable; i < a.length; ++i) a[i].style.left = l;
+    var gutterW = display.gutters.offsetWidth, left = comp + "px";
+    for (var i = 0; i < view.length; i++) if (!view[i].hidden) {
+      if (cm.options.fixedGutter && view[i].gutter)
+        view[i].gutter.style.left = left;
+      var align = view[i].alignable;
+      if (align) for (var j = 0; j < align.length; j++)
+        align[j].style.left = left;
     }
     if (cm.options.fixedGutter)
       display.gutters.style.left = (comp + gutterW) + "px";
   }
 
+  // Used to ensure that the line number gutter is still the right
+  // size for the current document size. Returns true when an update
+  // is needed.
   function maybeUpdateLineNumberWidth(cm) {
     if (!cm.options.lineNumbers) return false;
     var doc = cm.doc, last = lineNumberFor(cm.options, doc.first + doc.size - 1), display = cm.display;
     if (last.length != display.lineNumChars) {
       var test = display.measure.appendChild(elt("div", [elt("div", last)],
                                                  "CodeMirror-linenumber CodeMirror-gutter-elt"));
       var innerW = test.firstChild.offsetWidth, padding = test.offsetWidth - innerW;
       display.lineGutter.style.width = "";
       display.lineNumInnerWidth = Math.max(innerW, display.lineGutter.offsetWidth - padding);
       display.lineNumWidth = display.lineNumInnerWidth + padding;
       display.lineNumChars = display.lineNumInnerWidth ? last.length : -1;
       display.lineGutter.style.width = display.lineNumWidth + "px";
+      var width = display.gutters.offsetWidth;
+      display.scrollbarH.style.left = cm.options.fixedGutter ? width + "px" : 0;
+      display.sizer.style.marginLeft = width + "px";
       return true;
     }
     return false;
   }
 
   function lineNumberFor(options, i) {
     return String(options.lineNumberFormatter(i + options.firstLineNumber));
   }
+
+  // Computes display.scroller.scrollLeft + display.gutters.offsetWidth,
+  // but using getBoundingClientRect to get a sub-pixel-accurate
+  // result.
   function compensateForHScroll(display) {
-    return getRect(display.scroller).left - getRect(display.sizer).left;
+    return display.scroller.getBoundingClientRect().left - display.sizer.getBoundingClientRect().left;
   }
 
   // DISPLAY DRAWING
 
-  function updateDisplay(cm, changes, viewPort, forced) {
-    var oldFrom = cm.display.showingFrom, oldTo = cm.display.showingTo, updated;
+  // Updates the display, selection, and scrollbars, using the
+  // information in display.view to find out which nodes are no longer
+  // up-to-date. Tries to bail out early when no changes are needed,
+  // unless forced is true.
+  // Returns true if an actual update happened, false otherwise.
+  function updateDisplay(cm, viewPort, forced) {
+    var oldFrom = cm.display.viewFrom, oldTo = cm.display.viewTo, updated;
     var visible = visibleLines(cm.display, cm.doc, viewPort);
     for (var first = true;; first = false) {
       var oldWidth = cm.display.scroller.clientWidth;
-      if (!updateDisplayInner(cm, changes, visible, forced)) break;
+      if (!updateDisplayInner(cm, visible, forced)) break;
       updated = true;
-      changes = [];
+
+      // If the max line changed since it was last measured, measure it,
+      // and ensure the document's width matches it.
+      if (cm.display.maxLineChanged && !cm.options.lineWrapping)
+        adjustContentWidth(cm);
+
+      var barMeasure = measureForScrollbars(cm);
       updateSelection(cm);
-      updateScrollbars(cm);
+      setDocumentHeight(cm, barMeasure);
+      updateScrollbars(cm, barMeasure);
       if (first && cm.options.lineWrapping && oldWidth != cm.display.scroller.clientWidth) {
         forced = true;
         continue;
       }
       forced = false;
 
-      // Clip forced viewport to actual scrollable area
-      if (viewPort)
-        viewPort = Math.min(cm.display.scroller.scrollHeight - cm.display.scroller.clientHeight,
-                            typeof viewPort == "number" ? viewPort : viewPort.top);
+      // Clip forced viewport to actual scrollable area.
+      if (viewPort && viewPort.top != null)
+        viewPort = {top: Math.min(barMeasure.docHeight - scrollerCutOff - barMeasure.clientHeight, viewPort.top)};
+      // Updated line heights might result in the drawn area not
+      // actually covering the viewport. Keep looping until it does.
       visible = visibleLines(cm.display, cm.doc, viewPort);
-      if (visible.from >= cm.display.showingFrom && visible.to <= cm.display.showingTo)
+      if (visible.from >= cm.display.viewFrom && visible.to <= cm.display.viewTo)
         break;
     }
 
+    cm.display.updateLineNumbers = null;
     if (updated) {
       signalLater(cm, "update", cm);
-      if (cm.display.showingFrom != oldFrom || cm.display.showingTo != oldTo)
-        signalLater(cm, "viewportChange", cm, cm.display.showingFrom, cm.display.showingTo);
+      if (cm.display.viewFrom != oldFrom || cm.display.viewTo != oldTo)
+        signalLater(cm, "viewportChange", cm, cm.display.viewFrom, cm.display.viewTo);
     }
     return updated;
   }
 
-  // Uses a set of changes plus the current scroll position to
-  // determine which DOM updates have to be made, and makes the
-  // updates.
-  function updateDisplayInner(cm, changes, visible, forced) {
+  // Does the actual updating of the line display. Bails out
+  // (returning false) when there is nothing to be done and forced is
+  // false.
+  function updateDisplayInner(cm, visible, forced) {
     var display = cm.display, doc = cm.doc;
     if (!display.wrapper.offsetWidth) {
-      display.showingFrom = display.showingTo = doc.first;
-      display.viewOffset = 0;
+      resetView(cm);
       return;
     }
 
     // Bail out if the visible area is already rendered and nothing changed.
-    if (!forced && changes.length == 0 &&
-        visible.from > display.showingFrom && visible.to < display.showingTo)
+    if (!forced && visible.from >= display.viewFrom && visible.to <= display.viewTo &&
+        countDirtyView(cm) == 0)
       return;
 
     if (maybeUpdateLineNumberWidth(cm))
-      changes = [{from: doc.first, to: doc.first + doc.size}];
-    var gutterW = display.sizer.style.marginLeft = display.gutters.offsetWidth + "px";
-    display.scrollbarH.style.left = cm.options.fixedGutter ? gutterW : "0";
+      resetView(cm);
+    var dims = getDimensions(cm);
 
-    // Used to determine which lines need their line numbers updated
-    var positionsChangedFrom = Infinity;
-    if (cm.options.lineNumbers)
-      for (var i = 0; i < changes.length; ++i)
-        if (changes[i].diff && changes[i].from < positionsChangedFrom) { positionsChangedFrom = changes[i].from; }
-
+    // Compute a suitable new viewport (from & to)
     var end = doc.first + doc.size;
     var from = Math.max(visible.from - cm.options.viewportMargin, doc.first);
     var to = Math.min(end, visible.to + cm.options.viewportMargin);
-    if (display.showingFrom < from && from - display.showingFrom < 20) from = Math.max(doc.first, display.showingFrom);
-    if (display.showingTo > to && display.showingTo - to < 20) to = Math.min(end, display.showingTo);
+    if (display.viewFrom < from && from - display.viewFrom < 20) from = Math.max(doc.first, display.viewFrom);
+    if (display.viewTo > to && display.viewTo - to < 20) to = Math.min(end, display.viewTo);
     if (sawCollapsedSpans) {
-      from = lineNo(visualLine(doc, getLine(doc, from)));
-      while (to < end && lineIsHidden(doc, getLine(doc, to))) ++to;
+      from = visualLineNo(cm.doc, from);
+      to = visualLineEndNo(cm.doc, to);
     }
 
-    // Create a range of theoretically intact lines, and punch holes
-    // in that using the change info.
-    var intact = [{from: Math.max(display.showingFrom, doc.first),
-                   to: Math.min(display.showingTo, end)}];
-    if (intact[0].from >= intact[0].to) intact = [];
-    else intact = computeIntact(intact, changes);
-    // When merged lines are present, we might have to reduce the
-    // intact ranges because changes in continued fragments of the
-    // intact lines do require the lines to be redrawn.
-    if (sawCollapsedSpans)
-      for (var i = 0; i < intact.length; ++i) {
-        var range = intact[i], merged;
-        while (merged = collapsedSpanAtEnd(getLine(doc, range.to - 1))) {
-          var newTo = merged.find().from.line;
-          if (newTo > range.from) range.to = newTo;
-          else { intact.splice(i--, 1); break; }
-        }
-      }
+    var different = from != display.viewFrom || to != display.viewTo ||
+      display.lastSizeC != display.wrapper.clientHeight;
+    adjustView(cm, from, to);
 
-    // Clip off the parts that won't be visible
-    var intactLines = 0;
-    for (var i = 0; i < intact.length; ++i) {
-      var range = intact[i];
-      if (range.from < from) range.from = from;
-      if (range.to > to) range.to = to;
-      if (range.from >= range.to) intact.splice(i--, 1);
-      else intactLines += range.to - range.from;
-    }
-    if (!forced && intactLines == to - from && from == display.showingFrom && to == display.showingTo) {
-      updateViewOffset(cm);
-      return;
-    }
-    intact.sort(function(a, b) {return a.from - b.from;});
+    display.viewOffset = heightAtLine(getLine(cm.doc, display.viewFrom));
+    // Position the mover div to align with the current scroll position
+    cm.display.mover.style.top = display.viewOffset + "px";
 
-    // Avoid crashing on IE's "unspecified error" when in iframes
-    try {
-      var focused = document.activeElement;
-    } catch(e) {}
-    if (intactLines < (to - from) * .7) display.lineDiv.style.display = "none";
-    patchDisplay(cm, from, to, intact, positionsChangedFrom);
-    display.lineDiv.style.display = "";
-    if (focused && document.activeElement != focused && focused.offsetHeight) focused.focus();
+    var toUpdate = countDirtyView(cm);
+    if (!different && toUpdate == 0 && !forced) return;
 
-    var different = from != display.showingFrom || to != display.showingTo ||
-      display.lastSizeC != display.wrapper.clientHeight;
-    // This is just a bogus formula that detects when the editor is
-    // resized or the font size changes.
+    // For big changes, we hide the enclosing element during the
+    // update, since that speeds up the operations on most browsers.
+    var focused = activeElt();
+    if (toUpdate > 4) display.lineDiv.style.display = "none";
+    patchDisplay(cm, display.updateLineNumbers, dims);
+    if (toUpdate > 4) display.lineDiv.style.display = "";
+    // There might have been a widget with a focused element that got
+    // hidden or updated, if so re-focus it.
+    if (focused && activeElt() != focused && focused.offsetHeight) focused.focus();
+
+    // Prevent selection and cursors from interfering with the scroll
+    // width.
+    removeChildren(display.cursorDiv);
+    removeChildren(display.selectionDiv);
+
     if (different) {
       display.lastSizeC = display.wrapper.clientHeight;
       startWorker(cm, 400);
     }
-    display.showingFrom = from; display.showingTo = to;
 
-    display.gutters.style.height = "";
     updateHeightsInViewport(cm);
-    updateViewOffset(cm);
 
     return true;
   }
 
+  function adjustContentWidth(cm) {
+    var display = cm.display;
+    var width = measureChar(cm, display.maxLine, display.maxLine.text.length).left;
+    display.maxLineChanged = false;
+    var minWidth = Math.max(0, width + 3);
+    var maxScrollLeft = Math.max(0, display.sizer.offsetLeft + minWidth + scrollerCutOff - display.scroller.clientWidth);
+    display.sizer.style.minWidth = minWidth + "px";
+    if (maxScrollLeft < cm.doc.scrollLeft)
+      setScrollLeft(cm, Math.min(display.scroller.scrollLeft, maxScrollLeft), true);
+  }
+
+  function setDocumentHeight(cm, measure) {
+    cm.display.sizer.style.minHeight = cm.display.heightForcer.style.top = measure.docHeight + "px";
+    cm.display.gutters.style.height = Math.max(measure.docHeight, measure.clientHeight - scrollerCutOff) + "px";
+  }
+
+  // Read the actual heights of the rendered lines, and update their
+  // stored heights to match.
   function updateHeightsInViewport(cm) {
     var display = cm.display;
     var prevBottom = display.lineDiv.offsetTop;
-    for (var node = display.lineDiv.firstChild, height; node; node = node.nextSibling) if (node.lineObj) {
-      if (ie_lt8) {
-        var bot = node.offsetTop + node.offsetHeight;
+    for (var i = 0; i < display.view.length; i++) {
+      var cur = display.view[i], height;
+      if (cur.hidden) continue;
+      if (ie_upto7) {
+        var bot = cur.node.offsetTop + cur.node.offsetHeight;
         height = bot - prevBottom;
         prevBottom = bot;
       } else {
-        var box = getRect(node);
+        var box = cur.node.getBoundingClientRect();
         height = box.bottom - box.top;
       }
-      var diff = node.lineObj.height - height;
+      var diff = cur.line.height - height;
       if (height < 2) height = textHeight(display);
       if (diff > .001 || diff < -.001) {
-        updateLineHeight(node.lineObj, height);
-        var widgets = node.lineObj.widgets;
-        if (widgets) for (var i = 0; i < widgets.length; ++i)
-          widgets[i].height = widgets[i].node.offsetHeight;
+        updateLineHeight(cur.line, height);
+        updateWidgetHeight(cur.line);
+        if (cur.rest) for (var j = 0; j < cur.rest.length; j++)
+          updateWidgetHeight(cur.rest[j]);
       }
     }
   }
 
-  function updateViewOffset(cm) {
-    var off = cm.display.viewOffset = heightAtLine(cm, getLine(cm.doc, cm.display.showingFrom));
-    // Position the mover div to align with the current virtual scroll position
-    cm.display.mover.style.top = off + "px";
+  // Read and store the height of line widgets associated with the
+  // given line.
+  function updateWidgetHeight(line) {
+    if (line.widgets) for (var i = 0; i < line.widgets.length; ++i)
+      line.widgets[i].height = line.widgets[i].node.offsetHeight;
   }
 
-  function computeIntact(intact, changes) {
-    for (var i = 0, l = changes.length || 0; i < l; ++i) {
-      var change = changes[i], intact2 = [], diff = change.diff || 0;
-      for (var j = 0, l2 = intact.length; j < l2; ++j) {
-        var range = intact[j];
-        if (change.to <= range.from && change.diff) {
-          intact2.push({from: range.from + diff, to: range.to + diff});
-        } else if (change.to <= range.from || change.from >= range.to) {
-          intact2.push(range);
-        } else {
-          if (change.from > range.from)
-            intact2.push({from: range.from, to: change.from});
-          if (change.to < range.to)
-            intact2.push({from: change.to + diff, to: range.to + diff});
-        }
-      }
-      intact = intact2;
-    }
-    return intact;
-  }
-
+  // Do a bulk-read of the DOM positions and sizes needed to draw the
+  // view, so that we don't interleave reading and writing to the DOM.
   function getDimensions(cm) {
     var d = cm.display, left = {}, width = {};
     for (var n = d.gutters.firstChild, i = 0; n; n = n.nextSibling, ++i) {
       left[cm.options.gutters[i]] = n.offsetLeft;
       width[cm.options.gutters[i]] = n.offsetWidth;
     }
     return {fixedPos: compensateForHScroll(d),
             gutterTotalWidth: d.gutters.offsetWidth,
             gutterLeft: left,
             gutterWidth: width,
             wrapperWidth: d.wrapper.clientWidth};
   }
 
-  function patchDisplay(cm, from, to, intact, updateNumbersFrom) {
-    var dims = getDimensions(cm);
+  // Sync the actual display DOM structure with display.view, removing
+  // nodes for lines that are no longer in view, and creating the ones
+  // that are not there yet, and updating the ones that are out of
+  // date.
+  function patchDisplay(cm, updateNumbersFrom, dims) {
     var display = cm.display, lineNumbers = cm.options.lineNumbers;
-    if (!intact.length && (!webkit || !cm.display.currentWheelTarget))
-      removeChildren(display.lineDiv);
     var container = display.lineDiv, cur = container.firstChild;
 
     function rm(node) {
       var next = node.nextSibling;
-      if (webkit && mac && cm.display.currentWheelTarget == node) {
+      // Works around a throw-scroll bug in OS X Webkit
+      if (webkit && mac && cm.display.currentWheelTarget == node)
         node.style.display = "none";
-        node.lineObj = null;
-      } else {
+      else
         node.parentNode.removeChild(node);
+      return next;
+    }
+
+    var view = display.view, lineN = display.viewFrom;
+    // Loop over the elements in the view, syncing cur (the DOM nodes
+    // in display.lineDiv) with the view as we go.
+    for (var i = 0; i < view.length; i++) {
+      var lineView = view[i];
+      if (lineView.hidden) {
+      } else if (!lineView.node) { // Not drawn yet
+        var node = buildLineElement(cm, lineView, lineN, dims);
+        container.insertBefore(node, cur);
+      } else { // Already drawn
+        while (cur != lineView.node) cur = rm(cur);
+        var updateNumber = lineNumbers && updateNumbersFrom != null &&
+          updateNumbersFrom <= lineN && lineView.lineNumber;
+        if (lineView.changes) {
+          if (indexOf(lineView.changes, "gutter") > -1) updateNumber = false;
+          updateLineForChanges(cm, lineView, lineN, dims);
+        }
+        if (updateNumber) {
+          removeChildren(lineView.lineNumber);
+          lineView.lineNumber.appendChild(document.createTextNode(lineNumberFor(cm.options, lineN)));
+        }
+        cur = lineView.node.nextSibling;
       }
-      return next;
-    }
-
-    var nextIntact = intact.shift(), lineN = from;
-    cm.doc.iter(from, to, function(line) {
-      if (nextIntact && nextIntact.to == lineN) nextIntact = intact.shift();
-      if (lineIsHidden(cm.doc, line)) {
-        if (line.height != 0) updateLineHeight(line, 0);
-        if (line.widgets && cur && cur.previousSibling) for (var i = 0; i < line.widgets.length; ++i) {
-          var w = line.widgets[i];
-          if (w.showIfHidden) {
-            var prev = cur.previousSibling;
-            if (/pre/i.test(prev.nodeName)) {
-              var wrap = elt("div", null, null, "position: relative");
-              prev.parentNode.replaceChild(wrap, prev);
-              wrap.appendChild(prev);
-              prev = wrap;
-            }
-            var wnode = prev.appendChild(elt("div", [w.node], "CodeMirror-linewidget"));
-            if (!w.handleMouseEvents) wnode.ignoreEvents = true;
-            positionLineWidget(w, wnode, prev, dims);
-          }
-        }
-      } else if (nextIntact && nextIntact.from <= lineN && nextIntact.to > lineN) {
-        // This line is intact. Skip to the actual node. Update its
-        // line number if needed.
-        while (cur.lineObj != line) cur = rm(cur);
-        if (lineNumbers && updateNumbersFrom <= lineN && cur.lineNumber)
-          setTextContent(cur.lineNumber, lineNumberFor(cm.options, lineN));
-        cur = cur.nextSibling;
-      } else {
-        // For lines with widgets, make an attempt to find and reuse
-        // the existing element, so that widgets aren't needlessly
-        // removed and re-inserted into the dom
-        if (line.widgets) for (var j = 0, search = cur, reuse; search && j < 20; ++j, search = search.nextSibling)
-          if (search.lineObj == line && /div/i.test(search.nodeName)) { reuse = search; break; }
-        // This line needs to be generated.
-        var lineNode = buildLineElement(cm, line, lineN, dims, reuse);
-        if (lineNode != reuse) {
-          container.insertBefore(lineNode, cur);
-        } else {
-          while (cur != reuse) cur = rm(cur);
-          cur = cur.nextSibling;
-        }
-
-        lineNode.lineObj = line;
-      }
-      ++lineN;
-    });
+      lineN += lineView.size;
+    }
     while (cur) cur = rm(cur);
   }
 
-  function buildLineElement(cm, line, lineNo, dims, reuse) {
-    var built = buildLineContent(cm, line), lineElement = built.pre;
-    var markers = line.gutterMarkers, display = cm.display, wrap;
-
-    var bgClass = built.bgClass ? built.bgClass + " " + (line.bgClass || "") : line.bgClass;
-    if (!cm.options.lineNumbers && !markers && !bgClass && !line.wrapClass && !line.widgets)
-      return lineElement;
-
-    // Lines with gutter elements, widgets or a background class need
-    // to be wrapped again, and have the extra elements added to the
-    // wrapper div
-
-    if (reuse) {
-      reuse.alignable = null;
-      var isOk = true, widgetsSeen = 0, insertBefore = null;
-      for (var n = reuse.firstChild, next; n; n = next) {
-        next = n.nextSibling;
-        if (!/\bCodeMirror-linewidget\b/.test(n.className)) {
-          reuse.removeChild(n);
-        } else {
-          for (var i = 0; i < line.widgets.length; ++i) {
-            var widget = line.widgets[i];
-            if (widget.node == n.firstChild) {
-              if (!widget.above && !insertBefore) insertBefore = n;
-              positionLineWidget(widget, n, reuse, dims);
-              ++widgetsSeen;
-              break;
-            }
-          }
-          if (i == line.widgets.length) { isOk = false; break; }
-        }
-      }
-      reuse.insertBefore(lineElement, insertBefore);
-      if (isOk && widgetsSeen == line.widgets.length) {
-        wrap = reuse;
-        reuse.className = line.wrapClass || "";
-      }
-    }
-    if (!wrap) {
-      wrap = elt("div", null, line.wrapClass, "position: relative");
-      wrap.appendChild(lineElement);
-    }
-    // Kludge to make sure the styled element lies behind the selection (by z-index)
-    if (bgClass)
-      wrap.insertBefore(elt("div", null, bgClass + " CodeMirror-linebackground"), wrap.firstChild);
+  // When an aspect of a line changes, a string is added to
+  // lineView.changes. This updates the relevant part of the line's
+  // DOM structure.
+  function updateLineForChanges(cm, lineView, lineN, dims) {
+    for (var j = 0; j < lineView.changes.length; j++) {
+      var type = lineView.changes[j];
+      if (type == "text") updateLineText(cm, lineView);
+      else if (type == "gutter") updateLineGutter(cm, lineView, lineN, dims);
+      else if (type == "class") updateLineClasses(lineView);
+      else if (type == "widget") updateLineWidgets(lineView, dims);
+    }
+    lineView.changes = null;
+  }
+
+  // Lines with gutter elements, widgets or a background class need to
+  // be wrapped, and have the extra elements added to the wrapper div
+  function ensureLineWrapped(lineView) {
+    if (lineView.node == lineView.text) {
+      lineView.node = elt("div", null, null, "position: relative");
+      if (lineView.text.parentNode)
+        lineView.text.parentNode.replaceChild(lineView.node, lineView.text);
+      lineView.node.appendChild(lineView.text);
+      if (ie_upto7) lineView.node.style.zIndex = 2;
+    }
+    return lineView.node;
+  }
+
+  function updateLineBackground(lineView) {
+    var cls = lineView.bgClass ? lineView.bgClass + " " + (lineView.line.bgClass || "") : lineView.line.bgClass;
+    if (cls) cls += " CodeMirror-linebackground";
+    if (lineView.background) {
+      if (cls) lineView.background.className = cls;
+      else { lineView.background.parentNode.removeChild(lineView.background); lineView.background = null; }
+    } else if (cls) {
+      var wrap = ensureLineWrapped(lineView);
+      lineView.background = wrap.insertBefore(elt("div", null, cls), wrap.firstChild);
+    }
+  }
+
+  // Wrapper around buildLineContent which will reuse the structure
+  // in display.externalMeasured when possible.
+  function getLineContent(cm, lineView) {
+    var ext = cm.display.externalMeasured;
+    if (ext && ext.line == lineView.line) {
+      cm.display.externalMeasured = null;
+      lineView.measure = ext.measure;
+      return ext.built;
+    }
+    return buildLineContent(cm, lineView);
+  }
+
+  // Redraw the line's text. Interacts with the background and text
+  // classes because the mode may output tokens that influence these
+  // classes.
+  function updateLineText(cm, lineView) {
+    var cls = lineView.text.className;
+    var built = getLineContent(cm, lineView);
+    if (lineView.text == lineView.node) lineView.node = built.pre;
+    lineView.text.parentNode.replaceChild(built.pre, lineView.text);
+    lineView.text = built.pre;
+    if (built.bgClass != lineView.bgClass || built.textClass != lineView.textClass) {
+      lineView.bgClass = built.bgClass;
+      lineView.textClass = built.textClass;
+      updateLineClasses(lineView);
+    } else if (cls) {
+      lineView.text.className = cls;
+    }
+  }
+
+  function updateLineClasses(lineView) {
+    updateLineBackground(lineView);
+    if (lineView.line.wrapClass)
+      ensureLineWrapped(lineView).className = lineView.line.wrapClass;
+    else if (lineView.node != lineView.text)
+      lineView.node.className = "";
+    var textClass = lineView.textClass ? lineView.textClass + " " + (lineView.line.textClass || "") : lineView.line.textClass;
+    lineView.text.className = textClass || "";
+  }
+
+  function updateLineGutter(cm, lineView, lineN, dims) {
+    if (lineView.gutter) {
+      lineView.node.removeChild(lineView.gutter);
+      lineView.gutter = null;
+    }
+    var markers = lineView.line.gutterMarkers;
     if (cm.options.lineNumbers || markers) {
-      var gutterWrap = wrap.insertBefore(elt("div", null, "CodeMirror-gutter-wrapper", "position: absolute; left: " +
-                                             (cm.options.fixedGutter ? dims.fixedPos : -dims.gutterTotalWidth) + "px"),
-                                         lineElement);
-      if (cm.options.fixedGutter) (wrap.alignable || (wrap.alignable = [])).push(gutterWrap);
+      var wrap = ensureLineWrapped(lineView);
+      var gutterWrap = lineView.gutter =
+        wrap.insertBefore(elt("div", null, "CodeMirror-gutter-wrapper", "position: absolute; left: " +
+                              (cm.options.fixedGutter ? dims.fixedPos : -dims.gutterTotalWidth) + "px"),
+                          lineView.text);
       if (cm.options.lineNumbers && (!markers || !markers["CodeMirror-linenumbers"]))
-        wrap.lineNumber = gutterWrap.appendChild(
-          elt("div", lineNumberFor(cm.options, lineNo),
+        lineView.lineNumber = gutterWrap.appendChild(
+          elt("div", lineNumberFor(cm.options, lineN),
               "CodeMirror-linenumber CodeMirror-gutter-elt",
               "left: " + dims.gutterLeft["CodeMirror-linenumbers"] + "px; width: "
-              + display.lineNumInnerWidth + "px"));
-      if (markers)
-        for (var k = 0; k < cm.options.gutters.length; ++k) {
-          var id = cm.options.gutters[k], found = markers.hasOwnProperty(id) && markers[id];
-          if (found)
-            gutterWrap.appendChild(elt("div", [found], "CodeMirror-gutter-elt", "left: " +
-                                       dims.gutterLeft[id] + "px; width: " + dims.gutterWidth[id] + "px"));
-        }
-    }
-    if (ie_lt8) wrap.style.zIndex = 2;
-    if (line.widgets && wrap != reuse) for (var i = 0, ws = line.widgets; i < ws.length; ++i) {
+              + cm.display.lineNumInnerWidth + "px"));
+      if (markers) for (var k = 0; k < cm.options.gutters.length; ++k) {
+        var id = cm.options.gutters[k], found = markers.hasOwnProperty(id) && markers[id];
+        if (found)
+          gutterWrap.appendChild(elt("div", [found], "CodeMirror-gutter-elt", "left: " +
+                                     dims.gutterLeft[id] + "px; width: " + dims.gutterWidth[id] + "px"));
+      }
+    }
+  }
+
+  function updateLineWidgets(lineView, dims) {
+    if (lineView.alignable) lineView.alignable = null;
+    for (var node = lineView.node.firstChild, next; node; node = next) {
+      var next = node.nextSibling;
+      if (node.className == "CodeMirror-linewidget")
+        lineView.node.removeChild(node);
+    }
+    insertLineWidgets(lineView, dims);
+  }
+
+  // Build a line's DOM representation from scratch
+  function buildLineElement(cm, lineView, lineN, dims) {
+    var built = getLineContent(cm, lineView);
+    lineView.text = lineView.node = built.pre;
+    if (built.bgClass) lineView.bgClass = built.bgClass;
+    if (built.textClass) lineView.textClass = built.textClass;
+
+    updateLineClasses(lineView);
+    updateLineGutter(cm, lineView, lineN, dims);
+    insertLineWidgets(lineView, dims);
+    return lineView.node;
+  }
+
+  // A lineView may contain multiple logical lines (when merged by
+  // collapsed spans). The widgets for all of them need to be drawn.
+  function insertLineWidgets(lineView, dims) {
+    insertLineWidgetsFor(lineView.line, lineView, dims, true);
+    if (lineView.rest) for (var i = 0; i < lineView.rest.length; i++)
+      insertLineWidgetsFor(lineView.rest[i], lineView, dims, false);
+  }
+
+  function insertLineWidgetsFor(line, lineView, dims, allowAbove) {
+    if (!line.widgets) return;
+    var wrap = ensureLineWrapped(lineView);
+    for (var i = 0, ws = line.widgets; i < ws.length; ++i) {
       var widget = ws[i], node = elt("div", [widget.node], "CodeMirror-linewidget");
       if (!widget.handleMouseEvents) node.ignoreEvents = true;
-      positionLineWidget(widget, node, wrap, dims);
-      if (widget.above)
-        wrap.insertBefore(node, cm.options.lineNumbers && line.height != 0 ? gutterWrap : lineElement);
+      positionLineWidget(widget, node, lineView, dims);
+      if (allowAbove && widget.above)
+        wrap.insertBefore(node, lineView.gutter || lineView.text);
       else
         wrap.appendChild(node);
       signalLater(widget, "redraw");
     }
-    return wrap;
-  }
-
-  function positionLineWidget(widget, node, wrap, dims) {
+  }
+
+  function positionLineWidget(widget, node, lineView, dims) {
     if (widget.noHScroll) {
-      (wrap.alignable || (wrap.alignable = [])).push(node);
+      (lineView.alignable || (lineView.alignable = [])).push(node);
       var width = dims.wrapperWidth;
       node.style.left = dims.fixedPos + "px";
       if (!widget.coverGutter) {
         width -= dims.gutterTotalWidth;
         node.style.paddingLeft = dims.gutterTotalWidth + "px";
       }
       node.style.width = width + "px";
     }
     if (widget.coverGutter) {
       node.style.zIndex = 5;
       node.style.position = "relative";
       if (!widget.noHScroll) node.style.marginLeft = -dims.gutterTotalWidth + "px";
     }
   }
 
+  // POSITION OBJECT
+
+  // A Pos instance represents a position within the text.
+  var Pos = CodeMirror.Pos = function(line, ch) {
+    if (!(this instanceof Pos)) return new Pos(line, ch);
+    this.line = line; this.ch = ch;
+  };
+
+  // Compare two positions, return 0 if they are the same, a negative
+  // number when a is less, and a positive number otherwise.
+  var cmp = CodeMirror.cmpPos = function(a, b) { return a.line - b.line || a.ch - b.ch; };
+
+  function copyPos(x) {return Pos(x.line, x.ch);}
+  function maxPos(a, b) { return cmp(a, b) < 0 ? b : a; }
+  function minPos(a, b) { return cmp(a, b) < 0 ? a : b; }
+
   // SELECTION / CURSOR
 
+  // Selection objects are immutable. A new one is created every time
+  // the selection changes. A selection is one or more non-overlapping
+  // (and non-touching) ranges, sorted, and an integer that indicates
+  // which one is the primary selection (the one that's scrolled into
+  // view, that getCursor returns, etc).
+  function Selection(ranges, primIndex) {
+    this.ranges = ranges;
+    this.primIndex = primIndex;
+  }
+
+  Selection.prototype = {
+    primary: function() { return this.ranges[this.primIndex]; },
+    equals: function(other) {
+      if (other == this) return true;
+      if (other.primIndex != this.primIndex || other.ranges.length != this.ranges.length) return false;
+      for (var i = 0; i < this.ranges.length; i++) {
+        var here = this.ranges[i], there = other.ranges[i];
+        if (cmp(here.anchor, there.anchor) != 0 || cmp(here.head, there.head) != 0) return false;
+      }
+      return true;
+    },
+    deepCopy: function() {
+      for (var out = [], i = 0; i < this.ranges.length; i++)
+        out[i] = new Range(copyPos(this.ranges[i].anchor), copyPos(this.ranges[i].head));
+      return new Selection(out, this.primIndex);
+    },
+    somethingSelected: function() {
+      for (var i = 0; i < this.ranges.length; i++)
+        if (!this.ranges[i].empty()) return true;
+      return false;
+    },
+    contains: function(pos, end) {
+      if (!end) end = pos;
+      for (var i = 0; i < this.ranges.length; i++) {
+        var range = this.ranges[i];
+        if (cmp(end, range.from()) >= 0 && cmp(pos, range.to()) <= 0)
+          return i;
+      }
+      return -1;
+    }
+  };
+
+  function Range(anchor, head) {
+    this.anchor = anchor; this.head = head;
+  }
+
+  Range.prototype = {
+    from: function() { return minPos(this.anchor, this.head); },
+    to: function() { return maxPos(this.anchor, this.head); },
+    empty: function() {
+      return this.head.line == this.anchor.line && this.head.ch == this.anchor.ch;
+    }
+  };
+
+  // Take an unsorted, potentially overlapping set of ranges, and
+  // build a selection out of it. 'Consumes' ranges array (modifying
+  // it).
+  function normalizeSelection(ranges, primIndex) {
+    var prim = ranges[primIndex];
+    ranges.sort(function(a, b) { return cmp(a.from(), b.from()); });
+    primIndex = indexOf(ranges, prim);
+    for (var i = 1; i < ranges.length; i++) {
+      var cur = ranges[i], prev = ranges[i - 1];
+      if (cmp(prev.to(), cur.from()) >= 0) {
+        var from = minPos(prev.from(), cur.from()), to = maxPos(prev.to(), cur.to());
+        var inv = prev.empty() ? cur.from() == cur.head : prev.from() == prev.head;
+        if (i <= primIndex) --primIndex;
+        ranges.splice(--i, 2, new Range(inv ? to : from, inv ? from : to));
+      }
+    }
+    return new Selection(ranges, primIndex);
+  }
+
+  function simpleSelection(anchor, head) {
+    return new Selection([new Range(anchor, head || anchor)], 0);
+  }
+
+  // Most of the external API clips given positions to make sure they
+  // actually exist within the document.
+  function clipLine(doc, n) {return Math.max(doc.first, Math.min(n, doc.first + doc.size - 1));}
+  function clipPos(doc, pos) {
+    if (pos.line < doc.first) return Pos(doc.first, 0);
+    var last = doc.first + doc.size - 1;
+    if (pos.line > last) return Pos(last, getLine(doc, last).text.length);
+    return clipToLen(pos, getLine(doc, pos.line).text.length);
+  }
+  function clipToLen(pos, linelen) {
+    var ch = pos.ch;
+    if (ch == null || ch > linelen) return Pos(pos.line, linelen);
+    else if (ch < 0) return Pos(pos.line, 0);
+    else return pos;
+  }
+  function isLine(doc, l) {return l >= doc.first && l < doc.first + doc.size;}
+  function clipPosArray(doc, array) {
+    for (var out = [], i = 0; i < array.length; i++) out[i] = clipPos(doc, array[i]);
+    return out;
+  }
+
+  // SELECTION UPDATES
+
+  // The 'scroll' parameter given to many of these indicated whether
+  // the new cursor position should be scrolled into view after
+  // modifying the selection.
+
+  // If shift is held or the extend flag is set, extends a range to
+  // include a given position (and optionally a second position).
+  // Otherwise, simply returns the range between the given positions.
+  // Used for cursor motion and such.
+  function extendRange(doc, range, head, other) {
+    if (doc.cm && doc.cm.display.shift || doc.extend) {
+      var anchor = range.anchor;
+      if (other) {
+        var posBefore = cmp(head, anchor) < 0;
+        if (posBefore != (cmp(other, anchor) < 0)) {
+          anchor = head;
+          head = other;
+        } else if (posBefore != (cmp(head, other) < 0)) {
+          head = other;
+        }
+      }
+      return new Range(anchor, head);
+    } else {
+      return new Range(other || head, head);
+    }
+  }
+
+  // Extend the primary selection range, discard the rest.
+  function extendSelection(doc, head, other, options) {
+    setSelection(doc, new Selection([extendRange(doc, doc.sel.primary(), head, other)], 0), options);
+  }
+
+  // Extend all selections (pos is an array of selections with length
+  // equal the number of selections)
+  function extendSelections(doc, heads, options) {
+    for (var out = [], i = 0; i < doc.sel.ranges.length; i++)
+      out[i] = extendRange(doc, doc.sel.ranges[i], heads[i], null);
+    var newSel = normalizeSelection(out, doc.sel.primIndex);
+    setSelection(doc, newSel, options);
+  }
+
+  // Updates a single range in the selection.
+  function replaceOneSelection(doc, i, range, options) {
+    var ranges = doc.sel.ranges.slice(0);
+    ranges[i] = range;
+    setSelection(doc, normalizeSelection(ranges, doc.sel.primIndex), options);
+  }
+
+  // Reset the selection to a single range.
+  function setSimpleSelection(doc, anchor, head, options) {
+    setSelection(doc, simpleSelection(anchor, head), options);
+  }
+
+  // Give beforeSelectionChange handlers a change to influence a
+  // selection update.
+  function filterSelectionChange(doc, sel) {
+    var obj = {
+      ranges: sel.ranges,
+      update: function(ranges) {
+        this.ranges = [];
+        for (var i = 0; i < ranges.length; i++)
+          this.ranges[i] = new Range(clipPos(doc, ranges[i].anchor),
+                                     clipPos(doc, ranges[i].head));
+      }
+    };
+    signal(doc, "beforeSelectionChange", doc, obj);
+    if (doc.cm) signal(doc.cm, "beforeSelectionChange", doc.cm, obj);
+    if (obj.ranges != sel.ranges) return normalizeSelection(obj.ranges, obj.ranges.length - 1);
+    else return sel;
+  }
+
+  function setSelectionReplaceHistory(doc, sel, options) {
+    var done = doc.history.done, last = lst(done);
+    if (last && last.ranges) {
+      done[done.length - 1] = sel;
+      setSelectionNoUndo(doc, sel, options);
+    } else {
+      setSelection(doc, sel, options);
+    }
+  }
+
+  // Set a new selection.
+  function setSelection(doc, sel, options) {
+    setSelectionNoUndo(doc, sel, options);
+    addSelectionToHistory(doc, doc.sel, doc.cm ? doc.cm.curOp.id : NaN, options);
+  }
+
+  function setSelectionNoUndo(doc, sel, options) {
+    if (hasHandler(doc, "beforeSelectionChange") || doc.cm && hasHandler(doc.cm, "beforeSelectionChange"))
+      sel = filterSelectionChange(doc, sel);
+
+    var bias = cmp(sel.primary().head, doc.sel.primary().head) < 0 ? -1 : 1;
+    setSelectionInner(doc, skipAtomicInSelection(doc, sel, bias, true));
+
+    if (!(options && options.scroll === false) && doc.cm)
+      ensureCursorVisible(doc.cm);
+  }
+
+  function setSelectionInner(doc, sel) {
+    if (sel.equals(doc.sel)) return;
+
+    doc.sel = sel;
+
+    if (doc.cm)
+      doc.cm.curOp.updateInput = doc.cm.curOp.selectionChanged =
+        doc.cm.curOp.cursorActivity = true;
+    signalLater(doc, "cursorActivity", doc);
+  }
+
+  // Verify that the selection does not partially select any atomic
+  // marked ranges.
+  function reCheckSelection(doc) {
+    setSelectionInner(doc, skipAtomicInSelection(doc, doc.sel, null, false), sel_dontScroll);
+  }
+
+  // Return a selection that does not partially select any atomic
+  // ranges.
+  function skipAtomicInSelection(doc, sel, bias, mayClear) {
+    var out;
+    for (var i = 0; i < sel.ranges.length; i++) {
+      var range = sel.ranges[i];
+      var newAnchor = skipAtomic(doc, range.anchor, bias, mayClear);
+      var newHead = skipAtomic(doc, range.head, bias, mayClear);
+      if (out || newAnchor != range.anchor || newHead != range.head) {
+        if (!out) out = sel.ranges.slice(0, i);
+        out[i] = new Range(newAnchor, newHead);
+      }
+    }
+    return out ? normalizeSelection(out, sel.primIndex) : sel;
+  }
+
+  // Ensure a given position is not inside an atomic range.
+  function skipAtomic(doc, pos, bias, mayClear) {
+    var flipped = false, curPos = pos;
+    var dir = bias || 1;
+    doc.cantEdit = false;
+    search: for (;;) {
+      var line = getLine(doc, curPos.line);
+      if (line.markedSpans) {
+        for (var i = 0; i < line.markedSpans.length; ++i) {
+          var sp = line.markedSpans[i], m = sp.marker;
+          if ((sp.from == null || (m.inclusiveLeft ? sp.from <= curPos.ch : sp.from < curPos.ch)) &&
+              (sp.to == null || (m.inclusiveRight ? sp.to >= curPos.ch : sp.to > curPos.ch))) {
+            if (mayClear) {
+              signal(m, "beforeCursorEnter");
+              if (m.explicitlyCleared) {
+                if (!line.markedSpans) break;
+                else {--i; continue;}
+              }
+            }
+            if (!m.atomic) continue;
+            var newPos = m.find(dir < 0 ? -1 : 1);
+            if (cmp(newPos, curPos) == 0) {
+              newPos.ch += dir;
+              if (newPos.ch < 0) {
+                if (newPos.line > doc.first) newPos = clipPos(doc, Pos(newPos.line - 1));
+                else newPos = null;
+              } else if (newPos.ch > line.text.length) {
+                if (newPos.line < doc.first + doc.size - 1) newPos = Pos(newPos.line + 1, 0);
+                else newPos = null;
+              }
+              if (!newPos) {
+                if (flipped) {
+                  // Driven in a corner -- no valid cursor position found at all
+                  // -- try again *with* clearing, if we didn't already
+                  if (!mayClear) return skipAtomic(doc, pos, bias, true);
+                  // Otherwise, turn off editing until further notice, and return the start of the doc
+                  doc.cantEdit = true;
+                  return Pos(doc.first, 0);
+                }
+                flipped = true; newPos = pos; dir = -dir;
+              }
+            }
+            curPos = newPos;
+            continue search;
+          }
+        }
+      }
+      return curPos;
+    }
+  }
+
+  // SELECTION DRAWING
+
+  // Redraw the selection and/or cursor
   function updateSelection(cm) {
-    var display = cm.display;
-    var collapsed = posEq(cm.doc.sel.from, cm.doc.sel.to);
-    if (collapsed || cm.options.showCursorWhenSelecting)
-      updateSelectionCursor(cm);
-    else
-      display.cursor.style.display = display.otherCursor.style.display = "none";
-    if (!collapsed)
-      updateSelectionRange(cm);
-    else
-      display.selectionDiv.style.display = "none";
+    var display = cm.display, doc = cm.doc;
+    var curFragment = document.createDocumentFragment();
+    var selFragment = document.createDocumentFragment();
+
+    for (var i = 0; i < doc.sel.ranges.length; i++) {
+      var range = doc.sel.ranges[i];
+      var collapsed = range.empty();
+      if (collapsed || cm.options.showCursorWhenSelecting)
+        updateSelectionCursor(cm, range, curFragment);
+      if (!collapsed)
+        updateSelectionRange(cm, range, selFragment);
+    }
 
     // Move the hidden textarea near the cursor to prevent scrolling artifacts
     if (cm.options.moveInputWithCursor) {
-      var headPos = cursorCoords(cm, cm.doc.sel.head, "div");
-      var wrapOff = getRect(display.wrapper), lineOff = getRect(display.lineDiv);
-      display.inputDiv.style.top = Math.max(0, Math.min(display.wrapper.clientHeight - 10,
-                                                        headPos.top + lineOff.top - wrapOff.top)) + "px";
-      display.inputDiv.style.left = Math.max(0, Math.min(display.wrapper.clientWidth - 10,
-                                                         headPos.left + lineOff.left - wrapOff.left)) + "px";
-    }
-  }
-
-  // No selection, plain cursor
-  function updateSelectionCursor(cm) {
-    var display = cm.display, pos = cursorCoords(cm, cm.doc.sel.head, "div");
-    display.cursor.style.left = pos.left + "px";
-    display.cursor.style.top = pos.top + "px";
-    display.cursor.style.height = Math.max(0, pos.bottom - pos.top) * cm.options.cursorHeight + "px";
-    display.cursor.style.display = "";
+      var headPos = cursorCoords(cm, doc.sel.primary().head, "div");
+      var wrapOff = display.wrapper.getBoundingClientRect(), lineOff = display.lineDiv.getBoundingClientRect();
+      var top = Math.max(0, Math.min(display.wrapper.clientHeight - 10,
+                                     headPos.top + lineOff.top - wrapOff.top));
+      var left = Math.max(0, Math.min(display.wrapper.clientWidth - 10,
+                                      headPos.left + lineOff.left - wrapOff.left));
+      display.inputDiv.style.top = top + "px";
+      display.inputDiv.style.left = left + "px";
+    }
+
+    removeChildrenAndAdd(display.cursorDiv, curFragment);
+    removeChildrenAndAdd(display.selectionDiv, selFragment);
+  }
+
+  // Draws a cursor for the given range
+  function updateSelectionCursor(cm, range, output) {
+    var pos = cursorCoords(cm, range.head, "div");
+
+    var cursor = output.appendChild(elt("div", "\u00a0", "CodeMirror-cursor"));
+    cursor.style.left = pos.left + "px";
+    cursor.style.top = pos.top + "px";
+    cursor.style.height = Math.max(0, pos.bottom - pos.top) * cm.options.cursorHeight + "px";
 
     if (pos.other) {
-      display.otherCursor.style.display = "";
-      display.otherCursor.style.left = pos.other.left + "px";
-      display.otherCursor.style.top = pos.other.top + "px";
-      display.otherCursor.style.height = (pos.other.bottom - pos.other.top) * .85 + "px";
-    } else { display.otherCursor.style.display = "none"; }
-  }
-
-  // Highlight selection
-  function updateSelectionRange(cm) {
-    var display = cm.display, doc = cm.doc, sel = cm.doc.sel;
+      // Secondary cursor, shown when on a 'jump' in bi-directional text
+      var otherCursor = output.appendChild(elt("div", "\u00a0", "CodeMirror-cursor CodeMirror-secondarycursor"));
+      otherCursor.style.display = "";
+      otherCursor.style.left = pos.other.left + "px";
+      otherCursor.style.top = pos.other.top + "px";
+      otherCursor.style.height = (pos.other.bottom - pos.other.top) * .85 + "px";
+    }
+  }
+
+  // Draws the given range as a highlighted selection
+  function updateSelectionRange(cm, range, output) {
+    var display = cm.display, doc = cm.doc;
     var fragment = document.createDocumentFragment();
-    var clientWidth = display.lineSpace.offsetWidth, pl = paddingLeft(cm.display);
+    var padding = paddingH(cm.display), leftSide = padding.left, rightSide = display.lineSpace.offsetWidth - padding.right;
 
     function add(left, top, width, bottom) {
       if (top < 0) top = 0;
       fragment.appendChild(elt("div", null, "CodeMirror-selected", "position: absolute; left: " + left +
-                               "px; top: " + top + "px; width: " + (width == null ? clientWidth - left : width) +
+                               "px; top: " + top + "px; width: " + (width == null ? rightSide - left : width) +
                                "px; height: " + (bottom - top) + "px"));
     }
 
     function drawForLine(line, fromArg, toArg) {
       var lineObj = getLine(doc, line);
       var lineLen = lineObj.text.length;
       var start, end;
       function coords(ch, bias) {
         return charCoords(cm, Pos(line, ch), "div", lineObj, bias);
       }
 
       iterateBidiSections(getOrder(lineObj), fromArg || 0, toArg == null ? lineLen : toArg, function(from, to, dir) {
         var leftPos = coords(from, "left"), rightPos, left, right;
         if (from == to) {
           rightPos = leftPos;
           left = right = leftPos.left;
         } else {
           rightPos = coords(to - 1, "right");
           if (dir == "rtl") { var tmp = leftPos; leftPos = rightPos; rightPos = tmp; }
           left = leftPos.left;
           right = rightPos.right;
         }
-        if (fromArg == null && from == 0) left = pl;
+        if (fromArg == null && from == 0) left = leftSide;
         if (rightPos.top - leftPos.top > 3) { // Different lines, draw top part
           add(left, leftPos.top, null, leftPos.bottom);
-          left = pl;
+          left = leftSide;
           if (leftPos.bottom < rightPos.top) add(left, leftPos.bottom, null, rightPos.top);
         }
-        if (toArg == null && to == lineLen) right = clientWidth;
+        if (toArg == null && to == lineLen) right = rightSide;
         if (!start || leftPos.top < start.top || leftPos.top == start.top && leftPos.left < start.left)
           start = leftPos;
         if (!end || rightPos.bottom > end.bottom || rightPos.bottom == end.bottom && rightPos.right > end.right)
           end = rightPos;
-        if (left < pl + 1) left = pl;
+        if (left < leftSide + 1) left = leftSide;
         add(left, rightPos.top, right - left, rightPos.bottom);
       });
       return {start: start, end: end};
     }
 
-    if (sel.from.line == sel.to.line) {
-      drawForLine(sel.from.line, sel.from.ch, sel.to.ch);
+    var sFrom = range.from(), sTo = range.to();
+    if (sFrom.line == sTo.line) {
+      drawForLine(sFrom.line, sFrom.ch, sTo.ch);
     } else {
-      var fromLine = getLine(doc, sel.from.line), toLine = getLine(doc, sel.to.line);
-      var singleVLine = visualLine(doc, fromLine) == visualLine(doc, toLine);
-      var leftEnd = drawForLine(sel.from.line, sel.from.ch, singleVLine ? fromLine.text.length : null).end;
-      var rightStart = drawForLine(sel.to.line, singleVLine ? 0 : null, sel.to.ch).start;
+      var fromLine = getLine(doc, sFrom.line), toLine = getLine(doc, sTo.line);
+      var singleVLine = visualLine(fromLine) == visualLine(toLine);
+      var leftEnd = drawForLine(sFrom.line, sFrom.ch, singleVLine ? fromLine.text.length + 1 : null).end;
+      var rightStart = drawForLine(sTo.line, singleVLine ? 0 : null, sTo.ch).start;
       if (singleVLine) {
         if (leftEnd.top < rightStart.top - 2) {
           add(leftEnd.right, leftEnd.top, null, leftEnd.bottom);
-          add(pl, rightStart.top, rightStart.left, rightStart.bottom);
+          add(leftSide, rightStart.top, rightStart.left, rightStart.bottom);
         } else {
           add(leftEnd.right, leftEnd.top, rightStart.left - leftEnd.right, leftEnd.bottom);
         }
       }
       if (leftEnd.bottom < rightStart.top)
-        add(pl, leftEnd.bottom, null, rightStart.top);
+        add(leftSide, leftEnd.bottom, null, rightStart.top);
     }
 
-    removeChildrenAndAdd(display.selectionDiv, fragment);
-    display.selectionDiv.style.display = "";
+    output.appendChild(fragment);
   }
 
   // Cursor-blinking
   function restartBlink(cm) {
     if (!cm.state.focused) return;
     var display = cm.display;
     clearInterval(display.blinker);
     var on = true;
-    display.cursor.style.visibility = display.otherCursor.style.visibility = "";
+    display.cursorDiv.style.visibility = "";
     if (cm.options.cursorBlinkRate > 0)
       display.blinker = setInterval(function() {
-        display.cursor.style.visibility = display.otherCursor.style.visibility = (on = !on) ? "" : "hidden";
+        display.cursorDiv.style.visibility = (on = !on) ? "" : "hidden";
       }, cm.options.cursorBlinkRate);
   }
 
   // HIGHLIGHT WORKER
 
   function startWorker(cm, time) {
-    if (cm.doc.mode.startState && cm.doc.frontier < cm.display.showingTo)
+    if (cm.doc.mode.startState && cm.doc.frontier < cm.display.viewTo)
       cm.state.highlight.set(time, bind(highlightWorker, cm));
   }
 
   function highlightWorker(cm) {
     var doc = cm.doc;
     if (doc.frontier < doc.first) doc.frontier = doc.first;
-    if (doc.frontier >= cm.display.showingTo) return;
+    if (doc.frontier >= cm.display.viewTo) return;
     var end = +new Date + cm.options.workTime;
     var state = copyState(doc.mode, getStateBefore(cm, doc.frontier));
-    var changed = [], prevChange;
-    doc.iter(doc.frontier, Math.min(doc.first + doc.size, cm.display.showingTo + 500), function(line) {
-      if (doc.frontier >= cm.display.showingFrom) { // Visible
+
+    runInOp(cm, function() {
+    doc.iter(doc.frontier, Math.min(doc.first + doc.size, cm.display.viewTo + 500), function(line) {
+      if (doc.frontier >= cm.display.viewFrom) { // Visible
         var oldStyles = line.styles;
         line.styles = highlightLine(cm, line, state, true);
         var ischange = !oldStyles || oldStyles.length != line.styles.length;
         for (var i = 0; !ischange && i < oldStyles.length; ++i) ischange = oldStyles[i] != line.styles[i];
-        if (ischange) {
-          if (prevChange && prevChange.end == doc.frontier) prevChange.end++;
-          else changed.push(prevChange = {start: doc.frontier, end: doc.frontier + 1});
-        }
+        if (ischange) regLineChange(cm, doc.frontier, "text");
         line.stateAfter = copyState(doc.mode, state);
       } else {
         processLine(cm, line.text, state);
         line.stateAfter = doc.frontier % 5 == 0 ? copyState(doc.mode, state) : null;
       }
       ++doc.frontier;
       if (+new Date > end) {
         startWorker(cm, cm.options.workDelay);
         return true;
       }
     });
-    if (changed.length)
-      operation(cm, function() {
-        for (var i = 0; i < changed.length; ++i)
-          regChange(this, changed[i].start, changed[i].end);
-      })();
+    });
   }
 
   // Finds the line to start with when starting a parse. Tries to
   // find a line with a stateAfter, so that it can start with a
   // valid state. If that fails, it returns the line with the
   // smallest indentation, which tends to need the least context to
   // parse correctly.
   function findStartLine(cm, n, precise) {
     var minindent, minline, doc = cm.doc;
     var lim = precise ? -1 : n - (cm.doc.mode.innerMode ? 1000 : 100);
@@ skipping 11 matching lines @@
   }
 
   function getStateBefore(cm, n, precise) {
     var doc = cm.doc, display = cm.display;
     if (!doc.mode.startState) return true;
     var pos = findStartLine(cm, n, precise), state = pos > doc.first && getLine(doc, pos-1).stateAfter;
     if (!state) state = startState(doc.mode);
     else state = copyState(doc.mode, state);
     doc.iter(pos, n, function(line) {
       processLine(cm, line.text, state);
-      var save = pos == n - 1 || pos % 5 == 0 || pos >= display.showingFrom && pos < display.showingTo;
+      var save = pos == n - 1 || pos % 5 == 0 || pos >= display.viewFrom && pos < display.viewTo;
       line.stateAfter = save ? copyState(doc.mode, state) : null;
       ++pos;
     });
     if (precise) doc.frontier = pos;
     return state;
   }
 
   // POSITION MEASUREMENT
 
   function paddingTop(display) {return display.lineSpace.offsetTop;}
   function paddingVert(display) {return display.mover.offsetHeight - display.lineSpace.offsetHeight;}
-  function paddingLeft(display) {
-    var e = removeChildrenAndAdd(display.measure, elt("pre", null, null, "text-align: left")).appendChild(elt("span", "x"));
-    return e.offsetLeft;
-  }
-
-  function measureChar(cm, line, ch, data, bias) {
-    var dir = -1;
-    data = data || measureLine(cm, line);
-    if (data.crude) {
-      var left = data.left + ch * data.width;
-      return {left: left, right: left + data.width, top: data.top, bottom: data.bottom};
-    }
-
-    for (var pos = ch;; pos += dir) {
-      var r = data[pos];
-      if (r) break;
-      if (dir < 0 && pos == 0) dir = 1;
-    }
-    bias = pos > ch ? "left" : pos < ch ? "right" : bias;
-    if (bias == "left" && r.leftSide) r = r.leftSide;
-    else if (bias == "right" && r.rightSide) r = r.rightSide;
-    return {left: pos < ch ? r.right : r.left,
-            right: pos > ch ? r.left : r.right,
-            top: r.top,
-            bottom: r.bottom};
-  }
-
-  function findCachedMeasurement(cm, line) {
-    var cache = cm.display.measureLineCache;
-    for (var i = 0; i < cache.length; ++i) {
-      var memo = cache[i];
-      if (memo.text == line.text && memo.markedSpans == line.markedSpans &&
-          cm.display.scroller.clientWidth == memo.width &&
-          memo.classes == line.textClass + "|" + line.wrapClass)
-        return memo;
-    }
-  }
-
-  function clearCachedMeasurement(cm, line) {
-    var exists = findCachedMeasurement(cm, line);
-    if (exists) exists.text = exists.measure = exists.markedSpans = null;
-  }
-
-  function measureLine(cm, line) {
-    // First look in the cache
-    var cached = findCachedMeasurement(cm, line);
-    if (cached) return cached.measure;
-
-    // Failing that, recompute and store result in cache
-    var measure = measureLineInner(cm, line);
-    var cache = cm.display.measureLineCache;
-    var memo = {text: line.text, width: cm.display.scroller.clientWidth,
-                markedSpans: line.markedSpans, measure: measure,
-                classes: line.textClass + "|" + line.wrapClass};
-    if (cache.length == 16) cache[++cm.display.measureLineCachePos % 16] = memo;
-    else cache.push(memo);
-    return measure;
-  }
-
-  function measureLineInner(cm, line) {
-    if (!cm.options.lineWrapping && line.text.length >= cm.options.crudeMeasuringFrom)
-      return crudelyMeasureLine(cm, line);
-
-    var display = cm.display, measure = emptyArray(line.text.length);
-    var pre = buildLineContent(cm, line, measure, true).pre;
-
-    // IE does not cache element positions of inline elements between
-    // calls to getBoundingClientRect. This makes the loop below,
-    // which gathers the positions of all the characters on the line,
-    // do an amount of layout work quadratic to the number of
-    // characters. When line wrapping is off, we try to improve things
-    // by first subdividing the line into a bunch of inline blocks, so
-    // that IE can reuse most of the layout information from caches
-    // for those blocks. This does interfere with line wrapping, so it
-    // doesn't work when wrapping is on, but in that case the
-    // situation is slightly better, since IE does cache line-wrapping
-    // information and only recomputes per-line.
-    if (old_ie && !ie_lt8 && !cm.options.lineWrapping && pre.childNodes.length > 100) {
-      var fragment = document.createDocumentFragment();
-      var chunk = 10, n = pre.childNodes.length;
-      for (var i = 0, chunks = Math.ceil(n / chunk); i < chunks; ++i) {
-        var wrap = elt("div", null, null, "display: inline-block");
-        for (var j = 0; j < chunk && n; ++j) {
-          wrap.appendChild(pre.firstChild);
-          --n;
+  function paddingH(display) {
+    if (display.cachedPaddingH) return display.cachedPaddingH;
+    var e = removeChildrenAndAdd(display.measure, elt("pre", "x"));
+    var style = window.getComputedStyle ? window.getComputedStyle(e) : e.currentStyle;
+    return display.cachedPaddingH = {left: parseInt(style.paddingLeft),
+                                     right: parseInt(style.paddingRight)};
+  }
+
+  // Ensure the lineView.wrapping.heights array is populated. This is
+  // an array of bottom offsets for the lines that make up a drawn
+  // line. When lineWrapping is on, there might be more than one
+  // height.
+  function ensureLineHeights(cm, lineView, rect) {
+    var wrapping = cm.options.lineWrapping;
+    var curWidth = wrapping && cm.display.scroller.clientWidth;
+    if (!lineView.measure.heights || wrapping && lineView.measure.width != curWidth) {
+      var heights = lineView.measure.heights = [];
+      if (wrapping) {
+        lineView.measure.width = curWidth;
+        var rects = lineView.text.firstChild.getClientRects();
+        for (var i = 0; i < rects.length - 1; i++) {
+          var cur = rects[i], next = rects[i + 1];
+          if (Math.abs(cur.bottom - next.bottom) > 2)
+            heights.push((cur.bottom + next.top) / 2 - rect.top);
         }
-        fragment.appendChild(wrap);
-      }
-      pre.appendChild(fragment);
-    }
-
-    removeChildrenAndAdd(display.measure, pre);
-
-    var outer = getRect(display.lineDiv);
-    var vranges = [], data = emptyArray(line.text.length), maxBot = pre.offsetHeight;
-    // Work around an IE7/8 bug where it will sometimes have randomly
-    // replaced our pre with a clone at this point.
-    if (ie_lt9 && display.measure.first != pre)
-      removeChildrenAndAdd(display.measure, pre);
-
-    function measureRect(rect) {
-      var top = rect.top - outer.top, bot = rect.bottom - outer.top;
-      if (bot > maxBot) bot = maxBot;
-      if (top < 0) top = 0;
-      for (var i = vranges.length - 2; i >= 0; i -= 2) {
-        var rtop = vranges[i], rbot = vranges[i+1];
-        if (rtop > bot || rbot < top) continue;
-        if (rtop <= top && rbot >= bot ||
-            top <= rtop && bot >= rbot ||
-            Math.min(bot, rbot) - Math.max(top, rtop) >= (bot - top) >> 1) {
-          vranges[i] = Math.min(top, rtop);
-          vranges[i+1] = Math.max(bot, rbot);
-          break;
-        }
-      }
-      if (i < 0) { i = vranges.length; vranges.push(top, bot); }
-      return {left: rect.left - outer.left,
-              right: rect.right - outer.left,
-              top: i, bottom: null};
-    }
-    function finishRect(rect) {
-      rect.bottom = vranges[rect.top+1];
-      rect.top = vranges[rect.top];
-    }
-
-    for (var i = 0, cur; i < measure.length; ++i) if (cur = measure[i]) {
-      var node = cur, rect = null;
-      // A widget might wrap, needs special care
-      if (/\bCodeMirror-widget\b/.test(cur.className) && cur.getClientRects) {
-        if (cur.firstChild.nodeType == 1) node = cur.firstChild;
-        var rects = node.getClientRects();
-        if (rects.length > 1) {
-          rect = data[i] = measureRect(rects[0]);
-          rect.rightSide = measureRect(rects[rects.length - 1]);
-        }
-      }
-      if (!rect) rect = data[i] = measureRect(getRect(node));
-      if (cur.measureRight) rect.right = getRect(cur.measureRight).left - outer.left;
-      if (cur.leftSide) rect.leftSide = measureRect(getRect(cur.leftSide));
-    }
-    removeChildren(cm.display.measure);
-    for (var i = 0, cur; i < data.length; ++i) if (cur = data[i]) {
-      finishRect(cur);
-      if (cur.leftSide) finishRect(cur.leftSide);
-      if (cur.rightSide) finishRect(cur.rightSide);
-    }
-    return data;
-  }
-
-  function crudelyMeasureLine(cm, line) {
-    var copy = new Line(line.text.slice(0, 100), null);
-    if (line.textClass) copy.textClass = line.textClass;
-    var measure = measureLineInner(cm, copy);
-    var left = measureChar(cm, copy, 0, measure, "left");
-    var right = measureChar(cm, copy, 99, measure, "right");
-    return {crude: true, top: left.top, left: left.left, bottom: left.bottom, width: (right.right - left.left) / 100};
-  }
-
-  function measureLineWidth(cm, line) {
-    var hasBadSpan = false;
-    if (line.markedSpans) for (var i = 0; i < line.markedSpans; ++i) {
-      var sp = line.markedSpans[i];
-      if (sp.collapsed && (sp.to == null || sp.to == line.text.length)) hasBadSpan = true;
-    }
-    var cached = !hasBadSpan && findCachedMeasurement(cm, line);
-    if (cached || line.text.length >= cm.options.crudeMeasuringFrom)
-      return measureChar(cm, line, line.text.length, cached && cached.measure, "right").right;
-
-    var pre = buildLineContent(cm, line, null, true).pre;
-    var end = pre.appendChild(zeroWidthElement(cm.display.measure));
-    removeChildrenAndAdd(cm.display.measure, pre);
-    return getRect(end).right - getRect(cm.display.lineDiv).left;
+      }
+      heights.push(rect.bottom - rect.top);
+    }
+  }
+
+  // Find a line map (mapping character offsets to text nodes) and a
+  // measurement cache for the given line number. (A line view might
+  // contain multiple lines when collapsed ranges are present.)
+  function mapFromLineView(lineView, line, lineN) {
+    if (lineView.line == line)
+      return {map: lineView.measure.map, cache: lineView.measure.cache};
+    for (var i = 0; i < lineView.rest.length; i++)
+      if (lineView.rest[i] == line)
+        return {map: lineView.measure.maps[i], cache: lineView.measure.caches[i]};
+    for (var i = 0; i < lineView.rest.length; i++)
+      if (lineNo(lineView.rest[i]) > lineN)
+        return {map: lineView.measure.maps[i], cache: lineView.measure.caches[i], before: true};
+  }
+
+  // Render a line into the hidden node display.externalMeasured. Used
+  // when measurement is needed for a line that's not in the viewport.
+  function updateExternalMeasurement(cm, line) {
+    line = visualLine(line);
+    var lineN = lineNo(line);
+    var view = cm.display.externalMeasured = new LineView(cm.doc, line, lineN);
+    view.lineN = lineN;
+    var built = view.built = buildLineContent(cm, view);
+    view.text = built.pre;
+    removeChildrenAndAdd(cm.display.lineMeasure, built.pre);
+    return view;
+  }
+
+  // Get a {top, bottom, left, right} box (in line-local coordinates)
+  // for a given character.
+  function measureChar(cm, line, ch, bias) {
+    return measureCharPrepared(cm, prepareMeasureForLine(cm, line), ch, bias);
+  }
+
+  // Find a line view that corresponds to the given line number.
+  function findViewForLine(cm, lineN) {
+    if (lineN >= cm.display.viewFrom && lineN < cm.display.viewTo)
+      return cm.display.view[findViewIndex(cm, lineN)];
+    var ext = cm.display.externalMeasured;
+    if (ext && lineN >= ext.lineN && lineN < ext.lineN + ext.size)
+      return ext;
+  }
+
+  // Measurement can be split in two steps, the set-up work that
+  // applies to the whole line, and the measurement of the actual
+  // character. Functions like coordsChar, that need to do a lot of
+  // measurements in a row, can thus ensure that the set-up work is
+  // only done once.
+  function prepareMeasureForLine(cm, line) {
+    var lineN = lineNo(line);
+    var view = findViewForLine(cm, lineN);
+    if (view && !view.text)
+      view = null;
+    else if (view && view.changes)
+      updateLineForChanges(cm, view, lineN, getDimensions(cm));
+    if (!view)
+      view = updateExternalMeasurement(cm, line);
+
+    var info = mapFromLineView(view, line, lineN);
+    return {
+      line: line, view: view, rect: null,
+      map: info.map, cache: info.cache, before: info.before,
+      hasHeights: false
+    };
+  }
+
+  // Given a prepared measurement object, measures the position of an
+  // actual character (or fetches it from the cache).
+  function measureCharPrepared(cm, prepared, ch, bias) {
+    if (prepared.before) ch = -1;
+    var key = ch + (bias || ""), found;
+    if (prepared.cache.hasOwnProperty(key)) {
+      found = prepared.cache[key];
+    } else {
+      if (!prepared.rect)
+        prepared.rect = prepared.view.text.getBoundingClientRect();
+      if (!prepared.hasHeights) {
+        ensureLineHeights(cm, prepared.view, prepared.rect);
+        prepared.hasHeights = true;
+      }
+      found = measureCharInner(cm, prepared, ch, bias);
+      if (!found.bogus) prepared.cache[key] = found;
+    }
+    return {left: found.left, right: found.right, top: found.top, bottom: found.bottom};
+  }
+
+  var nullRect = {left: 0, right: 0, top: 0, bottom: 0};
+
+  function measureCharInner(cm, prepared, ch, bias) {
+    var map = prepared.map;
+
+    var node, start, end, collapse;
+    // First, search the line map for the text node corresponding to,
+    // or closest to, the target character.
+    for (var i = 0; i < map.length; i += 3) {
+      var mStart = map[i], mEnd = map[i + 1];
+      if (ch < mStart) {
+        start = 0; end = 1;
+        collapse = "left";
+      } else if (ch < mEnd) {
+        start = ch - mStart;
+        end = start + 1;
+      } else if (i == map.length - 3 || ch == mEnd && map[i + 3] > ch) {
+        end = mEnd - mStart;
+        start = end - 1;
+        if (ch >= mEnd) collapse = "right";
+      }
+      if (start != null) {
+        node = map[i + 2];
+        if (mStart == mEnd && bias == (node.insertLeft ? "left" : "right"))
+          collapse = bias;
+        if (bias == "left" && start == 0)
+          while (i && map[i - 2] == map[i - 3] && map[i - 1].insertLeft) {
+            node = map[(i -= 3) + 2];
+            collapse = "left";
+          }
+        if (bias == "right" && start == mEnd - mStart)
+          while (i < map.length - 3 && map[i + 3] == map[i + 4] && !map[i + 5].insertLeft) {
+            node = map[(i += 3) + 2];
+            collapse = "right";
+          }
+        break;
+      }
+    }
+
+    var rect;
+    if (node.nodeType == 3) { // If it is a text node, use a range to retrieve the coordinates.
+      while (start && isExtendingChar(prepared.line.text.charAt(mStart + start))) --start;
+      while (mStart + end < mEnd && isExtendingChar(prepared.line.text.charAt(mStart + end))) ++end;
+      if (ie_upto8 && start == 0 && end == mEnd - mStart) {
+        rect = node.parentNode.getBoundingClientRect();
+      } else if (ie && cm.options.lineWrapping) {
+        var rects = range(node, start, end).getClientRects();
+        if (rects.length)
+          rect = rects[bias == "right" ? rects.length - 1 : 0];
+        else
+          rect = nullRect;
+      } else {
+        rect = range(node, start, end).getBoundingClientRect();
+      }
+    } else { // If it is a widget, simply get the box for the whole widget.
+      if (start > 0) collapse = bias = "right";
+      var rects;
+      if (cm.options.lineWrapping && (rects = node.getClientRects()).length > 1)
+        rect = rects[bias == "right" ? rects.length - 1 : 0];
+      else
+        rect = node.getBoundingClientRect();
+    }
+    if (ie_upto8 && !start && (!rect || !rect.left && !rect.right)) {
+      var rSpan = node.parentNode.getClientRects()[0];
+      if (rSpan)
+        rect = {left: rSpan.left, right: rSpan.left + charWidth(cm.display), top: rSpan.top, bottom: rSpan.bottom};
+      else
+        rect = nullRect;
+    }
+
+    var top, bot = (rect.bottom + rect.top) / 2 - prepared.rect.top;
+    var heights = prepared.view.measure.heights;
+    for (var i = 0; i < heights.length - 1; i++)
+      if (bot < heights[i]) break;
+    top = i ? heights[i - 1] : 0; bot = heights[i];
+    var result = {left: (collapse == "right" ? rect.right : rect.left) - prepared.rect.left,
+                  right: (collapse == "left" ? rect.left : rect.right) - prepared.rect.left,
+                  top: top, bottom: bot};
+    if (!rect.left && !rect.right) result.bogus = true;
+    return result;
+  }
+
+  function clearLineMeasurementCacheFor(lineView) {
+    if (lineView.measure) {
+      lineView.measure.cache = {};
+      lineView.measure.heights = null;
+      if (lineView.rest) for (var i = 0; i < lineView.rest.length; i++)
+        lineView.measure.caches[i] = {};
+    }
+  }
+
+  function clearLineMeasurementCache(cm) {
+    cm.display.externalMeasure = null;
+    removeChildren(cm.display.lineMeasure);
+    for (var i = 0; i < cm.display.view.length; i++)
+      clearLineMeasurementCacheFor(cm.display.view[i]);
   }
 
   function clearCaches(cm) {
-    cm.display.measureLineCache.length = cm.display.measureLineCachePos = 0;
-    cm.display.cachedCharWidth = cm.display.cachedTextHeight = null;
+    clearLineMeasurementCache(cm);
+    cm.display.cachedCharWidth = cm.display.cachedTextHeight = cm.display.cachedPaddingH = null;
     if (!cm.options.lineWrapping) cm.display.maxLineChanged = true;
     cm.display.lineNumChars = null;
   }
 
   function pageScrollX() { return window.pageXOffset || (document.documentElement || document.body).scrollLeft; }
   function pageScrollY() { return window.pageYOffset || (document.documentElement || document.body).scrollTop; }
 
-  // Context is one of "line", "div" (display.lineDiv), "local"/null (editor), or "page"
+  // Converts a {top, bottom, left, right} box from line-local
+  // coordinates into another coordinate system. Context may be one of
+  // "line", "div" (display.lineDiv), "local"/null (editor), or "page".
   function intoCoordSystem(cm, lineObj, rect, context) {
     if (lineObj.widgets) for (var i = 0; i < lineObj.widgets.length; ++i) if (lineObj.widgets[i].above) {
       var size = widgetHeight(lineObj.widgets[i]);
       rect.top += size; rect.bottom += size;
     }
     if (context == "line") return rect;
     if (!context) context = "local";
-    var yOff = heightAtLine(cm, lineObj);
+    var yOff = heightAtLine(lineObj);
     if (context == "local") yOff += paddingTop(cm.display);
     else yOff -= cm.display.viewOffset;
     if (context == "page" || context == "window") {
-      var lOff = getRect(cm.display.lineSpace);
+      var lOff = cm.display.lineSpace.getBoundingClientRect();
       yOff += lOff.top + (context == "window" ? 0 : pageScrollY());
       var xOff = lOff.left + (context == "window" ? 0 : pageScrollX());
       rect.left += xOff; rect.right += xOff;
     }
     rect.top += yOff; rect.bottom += yOff;
     return rect;
   }
 
-  // Context may be "window", "page", "div", or "local"/null
-  // Result is in "div" coords
+  // Coverts a box from "div" coords to another coordinate system.
+  // Context may be "window", "page", "div", or "local"/null.
   function fromCoordSystem(cm, coords, context) {
     if (context == "div") return coords;
     var left = coords.left, top = coords.top;
     // First move into "page" coordinate system
     if (context == "page") {
       left -= pageScrollX();
       top -= pageScrollY();
     } else if (context == "local" || !context) {
-      var localBox = getRect(cm.display.sizer);
+      var localBox = cm.display.sizer.getBoundingClientRect();
       left += localBox.left;
       top += localBox.top;
     }
 
-    var lineSpaceBox = getRect(cm.display.lineSpace);
+    var lineSpaceBox = cm.display.lineSpace.getBoundingClientRect();
     return {left: left - lineSpaceBox.left, top: top - lineSpaceBox.top};
   }
 
   function charCoords(cm, pos, context, lineObj, bias) {
     if (!lineObj) lineObj = getLine(cm.doc, pos.line);
-    return intoCoordSystem(cm, lineObj, measureChar(cm, lineObj, pos.ch, null, bias), context);
+    return intoCoordSystem(cm, lineObj, measureChar(cm, lineObj, pos.ch, bias), context);
   }
 
-  function cursorCoords(cm, pos, context, lineObj, measurement) {
+  // Returns a box for a given cursor position, which may have an
+  // 'other' property containing the position of the secondary cursor
+  // on a bidi boundary.
+  function cursorCoords(cm, pos, context, lineObj, preparedMeasure) {
     lineObj = lineObj || getLine(cm.doc, pos.line);
-    if (!measurement) measurement = measureLine(cm, lineObj);
+    if (!preparedMeasure) preparedMeasure = prepareMeasureForLine(cm, lineObj);
     function get(ch, right) {
-      var m = measureChar(cm, lineObj, ch, measurement, right ? "right" : "left");
+      var m = measureCharPrepared(cm, preparedMeasure, ch, right ? "right" : "left");
       if (right) m.left = m.right; else m.right = m.left;
       return intoCoordSystem(cm, lineObj, m, context);
     }
     function getBidi(ch, partPos) {
       var part = order[partPos], right = part.level % 2;
       if (ch == bidiLeft(part) && partPos && part.level < order[partPos - 1].level) {
         part = order[--partPos];
         ch = bidiRight(part) - (part.level % 2 ? 0 : 1);
         right = true;
       } else if (ch == bidiRight(part) && partPos < order.length - 1 && part.level < order[partPos + 1].level) {
         part = order[++partPos];
         ch = bidiLeft(part) - part.level % 2;
         right = false;
       }
       if (right && ch == part.to && ch > part.from) return get(ch - 1);
       return get(ch, right);
     }
     var order = getOrder(lineObj), ch = pos.ch;
     if (!order) return get(ch);
     var partPos = getBidiPartAt(order, ch);
     var val = getBidi(ch, partPos);
     if (bidiOther != null) val.other = getBidi(ch, bidiOther);
     return val;
   }
 
+  // Used to cheaply estimate the coordinates for a position. Used for
+  // intermediate scroll updates.
+  function estimateCoords(cm, pos) {
+    var left = 0, pos = clipPos(cm.doc, pos);
+    if (!cm.options.lineWrapping) left = charWidth(cm.display) * pos.ch;
+    var lineObj = getLine(cm.doc, pos.line);
+    var top = heightAtLine(lineObj) + paddingTop(cm.display);
+    return {left: left, right: left, top: top, bottom: top + lineObj.height};
+  }
+
+  // Positions returned by coordsChar contain some extra information.
+  // xRel is the relative x position of the input coordinates compared
+  // to the found position (so xRel > 0 means the coordinates are to
+  // the right of the character position, for example). When outside
+  // is true, that means the coordinates lie outside the line's
+  // vertical range.
   function PosWithInfo(line, ch, outside, xRel) {
-    var pos = new Pos(line, ch);
+    var pos = Pos(line, ch);
     pos.xRel = xRel;
     if (outside) pos.outside = true;
     return pos;
   }
 
-  // Coords must be lineSpace-local
+  // Compute the character position closest to the given coordinates.
+  // Input must be lineSpace-local ("div" coordinate system).
   function coordsChar(cm, x, y) {
     var doc = cm.doc;
     y += cm.display.viewOffset;
     if (y < 0) return PosWithInfo(doc.first, 0, true, -1);
-    var lineNo = lineAtHeight(doc, y), last = doc.first + doc.size - 1;
-    if (lineNo > last)
+    var lineN = lineAtHeight(doc, y), last = doc.first + doc.size - 1;
+    if (lineN > last)
       return PosWithInfo(doc.first + doc.size - 1, getLine(doc, last).text.length, true, 1);
     if (x < 0) x = 0;
 
+    var lineObj = getLine(doc, lineN);
     for (;;) {
-      var lineObj = getLine(doc, lineNo);
-      var found = coordsCharInner(cm, lineObj, lineNo, x, y);
+      var found = coordsCharInner(cm, lineObj, lineN, x, y);
       var merged = collapsedSpanAtEnd(lineObj);
-      var mergedPos = merged && merged.find();
+      var mergedPos = merged && merged.find(0, true);
       if (merged && (found.ch > mergedPos.from.ch || found.ch == mergedPos.from.ch && found.xRel > 0))
-        lineNo = mergedPos.to.line;
+        lineN = lineNo(lineObj = mergedPos.to.line);
       else
         return found;
     }
   }
 
   function coordsCharInner(cm, lineObj, lineNo, x, y) {
-    var innerOff = y - heightAtLine(cm, lineObj);
+    var innerOff = y - heightAtLine(lineObj);
     var wrongLine = false, adjust = 2 * cm.display.wrapper.clientWidth;
-    var measurement = measureLine(cm, lineObj);
+    var preparedMeasure = prepareMeasureForLine(cm, lineObj);
 
     function getX(ch) {
-      var sp = cursorCoords(cm, Pos(lineNo, ch), "line",
-                            lineObj, measurement);
+      var sp = cursorCoords(cm, Pos(lineNo, ch), "line", lineObj, preparedMeasure);
       wrongLine = true;
       if (innerOff > sp.bottom) return sp.left - adjust;
       else if (innerOff < sp.top) return sp.left + adjust;
       else wrongLine = false;
       return sp.left;
     }
 
     var bidi = getOrder(lineObj), dist = lineObj.text.length;
     var from = lineLeft(lineObj), to = lineRight(lineObj);
     var fromX = getX(from), fromOutside = wrongLine, toX = getX(to), toOutside = wrongLine;
 
     if (x > toX) return PosWithInfo(lineNo, to, toOutside, 1);
     // Do a binary search between these bounds.
     for (;;) {
       if (bidi ? to == from || to == moveVisually(lineObj, from, 1) : to - from <= 1) {
         var ch = x < fromX || x - fromX <= toX - x ? from : to;
         var xDiff = x - (ch == from ? fromX : toX);
         while (isExtendingChar(lineObj.text.charAt(ch))) ++ch;
         var pos = PosWithInfo(lineNo, ch, ch == from ? fromOutside : toOutside,
-                              xDiff < 0 ? -1 : xDiff ? 1 : 0);
+                              xDiff < -1 ? -1 : xDiff > 1 ? 1 : 0);
         return pos;
       }
       var step = Math.ceil(dist / 2), middle = from + step;
       if (bidi) {
         middle = from;
         for (var i = 0; i < step; ++i) middle = moveVisually(lineObj, middle, 1);
       }
       var middleX = getX(middle);
       if (middleX > x) {to = middle; toX = middleX; if (toOutside = wrongLine) toX += 1000; dist = step;}
       else {from = middle; fromX = middleX; fromOutside = wrongLine; dist -= step;}
     }
   }
 
   var measureText;
+  // Compute the default text height.
   function textHeight(display) {
     if (display.cachedTextHeight != null) return display.cachedTextHeight;
     if (measureText == null) {
       measureText = elt("pre");
       // Measure a bunch of lines, for browsers that compute
       // fractional heights.
       for (var i = 0; i < 49; ++i) {
         measureText.appendChild(document.createTextNode("x"));
         measureText.appendChild(elt("br"));
       }
       measureText.appendChild(document.createTextNode("x"));
     }
     removeChildrenAndAdd(display.measure, measureText);
     var height = measureText.offsetHeight / 50;
     if (height > 3) display.cachedTextHeight = height;
     removeChildren(display.measure);
     return height || 1;
   }
 
+  // Compute the default character width.
   function charWidth(display) {
     if (display.cachedCharWidth != null) return display.cachedCharWidth;
-    var anchor = elt("span", "x");
+    var anchor = elt("span", "xxxxxxxxxx");
     var pre = elt("pre", [anchor]);
     removeChildrenAndAdd(display.measure, pre);
-    var width = anchor.offsetWidth;
+    var rect = anchor.getBoundingClientRect(), width = (rect.right - rect.left) / 10;
     if (width > 2) display.cachedCharWidth = width;
     return width || 10;
   }
 
   // OPERATIONS
 
-  // Operations are used to wrap changes in such a way that each
-  // change won't have to update the cursor and display (which would
-  // be awkward, slow, and error-prone), but instead updates are
-  // batched and then all combined and executed at once.
+  // Operations are used to wrap a series of changes to the editor
+  // state in such a way that each change won't have to update the
+  // cursor and display (which would be awkward, slow, and
+  // error-prone). Instead, display updates are batched and then all
+  // combined and executed at once.
 
   var nextOpId = 0;
+  // Start a new operation.
   function startOperation(cm) {
     cm.curOp = {
-      // An array of ranges of lines that have to be updated. See
-      // updateDisplay.
-      changes: [],
-      forceUpdate: false,
-      updateInput: null,
-      userSelChange: null,
-      textChanged: null,
-      selectionChanged: false,
-      cursorActivity: false,
-      updateMaxLine: false,
-      updateScrollPos: false,
-      id: ++nextOpId
+      viewChanged: false,      // Flag that indicates that lines might need to be redrawn
+      startHeight: cm.doc.height, // Used to detect need to update scrollbar
+      forceUpdate: false,      // Used to force a redraw
+      updateInput: null,       // Whether to reset the input textarea
+      typing: false,           // Whether this reset should be careful to leave existing text (for compositing)
+      changeObjs: null,        // Accumulated changes, for firing change events
+      cursorActivity: false,   // Whether to fire a cursorActivity event
+      selectionChanged: false, // Whether the selection needs to be redrawn
+      updateMaxLine: false,    // Set when the widest line needs to be determined anew
+      scrollLeft: null, scrollTop: null, // Intermediate scroll position, not pushed to DOM yet
+      scrollToPos: null,       // Used to scroll to a specific position
+      id: ++nextOpId           // Unique ID
     };
     if (!delayedCallbackDepth++) delayedCallbacks = [];
   }
 
+  // Finish an operation, updating the display and signalling delayed events
   function endOperation(cm) {
     var op = cm.curOp, doc = cm.doc, display = cm.display;
     cm.curOp = null;
 
-    if (op.updateMaxLine) computeMaxLength(cm);
-    if (display.maxLineChanged && !cm.options.lineWrapping && display.maxLine) {
-      var width = measureLineWidth(cm, display.maxLine);
-      display.sizer.style.minWidth = Math.max(0, width + 3 + scrollerCutOff) + "px";
-      display.maxLineChanged = false;
-      var maxScrollLeft = Math.max(0, display.sizer.offsetLeft + display.sizer.offsetWidth - display.scroller.clientWidth);
-      if (maxScrollLeft < doc.scrollLeft && !op.updateScrollPos)
-        setScrollLeft(cm, Math.min(display.scroller.scrollLeft, maxScrollLeft), true);
-    }
-    var newScrollPos, updated;
-    if (op.updateScrollPos) {
-      newScrollPos = op.updateScrollPos;
-    } else if (op.selectionChanged && display.scroller.clientHeight) { // don't rescroll if not visible
-      var coords = cursorCoords(cm, doc.sel.head);
-      newScrollPos = calculateScrollPos(cm, coords.left, coords.top, coords.left, coords.bottom);
-    }
-    if (op.changes.length || op.forceUpdate || newScrollPos && newScrollPos.scrollTop != null) {
-      updated = updateDisplay(cm, op.changes, newScrollPos && newScrollPos.scrollTop, op.forceUpdate);
+    if (op.updateMaxLine) findMaxLine(cm);
+
+    // If it looks like an update might be needed, call updateDisplay
+    if (op.viewChanged || op.forceUpdate || op.scrollTop != null ||
+        op.scrollToPos && (op.scrollToPos.from.line < display.viewFrom ||
+                           op.scrollToPos.to.line >= display.viewTo) ||
+        display.maxLineChanged && cm.options.lineWrapping) {
+      var updated = updateDisplay(cm, {top: op.scrollTop, ensure: op.scrollToPos}, op.forceUpdate);
       if (cm.display.scroller.offsetHeight) cm.doc.scrollTop = cm.display.scroller.scrollTop;
     }
+    // If no update was run, but the selection changed, redraw that.
     if (!updated && op.selectionChanged) updateSelection(cm);
-    if (op.updateScrollPos) {
-      var top = Math.max(0, Math.min(display.scroller.scrollHeight - display.scroller.clientHeight, newScrollPos.scrollTop));
-      var left = Math.max(0, Math.min(display.scroller.scrollWidth - display.scroller.clientWidth, newScrollPos.scrollLeft));
+    if (!updated && op.startHeight != cm.doc.height) updateScrollbars(cm);
+
+    // Propagate the scroll position to the actual DOM scroller
+    if (op.scrollTop != null && display.scroller.scrollTop != op.scrollTop) {
+      var top = Math.max(0, Math.min(display.scroller.scrollHeight - display.scroller.clientHeight, op.scrollTop));
       display.scroller.scrollTop = display.scrollbarV.scrollTop = doc.scrollTop = top;
+    }
+    if (op.scrollLeft != null && display.scroller.scrollLeft != op.scrollLeft) {
+      var left = Math.max(0, Math.min(display.scroller.scrollWidth - display.scroller.clientWidth, op.scrollLeft));
       display.scroller.scrollLeft = display.scrollbarH.scrollLeft = doc.scrollLeft = left;
       alignHorizontally(cm);
-      if (op.scrollToPos)
-        scrollPosIntoView(cm, clipPos(cm.doc, op.scrollToPos.from),
-                          clipPos(cm.doc, op.scrollToPos.to), op.scrollToPos.margin);
-    } else if (newScrollPos) {
-      scrollCursorIntoView(cm);
     }
+    // If we need to scroll a specific position into view, do so.
+    if (op.scrollToPos) {
+      var coords = scrollPosIntoView(cm, clipPos(cm.doc, op.scrollToPos.from),
+                                     clipPos(cm.doc, op.scrollToPos.to), op.scrollToPos.margin);
+      if (op.scrollToPos.isCursor && cm.state.focused) maybeScrollWindow(cm, coords);
+    }
+
     if (op.selectionChanged) restartBlink(cm);
 
     if (cm.state.focused && op.updateInput)
-      resetInput(cm, op.userSelChange);
+      resetInput(cm, op.typing);
 
+    // Fire events for markers that are hidden/unidden by editing or
+    // undoing
     var hidden = op.maybeHiddenMarkers, unhidden = op.maybeUnhiddenMarkers;
     if (hidden) for (var i = 0; i < hidden.length; ++i)
       if (!hidden[i].lines.length) signal(hidden[i], "hide");
     if (unhidden) for (var i = 0; i < unhidden.length; ++i)
       if (unhidden[i].lines.length) signal(unhidden[i], "unhide");
 
     var delayed;
     if (!--delayedCallbackDepth) {
       delayed = delayedCallbacks;
       delayedCallbacks = null;
     }
-    if (op.textChanged)
-      signal(cm, "change", cm, op.textChanged);
+    // Fire change events, and delayed event handlers
+    if (op.changeObjs) {
+      for (var i = 0; i < op.changeObjs.length; i++)
+        signal(cm, "change", cm, op.changeObjs[i]);
+      signal(cm, "changes", cm, op.changeObjs);
+    }
     if (op.cursorActivity) signal(cm, "cursorActivity", cm);
     if (delayed) for (var i = 0; i < delayed.length; ++i) delayed[i]();
   }
 
+  // Run the given function in an operation
+  function runInOp(cm, f) {
+    if (cm.curOp) return f();
+    startOperation(cm);
+    try { return f(); }
+    finally { endOperation(cm); }
+  }
   // Wraps a function in an operation. Returns the wrapped function.
-  function operation(cm1, f) {
+  function operation(cm, f) {
     return function() {
-      var cm = cm1 || this, withOp = !cm.curOp;
-      if (withOp) startOperation(cm);
-      try { var result = f.apply(cm, arguments); }
-      finally { if (withOp) endOperation(cm); }
-      return result;
+      if (cm.curOp) return f.apply(cm, arguments);
+      startOperation(cm);
+      try { return f.apply(cm, arguments); }
+      finally { endOperation(cm); }
     };
   }
-  function docOperation(f) {
+  // Used to add methods to editor and doc instances, wrapping them in
+  // operations.
+  function methodOp(f) {
     return function() {
-      var withOp = this.cm && !this.cm.curOp, result;
-      if (withOp) startOperation(this.cm);
-      try { result = f.apply(this, arguments); }
-      finally { if (withOp) endOperation(this.cm); }
-      return result;
+      if (this.curOp) return f.apply(this, arguments);
+      startOperation(this);
+      try { return f.apply(this, arguments); }
+      finally { endOperation(this); }
     };
   }
-  function runInOp(cm, f) {
-    var withOp = !cm.curOp, result;
-    if (withOp) startOperation(cm);
-    try { result = f(); }
-    finally { if (withOp) endOperation(cm); }
-    return result;
-  }
-
+  function docMethodOp(f) {
+    return function() {
+      var cm = this.cm;
+      if (!cm || cm.curOp) return f.apply(this, arguments);
+      startOperation(cm);
+      try { return f.apply(this, arguments); }
+      finally { endOperation(cm); }
+    };
+  }
+
+  // VIEW TRACKING
+
+  // These objects are used to represent the visible (currently drawn)
+  // part of the document. A LineView may correspond to multiple
+  // logical lines, if those are connected by collapsed ranges.
+  function LineView(doc, line, lineN) {
+    // The starting line
+    this.line = line;
+    // Continuing lines, if any
+    this.rest = visualLineContinued(line);
+    // Number of logical lines in this visual line
+    this.size = this.rest ? lineNo(lst(this.rest)) - lineN + 1 : 1;
+    this.node = this.text = null;
+    this.hidden = lineIsHidden(doc, line);
+  }
+
+  // Create a range of LineView objects for the given lines.
+  function buildViewArray(cm, from, to) {
+    var array = [], nextPos;
+    for (var pos = from; pos < to; pos = nextPos) {
+      var view = new LineView(cm.doc, getLine(cm.doc, pos), pos);
+      nextPos = pos + view.size;
+      array.push(view);
+    }
+    return array;
+  }
+
+  // Updates the display.view data structure for a given change to the
+  // document. From and to are in pre-change coordinates. Lendiff is
+  // the amount of lines added or subtracted by the change. This is
+  // used for changes that span multiple lines, or change the way
+  // lines are divided into visual lines. regLineChange (below)
+  // registers single-line changes.
   function regChange(cm, from, to, lendiff) {
     if (from == null) from = cm.doc.first;
     if (to == null) to = cm.doc.first + cm.doc.size;
-    cm.curOp.changes.push({from: from, to: to, diff: lendiff});
+    if (!lendiff) lendiff = 0;
+
+    var display = cm.display;
+    if (lendiff && to < display.viewTo &&
+        (display.updateLineNumbers == null || display.updateLineNumbers > from))
+      display.updateLineNumbers = from;
+
+    cm.curOp.viewChanged = true;
+
+    if (from >= display.viewTo) { // Change after
+      if (sawCollapsedSpans && visualLineNo(cm.doc, from) < display.viewTo)
+        resetView(cm);
+    } else if (to <= display.viewFrom) { // Change before
+      if (sawCollapsedSpans && visualLineEndNo(cm.doc, to + lendiff) > display.viewFrom) {
+        resetView(cm);
+      } else {
+        display.viewFrom += lendiff;
+        display.viewTo += lendiff;
+      }
+    } else if (from <= display.viewFrom && to >= display.viewTo) { // Full overlap
+      resetView(cm);
+    } else if (from <= display.viewFrom) { // Top overlap
+      var cut = viewCuttingPoint(cm, to, to + lendiff, 1);
+      if (cut) {
+        display.view = display.view.slice(cut.index);
+        display.viewFrom = cut.lineN;
+        display.viewTo += lendiff;
+      } else {
+        resetView(cm);
+      }
+    } else if (to >= display.viewTo) { // Bottom overlap
+      var cut = viewCuttingPoint(cm, from, from, -1);
+      if (cut) {
+        display.view = display.view.slice(0, cut.index);
+        display.viewTo = cut.lineN;
+      } else {
+        resetView(cm);
+      }
+    } else { // Gap in the middle
+      var cutTop = viewCuttingPoint(cm, from, from, -1);
+      var cutBot = viewCuttingPoint(cm, to, to + lendiff, 1);
+      if (cutTop && cutBot) {
+        display.view = display.view.slice(0, cutTop.index)
+          .concat(buildViewArray(cm, cutTop.lineN, cutBot.lineN))
+          .concat(display.view.slice(cutBot.index));
+        display.viewTo += lendiff;
+      } else {
+        resetView(cm);
+      }
+    }
+
+    var ext = display.externalMeasured;
+    if (ext) {
+      if (to < ext.lineN)
+        ext.lineN += lendiff;
+      else if (from < ext.lineN + ext.size)
+        display.externalMeasured = null;
+    }
+  }
+
+  // Register a change to a single line. Type must be one of "text",
+  // "gutter", "class", "widget"
+  function regLineChange(cm, line, type) {
+    cm.curOp.viewChanged = true;
+    var display = cm.display, ext = cm.display.externalMeasured;
+    if (ext && line >= ext.lineN && line < ext.lineN + ext.size)
+      display.externalMeasured = null;
+
+    if (line < display.viewFrom || line >= display.viewTo) return;
+    var lineView = display.view[findViewIndex(cm, line)];
+    if (lineView.node == null) return;
+    var arr = lineView.changes || (lineView.changes = []);
+    if (indexOf(arr, type) == -1) arr.push(type);
+  }
+
+  // Clear the view.
+  function resetView(cm) {
+    cm.display.viewFrom = cm.display.viewTo = cm.doc.first;
+    cm.display.view = [];
+    cm.display.viewOffset = 0;
+  }
+
+  // Find the view element corresponding to a given line. Return null
+  // when the line isn't visible.
+  function findViewIndex(cm, n) {
+    if (n >= cm.display.viewTo) return null;
+    n -= cm.display.viewFrom;
+    if (n < 0) return null;
+    var view = cm.display.view;
+    for (var i = 0; i < view.length; i++) {
+      n -= view[i].size;
+      if (n < 0) return i;
+    }
+  }
+
+  function viewCuttingPoint(cm, oldN, newN, dir) {
+    var index = findViewIndex(cm, oldN), diff, view = cm.display.view;
+    if (!sawCollapsedSpans) return {index: index, lineN: newN};
+    for (var i = 0, n = cm.display.viewFrom; i < index; i++)
+      n += view[i].size;
+    if (n != oldN) {
+      if (dir > 0) {
+        if (index == view.length - 1) return null;
+        diff = (n + view[index].size) - oldN;
+        index++;
+      } else {
+        diff = n - oldN;
+      }
+      oldN += diff; newN += diff;
+    }
+    while (visualLineNo(cm.doc, newN) != newN) {
+      if (index == (dir < 0 ? 0 : view.length - 1)) return null;
+      newN += dir * view[index - (dir < 0 ? 1 : 0)].size;
+      index += dir;
+    }
+    return {index: index, lineN: newN};
+  }
+
+  // Force the view to cover a given range, adding empty view element
+  // or clipping off existing ones as needed.
+  function adjustView(cm, from, to) {
+    var display = cm.display, view = display.view;
+    if (view.length == 0 || from >= display.viewTo || to <= display.viewFrom) {
+      display.view = buildViewArray(cm, from, to);
+      display.viewFrom = from;
+    } else {
+      if (display.viewFrom > from)
+        display.view = buildViewArray(cm, from, display.viewFrom).concat(display.view);
+      else if (display.viewFrom < from)
+        display.view = display.view.slice(findViewIndex(cm, from));
+      display.viewFrom = from;
+      if (display.viewTo < to)
+        display.view = display.view.concat(buildViewArray(cm, display.viewTo, to));
+      else if (display.viewTo > to)
+        display.view = display.view.slice(0, findViewIndex(cm, to));
+    }
+    display.viewTo = to;
+  }
+
+  // Count the number of lines in the view whose DOM representation is
+  // out of date (or nonexistent).
+  function countDirtyView(cm) {
+    var view = cm.display.view, dirty = 0;
+    for (var i = 0; i < view.length; i++) {
+      var lineView = view[i];
+      if (!lineView.hidden && (!lineView.node || lineView.changes)) ++dirty;
+    }
+    return dirty;
   }
 
   // INPUT HANDLING
 
+  // Poll for input changes, using the normal rate of polling. This
+  // runs as long as the editor is focused.
   function slowPoll(cm) {
     if (cm.display.pollingFast) return;
     cm.display.poll.set(cm.options.pollInterval, function() {
       readInput(cm);
       if (cm.state.focused) slowPoll(cm);
     });
   }
 
+  // When an event has just come in that is likely to add or change
+  // something in the input textarea, we poll faster, to ensure that
+  // the change appears on the screen quickly.
   function fastPoll(cm) {
     var missed = false;
     cm.display.pollingFast = true;
     function p() {
       var changed = readInput(cm);
       if (!changed && !missed) {missed = true; cm.display.poll.set(60, p);}
       else {cm.display.pollingFast = false; slowPoll(cm);}
     }
     cm.display.poll.set(20, p);
   }
 
-  // prevInput is a hack to work with IME. If we reset the textarea
-  // on every change, that breaks IME. So we look for changes
-  // compared to the previous content instead. (Modern browsers have
-  // events that indicate IME taking place, but these are not widely
-  // supported or compatible enough yet to rely on.)
+  // Read input from the textarea, and update the document to match.
+  // When something is selected, it is present in the textarea, and
+  // selected (unless it is huge, in which case a placeholder is
+  // used). When nothing is selected, the cursor sits after previously
+  // seen text (can be empty), which is stored in prevInput (we must
+  // not reset the textarea when typing, because that breaks IME).
   function readInput(cm) {
-    var input = cm.display.input, prevInput = cm.display.prevInput, doc = cm.doc, sel = doc.sel;
+    var input = cm.display.input, prevInput = cm.display.prevInput, doc = cm.doc;
+    // Since this is called a *lot*, try to bail out as cheaply as
+    // possible when it is clear that nothing happened. hasSelection
+    // will be the case when there is a lot of text in the textarea,
+    // in which case reading its value would be expensive.
     if (!cm.state.focused || hasSelection(input) || isReadOnly(cm) || cm.options.disableInput) return false;
-    if (cm.state.pasteIncoming && cm.state.fakedLastChar) {
-      input.value = input.value.substring(0, input.value.length - 1);
-      cm.state.fakedLastChar = false;
-    }
     var text = input.value;
-    if (text == prevInput && posEq(sel.from, sel.to)) return false;
-    if (ie && !ie_lt9 && cm.display.inputHasSelection === text) {
-      resetInput(cm, true);
+    // If nothing changed, bail.
+    if (text == prevInput && !cm.somethingSelected()) return false;
+    // Work around nonsensical selection resetting in IE9/10
+    if (ie && !ie_upto8 && cm.display.inputHasSelection === text) {
+      resetInput(cm);
       return false;
     }
 
     var withOp = !cm.curOp;
     if (withOp) startOperation(cm);
-    sel.shift = false;
+    cm.display.shift = false;
+
+    // Find the part of the input that is actually new
     var same = 0, l = Math.min(prevInput.length, text.length);
     while (same < l && prevInput.charCodeAt(same) == text.charCodeAt(same)) ++same;
-    var from = sel.from, to = sel.to;
-    var inserted = text.slice(same);
-    if (same < prevInput.length)
-      from = Pos(from.line, from.ch - (prevInput.length - same));
-    else if (cm.state.overwrite && posEq(from, to) && !cm.state.pasteIncoming)
-      to = Pos(to.line, Math.min(getLine(doc, to.line).text.length, to.ch + inserted.length));
+    var inserted = text.slice(same), textLines = splitLines(inserted);
 
-    var updateInput = cm.curOp.updateInput;
-    var changeEvent = {from: from, to: to, text: splitLines(inserted),
-                       origin: cm.state.pasteIncoming ? "paste" : cm.state.cutIncoming ? "cut" : "+input"};
-    makeChange(cm.doc, changeEvent, "end");
+    // When pasing N lines into N selections, insert one line per selection
+    var multiPaste = cm.state.pasteIncoming && textLines.length > 1 && doc.sel.ranges.length == textLines.length;
+
+    // Normal behavior is to insert the new text into every selection
+    for (var i = doc.sel.ranges.length - 1; i >= 0; i--) {
+      var range = doc.sel.ranges[i];
+      var from = range.from(), to = range.to();
+      // Handle deletion
+      if (same < prevInput.length)
+        from = Pos(from.line, from.ch - (prevInput.length - same));
+      // Handle overwrite
+      else if (cm.state.overwrite && range.empty() && !cm.state.pasteIncoming)
+        to = Pos(to.line, Math.min(getLine(doc, to.line).text.length, to.ch + lst(textLines).length));
+      var updateInput = cm.curOp.updateInput;
+      var changeEvent = {from: from, to: to, text: multiPaste ? [textLines[i]] : textLines,
+                         origin: cm.state.pasteIncoming ? "paste" : cm.state.cutIncoming ? "cut" : "+input"};
+      makeChange(cm.doc, changeEvent);
+      signalLater(cm, "inputRead", cm, changeEvent);
+      // When an 'electric' character is inserted, immediately trigger a reindent
+      if (inserted && !cm.state.pasteIncoming && cm.options.electricChars &&
+          cm.options.smartIndent && range.head.ch < 100 &&
+          (!i || doc.sel.ranges[i - 1].head.line != range.head.line)) {
+        var electric = cm.getModeAt(range.head).electricChars;
+        if (electric) for (var j = 0; j < electric.length; j++)
+          if (inserted.indexOf(electric.charAt(j)) > -1) {
+            indentLine(cm, range.head.line, "smart");
+            break;
+          }
+      }
+    }
+    ensureCursorVisible(cm);
     cm.curOp.updateInput = updateInput;
-    signalLater(cm, "inputRead", cm, changeEvent);
-    if (inserted && !cm.state.pasteIncoming && cm.options.electricChars &&
-        cm.options.smartIndent && sel.head.ch < 100) {
-      var electric = cm.getModeAt(sel.head).electricChars;
-      if (electric) for (var i = 0; i < electric.length; i++)
-        if (inserted.indexOf(electric.charAt(i)) > -1) {
-          indentLine(cm, sel.head.line, "smart");
-          break;
-        }
-    }
+    cm.curOp.typing = true;
 
+    // Don't leave long text in the textarea, since it makes further polling slow
     if (text.length > 1000 || text.indexOf("\n") > -1) input.value = cm.display.prevInput = "";
     else cm.display.prevInput = text;
     if (withOp) endOperation(cm);
     cm.state.pasteIncoming = cm.state.cutIncoming = false;
     return true;
   }
 
-  function resetInput(cm, user) {
+  // Reset the input to correspond to the selection (or to be empty,
+  // when not typing and nothing is selected)
+  function resetInput(cm, typing) {
     var minimal, selected, doc = cm.doc;
-    if (!posEq(doc.sel.from, doc.sel.to)) {
+    if (cm.somethingSelected()) {
       cm.display.prevInput = "";
+      var range = doc.sel.primary();
       minimal = hasCopyEvent &&
-        (doc.sel.to.line - doc.sel.from.line > 100 || (selected = cm.getSelection()).length > 1000);
+        (range.to().line - range.from().line > 100 || (selected = cm.getSelection()).length > 1000);
       var content = minimal ? "-" : selected || cm.getSelection();
       cm.display.input.value = content;
       if (cm.state.focused) selectInput(cm.display.input);
-      if (ie && !ie_lt9) cm.display.inputHasSelection = content;
-    } else if (user) {
+      if (ie && !ie_upto8) cm.display.inputHasSelection = content;
+    } else if (!typing) {
       cm.display.prevInput = cm.display.input.value = "";
-      if (ie && !ie_lt9) cm.display.inputHasSelection = null;
+      if (ie && !ie_upto8) cm.display.inputHasSelection = null;
     }
     cm.display.inaccurateSelection = minimal;
   }
 
   function focusInput(cm) {
-    if (cm.options.readOnly != "nocursor" && (!mobile || document.activeElement != cm.display.input))
+    if (cm.options.readOnly != "nocursor" && (!mobile || activeElt() != cm.display.input))
       cm.display.input.focus();
   }
 
+  function ensureFocus(cm) {
+    if (!cm.state.focused) { focusInput(cm); onFocus(cm); }
+  }
+
   function isReadOnly(cm) {
     return cm.options.readOnly || cm.doc.cantEdit;
   }
 
   // EVENT HANDLERS
 
+  // Attach the necessary event handlers when initializing the editor
   function registerEventHandlers(cm) {
     var d = cm.display;
     on(d.scroller, "mousedown", operation(cm, onMouseDown));
-    if (old_ie)
+    // Older IE's will not fire a second mousedown for a double click
+    if (ie_upto10)
       on(d.scroller, "dblclick", operation(cm, function(e) {
         if (signalDOMEvent(cm, e)) return;
         var pos = posFromMouse(cm, e);
         if (!pos || clickInGutter(cm, e) || eventInWidget(cm.display, e)) return;
         e_preventDefault(e);
-        var word = findWordAt(getLine(cm.doc, pos.line).text, pos);
-        extendSelection(cm.doc, word.from, word.to);
+        var word = findWordAt(cm.doc, pos);
+        extendSelection(cm.doc, word.anchor, word.head);
       }));
     else
       on(d.scroller, "dblclick", function(e) { signalDOMEvent(cm, e) || e_preventDefault(e); });
+    // Prevent normal selection in the editor (we handle our own)
     on(d.lineSpace, "selectstart", function(e) {
       if (!eventInWidget(d, e)) e_preventDefault(e);
     });
-    // Gecko browsers fire contextmenu *after* opening the menu, at
+    // Some browsers fire contextmenu *after* opening the menu, at
     // which point we can't mess with it anymore. Context menu is
-    // handled in onMouseDown for Gecko.
-    if (!captureMiddleClick) on(d.scroller, "contextmenu", function(e) {onContextMenu(cm, e);});
+    // handled in onMouseDown for these browsers.
+    if (!captureRightClick) on(d.scroller, "contextmenu", function(e) {onContextMenu(cm, e);});
 
+    // Sync scrolling between fake scrollbars and real scrollable
+    // area, ensure viewport is updated when scrolling.
     on(d.scroller, "scroll", function() {
       if (d.scroller.clientHeight) {
         setScrollTop(cm, d.scroller.scrollTop);
         setScrollLeft(cm, d.scroller.scrollLeft, true);
         signal(cm, "scroll", cm);
       }
     });
     on(d.scrollbarV, "scroll", function() {
       if (d.scroller.clientHeight) setScrollTop(cm, d.scrollbarV.scrollTop);
     });
     on(d.scrollbarH, "scroll", function() {
       if (d.scroller.clientHeight) setScrollLeft(cm, d.scrollbarH.scrollLeft);
     });
 
+    // Listen to wheel events in order to try and update the viewport on time.
     on(d.scroller, "mousewheel", function(e){onScrollWheel(cm, e);});
     on(d.scroller, "DOMMouseScroll", function(e){onScrollWheel(cm, e);});
 
+    // Prevent clicks in the scrollbars from killing focus
     function reFocus() { if (cm.state.focused) setTimeout(bind(focusInput, cm), 0); }
     on(d.scrollbarH, "mousedown", reFocus);
     on(d.scrollbarV, "mousedown", reFocus);
     // Prevent wrapper from ever scrolling
     on(d.wrapper, "scroll", function() { d.wrapper.scrollTop = d.wrapper.scrollLeft = 0; });
 
+    // When the window resizes, we need to refresh active editors.
     var resizeTimer;
     function onResize() {
       if (resizeTimer == null) resizeTimer = setTimeout(function() {
         resizeTimer = null;
         // Might be a text scaling operation, clear size caches.
-        d.cachedCharWidth = d.cachedTextHeight = knownScrollbarWidth = null;
-        clearCaches(cm);
-        runInOp(cm, bind(regChange, cm));
+        d.cachedCharWidth = d.cachedTextHeight = d.cachedPaddingH = knownScrollbarWidth = null;
+        cm.setSize();
       }, 100);
     }
     on(window, "resize", onResize);
-    // Above handler holds on to the editor and its data structures.
-    // Here we poll to unregister it when the editor is no longer in
-    // the document, so that it can be garbage-collected.
+    // The above handler holds on to the editor and its data
+    // structures. Here we poll to unregister it when the editor is no
+    // longer in the document, so that it can be garbage-collected.
     function unregister() {
-      for (var p = d.wrapper.parentNode; p && p != document.body; p = p.parentNode) {}
-      if (p) setTimeout(unregister, 5000);
+      if (contains(document.body, d.wrapper)) setTimeout(unregister, 5000);
       else off(window, "resize", onResize);
     }
     setTimeout(unregister, 5000);
 
     on(d.input, "keyup", operation(cm, onKeyUp));
     on(d.input, "input", function() {
-      if (ie && !ie_lt9 && cm.display.inputHasSelection) cm.display.inputHasSelection = null;
+      if (ie && !ie_upto8 && cm.display.inputHasSelection) cm.display.inputHasSelection = null;
       fastPoll(cm);
     });
     on(d.input, "keydown", operation(cm, onKeyDown));
     on(d.input, "keypress", operation(cm, onKeyPress));
     on(d.input, "focus", bind(onFocus, cm));
     on(d.input, "blur", bind(onBlur, cm));
 
     function drag_(e) {
-      if (signalDOMEvent(cm, e) || cm.options.onDragEvent && cm.options.onDragEvent(cm, addStop(e))) return;
-      e_stop(e);
+      if (!signalDOMEvent(cm, e)) e_stop(e);
     }
     if (cm.options.dragDrop) {
       on(d.scroller, "dragstart", function(e){onDragStart(cm, e);});
       on(d.scroller, "dragenter", drag_);
       on(d.scroller, "dragover", drag_);
       on(d.scroller, "drop", operation(cm, onDrop));
     }
     on(d.scroller, "paste", function(e) {
       if (eventInWidget(d, e)) return;
+      cm.state.pasteIncoming = true;
       focusInput(cm);
       fastPoll(cm);
     });
     on(d.input, "paste", function() {
-      // Workaround for webkit bug https://bugs.webkit.org/show_bug.cgi?id=90206
-      // Add a char to the end of textarea before paste occur so that
-      // selection doesn't span to the end of textarea.
-      if (webkit && !cm.state.fakedLastChar && !(new Date - cm.state.lastMiddleDown < 200)) {
-        var start = d.input.selectionStart, end = d.input.selectionEnd;
-        d.input.value += "$";
-        d.input.selectionStart = start;
-        d.input.selectionEnd = end;
-        cm.state.fakedLastChar = true;
-      }
       cm.state.pasteIncoming = true;
       fastPoll(cm);
     });
 
     function prepareCopy(e) {
       if (d.inaccurateSelection) {
         d.prevInput = "";
         d.inaccurateSelection = false;
         d.input.value = cm.getSelection();
         selectInput(d.input);
       }
       if (e.type == "cut") cm.state.cutIncoming = true;
     }
     on(d.input, "cut", prepareCopy);
     on(d.input, "copy", prepareCopy);
 
     // Needed to handle Tab key in KHTML
     if (khtml) on(d.sizer, "mouseup", function() {
-      if (document.activeElement == d.input) d.input.blur();
+      if (activeElt() == d.input) d.input.blur();
       focusInput(cm);
     });
   }
 
+  // MOUSE EVENTS
+
+  // Return true when the given mouse event happened in a widget
   function eventInWidget(display, e) {
     for (var n = e_target(e); n != display.wrapper; n = n.parentNode) {
       if (!n || n.ignoreEvents || n.parentNode == display.sizer && n != display.mover) return true;
     }
   }
 
-  function posFromMouse(cm, e, liberal) {
+  // Given a mouse event, find the corresponding position. If liberal
+  // is false, it checks whether a gutter or scrollbar was clicked,
+  // and returns null if it was. forRect is used by rectangular
+  // selections, and tries to estimate a character position even for
+  // coordinates beyond the right of the text.
+  function posFromMouse(cm, e, liberal, forRect) {
     var display = cm.display;
     if (!liberal) {
       var target = e_target(e);
-      if (target == display.scrollbarH || target == display.scrollbarH.firstChild ||
-          target == display.scrollbarV || target == display.scrollbarV.firstChild ||
+      if (target == display.scrollbarH || target == display.scrollbarV ||
           target == display.scrollbarFiller || target == display.gutterFiller) return null;
     }
-    var x, y, space = getRect(display.lineSpace);
+    var x, y, space = display.lineSpace.getBoundingClientRect();
     // Fails unpredictably on IE[67] when mouse is dragged around quickly.
-    try { x = e.clientX; y = e.clientY; } catch (e) { return null; }
-    return coordsChar(cm, x - space.left, y - space.top);
+    try { x = e.clientX - space.left; y = e.clientY - space.top; }
+    catch (e) { return null; }
+    var coords = coordsChar(cm, x, y), line;
+    if (forRect && coords.xRel == 1 && (line = getLine(cm.doc, coords.line).text).length == coords.ch) {
+      var colDiff = countColumn(line, line.length, cm.options.tabSize) - line.length;
+      coords = Pos(coords.line, Math.round((x - paddingH(cm.display).left) / charWidth(cm.display)) - colDiff);
+    }
+    return coords;
   }
 
-  var lastClick, lastDoubleClick;
+  // A mouse down can be a single click, double click, triple click,
+  // start of selection drag, start of text drag, new cursor
+  // (ctrl-click), rectangle drag (alt-drag), or xwin
+  // middle-click-paste. Or it might be a click on something we should
+  // not interfere with, such as a scrollbar or widget.
   function onMouseDown(e) {
     if (signalDOMEvent(this, e)) return;
-    var cm = this, display = cm.display, doc = cm.doc, sel = doc.sel;
-    sel.shift = e.shiftKey;
+    var cm = this, display = cm.display;
+    display.shift = e.shiftKey;
 
     if (eventInWidget(display, e)) {
       if (!webkit) {
+        // Briefly turn off draggability, to allow widgets to do
+        // normal dragging things.
         display.scroller.draggable = false;
         setTimeout(function(){display.scroller.draggable = true;}, 100);
       }
       return;
     }
     if (clickInGutter(cm, e)) return;
     var start = posFromMouse(cm, e);
+    window.focus();
 
     switch (e_button(e)) {
-    case 3:
-      if (captureMiddleClick) onContextMenu.call(cm, cm, e);
-      return;
+    case 1:
+      if (start)
+        leftButtonDown(cm, e, start);
+      else if (e_target(e) == display.scroller)
+        e_preventDefault(e);
+      break;
     case 2:
       if (webkit) cm.state.lastMiddleDown = +new Date;
       if (start) extendSelection(cm.doc, start);
       setTimeout(bind(focusInput, cm), 20);
       e_preventDefault(e);
-      return;
+      break;
+    case 3:
+      if (captureRightClick) onContextMenu(cm, e);
+      break;
     }
-    // For button 1, if it was clicked inside the editor
-    // (posFromMouse returning non-null), we have to adjust the
-    // selection.
-    if (!start) {if (e_target(e) == display.scroller) e_preventDefault(e); return;}
+  }
 
-    if (!cm.state.focused) onFocus(cm);
+  var lastClick, lastDoubleClick;
+  function leftButtonDown(cm, e, start) {
+    setTimeout(bind(ensureFocus, cm), 0);
 
-    var now = +new Date, type = "single";
-    if (lastDoubleClick && lastDoubleClick.time > now - 400 && posEq(lastDoubleClick.pos, start)) {
+    var now = +new Date, type;
+    if (lastDoubleClick && lastDoubleClick.time > now - 400 && cmp(lastDoubleClick.pos, start) == 0) {
       type = "triple";
-      e_preventDefault(e);
-      setTimeout(bind(focusInput, cm), 20);
-      selectLine(cm, start.line);
-    } else if (lastClick && lastClick.time > now - 400 && posEq(lastClick.pos, start)) {
+    } else if (lastClick && lastClick.time > now - 400 && cmp(lastClick.pos, start) == 0) {
       type = "double";
       lastDoubleClick = {time: now, pos: start};
-      e_preventDefault(e);
-      var word = findWordAt(getLine(doc, start.line).text, start);
-      extendSelection(cm.doc, word.from, word.to);
-    } else { lastClick = {time: now, pos: start}; }
+    } else {
+      type = "single";
+      lastClick = {time: now, pos: start};
+    }
 
-    var last = start;
-    if (cm.options.dragDrop && dragAndDrop && !isReadOnly(cm) && !posEq(sel.from, sel.to) &&
-        !posLess(start, sel.from) && !posLess(sel.to, start) && type == "single") {
-      var dragEnd = operation(cm, function(e2) {
-        if (webkit) display.scroller.draggable = false;
-        cm.state.draggingText = false;
-        off(document, "mouseup", dragEnd);
-        off(display.scroller, "drop", dragEnd);
-        if (Math.abs(e.clientX - e2.clientX) + Math.abs(e.clientY - e2.clientY) < 10) {
-          e_preventDefault(e2);
-          extendSelection(cm.doc, start);
-          focusInput(cm);
-          // Work around unexplainable focus problem in IE9 (#2127)
-          if (old_ie && !ie_lt9)
-            setTimeout(function() {document.body.focus(); focusInput(cm);}, 20);
+    var sel = cm.doc.sel, addNew = mac ? e.metaKey : e.ctrlKey;
+    if (cm.options.dragDrop && dragAndDrop && !addNew && !isReadOnly(cm) &&
+        type == "single" && sel.contains(start) > -1 && sel.somethingSelected())
+      leftButtonStartDrag(cm, e, start);
+    else
+      leftButtonSelect(cm, e, start, type, addNew);
+  }
+
+  // Start a text drag. When it ends, see if any dragging actually
+  // happen, and treat as a click if it didn't.
+  function leftButtonStartDrag(cm, e, start) {
+    var display = cm.display;
+    var dragEnd = operation(cm, function(e2) {
+      if (webkit) display.scroller.draggable = false;
+      cm.state.draggingText = false;
+      off(document, "mouseup", dragEnd);
+      off(display.scroller, "drop", dragEnd);
+      if (Math.abs(e.clientX - e2.clientX) + Math.abs(e.clientY - e2.clientY) < 10) {
+        e_preventDefault(e2);
+        extendSelection(cm.doc, start);
+        focusInput(cm);
+        // Work around unexplainable focus problem in IE9 (#2127)
+        if (ie_upto10 && !ie_upto8)
+          setTimeout(function() {document.body.focus(); focusInput(cm);}, 20);
+      }
+    });
+    // Let the drag handler handle this.
+    if (webkit) display.scroller.draggable = true;
+    cm.state.draggingText = dragEnd;
+    // IE's approach to draggable
+    if (display.scroller.dragDrop) display.scroller.dragDrop();
+    on(document, "mouseup", dragEnd);
+    on(display.scroller, "drop", dragEnd);
+  }
+
+  // Normal selection, as opposed to text dragging.
+  function leftButtonSelect(cm, e, start, type, addNew) {
+    var display = cm.display, doc = cm.doc;
+    e_preventDefault(e);
+
+    var ourRange, ourIndex, startSel = doc.sel;
+    if (addNew) {
+      ourIndex = doc.sel.contains(start);
+      if (ourIndex > -1)
+        ourRange = doc.sel.ranges[ourIndex];
+      else
+        ourRange = new Range(start, start);
+    } else {
+      ourRange = doc.sel.primary();
+    }
+
+    if (e.altKey) {
+      type = "rect";
+      if (!addNew) ourRange = new Range(start, start);
+      start = posFromMouse(cm, e, true, true);
+      ourIndex = -1;
+    } else if (type == "double") {
+      var word = findWordAt(doc, start);
+      if (cm.display.shift || doc.extend)
+        ourRange = extendRange(doc, ourRange, word.anchor, word.head);
+      else
+        ourRange = word;
+    } else if (type == "triple") {
+      var line = new Range(Pos(start.line, 0), clipPos(doc, Pos(start.line + 1, 0)));
+      if (cm.display.shift || doc.extend)
+        ourRange = extendRange(doc, ourRange, line.anchor, line.head);
+      else
+        ourRange = line;
+    } else {
+      ourRange = extendRange(doc, ourRange, start);
+    }
+
+    if (!addNew) {
+      ourIndex = 0;
+      setSelection(doc, new Selection([ourRange], 0), sel_mouse);
+    } else if (ourIndex > -1) {
+      replaceOneSelection(doc, ourIndex, ourRange, sel_mouse);
+    } else {
+      ourIndex = doc.sel.ranges.length;
+      setSelection(doc, normalizeSelection(doc.sel.ranges.concat([ourRange]), ourIndex),
+                   {scroll: false, origin: "*mouse"});
+    }
+
+    var lastPos = start;
+    function extendTo(pos) {
+      if (cmp(lastPos, pos) == 0) return;
+      lastPos = pos;
+
+      if (type == "rect") {
+        var ranges = [], tabSize = cm.options.tabSize;
+        var startCol = countColumn(getLine(doc, start.line).text, start.ch, tabSize);
+        var posCol = countColumn(getLine(doc, pos.line).text, pos.ch, tabSize);
+        var left = Math.min(startCol, posCol), right = Math.max(startCol, posCol);
+        for (var line = Math.min(start.line, pos.line), end = Math.min(cm.lastLine(), Math.max(start.line, pos.line));
+             line <= end; line++) {
+          var text = getLine(doc, line).text, leftPos = findColumn(text, left, tabSize);
+          if (left == right)
+            ranges.push(new Range(Pos(line, leftPos), Pos(line, leftPos)));
+          else if (text.length > leftPos)
+            ranges.push(new Range(Pos(line, leftPos), Pos(line, findColumn(text, right, tabSize))));
         }
-      });
-      // Let the drag handler handle this.
-      if (webkit) display.scroller.draggable = true;
-      cm.state.draggingText = dragEnd;
-      // IE's approach to draggable
-      if (display.scroller.dragDrop) display.scroller.dragDrop();
-      on(document, "mouseup", dragEnd);
-      on(display.scroller, "drop", dragEnd);
-      return;
-    }
-    e_preventDefault(e);
-    if (type == "single") extendSelection(cm.doc, clipPos(doc, start));
-
-    var startstart = sel.from, startend = sel.to, lastPos = start;
-
-    function doSelect(cur) {
-      if (posEq(lastPos, cur)) return;
-      lastPos = cur;
-
-      if (type == "single") {
-        extendSelection(cm.doc, clipPos(doc, start), cur);
-        return;
-      }
-
-      startstart = clipPos(doc, startstart);
-      startend = clipPos(doc, startend);
-      if (type == "double") {
-        var word = findWordAt(getLine(doc, cur.line).text, cur);
-        if (posLess(cur, startstart)) extendSelection(cm.doc, word.from, startend);
-        else extendSelection(cm.doc, startstart, word.to);
-      } else if (type == "triple") {
-        if (posLess(cur, startstart)) extendSelection(cm.doc, startend, clipPos(doc, Pos(cur.line, 0)));
-        else extendSelection(cm.doc, startstart, clipPos(doc, Pos(cur.line + 1, 0)));
+        if (!ranges.length) ranges.push(new Range(start, start));
+        setSelection(doc, normalizeSelection(startSel.ranges.slice(0, ourIndex).concat(ranges), ourIndex), sel_mouse);
+      } else {
+        var oldRange = ourRange;
+        var anchor = oldRange.anchor, head = pos;
+        if (type != "single") {
+          if (type == "double")
+            var range = findWordAt(doc, pos);
+          else
+            var range = new Range(Pos(pos.line, 0), clipPos(doc, Pos(pos.line + 1, 0)));
+          if (cmp(range.anchor, anchor) > 0) {
+            head = range.head;
+            anchor = minPos(oldRange.from(), range.anchor);
+          } else {
+            head = range.anchor;
+            anchor = maxPos(oldRange.to(), range.head);
+          }
+        }
+        var ranges = startSel.ranges.slice(0);
+        ranges[ourIndex] = new Range(clipPos(doc, anchor), head);
+        setSelection(doc, normalizeSelection(ranges, ourIndex), sel_mouse);
       }
     }
 
-    var editorSize = getRect(display.wrapper);
+    var editorSize = display.wrapper.getBoundingClientRect();
     // Used to ensure timeout re-tries don't fire when another extend
     // happened in the meantime (clearTimeout isn't reliable -- at
     // least on Chrome, the timeouts still happen even when cleared,
     // if the clear happens after their scheduled firing time).
     var counter = 0;
 
     function extend(e) {
       var curCount = ++counter;
-      var cur = posFromMouse(cm, e, true);
+      var cur = posFromMouse(cm, e, true, type == "rect");
       if (!cur) return;
-      if (!posEq(cur, last)) {
-        if (!cm.state.focused) onFocus(cm);
-        last = cur;
-        doSelect(cur);
+      if (cmp(cur, lastPos) != 0) {
+        ensureFocus(cm);
+        extendTo(cur);
         var visible = visibleLines(display, doc);
         if (cur.line >= visible.to || cur.line < visible.from)
           setTimeout(operation(cm, function(){if (counter == curCount) extend(e);}), 150);
       } else {
         var outside = e.clientY < editorSize.top ? -20 : e.clientY > editorSize.bottom ? 20 : 0;
         if (outside) setTimeout(operation(cm, function() {
           if (counter != curCount) return;
           display.scroller.scrollTop += outside;
           extend(e);
         }), 50);
       }
     }
 
     function done(e) {
       counter = Infinity;
       e_preventDefault(e);
       focusInput(cm);
       off(document, "mousemove", move);
       off(document, "mouseup", up);
+      doc.history.lastSelOrigin = null;
     }
 
     var move = operation(cm, function(e) {
-      if (!old_ie && !e_button(e)) done(e);
+      if ((ie && !ie_upto9) ?  !e.buttons : !e_button(e)) done(e);
       else extend(e);
     });
     var up = operation(cm, done);
     on(document, "mousemove", move);
     on(document, "mouseup", up);
   }
 
+  // Determines whether an event happened in the gutter, and fires the
+  // handlers for the corresponding event.
   function gutterEvent(cm, e, type, prevent, signalfn) {
     try { var mX = e.clientX, mY = e.clientY; }
     catch(e) { return false; }
-    if (mX >= Math.floor(getRect(cm.display.gutters).right)) return false;
+    if (mX >= Math.floor(cm.display.gutters.getBoundingClientRect().right)) return false;
     if (prevent) e_preventDefault(e);
 
     var display = cm.display;
-    var lineBox = getRect(display.lineDiv);
+    var lineBox = display.lineDiv.getBoundingClientRect();
 
     if (mY > lineBox.bottom || !hasHandler(cm, type)) return e_defaultPrevented(e);
     mY -= lineBox.top - display.viewOffset;
 
     for (var i = 0; i < cm.options.gutters.length; ++i) {
       var g = display.gutters.childNodes[i];
-      if (g && getRect(g).right >= mX) {
+      if (g && g.getBoundingClientRect().right >= mX) {
         var line = lineAtHeight(cm.doc, mY);
         var gutter = cm.options.gutters[i];
         signalfn(cm, type, cm, line, gutter, e);
         return e_defaultPrevented(e);
       }
     }
   }
 
-  function contextMenuInGutter(cm, e) {
-    if (!hasHandler(cm, "gutterContextMenu")) return false;
-    return gutterEvent(cm, e, "gutterContextMenu", false, signal);
-  }
-
   function clickInGutter(cm, e) {
     return gutterEvent(cm, e, "gutterClick", true, signalLater);
   }
 
   // Kludge to work around strange IE behavior where it'll sometimes
   // re-fire a series of drag-related events right after the drop (#1551)
   var lastDrop = 0;
 
   function onDrop(e) {
     var cm = this;
-    if (signalDOMEvent(cm, e) || eventInWidget(cm.display, e) || (cm.options.onDragEvent && cm.options.onDragEvent(cm, addStop(e))))
+    if (signalDOMEvent(cm, e) || eventInWidget(cm.display, e))
       return;
     e_preventDefault(e);
-    if (ie) lastDrop = +new Date;
+    if (ie_upto10) lastDrop = +new Date;
     var pos = posFromMouse(cm, e, true), files = e.dataTransfer.files;
     if (!pos || isReadOnly(cm)) return;
+    // Might be a file drop, in which case we simply extract the text
+    // and insert it.
     if (files && files.length && window.FileReader && window.File) {
       var n = files.length, text = Array(n), read = 0;
       var loadFile = function(file, i) {
         var reader = new FileReader;
         reader.onload = function() {
           text[i] = reader.result;
           if (++read == n) {
             pos = clipPos(cm.doc, pos);
-            makeChange(cm.doc, {from: pos, to: pos, text: splitLines(text.join("\n")), origin: "paste"}, "around");
+            var change = {from: pos, to: pos, text: splitLines(text.join("\n")), origin: "paste"};
+            makeChange(cm.doc, change);
+            setSelectionReplaceHistory(cm.doc, simpleSelection(pos, changeEnd(change)));
           }
         };
         reader.readAsText(file);
       };
       for (var i = 0; i < n; ++i) loadFile(files[i], i);
-    } else {
+    } else { // Normal drop
       // Don't do a replace if the drop happened inside of the selected text.
-      if (cm.state.draggingText && !(posLess(pos, cm.doc.sel.from) || posLess(cm.doc.sel.to, pos))) {
+      if (cm.state.draggingText && cm.doc.sel.contains(pos) > -1) {
         cm.state.draggingText(e);
         // Ensure the editor is re-focused
         setTimeout(bind(focusInput, cm), 20);
         return;
       }
       try {
         var text = e.dataTransfer.getData("Text");
         if (text) {
-          var curFrom = cm.doc.sel.from, curTo = cm.doc.sel.to;
-          setSelection(cm.doc, pos, pos);
-          if (cm.state.draggingText) replaceRange(cm.doc, "", curFrom, curTo, "paste");
-          cm.replaceSelection(text, null, "paste");
+          var selected = cm.state.draggingText && cm.listSelections();
+          setSelectionNoUndo(cm.doc, simpleSelection(pos, pos));
+          if (selected) for (var i = 0; i < selected.length; ++i)
+            replaceRange(cm.doc, "", selected[i].anchor, selected[i].head, "drag");
+          cm.replaceSelection(text, "around", "paste");
           focusInput(cm);
         }
       }
       catch(e){}
     }
   }
 
   function onDragStart(cm, e) {
-    if (ie && (!cm.state.draggingText || +new Date - lastDrop < 100)) { e_stop(e); return; }
+    if (ie_upto10 && (!cm.state.draggingText || +new Date - lastDrop < 100)) { e_stop(e); return; }
     if (signalDOMEvent(cm, e) || eventInWidget(cm.display, e)) return;
 
-    var txt = cm.getSelection();
-    e.dataTransfer.setData("Text", txt);
+    e.dataTransfer.setData("Text", cm.getSelection());
 
     // Use dummy image instead of default browsers image.
     // Recent Safari (~6.0.2) have a tendency to segfault when this happens, so we don't do it there.
     if (e.dataTransfer.setDragImage && !safari) {
       var img = elt("img", null, null, "position: fixed; left: 0; top: 0;");
       img.src = "data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==";
-      if (opera) {
+      if (presto) {
         img.width = img.height = 1;
         cm.display.wrapper.appendChild(img);
         // Force a relayout, or Opera won't use our image for some obscure reason
         img._top = img.offsetTop;
       }
       e.dataTransfer.setDragImage(img, 0, 0);
-      if (opera) img.parentNode.removeChild(img);
+      if (presto) img.parentNode.removeChild(img);
     }
   }
 
+  // SCROLL EVENTS
+
+  // Sync the scrollable area and scrollbars, ensure the viewport
+  // covers the visible area.
   function setScrollTop(cm, val) {
     if (Math.abs(cm.doc.scrollTop - val) < 2) return;
     cm.doc.scrollTop = val;
-    if (!gecko) updateDisplay(cm, [], val);
+    if (!gecko) updateDisplay(cm, {top: val});
     if (cm.display.scroller.scrollTop != val) cm.display.scroller.scrollTop = val;
     if (cm.display.scrollbarV.scrollTop != val) cm.display.scrollbarV.scrollTop = val;
-    if (gecko) updateDisplay(cm, []);
+    if (gecko) updateDisplay(cm);
     startWorker(cm, 100);
   }
+  // Sync scroller and scrollbar, ensure the gutter elements are
+  // aligned.
   function setScrollLeft(cm, val, isScroller) {
     if (isScroller ? val == cm.doc.scrollLeft : Math.abs(cm.doc.scrollLeft - val) < 2) return;
     val = Math.min(val, cm.display.scroller.scrollWidth - cm.display.scroller.clientWidth);
     cm.doc.scrollLeft = val;
     alignHorizontally(cm);
     if (cm.display.scroller.scrollLeft != val) cm.display.scroller.scrollLeft = val;
     if (cm.display.scrollbarH.scrollLeft != val) cm.display.scrollbarH.scrollLeft = val;
   }
 
   // Since the delta values reported on mouse wheel events are
   // unstandardized between browsers and even browser versions, and
   // generally horribly unpredictable, this code starts by measuring
   // the scroll effect that the first few mouse wheel events have,
   // and, from that, detects the way it can convert deltas to pixel
   // offsets afterwards.
   //
   // The reason we want to know the amount a wheel event will scroll
   // is that it gives us a chance to update the display before the
   // actual scrolling happens, reducing flickering.
 
   var wheelSamples = 0, wheelPixelsPerUnit = null;
   // Fill in a browser-detected starting value on browsers where we
   // know one. These don't have to be accurate -- the result of them
   // being wrong would just be a slight flicker on the first wheel
   // scroll (if it is large enough).
-  if (old_ie) wheelPixelsPerUnit = -.53;
+  if (ie) wheelPixelsPerUnit = -.53;
   else if (gecko) wheelPixelsPerUnit = 15;
   else if (chrome) wheelPixelsPerUnit = -.7;
   else if (safari) wheelPixelsPerUnit = -1/3;
 
   function onScrollWheel(cm, e) {
     var dx = e.wheelDeltaX, dy = e.wheelDeltaY;
     if (dx == null && e.detail && e.axis == e.HORIZONTAL_AXIS) dx = e.detail;
     if (dy == null && e.detail && e.axis == e.VERTICAL_AXIS) dy = e.detail;
     else if (dy == null) dy = e.wheelDelta;
 
     var display = cm.display, scroll = display.scroller;
     // Quit if there's nothing to scroll here
     if (!(dx && scroll.scrollWidth > scroll.clientWidth ||
           dy && scroll.scrollHeight > scroll.clientHeight)) return;
 
     // Webkit browsers on OS X abort momentum scrolls when the target
     // of the scroll event is removed from the scrollable element.
     // This hack (see related code in patchDisplay) makes sure the
     // element is kept around.
     if (dy && mac && webkit) {
-      for (var cur = e.target; cur != scroll; cur = cur.parentNode) {
-        if (cur.lineObj) {
-          cm.display.currentWheelTarget = cur;
-          break;
+      outer: for (var cur = e.target, view = display.view; cur != scroll; cur = cur.parentNode) {
+        for (var i = 0; i < view.length; i++) {
+          if (view[i].node == cur) {
+            cm.display.currentWheelTarget = cur;
+            break outer;
+          }
         }
       }
     }
 
     // On some browsers, horizontal scrolling will cause redraws to
     // happen before the gutter has been realigned, causing it to
     // wriggle around in a most unseemly way. When we have an
     // estimated pixels/delta value, we just handle horizontal
     // scrolling entirely here. It'll be slightly off from native, but
     // better than glitching out.
-    if (dx && !gecko && !opera && wheelPixelsPerUnit != null) {
+    if (dx && !gecko && !presto && wheelPixelsPerUnit != null) {
       if (dy)
         setScrollTop(cm, Math.max(0, Math.min(scroll.scrollTop + dy * wheelPixelsPerUnit, scroll.scrollHeight - scroll.clientHeight)));
       setScrollLeft(cm, Math.max(0, Math.min(scroll.scrollLeft + dx * wheelPixelsPerUnit, scroll.scrollWidth - scroll.clientWidth)));
       e_preventDefault(e);
       display.wheelStartX = null; // Abort measurement, if in progress
       return;
     }
 
+    // 'Project' the visible viewport to cover the area that is being
+    // scrolled into view (if we know enough to estimate it).
     if (dy && wheelPixelsPerUnit != null) {
       var pixels = dy * wheelPixelsPerUnit;
       var top = cm.doc.scrollTop, bot = top + display.wrapper.clientHeight;
       if (pixels < 0) top = Math.max(0, top + pixels - 50);
       else bot = Math.min(cm.doc.height, bot + pixels + 50);
-      updateDisplay(cm, [], {top: top, bottom: bot});
+      updateDisplay(cm, {top: top, bottom: bot});
     }
 
     if (wheelSamples < 20) {
       if (display.wheelStartX == null) {
         display.wheelStartX = scroll.scrollLeft; display.wheelStartY = scroll.scrollTop;
         display.wheelDX = dx; display.wheelDY = dy;
         setTimeout(function() {
           if (display.wheelStartX == null) return;
           var movedX = scroll.scrollLeft - display.wheelStartX;
           var movedY = scroll.scrollTop - display.wheelStartY;
           var sample = (movedY && display.wheelDY && movedY / display.wheelDY) ||
             (movedX && display.wheelDX && movedX / display.wheelDX);
           display.wheelStartX = display.wheelStartY = null;
           if (!sample) return;
           wheelPixelsPerUnit = (wheelPixelsPerUnit * wheelSamples + sample) / (wheelSamples + 1);
           ++wheelSamples;
         }, 200);
       } else {
         display.wheelDX += dx; display.wheelDY += dy;
       }
     }
   }
 
+  // KEY EVENTS
+
+  // Run a handler that was bound to a key.
   function doHandleBinding(cm, bound, dropShift) {
     if (typeof bound == "string") {
       bound = commands[bound];
       if (!bound) return false;
     }
     // Ensure previous input has been read, so that the handler sees a
     // consistent view of the document
     if (cm.display.pollingFast && readInput(cm)) cm.display.pollingFast = false;
-    var doc = cm.doc, prevShift = doc.sel.shift, done = false;
+    var prevShift = cm.display.shift, done = false;
     try {
       if (isReadOnly(cm)) cm.state.suppressEdits = true;
-      if (dropShift) doc.sel.shift = false;
+      if (dropShift) cm.display.shift = false;
       done = bound(cm) != Pass;
     } finally {
-      doc.sel.shift = prevShift;
+      cm.display.shift = prevShift;
       cm.state.suppressEdits = false;
     }
     return done;
   }
 
+  // Collect the currently active keymaps.
   function allKeyMaps(cm) {
     var maps = cm.state.keyMaps.slice(0);
     if (cm.options.extraKeys) maps.push(cm.options.extraKeys);
     maps.push(cm.options.keyMap);
     return maps;
   }
 
   var maybeTransition;
+  // Handle a key from the keydown event.
   function handleKeyBinding(cm, e) {
-    // Handle auto keymap transitions
+    // Handle automatic keymap transitions
     var startMap = getKeyMap(cm.options.keyMap), next = startMap.auto;
     clearTimeout(maybeTransition);
     if (next && !isModifierKey(e)) maybeTransition = setTimeout(function() {
       if (getKeyMap(cm.options.keyMap) == startMap) {
         cm.options.keyMap = (next.call ? next.call(null, cm) : next);
         keyMapChanged(cm);
       }
     }, 50);
 
     var name = keyName(e, true), handled = false;
     if (!name) return false;
     var keymaps = allKeyMaps(cm);
 
     if (e.shiftKey) {
       // First try to resolve full name (including 'Shift-'). Failing
       // that, see if there is a cursor-motion command (starting with
       // 'go') bound to the keyname without 'Shift-'.
       handled = lookupKey("Shift-" + name, keymaps, function(b) {return doHandleBinding(cm, b, true);})
              || lookupKey(name, keymaps, function(b) {
                   if (typeof b == "string" ? /^go[A-Z]/.test(b) : b.motion)
                     return doHandleBinding(cm, b);
                 });
     } else {
       handled = lookupKey(name, keymaps, function(b) { return doHandleBinding(cm, b); });
     }
 
     if (handled) {
       e_preventDefault(e);
       restartBlink(cm);
-      if (ie_lt9) { e.oldKeyCode = e.keyCode; e.keyCode = 0; }
       signalLater(cm, "keyHandled", cm, name, e);
     }
     return handled;
   }
 
+  // Handle a key from the keypress event
   function handleCharBinding(cm, e, ch) {
     var handled = lookupKey("'" + ch + "'", allKeyMaps(cm),
                             function(b) { return doHandleBinding(cm, b, true); });
     if (handled) {
       e_preventDefault(e);
       restartBlink(cm);
       signalLater(cm, "keyHandled", cm, "'" + ch + "'", e);
     }
     return handled;
   }
 
-  function onKeyUp(e) {
-    var cm = this;
-    if (signalDOMEvent(cm, e) || cm.options.onKeyEvent && cm.options.onKeyEvent(cm, addStop(e))) return;
-    if (e.keyCode == 16) cm.doc.sel.shift = false;
-  }
-
   var lastStoppedKey = null;
   function onKeyDown(e) {
     var cm = this;
-    if (!cm.state.focused) onFocus(cm);
-    if (signalDOMEvent(cm, e) || cm.options.onKeyEvent && cm.options.onKeyEvent(cm, addStop(e))) return;
-    if (old_ie && e.keyCode == 27) e.returnValue = false;
+    ensureFocus(cm);
+    if (signalDOMEvent(cm, e)) return;
+    // IE does strange things with escape.
+    if (ie_upto10 && e.keyCode == 27) e.returnValue = false;
     var code = e.keyCode;
-    // IE does strange things with escape.
-    cm.doc.sel.shift = code == 16 || e.shiftKey;
-    // First give onKeyEvent option a chance to handle this.
+    cm.display.shift = code == 16 || e.shiftKey;
     var handled = handleKeyBinding(cm, e);
-    if (opera) {
+    if (presto) {
       lastStoppedKey = handled ? code : null;
       // Opera has no cut event... we try to at least catch the key combo
       if (!handled && code == 88 && !hasCopyEvent && (mac ? e.metaKey : e.ctrlKey))
-        cm.replaceSelection("");
+        cm.replaceSelection("", null, "cut");
     }
   }
 
+  function onKeyUp(e) {
+    if (signalDOMEvent(this, e)) return;
+    if (e.keyCode == 16) this.doc.sel.shift = false;
+  }
+
   function onKeyPress(e) {
     var cm = this;
-    if (signalDOMEvent(cm, e) || cm.options.onKeyEvent && cm.options.onKeyEvent(cm, addStop(e))) return;
+    if (signalDOMEvent(cm, e)) return;
     var keyCode = e.keyCode, charCode = e.charCode;
-    if (opera && keyCode == lastStoppedKey) {lastStoppedKey = null; e_preventDefault(e); return;}
-    if (((opera && (!e.which || e.which < 10)) || khtml) && handleKeyBinding(cm, e)) return;
+    if (presto && keyCode == lastStoppedKey) {lastStoppedKey = null; e_preventDefault(e); return;}
+    if (((presto && (!e.which || e.which < 10)) || khtml) && handleKeyBinding(cm, e)) return;
     var ch = String.fromCharCode(charCode == null ? keyCode : charCode);
     if (handleCharBinding(cm, e, ch)) return;
-    if (ie && !ie_lt9) cm.display.inputHasSelection = null;
+    if (ie && !ie_upto8) cm.display.inputHasSelection = null;
     fastPoll(cm);
   }
 
+  // FOCUS/BLUR EVENTS
+
   function onFocus(cm) {
     if (cm.options.readOnly == "nocursor") return;
     if (!cm.state.focused) {
       signal(cm, "focus", cm);
       cm.state.focused = true;
       if (cm.display.wrapper.className.search(/\bCodeMirror-focused\b/) == -1)
         cm.display.wrapper.className += " CodeMirror-focused";
       if (!cm.curOp) {
-        resetInput(cm, true);
+        resetInput(cm);
         if (webkit) setTimeout(bind(resetInput, cm, true), 0); // Issue #1730
       }
     }
     slowPoll(cm);
     restartBlink(cm);
   }
   function onBlur(cm) {
     if (cm.state.focused) {
       signal(cm, "blur", cm);
       cm.state.focused = false;
       cm.display.wrapper.className = cm.display.wrapper.className.replace(" CodeMirror-focused", "");
     }
     clearInterval(cm.display.blinker);
-    setTimeout(function() {if (!cm.state.focused) cm.doc.sel.shift = false;}, 150);
+    setTimeout(function() {if (!cm.state.focused) cm.display.shift = false;}, 150);
   }
 
+  // CONTEXT MENU HANDLING
+
   var detectingSelectAll;
+  // To make the context menu work, we need to briefly unhide the
+  // textarea (making it as unobtrusive as possible) to let the
+  // right-click take effect on it.
   function onContextMenu(cm, e) {
     if (signalDOMEvent(cm, e, "contextmenu")) return;
-    var display = cm.display, sel = cm.doc.sel;
+    var display = cm.display;
     if (eventInWidget(display, e) || contextMenuInGutter(cm, e)) return;
 
     var pos = posFromMouse(cm, e), scrollPos = display.scroller.scrollTop;
-    if (!pos || opera) return; // Opera is difficult.
+    if (!pos || presto) return; // Opera is difficult.
 
     // Reset the current text selection only if the click is done outside of the selection
     // and 'resetSelectionOnContextMenu' option is true.
     var reset = cm.options.resetSelectionOnContextMenu;
-    if (reset && (posEq(sel.from, sel.to) || posLess(pos, sel.from) || !posLess(pos, sel.to)))
-      operation(cm, setSelection)(cm.doc, pos, pos);
+    if (reset && cm.doc.sel.contains(pos) == -1)
+      operation(cm, setSelection)(cm.doc, simpleSelection(pos), sel_dontScroll);
 
     var oldCSS = display.input.style.cssText;
     display.inputDiv.style.position = "absolute";
     display.input.style.cssText = "position: fixed; width: 30px; height: 30px; top: " + (e.clientY - 5) +
-      "px; left: " + (e.clientX - 5) + "px; z-index: 1000; background: transparent; outline: none;" +
-      "border-width: 0; outline: none; overflow: hidden; opacity: .05; -ms-opacity: .05; filter: alpha(opacity=5);";
+      "px; left: " + (e.clientX - 5) + "px; z-index: 1000; background: " +
+      (ie ? "rgba(255, 255, 255, .05)" : "transparent") +
+      "; outline: none; border-width: 0; outline: none; overflow: hidden; opacity: .05; filter: alpha(opacity=5);";
     focusInput(cm);
-    resetInput(cm, true);
+    resetInput(cm);
     // Adds "Select all" to context menu in FF
-    if (posEq(sel.from, sel.to)) display.input.value = display.prevInput = " ";
+    if (!cm.somethingSelected()) display.input.value = display.prevInput = " ";
 
+    // Select-all will be greyed out if there's nothing to select, so
+    // this adds a zero-width space so that we can later check whether
+    // it got selected.
     function prepareSelectAllHack() {
       if (display.input.selectionStart != null) {
-        var extval = display.input.value = "\u200b" + (posEq(sel.from, sel.to) ? "" : display.input.value);
+        var extval = display.input.value = "\u200b" + (cm.somethingSelected() ? display.input.value : "");
         display.prevInput = "\u200b";
         display.input.selectionStart = 1; display.input.selectionEnd = extval.length;
       }
     }
     function rehide() {
       display.inputDiv.style.position = "relative";
       display.input.style.cssText = oldCSS;
-      if (ie_lt9) display.scrollbarV.scrollTop = display.scroller.scrollTop = scrollPos;
+      if (ie_upto8) display.scrollbarV.scrollTop = display.scroller.scrollTop = scrollPos;
       slowPoll(cm);
 
       // Try to detect the user choosing select-all
       if (display.input.selectionStart != null) {
-        if (!old_ie || ie_lt9) prepareSelectAllHack();
+        if (!ie || ie_upto8) prepareSelectAllHack();
         clearTimeout(detectingSelectAll);
         var i = 0, poll = function(){
           if (display.prevInput == "\u200b" && display.input.selectionStart == 0)
             operation(cm, commands.selectAll)(cm);
           else if (i++ < 10) detectingSelectAll = setTimeout(poll, 500);
           else resetInput(cm);
         };
         detectingSelectAll = setTimeout(poll, 200);
       }
     }
 
-    if (old_ie && !ie_lt9) prepareSelectAllHack();
-    if (captureMiddleClick) {
+    if (ie && !ie_upto8) prepareSelectAllHack();
+    if (captureRightClick) {
       e_stop(e);
       var mouseup = function() {
         off(window, "mouseup", mouseup);
         setTimeout(rehide, 20);
       };
       on(window, "mouseup", mouseup);
     } else {
       setTimeout(rehide, 50);
     }
   }
 
+  function contextMenuInGutter(cm, e) {
+    if (!hasHandler(cm, "gutterContextMenu")) return false;
+    return gutterEvent(cm, e, "gutterContextMenu", false, signal);
+  }
+
   // UPDATING
 
+  // Compute the position of the end of a change (its 'to' property
+  // refers to the pre-change end).
   var changeEnd = CodeMirror.changeEnd = function(change) {
     if (!change.text) return change.to;
     return Pos(change.from.line + change.text.length - 1,
                lst(change.text).length + (change.text.length == 1 ? change.from.ch : 0));
   };
 
-  // Make sure a position will be valid after the given change.
-  function clipPostChange(doc, change, pos) {
-    if (!posLess(change.from, pos)) return clipPos(doc, pos);
-    var diff = (change.text.length - 1) - (change.to.line - change.from.line);
-    if (pos.line > change.to.line + diff) {
-      var preLine = pos.line - diff, lastLine = doc.first + doc.size - 1;
-      if (preLine > lastLine) return Pos(lastLine, getLine(doc, lastLine).text.length);
-      return clipToLen(pos, getLine(doc, preLine).text.length);
-    }
-    if (pos.line == change.to.line + diff)
-      return clipToLen(pos, lst(change.text).length + (change.text.length == 1 ? change.from.ch : 0) +
-                       getLine(doc, change.to.line).text.length - change.to.ch);
-    var inside = pos.line - change.from.line;
-    return clipToLen(pos, change.text[inside].length + (inside ? 0 : change.from.ch));
+  // Adjust a position to refer to the post-change position of the
+  // same text, or the end of the change if the change covers it.
+  function adjustForChange(pos, change) {
+    if (cmp(pos, change.from) < 0) return pos;
+    if (cmp(pos, change.to) <= 0) return changeEnd(change);
+
+    var line = pos.line + change.text.length - (change.to.line - change.from.line) - 1, ch = pos.ch;
+    if (pos.line == change.to.line) ch += changeEnd(change).ch - change.to.ch;
+    return Pos(line, ch);
   }
 
-  // Hint can be null|"end"|"start"|"around"|{anchor,head}
-  function computeSelAfterChange(doc, change, hint) {
-    if (hint && typeof hint == "object") // Assumed to be {anchor, head} object
-      return {anchor: clipPostChange(doc, change, hint.anchor),
-              head: clipPostChange(doc, change, hint.head)};
-
-    if (hint == "start") return {anchor: change.from, head: change.from};
-
-    var end = changeEnd(change);
-    if (hint == "around") return {anchor: change.from, head: end};
-    if (hint == "end") return {anchor: end, head: end};
-
-    // hint is null, leave the selection alone as much as possible
-    var adjustPos = function(pos) {
-      if (posLess(pos, change.from)) return pos;
-      if (!posLess(change.to, pos)) return end;
-
-      var line = pos.line + change.text.length - (change.to.line - change.from.line) - 1, ch = pos.ch;
-      if (pos.line == change.to.line) ch += end.ch - change.to.ch;
-      return Pos(line, ch);
-    };
-    return {anchor: adjustPos(doc.sel.anchor), head: adjustPos(doc.sel.head)};
+  function computeSelAfterChange(doc, change) {
+    var out = [];
+    for (var i = 0; i < doc.sel.ranges.length; i++) {
+      var range = doc.sel.ranges[i];
+      out.push(new Range(adjustForChange(range.anchor, change),
+                         adjustForChange(range.head, change)));
+    }
+    return normalizeSelection(out, doc.sel.primIndex);
   }
 
+  function offsetPos(pos, old, nw) {
+    if (pos.line == old.line)
+      return Pos(nw.line, pos.ch - old.ch + nw.ch);
+    else
+      return Pos(nw.line + (pos.line - old.line), pos.ch);
+  }
+
+  // Used by replaceSelections to allow moving the selection to the
+  // start or around the replaced test. Hint may be "start" or "around".
+  function computeReplacedSel(doc, changes, hint) {
+    var out = [];
+    var oldPrev = Pos(doc.first, 0), newPrev = oldPrev;
+    for (var i = 0; i < changes.length; i++) {
+      var change = changes[i];
+      var from = offsetPos(change.from, oldPrev, newPrev);
+      var to = offsetPos(changeEnd(change), oldPrev, newPrev);
+      oldPrev = change.to;
+      newPrev = to;
+      if (hint == "around") {
+        var range = doc.sel.ranges[i], inv = cmp(range.head, range.anchor) < 0;
+        out[i] = new Range(inv ? to : from, inv ? from : to);
+      } else {
+        out[i] = new Range(from, from);
+      }
+    }
+    return new Selection(out, doc.sel.primIndex);
+  }
+
+  // Allow "beforeChange" event handlers to influence a change
   function filterChange(doc, change, update) {
     var obj = {
       canceled: false,
       from: change.from,
       to: change.to,
       text: change.text,
       origin: change.origin,
       cancel: function() { this.canceled = true; }
     };
     if (update) obj.update = function(from, to, text, origin) {
       if (from) this.from = clipPos(doc, from);
       if (to) this.to = clipPos(doc, to);
       if (text) this.text = text;
       if (origin !== undefined) this.origin = origin;
     };
     signal(doc, "beforeChange", doc, obj);
     if (doc.cm) signal(doc.cm, "beforeChange", doc.cm, obj);
 
     if (obj.canceled) return null;
     return {from: obj.from, to: obj.to, text: obj.text, origin: obj.origin};
   }
 
-  // Replace the range from from to to by the strings in replacement.
-  // change is a {from, to, text [, origin]} object
-  function makeChange(doc, change, selUpdate, ignoreReadOnly) {
+  // Apply a change to a document, and add it to the document's
+  // history, and propagating it to all linked documents.
+  function makeChange(doc, change, ignoreReadOnly) {
     if (doc.cm) {
-      if (!doc.cm.curOp) return operation(doc.cm, makeChange)(doc, change, selUpdate, ignoreReadOnly);
+      if (!doc.cm.curOp) return operation(doc.cm, makeChange)(doc, change, ignoreReadOnly);
       if (doc.cm.state.suppressEdits) return;
     }
 
     if (hasHandler(doc, "beforeChange") || doc.cm && hasHandler(doc.cm, "beforeChange")) {
       change = filterChange(doc, change, true);
       if (!change) return;
     }
 
     // Possibly split or suppress the update based on the presence
     // of read-only spans in its range.
     var split = sawReadOnlySpans && !ignoreReadOnly && removeReadOnlyRanges(doc, change.from, change.to);
     if (split) {
-      for (var i = split.length - 1; i >= 1; --i)
-        makeChangeNoReadonly(doc, {from: split[i].from, to: split[i].to, text: [""]});
-      if (split.length)
-        makeChangeNoReadonly(doc, {from: split[0].from, to: split[0].to, text: change.text}, selUpdate);
+      for (var i = split.length - 1; i >= 0; --i)
+        makeChangeInner(doc, {from: split[i].from, to: split[i].to, text: i ? [""] : change.text});
     } else {
-      makeChangeNoReadonly(doc, change, selUpdate);
+      makeChangeInner(doc, change);
     }
   }
 
-  function makeChangeNoReadonly(doc, change, selUpdate) {
-    if (change.text.length == 1 && change.text[0] == "" && posEq(change.from, change.to)) return;
-    var selAfter = computeSelAfterChange(doc, change, selUpdate);
-    addToHistory(doc, change, selAfter, doc.cm ? doc.cm.curOp.id : NaN);
+  function makeChangeInner(doc, change) {
+    if (change.text.length == 1 && change.text[0] == "" && cmp(change.from, change.to) == 0) return;
+    var selAfter = computeSelAfterChange(doc, change);
+    addChangeToHistory(doc, change, selAfter, doc.cm ? doc.cm.curOp.id : NaN);
 
     makeChangeSingleDoc(doc, change, selAfter, stretchSpansOverChange(doc, change));
     var rebased = [];
 
     linkedDocs(doc, function(doc, sharedHist) {
       if (!sharedHist && indexOf(rebased, doc.history) == -1) {
         rebaseHist(doc.history, change);
         rebased.push(doc.history);
       }
       makeChangeSingleDoc(doc, change, null, stretchSpansOverChange(doc, change));
     });
   }
 
-  function makeChangeFromHistory(doc, type) {
+  // Revert a change stored in a document's history.
+  function makeChangeFromHistory(doc, type, allowSelectionOnly) {
     if (doc.cm && doc.cm.state.suppressEdits) return;
 
-    var hist = doc.history;
-    var event = (type == "undo" ? hist.done : hist.undone).pop();
-    if (!event) return;
+    var hist = doc.history, event, selAfter = doc.sel;
+    var source = type == "undo" ? hist.done : hist.undone, dest = type == "undo" ? hist.undone : hist.done;
 
-    var anti = {changes: [], anchorBefore: event.anchorAfter, headBefore: event.headAfter,
-                anchorAfter: event.anchorBefore, headAfter: event.headBefore,
-                generation: hist.generation};
-    (type == "undo" ? hist.undone : hist.done).push(anti);
+    // Verify that there is a useable event (so that ctrl-z won't
+    // needlessly clear selection events)
+    for (var i = 0; i < source.length; i++) {
+      event = source[i];
+      if (allowSelectionOnly ? event.ranges && !event.equals(doc.sel) : !event.ranges)
+        break;
+    }
+    if (i == source.length) return;
+    hist.lastOrigin = hist.lastSelOrigin = null;
+
+    for (;;) {
+      event = source.pop();
+      if (event.ranges) {
+        pushSelectionToHistory(event, dest);
+        if (allowSelectionOnly && !event.equals(doc.sel)) {
+          setSelection(doc, event, {clearRedo: false});
+          return;
+        }
+        selAfter = event;
+      }
+      else break;
+    }
+
+    // Build up a reverse change object to add to the opposite history
+    // stack (redo when undoing, and vice versa).
+    var antiChanges = [];
+    pushSelectionToHistory(selAfter, dest);
+    dest.push({changes: antiChanges, generation: hist.generation});
     hist.generation = event.generation || ++hist.maxGeneration;
 
     var filter = hasHandler(doc, "beforeChange") || doc.cm && hasHandler(doc.cm, "beforeChange");
 
     for (var i = event.changes.length - 1; i >= 0; --i) {
       var change = event.changes[i];
       change.origin = type;
       if (filter && !filterChange(doc, change, false)) {
-        (type == "undo" ? hist.done : hist.undone).length = 0;
+        source.length = 0;
         return;
       }
 
-      anti.changes.push(historyChangeFromChange(doc, change));
+      antiChanges.push(historyChangeFromChange(doc, change));
 
-      var after = i ? computeSelAfterChange(doc, change, null)
-                    : {anchor: event.anchorBefore, head: event.headBefore};
+      var after = i ? computeSelAfterChange(doc, change, null) : lst(source);
       makeChangeSingleDoc(doc, change, after, mergeOldSpans(doc, change));
+      if (doc.cm) ensureCursorVisible(doc.cm);
       var rebased = [];
 
+      // Propagate to the linked documents
       linkedDocs(doc, function(doc, sharedHist) {
         if (!sharedHist && indexOf(rebased, doc.history) == -1) {
           rebaseHist(doc.history, change);
           rebased.push(doc.history);
         }
         makeChangeSingleDoc(doc, change, null, mergeOldSpans(doc, change));
       });
     }
   }
 
+  // Sub-views need their line numbers shifted when text is added
+  // above or below them in the parent document.
   function shiftDoc(doc, distance) {
-    function shiftPos(pos) {return Pos(pos.line + distance, pos.ch);}
     doc.first += distance;
-    if (doc.cm) regChange(doc.cm, doc.first, doc.first, distance);
-    doc.sel.head = shiftPos(doc.sel.head); doc.sel.anchor = shiftPos(doc.sel.anchor);
-    doc.sel.from = shiftPos(doc.sel.from); doc.sel.to = shiftPos(doc.sel.to);
+    doc.sel = new Selection(map(doc.sel.ranges, function(range) {
+      return new Range(Pos(range.anchor.line + distance, range.anchor.ch),
+                       Pos(range.head.line + distance, range.head.ch));
+    }), doc.sel.primIndex);
+    if (doc.cm) regChange(doc.cm, doc.first, doc.first - distance, distance);
   }
 
+  // More lower-level change function, handling only a single document
+  // (not linked ones).
   function makeChangeSingleDoc(doc, change, selAfter, spans) {
     if (doc.cm && !doc.cm.curOp)
       return operation(doc.cm, makeChangeSingleDoc)(doc, change, selAfter, spans);
 
     if (change.to.line < doc.first) {
       shiftDoc(doc, change.text.length - 1 - (change.to.line - change.from.line));
       return;
     }
     if (change.from.line > doc.lastLine()) return;
 
     // Clip the change to the size of this doc
     if (change.from.line < doc.first) {
       var shift = change.text.length - 1 - (doc.first - change.from.line);
       shiftDoc(doc, shift);
       change = {from: Pos(doc.first, 0), to: Pos(change.to.line + shift, change.to.ch),
                 text: [lst(change.text)], origin: change.origin};
     }
     var last = doc.lastLine();
     if (change.to.line > last) {
       change = {from: change.from, to: Pos(last, getLine(doc, last).text.length),
                 text: [change.text[0]], origin: change.origin};
     }
 
     change.removed = getBetween(doc, change.from, change.to);
 
     if (!selAfter) selAfter = computeSelAfterChange(doc, change, null);
-    if (doc.cm) makeChangeSingleDocInEditor(doc.cm, change, spans, selAfter);
-    else updateDoc(doc, change, spans, selAfter);
+    if (doc.cm) makeChangeSingleDocInEditor(doc.cm, change, spans);
+    else updateDoc(doc, change, spans);
+    setSelectionNoUndo(doc, selAfter, sel_dontScroll);
   }
 
-  function makeChangeSingleDocInEditor(cm, change, spans, selAfter) {
+  // Handle the interaction of a change to a document with the editor
+  // that this document is part of.
+  function makeChangeSingleDocInEditor(cm, change, spans) {
     var doc = cm.doc, display = cm.display, from = change.from, to = change.to;
 
     var recomputeMaxLength = false, checkWidthStart = from.line;
     if (!cm.options.lineWrapping) {
-      checkWidthStart = lineNo(visualLine(doc, getLine(doc, from.line)));
+      checkWidthStart = lineNo(visualLine(getLine(doc, from.line)));
       doc.iter(checkWidthStart, to.line + 1, function(line) {
         if (line == display.maxLine) {
           recomputeMaxLength = true;
           return true;
         }
       });
     }
 
-    if (!posLess(doc.sel.head, change.from) && !posLess(change.to, doc.sel.head))
+    if (doc.sel.contains(change.from, change.to) > -1)
       cm.curOp.cursorActivity = true;
 
-    updateDoc(doc, change, spans, selAfter, estimateHeight(cm));
+    updateDoc(doc, change, spans, estimateHeight(cm));
 
     if (!cm.options.lineWrapping) {
       doc.iter(checkWidthStart, from.line + change.text.length, function(line) {
-        var len = lineLength(doc, line);
+        var len = lineLength(line);
         if (len > display.maxLineLength) {
           display.maxLine = line;
           display.maxLineLength = len;
           display.maxLineChanged = true;
           recomputeMaxLength = false;
         }
       });
       if (recomputeMaxLength) cm.curOp.updateMaxLine = true;
     }
 
     // Adjust frontier, schedule worker
     doc.frontier = Math.min(doc.frontier, from.line);
     startWorker(cm, 400);
 
     var lendiff = change.text.length - (to.line - from.line) - 1;
     // Remember that these lines changed, for updating the display
-    regChange(cm, from.line, to.line + 1, lendiff);
+    if (from.line == to.line && change.text.length == 1 && !isWholeLineUpdate(cm.doc, change))
+      regLineChange(cm, from.line, "text");
+    else
+      regChange(cm, from.line, to.line + 1, lendiff);
 
-    if (hasHandler(cm, "change")) {
-      var changeObj = {from: from, to: to,
-                       text: change.text,
-                       removed: change.removed,
-                       origin: change.origin};
-      if (cm.curOp.textChanged) {
-        for (var cur = cm.curOp.textChanged; cur.next; cur = cur.next) {}
-        cur.next = changeObj;
-      } else cm.curOp.textChanged = changeObj;
-    }
+    if (hasHandler(cm, "change") || hasHandler(cm, "changes"))
+      (cm.curOp.changeObjs || (cm.curOp.changeObjs = [])).push({
+        from: from, to: to,
+        text: change.text,
+        removed: change.removed,
+        origin: change.origin
+      });
   }
 
   function replaceRange(doc, code, from, to, origin) {
     if (!to) to = from;
-    if (posLess(to, from)) { var tmp = to; to = from; from = tmp; }
+    if (cmp(to, from) < 0) { var tmp = to; to = from; from = tmp; }
     if (typeof code == "string") code = splitLines(code);
-    makeChange(doc, {from: from, to: to, text: code, origin: origin}, null);
+    makeChange(doc, {from: from, to: to, text: code, origin: origin});
   }
 
-  // POSITION OBJECT
+  // SCROLLING THINGS INTO VIEW
 
-  function Pos(line, ch) {
-    if (!(this instanceof Pos)) return new Pos(line, ch);
-    this.line = line; this.ch = ch;
-  }
-  CodeMirror.Pos = Pos;
-
-  function posEq(a, b) {return a.line == b.line && a.ch == b.ch;}
-  function posLess(a, b) {return a.line < b.line || (a.line == b.line && a.ch < b.ch);}
-  function cmp(a, b) {return a.line - b.line || a.ch - b.ch;}
-  function copyPos(x) {return Pos(x.line, x.ch);}
-
-  // SELECTION
-
-  function clipLine(doc, n) {return Math.max(doc.first, Math.min(n, doc.first + doc.size - 1));}
-  function clipPos(doc, pos) {
-    if (pos.line < doc.first) return Pos(doc.first, 0);
-    var last = doc.first + doc.size - 1;
-    if (pos.line > last) return Pos(last, getLine(doc, last).text.length);
-    return clipToLen(pos, getLine(doc, pos.line).text.length);
-  }
-  function clipToLen(pos, linelen) {
-    var ch = pos.ch;
-    if (ch == null || ch > linelen) return Pos(pos.line, linelen);
-    else if (ch < 0) return Pos(pos.line, 0);
-    else return pos;
-  }
-  function isLine(doc, l) {return l >= doc.first && l < doc.first + doc.size;}
-
-  // If shift is held, this will move the selection anchor. Otherwise,
-  // it'll set the whole selection.
-  function extendSelection(doc, pos, other, bias) {
-    if (doc.sel.shift || doc.sel.extend) {
-      var anchor = doc.sel.anchor;
-      if (other) {
-        var posBefore = posLess(pos, anchor);
-        if (posBefore != posLess(other, anchor)) {
-          anchor = pos;
-          pos = other;
-        } else if (posBefore != posLess(pos, other)) {
-          pos = other;
-        }
-      }
-      setSelection(doc, anchor, pos, bias);
-    } else {
-      setSelection(doc, pos, other || pos, bias);
-    }
-    if (doc.cm) doc.cm.curOp.userSelChange = true;
-  }
-
-  function filterSelectionChange(doc, anchor, head) {
-    var obj = {anchor: anchor, head: head};
-    signal(doc, "beforeSelectionChange", doc, obj);
-    if (doc.cm) signal(doc.cm, "beforeSelectionChange", doc.cm, obj);
-    obj.anchor = clipPos(doc, obj.anchor); obj.head = clipPos(doc, obj.head);
-    return obj;
-  }
-
-  // Update the selection. Last two args are only used by
-  // updateDoc, since they have to be expressed in the line
-  // numbers before the update.
-  function setSelection(doc, anchor, head, bias, checkAtomic) {
-    if (!checkAtomic && hasHandler(doc, "beforeSelectionChange") || doc.cm && hasHandler(doc.cm, "beforeSelectionChange")) {
-      var filtered = filterSelectionChange(doc, anchor, head);
-      head = filtered.head;
-      anchor = filtered.anchor;
-    }
-
-    var sel = doc.sel;
-    sel.goalColumn = null;
-    if (bias == null) bias = posLess(head, sel.head) ? -1 : 1;
-    // Skip over atomic spans.
-    if (checkAtomic || !posEq(anchor, sel.anchor))
-      anchor = skipAtomic(doc, anchor, bias, checkAtomic != "push");
-    if (checkAtomic || !posEq(head, sel.head))
-      head = skipAtomic(doc, head, bias, checkAtomic != "push");
-
-    if (posEq(sel.anchor, anchor) && posEq(sel.head, head)) return;
-
-    sel.anchor = anchor; sel.head = head;
-    var inv = posLess(head, anchor);
-    sel.from = inv ? head : anchor;
-    sel.to = inv ? anchor : head;
-
-    if (doc.cm)
-      doc.cm.curOp.updateInput = doc.cm.curOp.selectionChanged =
-        doc.cm.curOp.cursorActivity = true;
-
-    signalLater(doc, "cursorActivity", doc);
-  }
-
-  function reCheckSelection(cm) {
-    setSelection(cm.doc, cm.doc.sel.from, cm.doc.sel.to, null, "push");
-  }
-
-  function skipAtomic(doc, pos, bias, mayClear) {
-    var flipped = false, curPos = pos;
-    var dir = bias || 1;
-    doc.cantEdit = false;
-    search: for (;;) {
-      var line = getLine(doc, curPos.line);
-      if (line.markedSpans) {
-        for (var i = 0; i < line.markedSpans.length; ++i) {
-          var sp = line.markedSpans[i], m = sp.marker;
-          if ((sp.from == null || (m.inclusiveLeft ? sp.from <= curPos.ch : sp.from < curPos.ch)) &&
-              (sp.to == null || (m.inclusiveRight ? sp.to >= curPos.ch : sp.to > curPos.ch))) {
-            if (mayClear) {
-              signal(m, "beforeCursorEnter");
-              if (m.explicitlyCleared) {
-                if (!line.markedSpans) break;
-                else {--i; continue;}
-              }
-            }
-            if (!m.atomic) continue;
-            var newPos = m.find()[dir < 0 ? "from" : "to"];
-            if (posEq(newPos, curPos)) {
-              newPos.ch += dir;
-              if (newPos.ch < 0) {
-                if (newPos.line > doc.first) newPos = clipPos(doc, Pos(newPos.line - 1));
-                else newPos = null;
-              } else if (newPos.ch > line.text.length) {
-                if (newPos.line < doc.first + doc.size - 1) newPos = Pos(newPos.line + 1, 0);
-                else newPos = null;
-              }
-              if (!newPos) {
-                if (flipped) {
-                  // Driven in a corner -- no valid cursor position found at all
-                  // -- try again *with* clearing, if we didn't already
-                  if (!mayClear) return skipAtomic(doc, pos, bias, true);
-                  // Otherwise, turn off editing until further notice, and return the start of the doc
-                  doc.cantEdit = true;
-                  return Pos(doc.first, 0);
-                }
-                flipped = true; newPos = pos; dir = -dir;
-              }
-            }
-            curPos = newPos;
-            continue search;
-          }
-        }
-      }
-      return curPos;
-    }
-  }
-
-  // SCROLLING
-
-  function scrollCursorIntoView(cm) {
-    var coords = scrollPosIntoView(cm, cm.doc.sel.head, null, cm.options.cursorScrollMargin);
-    if (!cm.state.focused) return;
-    var display = cm.display, box = getRect(display.sizer), doScroll = null;
+  // If an editor sits on the top or bottom of the window, partially
+  // scrolled out of view, this ensures that the cursor is visible.
+  function maybeScrollWindow(cm, coords) {
+    var display = cm.display, box = display.sizer.getBoundingClientRect(), doScroll = null;
     if (coords.top + box.top < 0) doScroll = true;
     else if (coords.bottom + box.top > (window.innerHeight || document.documentElement.clientHeight)) doScroll = false;
     if (doScroll != null && !phantom) {
       var scrollNode = elt("div", "\u200b", null, "position: absolute; top: " +
-                           (coords.top - display.viewOffset) + "px; height: " +
+                           (coords.top - display.viewOffset - paddingTop(cm.display)) + "px; height: " +
                            (coords.bottom - coords.top + scrollerCutOff) + "px; left: " +
                            coords.left + "px; width: 2px;");
       cm.display.lineSpace.appendChild(scrollNode);
       scrollNode.scrollIntoView(doScroll);
       cm.display.lineSpace.removeChild(scrollNode);
     }
   }
 
+  // Scroll a given position into view (immediately), verifying that
+  // it actually became visible (as line heights are accurately
+  // measured, the position of something may 'drift' during drawing).
   function scrollPosIntoView(cm, pos, end, margin) {
     if (margin == null) margin = 0;
     for (;;) {
       var changed = false, coords = cursorCoords(cm, pos);
       var endCoords = !end || end == pos ? coords : cursorCoords(cm, end);
       var scrollPos = calculateScrollPos(cm, Math.min(coords.left, endCoords.left),
                                          Math.min(coords.top, endCoords.top) - margin,
                                          Math.max(coords.left, endCoords.left),
                                          Math.max(coords.bottom, endCoords.bottom) + margin);
       var startTop = cm.doc.scrollTop, startLeft = cm.doc.scrollLeft;
       if (scrollPos.scrollTop != null) {
         setScrollTop(cm, scrollPos.scrollTop);
         if (Math.abs(cm.doc.scrollTop - startTop) > 1) changed = true;
       }
       if (scrollPos.scrollLeft != null) {
         setScrollLeft(cm, scrollPos.scrollLeft);
         if (Math.abs(cm.doc.scrollLeft - startLeft) > 1) changed = true;
       }
       if (!changed) return coords;
     }
   }
 
+  // Scroll a given set of coordinates into view (immediately).
   function scrollIntoView(cm, x1, y1, x2, y2) {
     var scrollPos = calculateScrollPos(cm, x1, y1, x2, y2);
     if (scrollPos.scrollTop != null) setScrollTop(cm, scrollPos.scrollTop);
     if (scrollPos.scrollLeft != null) setScrollLeft(cm, scrollPos.scrollLeft);
   }
 
+  // Calculate a new scroll position needed to scroll the given
+  // rectangle into view. Returns an object with scrollTop and
+  // scrollLeft properties. When these are undefined, the
+  // vertical/horizontal position does not need to be adjusted.
   function calculateScrollPos(cm, x1, y1, x2, y2) {
     var display = cm.display, snapMargin = textHeight(cm.display);
     if (y1 < 0) y1 = 0;
-    var screen = display.scroller.clientHeight - scrollerCutOff, screentop = display.scroller.scrollTop, result = {};
+    var screentop = cm.curOp && cm.curOp.scrollTop != null ? cm.curOp.scrollTop : display.scroller.scrollTop;
+    var screen = display.scroller.clientHeight - scrollerCutOff, result = {};
     var docBottom = cm.doc.height + paddingVert(display);
     var atTop = y1 < snapMargin, atBottom = y2 > docBottom - snapMargin;
     if (y1 < screentop) {
       result.scrollTop = atTop ? 0 : y1;
     } else if (y2 > screentop + screen) {
       var newTop = Math.min(y1, (atBottom ? docBottom : y2) - screen);
       if (newTop != screentop) result.scrollTop = newTop;
     }
 
-    var screenw = display.scroller.clientWidth - scrollerCutOff, screenleft = display.scroller.scrollLeft;
+    var screenleft = cm.curOp && cm.curOp.scrollLeft != null ? cm.curOp.scrollLeft : display.scroller.scrollLeft;
+    var screenw = display.scroller.clientWidth - scrollerCutOff;
     x1 += display.gutters.offsetWidth; x2 += display.gutters.offsetWidth;
     var gutterw = display.gutters.offsetWidth;
     var atLeft = x1 < gutterw + 10;
     if (x1 < screenleft + gutterw || atLeft) {
       if (atLeft) x1 = 0;
       result.scrollLeft = Math.max(0, x1 - 10 - gutterw);
     } else if (x2 > screenw + screenleft - 3) {
       result.scrollLeft = x2 + 10 - screenw;
     }
     return result;
   }
 
-  function updateScrollPos(cm, left, top) {
-    cm.curOp.updateScrollPos = {scrollLeft: left == null ? cm.doc.scrollLeft : left,
-                                scrollTop: top == null ? cm.doc.scrollTop : top};
+  // Store a relative adjustment to the scroll position in the current
+  // operation (to be applied when the operation finishes).
+  function addToScrollPos(cm, left, top) {
+    if (left != null || top != null) resolveScrollToPos(cm);
+    if (left != null)
+      cm.curOp.scrollLeft = (cm.curOp.scrollLeft == null ? cm.doc.scrollLeft : cm.curOp.scrollLeft) + left;
+    if (top != null)
+      cm.curOp.scrollTop = (cm.curOp.scrollTop == null ? cm.doc.scrollTop : cm.curOp.scrollTop) + top;
   }
 
-  function addToScrollPos(cm, left, top) {
-    var pos = cm.curOp.updateScrollPos || (cm.curOp.updateScrollPos = {scrollLeft: cm.doc.scrollLeft, scrollTop: cm.doc.scrollTop});
-    var scroll = cm.display.scroller;
-    pos.scrollTop = Math.max(0, Math.min(scroll.scrollHeight - scroll.clientHeight, pos.scrollTop + top));
-    pos.scrollLeft = Math.max(0, Math.min(scroll.scrollWidth - scroll.clientWidth, pos.scrollLeft + left));
+  // Make sure that at the end of the operation the current cursor is
+  // shown.
+  function ensureCursorVisible(cm) {
+    resolveScrollToPos(cm);
+    var cur = cm.getCursor(), from = cur, to = cur;
+    if (!cm.options.lineWrapping) {
+      from = cur.ch ? Pos(cur.line, cur.ch - 1) : cur;
+      to = Pos(cur.line, cur.ch + 1);
+    }
+    cm.curOp.scrollToPos = {from: from, to: to, margin: cm.options.cursorScrollMargin, isCursor: true};
+  }
+
+  // When an operation has its scrollToPos property set, and another
+  // scroll action is applied before the end of the operation, this
+  // 'simulates' scrolling that position into view in a cheap way, so
+  // that the effect of intermediate scroll commands is not ignored.
+  function resolveScrollToPos(cm) {
+    var range = cm.curOp.scrollToPos;
+    if (range) {
+      cm.curOp.scrollToPos = null;
+      var from = estimateCoords(cm, range.from), to = estimateCoords(cm, range.to);
+      var sPos = calculateScrollPos(cm, Math.min(from.left, to.left),
+                                    Math.min(from.top, to.top) - range.margin,
+                                    Math.max(from.right, to.right),
+                                    Math.max(from.bottom, to.bottom) + range.margin);
+      cm.scrollTo(sPos.scrollLeft, sPos.scrollTop);
+    }
   }
 
   // API UTILITIES
 
+  // Indent the given line. The how parameter can be "smart",
+  // "add"/null, "subtract", or "prev". When aggressive is false
+  // (typically set to true for forced single-line indents), empty
+  // lines are not indented, and places where the mode returns Pass
+  // are left alone.
   function indentLine(cm, n, how, aggressive) {
-    var doc = cm.doc;
+    var doc = cm.doc, state;
     if (how == null) how = "add";
     if (how == "smart") {
+      // Fall back to "prev" when the mode doesn't have an indentation
+      // method.
       if (!cm.doc.mode.indent) how = "prev";
-      else var state = getStateBefore(cm, n);
+      else state = getStateBefore(cm, n);
     }
 
     var tabSize = cm.options.tabSize;
     var line = getLine(doc, n), curSpace = countColumn(line.text, null, tabSize);
+    if (line.stateAfter) line.stateAfter = null;
     var curSpaceString = line.text.match(/^\s*/)[0], indentation;
     if (!aggressive && !/\S/.test(line.text)) {
       indentation = 0;
       how = "not";
     } else if (how == "smart") {
       indentation = cm.doc.mode.indent(state, line.text.slice(curSpaceString.length), line.text);
       if (indentation == Pass) {
         if (!aggressive) return;
         how = "prev";
       }
     }
     if (how == "prev") {
       if (n > doc.first) indentation = countColumn(getLine(doc, n-1).text, null, tabSize);
       else indentation = 0;
     } else if (how == "add") {
       indentation = curSpace + cm.options.indentUnit;
     } else if (how == "subtract") {
       indentation = curSpace - cm.options.indentUnit;
     } else if (typeof how == "number") {
       indentation = curSpace + how;
     }
     indentation = Math.max(0, indentation);
 
     var indentString = "", pos = 0;
     if (cm.options.indentWithTabs)
       for (var i = Math.floor(indentation / tabSize); i; --i) {pos += tabSize; indentString += "\t";}
     if (pos < indentation) indentString += spaceStr(indentation - pos);
 
-    if (indentString != curSpaceString)
+    if (indentString != curSpaceString) {
       replaceRange(cm.doc, indentString, Pos(n, 0), Pos(n, curSpaceString.length), "+input");
-    else if (doc.sel.head.line == n && doc.sel.head.ch < curSpaceString.length)
-      setSelection(doc, Pos(n, curSpaceString.length), Pos(n, curSpaceString.length), 1);
+    } else {
+      // Ensure that, if the cursor was in the whitespace at the start
+      // of the line, it is moved to the end of that space.
+      for (var i = 0; i < doc.sel.ranges.length; i++) {
+        var range = doc.sel.ranges[i];
+        if (range.head.line == n && range.head.ch < curSpaceString.length) {
+          var pos = Pos(n, curSpaceString.length);
+          replaceOneSelection(doc, i, new Range(pos, pos));
+          break;
+        }
+      }
+    }
     line.stateAfter = null;
   }
 
-  function changeLine(cm, handle, op) {
+  // Utility for applying a change to a line by handle or number,
+  // returning the number and optionally registering the line as
+  // changed.
+  function changeLine(cm, handle, changeType, op) {
     var no = handle, line = handle, doc = cm.doc;
     if (typeof handle == "number") line = getLine(doc, clipLine(doc, handle));
     else no = lineNo(handle);
     if (no == null) return null;
-    if (op(line, no)) regChange(cm, no, no + 1);
+    if (op(line, no)) regLineChange(cm, no, changeType);
     else return null;
     return line;
   }
 
+  // Helper for deleting text near the selection(s), used to implement
+  // backspace, delete, and similar functionality.
+  function deleteNearSelection(cm, compute) {
+    var ranges = cm.doc.sel.ranges, kill = [];
+    // Build up a set of ranges to kill first, merging overlapping
+    // ranges.
+    for (var i = 0; i < ranges.length; i++) {
+      var toKill = compute(ranges[i]);
+      while (kill.length && cmp(toKill.from, lst(kill).to) <= 0) {
+        var replaced = kill.pop();
+        if (cmp(replaced.from, toKill.from) < 0) {
+          toKill.from = replaced.from;
+          break;
+        }
+      }
+      kill.push(toKill);
+    }
+    // Next, remove those actual ranges.
+    runInOp(cm, function() {
+      for (var i = kill.length - 1; i >= 0; i--)
+        replaceRange(cm.doc, "", kill[i].from, kill[i].to, "+delete");
+      ensureCursorVisible(cm);
+    });
+  }
+
+  // Used for horizontal relative motion. Dir is -1 or 1 (left or
+  // right), unit can be "char", "column" (like char, but doesn't
+  // cross line boundaries), "word" (across next word), or "group" (to
+  // the start of next group of word or non-word-non-whitespace
+  // chars). The visually param controls whether, in right-to-left
+  // text, direction 1 means to move towards the next index in the
+  // string, or towards the character to the right of the current
+  // position. The resulting position will have a hitSide=true
+  // property if it reached the end of the document.
   function findPosH(doc, pos, dir, unit, visually) {
     var line = pos.line, ch = pos.ch, origDir = dir;
     var lineObj = getLine(doc, line);
     var possible = true;
     function findNextLine() {
       var l = line + dir;
       if (l < doc.first || l >= doc.first + doc.size) return (possible = false);
       line = l;
       return lineObj = getLine(doc, l);
     }
     function moveOnce(boundToLine) {
       var next = (visually ? moveVisually : moveLogically)(lineObj, ch, dir, true);
       if (next == null) {
         if (!boundToLine && findNextLine()) {
           if (visually) ch = (dir < 0 ? lineRight : lineLeft)(lineObj);
           else ch = dir < 0 ? lineObj.text.length : 0;
         } else return (possible = false);
       } else ch = next;
       return true;
     }
 
     if (unit == "char") moveOnce();
     else if (unit == "column") moveOnce(true);
     else if (unit == "word" || unit == "group") {
       var sawType = null, group = unit == "group";
       for (var first = true;; first = false) {
         if (dir < 0 && !moveOnce(!first)) break;
         var cur = lineObj.text.charAt(ch) || "\n";
         var type = isWordChar(cur) ? "w"
-          : !group ? null
-          : /\s/.test(cur) ? null
+          : group && cur == "\n" ? "n"
+          : !group || /\s/.test(cur) ? null
           : "p";
+        if (group && !first && !type) type = "s";
         if (sawType && sawType != type) {
           if (dir < 0) {dir = 1; moveOnce();}
           break;
         }
+
         if (type) sawType = type;
         if (dir > 0 && !moveOnce(!first)) break;
       }
     }
     var result = skipAtomic(doc, Pos(line, ch), origDir, true);
     if (!possible) result.hitSide = true;
     return result;
   }
 
+  // For relative vertical movement. Dir may be -1 or 1. Unit can be
+  // "page" or "line". The resulting position will have a hitSide=true
+  // property if it reached the end of the document.
   function findPosV(cm, pos, dir, unit) {
     var doc = cm.doc, x = pos.left, y;
     if (unit == "page") {
       var pageSize = Math.min(cm.display.wrapper.clientHeight, window.innerHeight || document.documentElement.clientHeight);
       y = pos.top + dir * (pageSize - (dir < 0 ? 1.5 : .5) * textHeight(cm.display));
     } else if (unit == "line") {
       y = dir > 0 ? pos.bottom + 3 : pos.top - 3;
     }
     for (;;) {
       var target = coordsChar(cm, x, y);
       if (!target.outside) break;
       if (dir < 0 ? y <= 0 : y >= doc.height) { target.hitSide = true; break; }
       y += dir * 5;
     }
     return target;
   }
 
-  function findWordAt(line, pos) {
+  // Find the word at the given position (as returned by coordsChar).
+  function findWordAt(doc, pos) {
+    var line = getLine(doc, pos.line).text;
     var start = pos.ch, end = pos.ch;
     if (line) {
       if ((pos.xRel < 0 || end == line.length) && start) --start; else ++end;
       var startChar = line.charAt(start);
       var check = isWordChar(startChar) ? isWordChar
         : /\s/.test(startChar) ? function(ch) {return /\s/.test(ch);}
         : function(ch) {return !/\s/.test(ch) && !isWordChar(ch);};
       while (start > 0 && check(line.charAt(start - 1))) --start;
       while (end < line.length && check(line.charAt(end))) ++end;
     }
-    return {from: Pos(pos.line, start), to: Pos(pos.line, end)};
+    return new Range(Pos(pos.line, start), Pos(pos.line, end));
   }
 
-  function selectLine(cm, line) {
-    extendSelection(cm.doc, Pos(line, 0), clipPos(cm.doc, Pos(line + 1, 0)));
-  }
+  // EDITOR METHODS
 
-  // PROTOTYPE
+  // The publicly visible API. Note that methodOp(f) means
+  // 'wrap f in an operation, performed on its `this` parameter'.
 
-  // The publicly visible API. Note that operation(null, f) means
-  // 'wrap f in an operation, performed on its `this` parameter'
+  // This is not the complete set of editor methods. Most of the
+  // methods defined on the Doc type are also injected into
+  // CodeMirror.prototype, for backwards compatibility and
+  // convenience.
 
   CodeMirror.prototype = {
     constructor: CodeMirror,
     focus: function(){window.focus(); focusInput(this); fastPoll(this);},
 
     setOption: function(option, value) {
       var options = this.options, old = options[option];
       if (options[option] == value && option != "mode") return;
       options[option] = value;
       if (optionHandlers.hasOwnProperty(option))
         operation(this, optionHandlers[option])(this, value, old);
     },
 
     getOption: function(option) {return this.options[option];},
     getDoc: function() {return this.doc;},
 
     addKeyMap: function(map, bottom) {
       this.state.keyMaps[bottom ? "push" : "unshift"](map);
     },
     removeKeyMap: function(map) {
       var maps = this.state.keyMaps;
       for (var i = 0; i < maps.length; ++i)
         if (maps[i] == map || (typeof maps[i] != "string" && maps[i].name == map)) {
           maps.splice(i, 1);
           return true;
         }
     },
 
-    addOverlay: operation(null, function(spec, options) {
+    addOverlay: methodOp(function(spec, options) {
       var mode = spec.token ? spec : CodeMirror.getMode(this.options, spec);
       if (mode.startState) throw new Error("Overlays may not be stateful.");
       this.state.overlays.push({mode: mode, modeSpec: spec, opaque: options && options.opaque});
       this.state.modeGen++;
       regChange(this);
     }),
-    removeOverlay: operation(null, function(spec) {
+    removeOverlay: methodOp(function(spec) {
       var overlays = this.state.overlays;
       for (var i = 0; i < overlays.length; ++i) {
         var cur = overlays[i].modeSpec;
         if (cur == spec || typeof spec == "string" && cur.name == spec) {
           overlays.splice(i, 1);
           this.state.modeGen++;
           regChange(this);
           return;
         }
       }
     }),
 
-    indentLine: operation(null, function(n, dir, aggressive) {
+    indentLine: methodOp(function(n, dir, aggressive) {
       if (typeof dir != "string" && typeof dir != "number") {
         if (dir == null) dir = this.options.smartIndent ? "smart" : "prev";
         else dir = dir ? "add" : "subtract";
       }
       if (isLine(this.doc, n)) indentLine(this, n, dir, aggressive);
     }),
-    indentSelection: operation(null, function(how) {
-      var sel = this.doc.sel;
-      if (posEq(sel.from, sel.to)) return indentLine(this, sel.from.line, how, true);
-      var e = sel.to.line - (sel.to.ch ? 0 : 1);
-      for (var i = sel.from.line; i <= e; ++i) indentLine(this, i, how);
+    indentSelection: methodOp(function(how) {
+      var ranges = this.doc.sel.ranges, end = -1;
+      for (var i = 0; i < ranges.length; i++) {
+        var range = ranges[i];
+        if (!range.empty()) {
+          var start = Math.max(end, range.from().line);
+          var to = range.to();
+          end = Math.min(this.lastLine(), to.line - (to.ch ? 0 : 1)) + 1;
+          for (var j = start; j < end; ++j)
+            indentLine(this, j, how);
+        } else if (range.head.line > end) {
+          indentLine(this, range.head.line, how, true);
+          end = range.head.line;
+          if (i == this.doc.sel.primIndex) ensureCursorVisible(this);
+        }
+      }
     }),
 
     // Fetch the parser token for a given character. Useful for hacks
     // that want to inspect the mode state (say, for completion).
     getTokenAt: function(pos, precise) {
       var doc = this.doc;
       pos = clipPos(doc, pos);
       var state = getStateBefore(this, pos.line, precise), mode = this.doc.mode;
       var line = getLine(doc, pos.line);
       var stream = new StringStream(line.text, this.options.tabSize);
       while (stream.pos < pos.ch && !stream.eol()) {
         stream.start = stream.pos;
         var style = mode.token(stream, state);
       }
       return {start: stream.start,
               end: stream.pos,
               string: stream.current(),
-              className: style || null, // Deprecated, use 'type' instead
               type: style || null,
               state: state};
     },
 
     getTokenTypeAt: function(pos) {
       pos = clipPos(this.doc, pos);
       var styles = getLineStyles(this, getLine(this.doc, pos.line));
       var before = 0, after = (styles.length - 1) / 2, ch = pos.ch;
       if (ch == 0) return styles[2];
       for (;;) {
@@ skipping 38 matching lines @@
       return found;
     },
 
     getStateAfter: function(line, precise) {
       var doc = this.doc;
       line = clipLine(doc, line == null ? doc.first + doc.size - 1: line);
       return getStateBefore(this, line + 1, precise);
     },
 
     cursorCoords: function(start, mode) {
-      var pos, sel = this.doc.sel;
-      if (start == null) pos = sel.head;
+      var pos, range = this.doc.sel.primary();
+      if (start == null) pos = range.head;
       else if (typeof start == "object") pos = clipPos(this.doc, start);
-      else pos = start ? sel.from : sel.to;
+      else pos = start ? range.from() : range.to();
       return cursorCoords(this, pos, mode || "page");
     },
 
     charCoords: function(pos, mode) {
       return charCoords(this, clipPos(this.doc, pos), mode || "page");
     },
 
     coordsChar: function(coords, mode) {
       coords = fromCoordSystem(this, coords, mode || "page");
       return coordsChar(this, coords.left, coords.top);
     },
 
     lineAtHeight: function(height, mode) {
       height = fromCoordSystem(this, {top: height, left: 0}, mode || "page").top;
       return lineAtHeight(this.doc, height + this.display.viewOffset);
     },
     heightAtLine: function(line, mode) {
       var end = false, last = this.doc.first + this.doc.size - 1;
       if (line < this.doc.first) line = this.doc.first;
       else if (line > last) { line = last; end = true; }
       var lineObj = getLine(this.doc, line);
-      return intoCoordSystem(this, getLine(this.doc, line), {top: 0, left: 0}, mode || "page").top +
-        (end ? lineObj.height : 0);
+      return intoCoordSystem(this, lineObj, {top: 0, left: 0}, mode || "page").top +
+        (end ? this.doc.height - heightAtLine(lineObj) : 0);
     },
 
     defaultTextHeight: function() { return textHeight(this.display); },
     defaultCharWidth: function() { return charWidth(this.display); },
 
-    setGutterMarker: operation(null, function(line, gutterID, value) {
-      return changeLine(this, line, function(line) {
+    setGutterMarker: methodOp(function(line, gutterID, value) {
+      return changeLine(this, line, "gutter", function(line) {
         var markers = line.gutterMarkers || (line.gutterMarkers = {});
         markers[gutterID] = value;
         if (!value && isEmpty(markers)) line.gutterMarkers = null;
         return true;
       });
     }),
 
-    clearGutter: operation(null, function(gutterID) {
+    clearGutter: methodOp(function(gutterID) {
       var cm = this, doc = cm.doc, i = doc.first;
       doc.iter(function(line) {
         if (line.gutterMarkers && line.gutterMarkers[gutterID]) {
           line.gutterMarkers[gutterID] = null;
-          regChange(cm, i, i + 1);
+          regLineChange(cm, i, "gutter");
           if (isEmpty(line.gutterMarkers)) line.gutterMarkers = null;
         }
         ++i;
       });
     }),
 
-    addLineClass: operation(null, function(handle, where, cls) {
-      return changeLine(this, handle, function(line) {
+    addLineClass: methodOp(function(handle, where, cls) {
+      return changeLine(this, handle, "class", function(line) {
         var prop = where == "text" ? "textClass" : where == "background" ? "bgClass" : "wrapClass";
         if (!line[prop]) line[prop] = cls;
         else if (new RegExp("(?:^|\\s)" + cls + "(?:$|\\s)").test(line[prop])) return false;
         else line[prop] += " " + cls;
         return true;
       });
     }),
 
-    removeLineClass: operation(null, function(handle, where, cls) {
-      return changeLine(this, handle, function(line) {
+    removeLineClass: methodOp(function(handle, where, cls) {
+      return changeLine(this, handle, "class", function(line) {
         var prop = where == "text" ? "textClass" : where == "background" ? "bgClass" : "wrapClass";
         var cur = line[prop];
         if (!cur) return false;
         else if (cls == null) line[prop] = null;
         else {
           var found = cur.match(new RegExp("(?:^|\\s+)" + cls + "(?:$|\\s+)"));
           if (!found) return false;
           var end = found.index + found[0].length;
           line[prop] = cur.slice(0, found.index) + (!found.index || end == cur.length ? "" : " ") + cur.slice(end) || null;
         }
         return true;
       });
     }),
 
-    addLineWidget: operation(null, function(handle, node, options) {
+    addLineWidget: methodOp(function(handle, node, options) {
       return addLineWidget(this, handle, node, options);
     }),
 
     removeLineWidget: function(widget) { widget.clear(); },
 
     lineInfo: function(line) {
       if (typeof line == "number") {
         if (!isLine(this.doc, line)) return null;
         var n = line;
         line = getLine(this.doc, line);
         if (!line) return null;
       } else {
         var n = lineNo(line);
         if (n == null) return null;
       }
       return {line: n, handle: line, text: line.text, gutterMarkers: line.gutterMarkers,
               textClass: line.textClass, bgClass: line.bgClass, wrapClass: line.wrapClass,
               widgets: line.widgets};
     },
 
-    getViewport: function() { return {from: this.display.showingFrom, to: this.display.showingTo};},
+    getViewport: function() { return {from: this.display.viewFrom, to: this.display.viewTo};},
 
     addWidget: function(pos, node, scroll, vert, horiz) {
       var display = this.display;
       pos = cursorCoords(this, clipPos(this.doc, pos));
       var top = pos.bottom, left = pos.left;
       node.style.position = "absolute";
       display.sizer.appendChild(node);
       if (vert == "over") {
         top = pos.top;
       } else if (vert == "above" || vert == "near") {
@@ skipping 14 matching lines @@
         node.style.right = "0px";
       } else {
         if (horiz == "left") left = 0;
         else if (horiz == "middle") left = (display.sizer.clientWidth - node.offsetWidth) / 2;
         node.style.left = left + "px";
       }
       if (scroll)
         scrollIntoView(this, left, top, left + node.offsetWidth, top + node.offsetHeight);
     },
 
-    triggerOnKeyDown: operation(null, onKeyDown),
-    triggerOnKeyPress: operation(null, onKeyPress),
-    triggerOnKeyUp: operation(null, onKeyUp),
+    triggerOnKeyDown: methodOp(onKeyDown),
+    triggerOnKeyPress: methodOp(onKeyPress),
+    triggerOnKeyUp: methodOp(onKeyUp),
 
     execCommand: function(cmd) {
       if (commands.hasOwnProperty(cmd))
         return commands[cmd](this);
     },
 
     findPosH: function(from, amount, unit, visually) {
       var dir = 1;
       if (amount < 0) { dir = -1; amount = -amount; }
       for (var i = 0, cur = clipPos(this.doc, from); i < amount; ++i) {
         cur = findPosH(this.doc, cur, dir, unit, visually);
         if (cur.hitSide) break;
       }
       return cur;
     },
 
-    moveH: operation(null, function(dir, unit) {
-      var sel = this.doc.sel, pos;
-      if (sel.shift || sel.extend || posEq(sel.from, sel.to))
-        pos = findPosH(this.doc, sel.head, dir, unit, this.options.rtlMoveVisually);
-      else
-        pos = dir < 0 ? sel.from : sel.to;
-      extendSelection(this.doc, pos, pos, dir);
+    moveH: methodOp(function(dir, unit) {
+      var cm = this;
+      cm.extendSelectionsBy(function(range) {
+        if (cm.display.shift || cm.doc.extend || range.empty())
+          return findPosH(cm.doc, range.head, dir, unit, cm.options.rtlMoveVisually);
+        else
+          return dir < 0 ? range.from() : range.to();
+      }, sel_move);
     }),
 
-    deleteH: operation(null, function(dir, unit) {
-      var sel = this.doc.sel;
-      if (!posEq(sel.from, sel.to)) replaceRange(this.doc, "", sel.from, sel.to, "+delete");
-      else replaceRange(this.doc, "", sel.from, findPosH(this.doc, sel.head, dir, unit, false), "+delete");
-      this.curOp.userSelChange = true;
+    deleteH: methodOp(function(dir, unit) {
+      var sel = this.doc.sel, doc = this.doc;
+      if (sel.somethingSelected())
+        doc.replaceSelection("", null, "+delete");
+      else
+        deleteNearSelection(this, function(range) {
+          var other = findPosH(doc, range.head, dir, unit, false);
+          return dir < 0 ? {from: other, to: range.head} : {from: range.head, to: other};
+        });
     }),
 
     findPosV: function(from, amount, unit, goalColumn) {
       var dir = 1, x = goalColumn;
       if (amount < 0) { dir = -1; amount = -amount; }
       for (var i = 0, cur = clipPos(this.doc, from); i < amount; ++i) {
         var coords = cursorCoords(this, cur, "div");
         if (x == null) x = coords.left;
         else coords.left = x;
         cur = findPosV(this, coords, dir, unit);
         if (cur.hitSide) break;
       }
       return cur;
     },
 
-    moveV: operation(null, function(dir, unit) {
-      var sel = this.doc.sel, target, goal;
-      if (sel.shift || sel.extend || posEq(sel.from, sel.to)) {
-        var pos = cursorCoords(this, sel.head, "div");
-        if (sel.goalColumn != null) pos.left = sel.goalColumn;
-        target = findPosV(this, pos, dir, unit);
-        if (unit == "page") addToScrollPos(this, 0, charCoords(this, target, "div").top - pos.top);
-        goal = pos.left;
-      } else {
-        target = dir < 0 ? sel.from : sel.to;
-      }
-      extendSelection(this.doc, target, target, dir);
-      if (goal != null) sel.goalColumn = goal;
+    moveV: methodOp(function(dir, unit) {
+      var cm = this, doc = this.doc, goals = [];
+      var collapse = !cm.display.shift && !doc.extend && doc.sel.somethingSelected();
+      doc.extendSelectionsBy(function(range) {
+        if (collapse)
+          return dir < 0 ? range.from() : range.to();
+        var headPos = cursorCoords(cm, range.head, "div");
+        if (range.goalColumn != null) headPos.left = range.goalColumn;
+        goals.push(headPos.left);
+        var pos = findPosV(cm, headPos, dir, unit);
+        if (unit == "page" && range == doc.sel.primary())
+          addToScrollPos(cm, null, charCoords(cm, pos, "div").top - headPos.top);
+        return pos;
+      }, sel_move);
+      if (goals.length) for (var i = 0; i < doc.sel.ranges.length; i++)
+        doc.sel.ranges[i].goalColumn = goals[i];
     }),
 
     toggleOverwrite: function(value) {
       if (value != null && value == this.state.overwrite) return;
       if (this.state.overwrite = !this.state.overwrite)
-        this.display.cursor.className += " CodeMirror-overwrite";
+        this.display.cursorDiv.className += " CodeMirror-overwrite";
       else
-        this.display.cursor.className = this.display.cursor.className.replace(" CodeMirror-overwrite", "");
+        this.display.cursorDiv.className = this.display.cursorDiv.className.replace(" CodeMirror-overwrite", "");
+
+      signal(this, "overwriteToggle", this, this.state.overwrite);
     },
-    hasFocus: function() { return document.activeElement == this.display.input; },
+    hasFocus: function() { return activeElt() == this.display.input; },
 
-    scrollTo: operation(null, function(x, y) {
-      updateScrollPos(this, x, y);
+    scrollTo: methodOp(function(x, y) {
+      if (x != null || y != null) resolveScrollToPos(this);
+      if (x != null) this.curOp.scrollLeft = x;
+      if (y != null) this.curOp.scrollTop = y;
     }),
     getScrollInfo: function() {
       var scroller = this.display.scroller, co = scrollerCutOff;
       return {left: scroller.scrollLeft, top: scroller.scrollTop,
               height: scroller.scrollHeight - co, width: scroller.scrollWidth - co,
               clientHeight: scroller.clientHeight - co, clientWidth: scroller.clientWidth - co};
     },
 
-    scrollIntoView: operation(null, function(range, margin) {
-      if (range == null) range = {from: this.doc.sel.head, to: null};
-      else if (typeof range == "number") range = {from: Pos(range, 0), to: null};
-      else if (range.from == null) range = {from: range, to: null};
+    scrollIntoView: methodOp(function(range, margin) {
+      if (range == null) {
+        range = {from: this.doc.sel.primary().head, to: null};
+        if (margin == null) margin = this.options.cursorScrollMargin;
+      } else if (typeof range == "number") {
+        range = {from: Pos(range, 0), to: null};
+      } else if (range.from == null) {
+        range = {from: range, to: null};
+      }
       if (!range.to) range.to = range.from;
-      if (!margin) margin = 0;
+      range.margin = margin || 0;
 
-      var coords = range;
       if (range.from.line != null) {
-        this.curOp.scrollToPos = {from: range.from, to: range.to, margin: margin};
-        coords = {from: cursorCoords(this, range.from),
-                  to: cursorCoords(this, range.to)};
+        resolveScrollToPos(this);
+        this.curOp.scrollToPos = range;
+      } else {
+        var sPos = calculateScrollPos(this, Math.min(range.from.left, range.to.left),
+                                      Math.min(range.from.top, range.to.top) - range.margin,
+                                      Math.max(range.from.right, range.to.right),
+                                      Math.max(range.from.bottom, range.to.bottom) + range.margin);
+        this.scrollTo(sPos.scrollLeft, sPos.scrollTop);
       }
-      var sPos = calculateScrollPos(this, Math.min(coords.from.left, coords.to.left),
-                                    Math.min(coords.from.top, coords.to.top) - margin,
-                                    Math.max(coords.from.right, coords.to.right),
-                                    Math.max(coords.from.bottom, coords.to.bottom) + margin);
-      updateScrollPos(this, sPos.scrollLeft, sPos.scrollTop);
     }),
 
-    setSize: operation(null, function(width, height) {
+    setSize: methodOp(function(width, height) {
       function interpret(val) {
         return typeof val == "number" || /^\d+$/.test(String(val)) ? val + "px" : val;
       }
       if (width != null) this.display.wrapper.style.width = interpret(width);
       if (height != null) this.display.wrapper.style.height = interpret(height);
-      if (this.options.lineWrapping)
-        this.display.measureLineCache.length = this.display.measureLineCachePos = 0;
+      if (this.options.lineWrapping) clearLineMeasurementCache(this);
       this.curOp.forceUpdate = true;
       signal(this, "refresh", this);
     }),
 
     operation: function(f){return runInOp(this, f);},
 
-    refresh: operation(null, function() {
+    refresh: methodOp(function() {
       var oldHeight = this.display.cachedTextHeight;
+      regChange(this);
       clearCaches(this);
-      updateScrollPos(this, this.doc.scrollLeft, this.doc.scrollTop);
-      regChange(this);
+      this.scrollTo(this.doc.scrollLeft, this.doc.scrollTop);
       if (oldHeight == null || Math.abs(oldHeight - textHeight(this.display)) > .5)
         estimateLineHeights(this);
       signal(this, "refresh", this);
     }),
 
-    swapDoc: operation(null, function(doc) {
+    swapDoc: methodOp(function(doc) {
       var old = this.doc;
       old.cm = null;
       attachDoc(this, doc);
       clearCaches(this);
-      resetInput(this, true);
-      updateScrollPos(this, doc.scrollLeft, doc.scrollTop);
+      resetInput(this);
+      this.scrollTo(doc.scrollLeft, doc.scrollTop);
       signalLater(this, "swapDoc", this, old);
       return old;
     }),
 
     getInputField: function(){return this.display.input;},
     getWrapperElement: function(){return this.display.wrapper;},
     getScrollerElement: function(){return this.display.scroller;},
     getGutterElement: function(){return this.display.gutters;}
   };
   eventMixin(CodeMirror);
 
   // OPTION DEFAULTS
 
-  var optionHandlers = CodeMirror.optionHandlers = {};
-
   // The default configuration options.
   var defaults = CodeMirror.defaults = {};
+  // Functions to run when options are changed.
+  var optionHandlers = CodeMirror.optionHandlers = {};
 
   function option(name, deflt, handle, notOnInit) {
     CodeMirror.defaults[name] = deflt;
     if (handle) optionHandlers[name] =
       notOnInit ? function(cm, val, old) {if (old != Init) handle(cm, val, old);} : handle;
   }
 
+  // Passed to option handlers when there is no old value.
   var Init = CodeMirror.Init = {toString: function(){return "CodeMirror.Init";}};
 
   // These two are, on init, called from the constructor because they
   // have to be initialized before the editor can start at all.
   option("value", "", function(cm, val) {
     cm.setValue(val);
   }, true);
   option("mode", null, function(cm, val) {
     cm.doc.modeOption = val;
     loadMode(cm);
@@ skipping 16 matching lines @@
   option("rtlMoveVisually", !windows);
   option("wholeLineUpdateBefore", true);
 
   option("theme", "default", function(cm) {
     themeChanged(cm);
     guttersChanged(cm);
   }, true);
   option("keyMap", "default", keyMapChanged);
   option("extraKeys", null);
 
-  option("onKeyEvent", null);
-  option("onDragEvent", null);
-
   option("lineWrapping", false, wrappingChanged, true);
   option("gutters", [], function(cm) {
     setGuttersForLineNumbers(cm.options);
     guttersChanged(cm);
   }, true);
   option("fixedGutter", true, function(cm, val) {
     cm.display.gutters.style.left = val ? compensateForHScroll(cm.display) + "px" : "0";
     cm.refresh();
   }, true);
   option("coverGutterNextToScrollbar", false, updateScrollbars, true);
   option("lineNumbers", false, function(cm) {
     setGuttersForLineNumbers(cm.options);
     guttersChanged(cm);
   }, true);
   option("firstLineNumber", 1, guttersChanged, true);
   option("lineNumberFormatter", function(integer) {return integer;}, guttersChanged, true);
   option("showCursorWhenSelecting", false, updateSelection, true);
 
   option("resetSelectionOnContextMenu", true);
 
   option("readOnly", false, function(cm, val) {
     if (val == "nocursor") {
       onBlur(cm);
       cm.display.input.blur();
       cm.display.disabled = true;
     } else {
       cm.display.disabled = false;
-      if (!val) resetInput(cm, true);
+      if (!val) resetInput(cm);
     }
   });
-  option("disableInput", false, function(cm, val) {if (!val) resetInput(cm, true);}, true);
+  option("disableInput", false, function(cm, val) {if (!val) resetInput(cm);}, true);
   option("dragDrop", true);
 
   option("cursorBlinkRate", 530);
   option("cursorScrollMargin", 0);
   option("cursorHeight", 1);
   option("workTime", 100);
   option("workDelay", 100);
   option("flattenSpans", true, resetModeState, true);
   option("addModeClass", false, resetModeState, true);
   option("pollInterval", 100);
-  option("undoDepth", 40, function(cm, val){cm.doc.history.undoDepth = val;});
-  option("historyEventDelay", 500);
+  option("undoDepth", 200, function(cm, val){cm.doc.history.undoDepth = val;});
+  option("historyEventDelay", 1250);
   option("viewportMargin", 10, function(cm){cm.refresh();}, true);
   option("maxHighlightLength", 10000, resetModeState, true);
-  option("crudeMeasuringFrom", 10000);
   option("moveInputWithCursor", true, function(cm, val) {
     if (!val) cm.display.inputDiv.style.top = cm.display.inputDiv.style.left = 0;
   });
 
   option("tabindex", null, function(cm, val) {
     cm.display.input.tabIndex = val || "";
   });
   option("autofocus", null);
 
   // MODE DEFINITION AND QUERYING
 
   // Known modes, by name and by MIME
   var modes = CodeMirror.modes = {}, mimeModes = CodeMirror.mimeModes = {};
 
+  // Extra arguments are stored as the mode's dependencies, which is
+  // used by (legacy) mechanisms like loadmode.js to automatically
+  // load a mode. (Preferred mechanism is the require/define calls.)
   CodeMirror.defineMode = function(name, mode) {
     if (!CodeMirror.defaults.mode && name != "null") CodeMirror.defaults.mode = name;
     if (arguments.length > 2) {
       mode.dependencies = [];
       for (var i = 2; i < arguments.length; ++i) mode.dependencies.push(arguments[i]);
     }
     modes[name] = mode;
   };
 
   CodeMirror.defineMIME = function(mime, spec) {
     mimeModes[mime] = spec;
   };
 
+  // Given a MIME type, a {name, ...options} config object, or a name
+  // string, return a mode config object.
   CodeMirror.resolveMode = function(spec) {
     if (typeof spec == "string" && mimeModes.hasOwnProperty(spec)) {
       spec = mimeModes[spec];
     } else if (spec && typeof spec.name == "string" && mimeModes.hasOwnProperty(spec.name)) {
       var found = mimeModes[spec.name];
+      if (typeof found == "string") found = {name: found};
       spec = createObj(found, spec);
       spec.name = found.name;
     } else if (typeof spec == "string" && /^[\w\-]+\/[\w\-]+\+xml$/.test(spec)) {
       return CodeMirror.resolveMode("application/xml");
     }
     if (typeof spec == "string") return {name: spec};
     else return spec || {name: "null"};
   };
 
+  // Given a mode spec (anything that resolveMode accepts), find and
+  // initialize an actual mode object.
   CodeMirror.getMode = function(options, spec) {
     var spec = CodeMirror.resolveMode(spec);
     var mfactory = modes[spec.name];
     if (!mfactory) return CodeMirror.getMode(options, "text/plain");
     var modeObj = mfactory(options, spec);
     if (modeExtensions.hasOwnProperty(spec.name)) {
       var exts = modeExtensions[spec.name];
       for (var prop in exts) {
         if (!exts.hasOwnProperty(prop)) continue;
         if (modeObj.hasOwnProperty(prop)) modeObj["_" + prop] = modeObj[prop];
         modeObj[prop] = exts[prop];
       }
     }
     modeObj.name = spec.name;
     if (spec.helperType) modeObj.helperType = spec.helperType;
     if (spec.modeProps) for (var prop in spec.modeProps)
       modeObj[prop] = spec.modeProps[prop];
 
     return modeObj;
   };
 
+  // Minimal default mode.
   CodeMirror.defineMode("null", function() {
     return {token: function(stream) {stream.skipToEnd();}};
   });
   CodeMirror.defineMIME("text/plain", "null");
 
+  // This can be used to attach properties to mode objects from
+  // outside the actual mode definition.
   var modeExtensions = CodeMirror.modeExtensions = {};
   CodeMirror.extendMode = function(mode, properties) {
     var exts = modeExtensions.hasOwnProperty(mode) ? modeExtensions[mode] : (modeExtensions[mode] = {});
     copyObj(properties, exts);
   };
 
   // EXTENSIONS
 
   CodeMirror.defineExtension = function(name, func) {
     CodeMirror.prototype[name] = func;
   };
   CodeMirror.defineDocExtension = function(name, func) {
     Doc.prototype[name] = func;
   };
   CodeMirror.defineOption = option;
 
   var initHooks = [];
   CodeMirror.defineInitHook = function(f) {initHooks.push(f);};
 
   var helpers = CodeMirror.helpers = {};
   CodeMirror.registerHelper = function(type, name, value) {
     if (!helpers.hasOwnProperty(type)) helpers[type] = CodeMirror[type] = {_global: []};
     helpers[type][name] = value;
   };
   CodeMirror.registerGlobalHelper = function(type, name, predicate, value) {
     CodeMirror.registerHelper(type, name, value);
     helpers[type]._global.push({pred: predicate, val: value});
   };
 
-  // UTILITIES
-
-  CodeMirror.isWordChar = isWordChar;
-
   // MODE STATE HANDLING
 
-  // Utility functions for working with state. Exported because modes
-  // sometimes need to do this.
-  function copyState(mode, state) {
+  // Utility functions for working with state. Exported because nested
+  // modes need to do this for their inner modes.
+
+  var copyState = CodeMirror.copyState = function(mode, state) {
     if (state === true) return state;
     if (mode.copyState) return mode.copyState(state);
     var nstate = {};
     for (var n in state) {
       var val = state[n];
       if (val instanceof Array) val = val.concat([]);
       nstate[n] = val;
     }
     return nstate;
-  }
-  CodeMirror.copyState = copyState;
+  };
 
-  function startState(mode, a1, a2) {
+  var startState = CodeMirror.startState = function(mode, a1, a2) {
     return mode.startState ? mode.startState(a1, a2) : true;
-  }
-  CodeMirror.startState = startState;
+  };
 
+  // Given a mode and a state (for that mode), find the inner mode and
+  // state at the position that the state refers to.
   CodeMirror.innerMode = function(mode, state) {
     while (mode.innerMode) {
       var info = mode.innerMode(state);
       if (!info || info.mode == mode) break;
       state = info.state;
       mode = info.mode;
     }
     return info || {mode: mode, state: state};
   };
 
   // STANDARD COMMANDS
 
+  // Commands are parameter-less actions that can be performed on an
+  // editor, mostly used for keybindings.
   var commands = CodeMirror.commands = {
-    selectAll: function(cm) {cm.setSelection(Pos(cm.firstLine(), 0), Pos(cm.lastLine()));},
+    selectAll: function(cm) {cm.setSelection(Pos(cm.firstLine(), 0), Pos(cm.lastLine()), sel_dontScroll);},
+    singleSelection: function(cm) {
+      cm.setSelection(cm.getCursor("anchor"), cm.getCursor("head"), sel_dontScroll);
+    },
     killLine: function(cm) {
-      var from = cm.getCursor(true), to = cm.getCursor(false), sel = !posEq(from, to);
-      if (!sel && cm.getLine(from.line).length == from.ch)
-        cm.replaceRange("", from, Pos(from.line + 1, 0), "+delete");
-      else cm.replaceRange("", from, sel ? to : Pos(from.line), "+delete");
+      deleteNearSelection(cm, function(range) {
+        if (range.empty()) {
+          var len = getLine(cm.doc, range.head.line).text.length;
+          if (range.head.ch == len && range.head.line < cm.lastLine())
+            return {from: range.head, to: Pos(range.head.line + 1, 0)};
+          else
+            return {from: range.head, to: Pos(range.head.line, len)};
+        } else {
+          return {from: range.from(), to: range.to()};
+        }
+      });
     },
     deleteLine: function(cm) {
-      var l = cm.getCursor().line;
-      cm.replaceRange("", Pos(l, 0), Pos(l), "+delete");
+      deleteNearSelection(cm, function(range) {
+        return {from: Pos(range.from().line, 0),
+                to: clipPos(cm.doc, Pos(range.to().line + 1, 0))};
+      });
     },
     delLineLeft: function(cm) {
-      var cur = cm.getCursor();
-      cm.replaceRange("", Pos(cur.line, 0), cur, "+delete");
+      deleteNearSelection(cm, function(range) {
+        return {from: Pos(range.from().line, 0), to: range.from()};
+      });
     },
     undo: function(cm) {cm.undo();},
     redo: function(cm) {cm.redo();},
+    undoSelection: function(cm) {cm.undoSelection();},
+    redoSelection: function(cm) {cm.redoSelection();},
     goDocStart: function(cm) {cm.extendSelection(Pos(cm.firstLine(), 0));},
     goDocEnd: function(cm) {cm.extendSelection(Pos(cm.lastLine()));},
     goLineStart: function(cm) {
-      cm.extendSelection(lineStart(cm, cm.getCursor().line));
+      cm.extendSelectionsBy(function(range) { return lineStart(cm, range.head.line); }, sel_move);
     },
     goLineStartSmart: function(cm) {
-      var cur = cm.getCursor(), start = lineStart(cm, cur.line);
-      var line = cm.getLineHandle(start.line);
-      var order = getOrder(line);
-      if (!order || order[0].level == 0) {
-        var firstNonWS = Math.max(0, line.text.search(/\S/));
-        var inWS = cur.line == start.line && cur.ch <= firstNonWS && cur.ch;
-        cm.extendSelection(Pos(start.line, inWS ? 0 : firstNonWS));
-      } else cm.extendSelection(start);
+      cm.extendSelectionsBy(function(range) {
+        var start = lineStart(cm, range.head.line);
+        var line = cm.getLineHandle(start.line);
+        var order = getOrder(line);
+        if (!order || order[0].level == 0) {
+          var firstNonWS = Math.max(0, line.text.search(/\S/));
+          var inWS = range.head.line == start.line && range.head.ch <= firstNonWS && range.head.ch;
+          return Pos(start.line, inWS ? 0 : firstNonWS);
+        }
+        return start;
+      }, sel_move);
     },
     goLineEnd: function(cm) {
-      cm.extendSelection(lineEnd(cm, cm.getCursor().line));
+      cm.extendSelectionsBy(function(range) { return lineEnd(cm, range.head.line); }, sel_move);
     },
     goLineRight: function(cm) {
-      var top = cm.charCoords(cm.getCursor(), "div").top + 5;
-      cm.extendSelection(cm.coordsChar({left: cm.display.lineDiv.offsetWidth + 100, top: top}, "div"));
+      cm.extendSelectionsBy(function(range) {
+        var top = cm.charCoords(range.head, "div").top + 5;
+        return cm.coordsChar({left: cm.display.lineDiv.offsetWidth + 100, top: top}, "div");
+      }, sel_move);
     },
     goLineLeft: function(cm) {
-      var top = cm.charCoords(cm.getCursor(), "div").top + 5;
-      cm.extendSelection(cm.coordsChar({left: 0, top: top}, "div"));
+      cm.extendSelectionsBy(function(range) {
+        var top = cm.charCoords(range.head, "div").top + 5;
+        return cm.coordsChar({left: 0, top: top}, "div");
+      }, sel_move);
     },
     goLineUp: function(cm) {cm.moveV(-1, "line");},
     goLineDown: function(cm) {cm.moveV(1, "line");},
     goPageUp: function(cm) {cm.moveV(-1, "page");},
     goPageDown: function(cm) {cm.moveV(1, "page");},
     goCharLeft: function(cm) {cm.moveH(-1, "char");},
     goCharRight: function(cm) {cm.moveH(1, "char");},
     goColumnLeft: function(cm) {cm.moveH(-1, "column");},
     goColumnRight: function(cm) {cm.moveH(1, "column");},
     goWordLeft: function(cm) {cm.moveH(-1, "word");},
     goGroupRight: function(cm) {cm.moveH(1, "group");},
     goGroupLeft: function(cm) {cm.moveH(-1, "group");},
     goWordRight: function(cm) {cm.moveH(1, "word");},
     delCharBefore: function(cm) {cm.deleteH(-1, "char");},
     delCharAfter: function(cm) {cm.deleteH(1, "char");},
     delWordBefore: function(cm) {cm.deleteH(-1, "word");},
     delWordAfter: function(cm) {cm.deleteH(1, "word");},
     delGroupBefore: function(cm) {cm.deleteH(-1, "group");},
     delGroupAfter: function(cm) {cm.deleteH(1, "group");},
     indentAuto: function(cm) {cm.indentSelection("smart");},
     indentMore: function(cm) {cm.indentSelection("add");},
     indentLess: function(cm) {cm.indentSelection("subtract");},
-    insertTab: function(cm) {
-      cm.replaceSelection("\t", "end", "+input");
-    },
+    insertTab: function(cm) {cm.replaceSelection("\t");},
     defaultTab: function(cm) {
       if (cm.somethingSelected()) cm.indentSelection("add");
-      else cm.replaceSelection("\t", "end", "+input");
+      else cm.execCommand("insertTab");
     },
     transposeChars: function(cm) {
-      var cur = cm.getCursor(), line = cm.getLine(cur.line);
-      if (cur.ch > 0 && cur.ch < line.length - 1)
-        cm.replaceRange(line.charAt(cur.ch) + line.charAt(cur.ch - 1),
-                        Pos(cur.line, cur.ch - 1), Pos(cur.line, cur.ch + 1));
+      runInOp(cm, function() {
+        var ranges = cm.listSelections();
+        for (var i = 0; i < ranges.length; i++) {
+          var cur = ranges[i].head, line = getLine(cm.doc, cur.line).text;
+          if (cur.ch > 0 && cur.ch < line.length - 1)
+            cm.replaceRange(line.charAt(cur.ch) + line.charAt(cur.ch - 1),
+                            Pos(cur.line, cur.ch - 1), Pos(cur.line, cur.ch + 1));
+        }
+      });
     },
     newlineAndIndent: function(cm) {
-      operation(cm, function() {
-        cm.replaceSelection("\n", "end", "+input");
-        cm.indentLine(cm.getCursor().line, null, true);
-      })();
+      runInOp(cm, function() {
+        var len = cm.listSelections().length;
+        for (var i = 0; i < len; i++) {
+          var range = cm.listSelections()[i];
+          cm.replaceRange("\n", range.anchor, range.head, "+input");
+          cm.indentLine(range.from().line + 1, null, true);
+          ensureCursorVisible(cm);
+        }
+      });
     },
     toggleOverwrite: function(cm) {cm.toggleOverwrite();}
   };
 
   // STANDARD KEYMAPS
 
   var keyMap = CodeMirror.keyMap = {};
   keyMap.basic = {
     "Left": "goCharLeft", "Right": "goCharRight", "Up": "goLineUp", "Down": "goLineDown",
     "End": "goLineEnd", "Home": "goLineStartSmart", "PageUp": "goPageUp", "PageDown": "goPageDown",
     "Delete": "delCharAfter", "Backspace": "delCharBefore", "Shift-Backspace": "delCharBefore",
     "Tab": "defaultTab", "Shift-Tab": "indentAuto",
-    "Enter": "newlineAndIndent", "Insert": "toggleOverwrite"
+    "Enter": "newlineAndIndent", "Insert": "toggleOverwrite",
+    "Esc": "singleSelection"
   };
   // Note that the save and find-related commands aren't defined by
-  // default. Unknown commands are simply ignored.
+  // default. User code or addons can define them. Unknown commands
+  // are simply ignored.
   keyMap.pcDefault = {
     "Ctrl-A": "selectAll", "Ctrl-D": "deleteLine", "Ctrl-Z": "undo", "Shift-Ctrl-Z": "redo", "Ctrl-Y": "redo",
-    "Ctrl-Home": "goDocStart", "Alt-Up": "goDocStart", "Ctrl-End": "goDocEnd", "Ctrl-Down": "goDocEnd",
+    "Ctrl-Home": "goDocStart", "Ctrl-Up": "goDocStart", "Ctrl-End": "goDocEnd", "Ctrl-Down": "goDocEnd",
     "Ctrl-Left": "goGroupLeft", "Ctrl-Right": "goGroupRight", "Alt-Left": "goLineStart", "Alt-Right": "goLineEnd",
     "Ctrl-Backspace": "delGroupBefore", "Ctrl-Delete": "delGroupAfter", "Ctrl-S": "save", "Ctrl-F": "find",
     "Ctrl-G": "findNext", "Shift-Ctrl-G": "findPrev", "Shift-Ctrl-F": "replace", "Shift-Ctrl-R": "replaceAll",
     "Ctrl-[": "indentLess", "Ctrl-]": "indentMore",
+    "Ctrl-U": "undoSelection", "Shift-Ctrl-U": "redoSelection", "Alt-U": "redoSelection",
     fallthrough: "basic"
   };
   keyMap.macDefault = {
     "Cmd-A": "selectAll", "Cmd-D": "deleteLine", "Cmd-Z": "undo", "Shift-Cmd-Z": "redo", "Cmd-Y": "redo",
     "Cmd-Up": "goDocStart", "Cmd-End": "goDocEnd", "Cmd-Down": "goDocEnd", "Alt-Left": "goGroupLeft",
     "Alt-Right": "goGroupRight", "Cmd-Left": "goLineStart", "Cmd-Right": "goLineEnd", "Alt-Backspace": "delGroupBefore",
     "Ctrl-Alt-Backspace": "delGroupAfter", "Alt-Delete": "delGroupAfter", "Cmd-S": "save", "Cmd-F": "find",
     "Cmd-G": "findNext", "Shift-Cmd-G": "findPrev", "Cmd-Alt-F": "replace", "Shift-Cmd-Alt-F": "replaceAll",
     "Cmd-[": "indentLess", "Cmd-]": "indentMore", "Cmd-Backspace": "delLineLeft",
+    "Cmd-U": "undoSelection", "Shift-Cmd-U": "redoSelection",
     fallthrough: ["basic", "emacsy"]
   };
-  keyMap["default"] = mac ? keyMap.macDefault : keyMap.pcDefault;
+  // Very basic readline/emacs-style bindings, which are standard on Mac.
   keyMap.emacsy = {
     "Ctrl-F": "goCharRight", "Ctrl-B": "goCharLeft", "Ctrl-P": "goLineUp", "Ctrl-N": "goLineDown",
     "Alt-F": "goWordRight", "Alt-B": "goWordLeft", "Ctrl-A": "goLineStart", "Ctrl-E": "goLineEnd",
     "Ctrl-V": "goPageDown", "Shift-Ctrl-V": "goPageUp", "Ctrl-D": "delCharAfter", "Ctrl-H": "delCharBefore",
     "Alt-D": "delWordAfter", "Alt-Backspace": "delWordBefore", "Ctrl-K": "killLine", "Ctrl-T": "transposeChars"
   };
+  keyMap["default"] = mac ? keyMap.macDefault : keyMap.pcDefault;
 
   // KEYMAP DISPATCH
 
   function getKeyMap(val) {
     if (typeof val == "string") return keyMap[val];
     else return val;
   }
 
-  function lookupKey(name, maps, handle) {
+  // Given an array of keymaps and a key name, call handle on any
+  // bindings found, until that returns a truthy value, at which point
+  // we consider the key handled. Implements things like binding a key
+  // to false stopping further handling and keymap fallthrough.
+  var lookupKey = CodeMirror.lookupKey = function(name, maps, handle) {
     function lookup(map) {
       map = getKeyMap(map);
       var found = map[name];
       if (found === false) return "stop";
       if (found != null && handle(found)) return true;
       if (map.nofallthrough) return "stop";
 
       var fallthrough = map.fallthrough;
       if (fallthrough == null) return false;
       if (Object.prototype.toString.call(fallthrough) != "[object Array]")
         return lookup(fallthrough);
-      for (var i = 0, e = fallthrough.length; i < e; ++i) {
+      for (var i = 0; i < fallthrough.length; ++i) {
         var done = lookup(fallthrough[i]);
         if (done) return done;
       }
       return false;
     }
 
     for (var i = 0; i < maps.length; ++i) {
       var done = lookup(maps[i]);
       if (done) return done != "stop";
     }
-  }
-  function isModifierKey(event) {
+  };
+
+  // Modifier key presses don't count as 'real' key presses for the
+  // purpose of keymap fallthrough.
+  var isModifierKey = CodeMirror.isModifierKey = function(event) {
     var name = keyNames[event.keyCode];
     return name == "Ctrl" || name == "Alt" || name == "Shift" || name == "Mod";
-  }
-  function keyName(event, noShift) {
-    if (opera && event.keyCode == 34 && event["char"]) return false;
+  };
+
+  // Look up the name of a key as indicated by an event object.
+  var keyName = CodeMirror.keyName = function(event, noShift) {
+    if (presto && event.keyCode == 34 && event["char"]) return false;
     var name = keyNames[event.keyCode];
     if (name == null || event.altGraphKey) return false;
     if (event.altKey) name = "Alt-" + name;
     if (flipCtrlCmd ? event.metaKey : event.ctrlKey) name = "Ctrl-" + name;
     if (flipCtrlCmd ? event.ctrlKey : event.metaKey) name = "Cmd-" + name;
     if (!noShift && event.shiftKey) name = "Shift-" + name;
     return name;
-  }
-  CodeMirror.lookupKey = lookupKey;
-  CodeMirror.isModifierKey = isModifierKey;
-  CodeMirror.keyName = keyName;
+  };
 
   // FROMTEXTAREA
 
   CodeMirror.fromTextArea = function(textarea, options) {
     if (!options) options = {};
     options.value = textarea.value;
     if (!options.tabindex && textarea.tabindex)
       options.tabindex = textarea.tabindex;
     if (!options.placeholder && textarea.placeholder)
       options.placeholder = textarea.placeholder;
     // Set autofocus to true if this textarea is focused, or if it has
     // autofocus and no other element is focused.
     if (options.autofocus == null) {
-      var hasFocus = document.body;
-      // doc.activeElement occasionally throws on IE
-      try { hasFocus = document.activeElement; } catch(e) {}
+      var hasFocus = activeElt();
       options.autofocus = hasFocus == textarea ||
         textarea.getAttribute("autofocus") != null && hasFocus == document.body;
     }
 
     function save() {textarea.value = cm.getValue();}
     if (textarea.form) {
       on(textarea.form, "submit", save);
       // Deplorable hack to make the submit method do the right thing.
       if (!options.leaveSubmitMethodAlone) {
         var form = textarea.form, realSubmit = form.submit;
@@ skipping 25 matching lines @@
       }
     };
     return cm;
   };
 
   // STRING STREAM
 
   // Fed to the mode parsers, provides helper functions to make
   // parsers more succinct.
 
-  // The character stream used by a mode's parser.
-  function StringStream(string, tabSize) {
+  var StringStream = CodeMirror.StringStream = function(string, tabSize) {
     this.pos = this.start = 0;
     this.string = string;
     this.tabSize = tabSize || 8;
     this.lastColumnPos = this.lastColumnValue = 0;
     this.lineStart = 0;
-  }
+  };
 
   StringStream.prototype = {
     eol: function() {return this.pos >= this.string.length;},
     sol: function() {return this.pos == this.lineStart;},
     peek: function() {return this.string.charAt(this.pos) || undefined;},
     next: function() {
       if (this.pos < this.string.length)
         return this.string.charAt(this.pos++);
     },
     eat: function(match) {
@@ skipping 44 matching lines @@
         return match;
       }
     },
     current: function(){return this.string.slice(this.start, this.pos);},
     hideFirstChars: function(n, inner) {
       this.lineStart += n;
       try { return inner(); }
       finally { this.lineStart -= n; }
     }
   };
-  CodeMirror.StringStream = StringStream;
 
   // TEXTMARKERS
 
-  function TextMarker(doc, type) {
+  // Created with markText and setBookmark methods. A TextMarker is a
+  // handle that can be used to clear or find a marked position in the
+  // document. Line objects hold arrays (markedSpans) containing
+  // {from, to, marker} object pointing to such marker objects, and
+  // indicating that such a marker is present on that line. Multiple
+  // lines may point to the same marker when it spans across lines.
+  // The spans will have null for their from/to properties when the
+  // marker continues beyond the start/end of the line. Markers have
+  // links back to the lines they currently touch.
+
+  var TextMarker = CodeMirror.TextMarker = function(doc, type) {
     this.lines = [];
     this.type = type;
     this.doc = doc;
-  }
-  CodeMirror.TextMarker = TextMarker;
+  };
   eventMixin(TextMarker);
 
+  // Clear the marker.
   TextMarker.prototype.clear = function() {
     if (this.explicitlyCleared) return;
     var cm = this.doc.cm, withOp = cm && !cm.curOp;
     if (withOp) startOperation(cm);
     if (hasHandler(this, "clear")) {
       var found = this.find();
       if (found) signalLater(this, "clear", found.from, found.to);
     }
     var min = null, max = null;
     for (var i = 0; i < this.lines.length; ++i) {
       var line = this.lines[i];
       var span = getMarkedSpanFor(line.markedSpans, this);
-      if (span.to != null) max = lineNo(line);
+      if (cm && !this.collapsed) regLineChange(cm, lineNo(line), "text");
+      else if (cm) {
+        if (span.to != null) max = lineNo(line);
+        if (span.from != null) min = lineNo(line);
+      }
       line.markedSpans = removeMarkedSpan(line.markedSpans, span);
-      if (span.from != null)
-        min = lineNo(line);
-      else if (this.collapsed && !lineIsHidden(this.doc, line) && cm)
+      if (span.from == null && this.collapsed && !lineIsHidden(this.doc, line) && cm)
         updateLineHeight(line, textHeight(cm.display));
     }
     if (cm && this.collapsed && !cm.options.lineWrapping) for (var i = 0; i < this.lines.length; ++i) {
-      var visual = visualLine(cm.doc, this.lines[i]), len = lineLength(cm.doc, visual);
+      var visual = visualLine(this.lines[i]), len = lineLength(visual);
       if (len > cm.display.maxLineLength) {
         cm.display.maxLine = visual;
         cm.display.maxLineLength = len;
         cm.display.maxLineChanged = true;
       }
     }
 
-    if (min != null && cm) regChange(cm, min, max + 1);
+    if (min != null && cm && this.collapsed) regChange(cm, min, max + 1);
     this.lines.length = 0;
     this.explicitlyCleared = true;
     if (this.atomic && this.doc.cantEdit) {
       this.doc.cantEdit = false;
-      if (cm) reCheckSelection(cm);
+      if (cm) reCheckSelection(cm.doc);
     }
+    if (cm) signalLater(cm, "markerCleared", cm, this);
     if (withOp) endOperation(cm);
   };
 
-  TextMarker.prototype.find = function(bothSides) {
+  // Find the position of the marker in the document. Returns a {from,
+  // to} object by default. Side can be passed to get a specific side
+  // -- 0 (both), -1 (left), or 1 (right). When lineObj is true, the
+  // Pos objects returned contain a line object, rather than a line
+  // number (used to prevent looking up the same line twice).
+  TextMarker.prototype.find = function(side, lineObj) {
+    if (side == null && this.type == "bookmark") side = 1;
     var from, to;
     for (var i = 0; i < this.lines.length; ++i) {
       var line = this.lines[i];
       var span = getMarkedSpanFor(line.markedSpans, this);
-      if (span.from != null || span.to != null) {
-        var found = lineNo(line);
-        if (span.from != null) from = Pos(found, span.from);
-        if (span.to != null) to = Pos(found, span.to);
+      if (span.from != null) {
+        from = Pos(lineObj ? line : lineNo(line), span.from);
+        if (side == -1) return from;
+      }
+      if (span.to != null) {
+        to = Pos(lineObj ? line : lineNo(line), span.to);
+        if (side == 1) return to;
       }
     }
-    if (this.type == "bookmark" && !bothSides) return from;
     return from && {from: from, to: to};
   };
 
+  // Signals that the marker's widget changed, and surrounding layout
+  // should be recomputed.
   TextMarker.prototype.changed = function() {
-    var pos = this.find(), cm = this.doc.cm;
+    var pos = this.find(-1, true), widget = this, cm = this.doc.cm;
     if (!pos || !cm) return;
-    if (this.type != "bookmark") pos = pos.from;
-    var line = getLine(this.doc, pos.line);
-    clearCachedMeasurement(cm, line);
-    if (pos.line >= cm.display.showingFrom && pos.line < cm.display.showingTo) {
-      for (var node = cm.display.lineDiv.firstChild; node; node = node.nextSibling) if (node.lineObj == line) {
-        if (node.offsetHeight != line.height) updateLineHeight(line, node.offsetHeight);
-        break;
+    runInOp(cm, function() {
+      var line = pos.line, lineN = lineNo(pos.line);
+      var view = findViewForLine(cm, lineN);
+      if (view) {
+        clearLineMeasurementCacheFor(view);
+        cm.curOp.selectionChanged = cm.curOp.forceUpdate = true;
       }
-      runInOp(cm, function() {
-        cm.curOp.selectionChanged = cm.curOp.forceUpdate = cm.curOp.updateMaxLine = true;
-      });
-    }
+      cm.curOp.updateMaxLine = true;
+      if (!lineIsHidden(widget.doc, line) && widget.height != null) {
+        var oldHeight = widget.height;
+        widget.height = null;
+        var dHeight = widgetHeight(widget) - oldHeight;
+        if (dHeight)
+          updateLineHeight(line, line.height + dHeight);
+      }
+    });
   };
 
   TextMarker.prototype.attachLine = function(line) {
     if (!this.lines.length && this.doc.cm) {
       var op = this.doc.cm.curOp;
       if (!op.maybeHiddenMarkers || indexOf(op.maybeHiddenMarkers, this) == -1)
         (op.maybeUnhiddenMarkers || (op.maybeUnhiddenMarkers = [])).push(this);
     }
     this.lines.push(line);
   };
   TextMarker.prototype.detachLine = function(line) {
     this.lines.splice(indexOf(this.lines, line), 1);
     if (!this.lines.length && this.doc.cm) {
       var op = this.doc.cm.curOp;
       (op.maybeHiddenMarkers || (op.maybeHiddenMarkers = [])).push(this);
     }
   };
 
+  // Collapsed markers have unique ids, in order to be able to order
+  // them, which is needed for uniquely determining an outer marker
+  // when they overlap (they may nest, but not partially overlap).
   var nextMarkerId = 0;
 
+  // Create a marker, wire it up to the right lines, and
   function markText(doc, from, to, options, type) {
+    // Shared markers (across linked documents) are handled separately
+    // (markTextShared will call out to this again, once per
+    // document).
     if (options && options.shared) return markTextShared(doc, from, to, options, type);
+    // Ensure we are in an operation.
     if (doc.cm && !doc.cm.curOp) return operation(doc.cm, markText)(doc, from, to, options, type);
 
-    var marker = new TextMarker(doc, type);
+    var marker = new TextMarker(doc, type), diff = cmp(from, to);
     if (options) copyObj(options, marker);
-    if (posLess(to, from) || posEq(from, to) && marker.clearWhenEmpty !== false)
+    // Don't connect empty markers unless clearWhenEmpty is false
+    if (diff > 0 || diff == 0 && marker.clearWhenEmpty !== false)
       return marker;
     if (marker.replacedWith) {
+      // Showing up as a widget implies collapsed (widget replaces text)
       marker.collapsed = true;
-      marker.replacedWith = elt("span", [marker.replacedWith], "CodeMirror-widget");
-      if (!options.handleMouseEvents) marker.replacedWith.ignoreEvents = true;
+      marker.widgetNode = elt("span", [marker.replacedWith], "CodeMirror-widget");
+      if (!options.handleMouseEvents) marker.widgetNode.ignoreEvents = true;
+      if (options.insertLeft) marker.widgetNode.insertLeft = true;
     }
     if (marker.collapsed) {
       if (conflictingCollapsedRange(doc, from.line, from, to, marker) ||
           from.line != to.line && conflictingCollapsedRange(doc, to.line, from, to, marker))
         throw new Error("Inserting collapsed marker partially overlapping an existing one");
       sawCollapsedSpans = true;
     }
 
     if (marker.addToHistory)
-      addToHistory(doc, {from: from, to: to, origin: "markText"},
-                   {head: doc.sel.head, anchor: doc.sel.anchor}, NaN);
+      addChangeToHistory(doc, {from: from, to: to, origin: "markText"}, doc.sel, NaN);
 
     var curLine = from.line, cm = doc.cm, updateMaxLine;
     doc.iter(curLine, to.line + 1, function(line) {
-      if (cm && marker.collapsed && !cm.options.lineWrapping && visualLine(doc, line) == cm.display.maxLine)
+      if (cm && marker.collapsed && !cm.options.lineWrapping && visualLine(line) == cm.display.maxLine)
         updateMaxLine = true;
-      var span = {from: null, to: null, marker: marker};
-      if (curLine == from.line) span.from = from.ch;
-      if (curLine == to.line) span.to = to.ch;
       if (marker.collapsed && curLine != from.line) updateLineHeight(line, 0);
-      addMarkedSpan(line, span);
+      addMarkedSpan(line, new MarkedSpan(marker,
+                                         curLine == from.line ? from.ch : null,
+                                         curLine == to.line ? to.ch : null));
       ++curLine;
     });
+    // lineIsHidden depends on the presence of the spans, so needs a second pass
     if (marker.collapsed) doc.iter(from.line, to.line + 1, function(line) {
       if (lineIsHidden(doc, line)) updateLineHeight(line, 0);
     });
 
     if (marker.clearOnEnter) on(marker, "beforeCursorEnter", function() { marker.clear(); });
 
     if (marker.readOnly) {
       sawReadOnlySpans = true;
       if (doc.history.done.length || doc.history.undone.length)
         doc.clearHistory();
     }
     if (marker.collapsed) {
       marker.id = ++nextMarkerId;
       marker.atomic = true;
     }
     if (cm) {
+      // Sync editor state
       if (updateMaxLine) cm.curOp.updateMaxLine = true;
-      if (marker.className || marker.title || marker.startStyle || marker.endStyle || marker.collapsed)
+      if (marker.collapsed)
         regChange(cm, from.line, to.line + 1);
-      if (marker.atomic) reCheckSelection(cm);
+      else if (marker.className || marker.title || marker.startStyle || marker.endStyle)
+        for (var i = from.line; i <= to.line; i++) regLineChange(cm, i, "text");
+      if (marker.atomic) reCheckSelection(cm.doc);
+      signalLater(cm, "markerAdded", cm, marker);
     }
     return marker;
   }
 
   // SHARED TEXTMARKERS
 
-  function SharedTextMarker(markers, primary) {
+  // A shared marker spans multiple linked documents. It is
+  // implemented as a meta-marker-object controlling multiple normal
+  // markers.
+  var SharedTextMarker = CodeMirror.SharedTextMarker = function(markers, primary) {
     this.markers = markers;
     this.primary = primary;
     for (var i = 0, me = this; i < markers.length; ++i) {
       markers[i].parent = this;
       on(markers[i], "clear", function(){me.clear();});
     }
-  }
-  CodeMirror.SharedTextMarker = SharedTextMarker;
+  };
   eventMixin(SharedTextMarker);
 
   SharedTextMarker.prototype.clear = function() {
     if (this.explicitlyCleared) return;
     this.explicitlyCleared = true;
     for (var i = 0; i < this.markers.length; ++i)
       this.markers[i].clear();
     signalLater(this, "clear");
   };
-  SharedTextMarker.prototype.find = function() {
-    return this.primary.find();
+  SharedTextMarker.prototype.find = function(side, lineObj) {
+    return this.primary.find(side, lineObj);
   };
 
   function markTextShared(doc, from, to, options, type) {
     options = copyObj(options);
     options.shared = false;
     var markers = [markText(doc, from, to, options, type)], primary = markers[0];
-    var widget = options.replacedWith;
+    var widget = options.widgetNode;
     linkedDocs(doc, function(doc) {
-      if (widget) options.replacedWith = widget.cloneNode(true);
+      if (widget) options.widgetNode = widget.cloneNode(true);
       markers.push(markText(doc, clipPos(doc, from), clipPos(doc, to), options, type));
       for (var i = 0; i < doc.linked.length; ++i)
         if (doc.linked[i].isParent) return;
       primary = lst(markers);
     });
     return new SharedTextMarker(markers, primary);
   }
 
   // TEXTMARKER SPANS
 
+  function MarkedSpan(marker, from, to) {
+    this.marker = marker;
+    this.from = from; this.to = to;
+  }
+
+  // Search an array of spans for a span matching the given marker.
   function getMarkedSpanFor(spans, marker) {
     if (spans) for (var i = 0; i < spans.length; ++i) {
       var span = spans[i];
       if (span.marker == marker) return span;
     }
   }
+  // Remove a span from an array, returning undefined if no spans are
+  // left (we don't store arrays for lines without spans).
   function removeMarkedSpan(spans, span) {
     for (var r, i = 0; i < spans.length; ++i)
       if (spans[i] != span) (r || (r = [])).push(spans[i]);
     return r;
   }
+  // Add a span to a line.
   function addMarkedSpan(line, span) {
     line.markedSpans = line.markedSpans ? line.markedSpans.concat([span]) : [span];
     span.marker.attachLine(line);
   }
 
+  // Used for the algorithm that adjusts markers for a change in the
+  // document. These functions cut an array of spans at a given
+  // character position, returning an array of remaining chunks (or
+  // undefined if nothing remains).
   function markedSpansBefore(old, startCh, isInsert) {
     if (old) for (var i = 0, nw; i < old.length; ++i) {
       var span = old[i], marker = span.marker;
       var startsBefore = span.from == null || (marker.inclusiveLeft ? span.from <= startCh : span.from < startCh);
       if (startsBefore || span.from == startCh && marker.type == "bookmark" && (!isInsert || !span.marker.insertLeft)) {
         var endsAfter = span.to == null || (marker.inclusiveRight ? span.to >= startCh : span.to > startCh);
-        (nw || (nw = [])).push({from: span.from,
-                                to: endsAfter ? null : span.to,
-                                marker: marker});
+        (nw || (nw = [])).push(new MarkedSpan(marker, span.from, endsAfter ? null : span.to));
       }
     }
     return nw;
   }
-
   function markedSpansAfter(old, endCh, isInsert) {
     if (old) for (var i = 0, nw; i < old.length; ++i) {
       var span = old[i], marker = span.marker;
       var endsAfter = span.to == null || (marker.inclusiveRight ? span.to >= endCh : span.to > endCh);
       if (endsAfter || span.from == endCh && marker.type == "bookmark" && (!isInsert || span.marker.insertLeft)) {
         var startsBefore = span.from == null || (marker.inclusiveLeft ? span.from <= endCh : span.from < endCh);
-        (nw || (nw = [])).push({from: startsBefore ? null : span.from - endCh,
-                                to: span.to == null ? null : span.to - endCh,
-                                marker: marker});
+        (nw || (nw = [])).push(new MarkedSpan(marker, startsBefore ? null : span.from - endCh,
+                                              span.to == null ? null : span.to - endCh));
       }
     }
     return nw;
   }
 
+  // Given a change object, compute the new set of marker spans that
+  // cover the line in which the change took place. Removes spans
+  // entirely within the change, reconnects spans belonging to the
+  // same marker that appear on both sides of the change, and cuts off
+  // spans partially within the change. Returns an array of span
+  // arrays with one element for each line in (after) the change.
   function stretchSpansOverChange(doc, change) {
     var oldFirst = isLine(doc, change.from.line) && getLine(doc, change.from.line).markedSpans;
     var oldLast = isLine(doc, change.to.line) && getLine(doc, change.to.line).markedSpans;
     if (!oldFirst && !oldLast) return null;
 
-    var startCh = change.from.ch, endCh = change.to.ch, isInsert = posEq(change.from, change.to);
+    var startCh = change.from.ch, endCh = change.to.ch, isInsert = cmp(change.from, change.to) == 0;
     // Get the spans that 'stick out' on both sides
     var first = markedSpansBefore(oldFirst, startCh, isInsert);
     var last = markedSpansAfter(oldLast, endCh, isInsert);
 
     // Next, merge those two ends
     var sameLine = change.text.length == 1, offset = lst(change.text).length + (sameLine ? startCh : 0);
     if (first) {
       // Fix up .to properties of first
       for (var i = 0; i < first.length; ++i) {
         var span = first[i];
@@ skipping 25 matching lines @@
     if (first) first = clearEmptySpans(first);
     if (last && last != first) last = clearEmptySpans(last);
 
     var newMarkers = [first];
     if (!sameLine) {
       // Fill gap with whole-line-spans
       var gap = change.text.length - 2, gapMarkers;
       if (gap > 0 && first)
         for (var i = 0; i < first.length; ++i)
           if (first[i].to == null)
-            (gapMarkers || (gapMarkers = [])).push({from: null, to: null, marker: first[i].marker});
+            (gapMarkers || (gapMarkers = [])).push(new MarkedSpan(first[i].marker, null, null));
       for (var i = 0; i < gap; ++i)
         newMarkers.push(gapMarkers);
       newMarkers.push(last);
     }
     return newMarkers;
   }
 
+  // Remove spans that are empty and don't have a clearWhenEmpty
+  // option of false.
   function clearEmptySpans(spans) {
     for (var i = 0; i < spans.length; ++i) {
       var span = spans[i];
       if (span.from != null && span.from == span.to && span.marker.clearWhenEmpty !== false)
         spans.splice(i--, 1);
     }
     if (!spans.length) return null;
     return spans;
   }
 
+  // Used for un/re-doing changes from the history. Combines the
+  // result of computing the existing spans with the set of spans that
+  // existed in the history (so that deleting around a span and then
+  // undoing brings back the span).
   function mergeOldSpans(doc, change) {
     var old = getOldSpans(doc, change);
     var stretched = stretchSpansOverChange(doc, change);
     if (!old) return stretched;
     if (!stretched) return old;
 
     for (var i = 0; i < old.length; ++i) {
       var oldCur = old[i], stretchCur = stretched[i];
       if (oldCur && stretchCur) {
         spans: for (var j = 0; j < stretchCur.length; ++j) {
           var span = stretchCur[j];
           for (var k = 0; k < oldCur.length; ++k)
             if (oldCur[k].marker == span.marker) continue spans;
           oldCur.push(span);
         }
       } else if (stretchCur) {
         old[i] = stretchCur;
       }
     }
     return old;
   }
 
+  // Used to 'clip' out readOnly ranges when making a change.
   function removeReadOnlyRanges(doc, from, to) {
     var markers = null;
     doc.iter(from.line, to.line + 1, function(line) {
       if (line.markedSpans) for (var i = 0; i < line.markedSpans.length; ++i) {
         var mark = line.markedSpans[i].marker;
         if (mark.readOnly && (!markers || indexOf(markers, mark) == -1))
           (markers || (markers = [])).push(mark);
       }
     });
     if (!markers) return null;
     var parts = [{from: from, to: to}];
     for (var i = 0; i < markers.length; ++i) {
-      var mk = markers[i], m = mk.find();
+      var mk = markers[i], m = mk.find(0);
       for (var j = 0; j < parts.length; ++j) {
         var p = parts[j];
-        if (posLess(p.to, m.from) || posLess(m.to, p.from)) continue;
-        var newParts = [j, 1];
-        if (posLess(p.from, m.from) || !mk.inclusiveLeft && posEq(p.from, m.from))
+        if (cmp(p.to, m.from) < 0 || cmp(p.from, m.to) > 0) continue;
+        var newParts = [j, 1], dfrom = cmp(p.from, m.from), dto = cmp(p.to, m.to);
+        if (dfrom < 0 || !mk.inclusiveLeft && !dfrom)
           newParts.push({from: p.from, to: m.from});
-        if (posLess(m.to, p.to) || !mk.inclusiveRight && posEq(p.to, m.to))
+        if (dto > 0 || !mk.inclusiveRight && !dto)
           newParts.push({from: m.to, to: p.to});
         parts.splice.apply(parts, newParts);
         j += newParts.length - 1;
       }
     }
     return parts;
   }
 
+  // Connect or disconnect spans from a line.
+  function detachMarkedSpans(line) {
+    var spans = line.markedSpans;
+    if (!spans) return;
+    for (var i = 0; i < spans.length; ++i)
+      spans[i].marker.detachLine(line);
+    line.markedSpans = null;
+  }
+  function attachMarkedSpans(line, spans) {
+    if (!spans) return;
+    for (var i = 0; i < spans.length; ++i)
+      spans[i].marker.attachLine(line);
+    line.markedSpans = spans;
+  }
+
+  // Helpers used when computing which overlapping collapsed span
+  // counts as the larger one.
   function extraLeft(marker) { return marker.inclusiveLeft ? -1 : 0; }
   function extraRight(marker) { return marker.inclusiveRight ? 1 : 0; }
 
+  // Returns a number indicating which of two overlapping collapsed
+  // spans is larger (and thus includes the other). Falls back to
+  // comparing ids when the spans cover exactly the same range.
   function compareCollapsedMarkers(a, b) {
     var lenDiff = a.lines.length - b.lines.length;
     if (lenDiff != 0) return lenDiff;
     var aPos = a.find(), bPos = b.find();
     var fromCmp = cmp(aPos.from, bPos.from) || extraLeft(a) - extraLeft(b);
     if (fromCmp) return -fromCmp;
     var toCmp = cmp(aPos.to, bPos.to) || extraRight(a) - extraRight(b);
     if (toCmp) return toCmp;
     return b.id - a.id;
   }
 
+  // Find out whether a line ends or starts in a collapsed span. If
+  // so, return the marker for that span.
   function collapsedSpanAtSide(line, start) {
     var sps = sawCollapsedSpans && line.markedSpans, found;
     if (sps) for (var sp, i = 0; i < sps.length; ++i) {
       sp = sps[i];
       if (sp.marker.collapsed && (start ? sp.from : sp.to) == null &&
           (!found || compareCollapsedMarkers(found, sp.marker) < 0))
         found = sp.marker;
     }
     return found;
   }
   function collapsedSpanAtStart(line) { return collapsedSpanAtSide(line, true); }
   function collapsedSpanAtEnd(line) { return collapsedSpanAtSide(line, false); }
 
+  // Test whether there exists a collapsed span that partially
+  // overlaps (covers the start or end, but not both) of a new span.
+  // Such overlap is not allowed.
   function conflictingCollapsedRange(doc, lineNo, from, to, marker) {
     var line = getLine(doc, lineNo);
     var sps = sawCollapsedSpans && line.markedSpans;
     if (sps) for (var i = 0; i < sps.length; ++i) {
       var sp = sps[i];
       if (!sp.marker.collapsed) continue;
-      var found = sp.marker.find(true);
+      var found = sp.marker.find(0);
       var fromCmp = cmp(found.from, from) || extraLeft(sp.marker) - extraLeft(marker);
       var toCmp = cmp(found.to, to) || extraRight(sp.marker) - extraRight(marker);
       if (fromCmp >= 0 && toCmp <= 0 || fromCmp <= 0 && toCmp >= 0) continue;
       if (fromCmp <= 0 && (cmp(found.to, from) || extraRight(sp.marker) - extraLeft(marker)) > 0 ||
           fromCmp >= 0 && (cmp(found.from, to) || extraLeft(sp.marker) - extraRight(marker)) < 0)
         return true;
     }
   }
 
-  function visualLine(doc, line) {
+  // A visual line is a line as drawn on the screen. Folding, for
+  // example, can cause multiple logical lines to appear on the same
+  // visual line. This finds the start of the visual line that the
+  // given line is part of (usually that is the line itself).
+  function visualLine(line) {
     var merged;
     while (merged = collapsedSpanAtStart(line))
-      line = getLine(doc, merged.find().from.line);
+      line = merged.find(-1, true).line;
     return line;
   }
 
+  // Returns an array of logical lines that continue the visual line
+  // started by the argument, or undefined if there are no such lines.
+  function visualLineContinued(line) {
+    var merged, lines;
+    while (merged = collapsedSpanAtEnd(line)) {
+      line = merged.find(1, true).line;
+      (lines || (lines = [])).push(line);
+    }
+    return lines;
+  }
+
+  // Get the line number of the start of the visual line that the
+  // given line number is part of.
+  function visualLineNo(doc, lineN) {
+    var line = getLine(doc, lineN), vis = visualLine(line);
+    if (line == vis) return lineN;
+    return lineNo(vis);
+  }
+  // Get the line number of the start of the next visual line after
+  // the given line.
+  function visualLineEndNo(doc, lineN) {
+    if (lineN > doc.lastLine()) return lineN;
+    var line = getLine(doc, lineN), merged;
+    if (!lineIsHidden(doc, line)) return lineN;
+    while (merged = collapsedSpanAtEnd(line))
+      line = merged.find(1, true).line;
+    return lineNo(line) + 1;
+  }
+
+  // Compute whether a line is hidden. Lines count as hidden when they
+  // are part of a visual line that starts with another line, or when
+  // they are entirely covered by collapsed, non-widget span.
   function lineIsHidden(doc, line) {
     var sps = sawCollapsedSpans && line.markedSpans;
     if (sps) for (var sp, i = 0; i < sps.length; ++i) {
       sp = sps[i];
       if (!sp.marker.collapsed) continue;
       if (sp.from == null) return true;
-      if (sp.marker.replacedWith) continue;
+      if (sp.marker.widgetNode) continue;
       if (sp.from == 0 && sp.marker.inclusiveLeft && lineIsHiddenInner(doc, line, sp))
         return true;
     }
   }
   function lineIsHiddenInner(doc, line, span) {
     if (span.to == null) {
-      var end = span.marker.find().to, endLine = getLine(doc, end.line);
-      return lineIsHiddenInner(doc, endLine, getMarkedSpanFor(endLine.markedSpans, span.marker));
+      var end = span.marker.find(1, true);
+      return lineIsHiddenInner(doc, end.line, getMarkedSpanFor(end.line.markedSpans, span.marker));
     }
     if (span.marker.inclusiveRight && span.to == line.text.length)
       return true;
     for (var sp, i = 0; i < line.markedSpans.length; ++i) {
       sp = line.markedSpans[i];
-      if (sp.marker.collapsed && !sp.marker.replacedWith && sp.from == span.to &&
+      if (sp.marker.collapsed && !sp.marker.widgetNode && sp.from == span.to &&
           (sp.to == null || sp.to != span.from) &&
           (sp.marker.inclusiveLeft || span.marker.inclusiveRight) &&
           lineIsHiddenInner(doc, line, sp)) return true;
     }
   }
 
-  function detachMarkedSpans(line) {
-    var spans = line.markedSpans;
-    if (!spans) return;
-    for (var i = 0; i < spans.length; ++i)
-      spans[i].marker.detachLine(line);
-    line.markedSpans = null;
-  }
+  // LINE WIDGETS
 
-  function attachMarkedSpans(line, spans) {
-    if (!spans) return;
-    for (var i = 0; i < spans.length; ++i)
-      spans[i].marker.attachLine(line);
-    line.markedSpans = spans;
-  }
-
-  // LINE WIDGETS
+  // Line widgets are block elements displayed above or below a line.
 
   var LineWidget = CodeMirror.LineWidget = function(cm, node, options) {
     if (options) for (var opt in options) if (options.hasOwnProperty(opt))
       this[opt] = options[opt];
     this.cm = cm;
     this.node = node;
   };
   eventMixin(LineWidget);
-  function widgetOperation(f) {
-    return function() {
-      var withOp = !this.cm.curOp;
-      if (withOp) startOperation(this.cm);
-      try {var result = f.apply(this, arguments);}
-      finally {if (withOp) endOperation(this.cm);}
-      return result;
-    };
+
+  function adjustScrollWhenAboveVisible(cm, line, diff) {
+    if (heightAtLine(line) < ((cm.curOp && cm.curOp.scrollTop) || cm.doc.scrollTop))
+      addToScrollPos(cm, null, diff);
   }
-  LineWidget.prototype.clear = widgetOperation(function() {
-    var ws = this.line.widgets, no = lineNo(this.line);
+
+  LineWidget.prototype.clear = function() {
+    var cm = this.cm, ws = this.line.widgets, line = this.line, no = lineNo(line);
     if (no == null || !ws) return;
     for (var i = 0; i < ws.length; ++i) if (ws[i] == this) ws.splice(i--, 1);
-    if (!ws.length) this.line.widgets = null;
-    var aboveVisible = heightAtLine(this.cm, this.line) < this.cm.doc.scrollTop;
-    updateLineHeight(this.line, Math.max(0, this.line.height - widgetHeight(this)));
-    if (aboveVisible) addToScrollPos(this.cm, 0, -this.height);
-    regChange(this.cm, no, no + 1);
-  });
-  LineWidget.prototype.changed = widgetOperation(function() {
-    var oldH = this.height;
+    if (!ws.length) line.widgets = null;
+    var height = widgetHeight(this);
+    runInOp(cm, function() {
+      adjustScrollWhenAboveVisible(cm, line, -height);
+      regLineChange(cm, no, "widget");
+      updateLineHeight(line, Math.max(0, line.height - height));
+    });
+  };
+  LineWidget.prototype.changed = function() {
+    var oldH = this.height, cm = this.cm, line = this.line;
     this.height = null;
     var diff = widgetHeight(this) - oldH;
     if (!diff) return;
-    updateLineHeight(this.line, this.line.height + diff);
-    var no = lineNo(this.line);
-    regChange(this.cm, no, no + 1);
-  });
+    runInOp(cm, function() {
+      cm.curOp.forceUpdate = true;
+      adjustScrollWhenAboveVisible(cm, line, diff);
+      updateLineHeight(line, line.height + diff);
+    });
+  };
 
   function widgetHeight(widget) {
     if (widget.height != null) return widget.height;
-    if (!widget.node.parentNode || widget.node.parentNode.nodeType != 1)
+    if (!contains(document.body, widget.node))
       removeChildrenAndAdd(widget.cm.display.measure, elt("div", [widget.node], null, "position: relative"));
     return widget.height = widget.node.offsetHeight;
   }
 
   function addLineWidget(cm, handle, node, options) {
     var widget = new LineWidget(cm, node, options);
     if (widget.noHScroll) cm.display.alignWidgets = true;
-    changeLine(cm, handle, function(line) {
+    changeLine(cm, handle, "widget", function(line) {
       var widgets = line.widgets || (line.widgets = []);
       if (widget.insertAt == null) widgets.push(widget);
       else widgets.splice(Math.min(widgets.length - 1, Math.max(0, widget.insertAt)), 0, widget);
       widget.line = line;
-      if (!lineIsHidden(cm.doc, line) || widget.showIfHidden) {
-        var aboveVisible = heightAtLine(cm, line) < cm.doc.scrollTop;
+      if (!lineIsHidden(cm.doc, line)) {
+        var aboveVisible = heightAtLine(line) < cm.doc.scrollTop;
         updateLineHeight(line, line.height + widgetHeight(widget));
-        if (aboveVisible) addToScrollPos(cm, 0, widget.height);
+        if (aboveVisible) addToScrollPos(cm, null, widget.height);
+        cm.curOp.forceUpdate = true;
       }
       return true;
     });
     return widget;
   }
 
   // LINE DATA STRUCTURE
 
   // Line objects. These hold state related to a line, including
   // highlighting info (the styles array).
   var Line = CodeMirror.Line = function(text, markedSpans, estimateHeight) {
     this.text = text;
     attachMarkedSpans(this, markedSpans);
     this.height = estimateHeight ? estimateHeight(this) : 1;
   };
   eventMixin(Line);
   Line.prototype.lineNo = function() { return lineNo(this); };
 
+  // Change the content (text, markers) of a line. Automatically
+  // invalidates cached information and tries to re-estimate the
+  // line's height.
   function updateLine(line, text, markedSpans, estimateHeight) {
     line.text = text;
     if (line.stateAfter) line.stateAfter = null;
     if (line.styles) line.styles = null;
     if (line.order != null) line.order = null;
     detachMarkedSpans(line);
     attachMarkedSpans(line, markedSpans);
     var estHeight = estimateHeight ? estimateHeight(line) : 1;
     if (estHeight != line.height) updateLineHeight(line, estHeight);
   }
 
+  // Detach a line from the document tree and its markers.
   function cleanUpLine(line) {
     line.parent = null;
     detachMarkedSpans(line);
   }
 
-  // Run the given mode's parser over a line, update the styles
-  // array, which contains alternating fragments of text and CSS
-  // classes.
+  // Run the given mode's parser over a line, calling f for each token.
   function runMode(cm, text, mode, state, f, forceToEnd) {
     var flattenSpans = mode.flattenSpans;
     if (flattenSpans == null) flattenSpans = cm.options.flattenSpans;
     var curStart = 0, curStyle = null;
     var stream = new StringStream(text, cm.options.tabSize), style;
     if (text == "" && mode.blankLine) mode.blankLine(state);
     while (!stream.eol()) {
       if (stream.pos > cm.options.maxHighlightLength) {
         flattenSpans = false;
         if (forceToEnd) processLine(cm, text, state, stream.pos);
@@ skipping 13 matching lines @@
       stream.start = stream.pos;
     }
     while (curStart < stream.pos) {
       // Webkit seems to refuse to render text nodes longer than 57444 characters
       var pos = Math.min(stream.pos, curStart + 50000);
       f(pos, curStyle);
       curStart = pos;
     }
   }
 
+  // Compute a style array (an array starting with a mode generation
+  // -- for invalidation -- followed by pairs of end positions and
+  // style strings), which is used to highlight the tokens on the
+  // line.
   function highlightLine(cm, line, state, forceToEnd) {
     // A styles array always starts with a number identifying the
     // mode/overlays that it is based on (for easy invalidation).
     var st = [cm.state.modeGen];
     // Compute the base array of styles
     runMode(cm, line.text, cm.doc.mode, state, function(end, style) {
       st.push(end, style);
     }, forceToEnd);
 
     // Run overlays, adjust style array.
@@ skipping 25 matching lines @@
     return st;
   }
 
   function getLineStyles(cm, line) {
     if (!line.styles || line.styles[0] != cm.state.modeGen)
       line.styles = highlightLine(cm, line, line.stateAfter = getStateBefore(cm, lineNo(line)));
     return line.styles;
   }
 
   // Lightweight form of highlight -- proceed over this line and
-  // update state, but don't save a style array.
+  // update state, but don't save a style array. Used for lines that
+  // aren't currently visible.
   function processLine(cm, text, state, startAt) {
     var mode = cm.doc.mode;
     var stream = new StringStream(text, cm.options.tabSize);
     stream.start = stream.pos = startAt || 0;
     if (text == "" && mode.blankLine) mode.blankLine(state);
     while (!stream.eol() && stream.pos <= cm.options.maxHighlightLength) {
       mode.token(stream, state);
       stream.start = stream.pos;
     }
   }
 
+  // Convert a style as returned by a mode (either null, or a string
+  // containing one or more styles) to a CSS style. This is cached,
+  // and also looks for line-wide styles.
   var styleToClassCache = {}, styleToClassCacheWithMode = {};
   function interpretTokenStyle(style, builder) {
     if (!style) return null;
     for (;;) {
       var lineClass = style.match(/(?:^|\s+)line-(background-)?(\S+)/);
       if (!lineClass) break;
       style = style.slice(0, lineClass.index) + style.slice(lineClass.index + lineClass[0].length);
       var prop = lineClass[1] ? "bgClass" : "textClass";
       if (builder[prop] == null)
         builder[prop] = lineClass[2];
       else if (!(new RegExp("(?:^|\s)" + lineClass[2] + "(?:$|\s)")).test(builder[prop]))
         builder[prop] += " " + lineClass[2];
     }
     if (/^\s*$/.test(style)) return null;
     var cache = builder.cm.options.addModeClass ? styleToClassCacheWithMode : styleToClassCache;
     return cache[style] ||
       (cache[style] = style.replace(/\S+/g, "cm-$&"));
   }
 
-  function buildLineContent(cm, realLine, measure, copyWidgets) {
-    var merged, line = realLine, empty = true;
-    while (merged = collapsedSpanAtStart(line))
-      line = getLine(cm.doc, merged.find().from.line);
+  // Render the DOM representation of the text of a line. Also builds
+  // up a 'line map', which points at the DOM nodes that represent
+  // specific stretches of text, and is used by the measuring code.
+  // The returned object contains the DOM node, this map, and
+  // information about line-wide styles that were set by the mode.
+  function buildLineContent(cm, lineView) {
+    // The padding-right forces the element to have a 'border', which
+    // is needed on Webkit to be able to get line-level bounding
+    // rectangles for it (in measureChar).
+    var content = elt("span", null, null, webkit ? "padding-right: .1px" : null);
+    var builder = {pre: elt("pre", [content]), content: content, col: 0, pos: 0, cm: cm};
+    lineView.measure = {};
 
-    var builder = {pre: elt("pre"), col: 0, pos: 0,
-                   measure: null, measuredSomething: false, cm: cm,
-                   copyWidgets: copyWidgets};
+    // Iterate over the logical lines that make up this visual line.
+    for (var i = 0; i <= (lineView.rest ? lineView.rest.length : 0); i++) {
+      var line = i ? lineView.rest[i - 1] : lineView.line, order;
+      builder.pos = 0;
+      builder.addToken = buildToken;
+      // Optionally wire in some hacks into the token-rendering
+      // algorithm, to deal with browser quirks.
+      if ((ie || webkit) && cm.getOption("lineWrapping"))
+        builder.addToken = buildTokenSplitSpaces(builder.addToken);
+      if (hasBadBidiRects(cm.display.measure) && (order = getOrder(line)))
+        builder.addToken = buildTokenBadBidi(builder.addToken, order);
+      builder.map = [];
+      insertLineContent(line, builder, getLineStyles(cm, line));
 
-    do {
-      if (line.text) empty = false;
-      builder.measure = line == realLine && measure;
-      builder.pos = 0;
-      builder.addToken = builder.measure ? buildTokenMeasure : buildToken;
-      if ((old_ie || webkit) && cm.getOption("lineWrapping"))
-        builder.addToken = buildTokenSplitSpaces(builder.addToken);
-      var next = insertLineContent(line, builder, getLineStyles(cm, line));
-      if (measure && line == realLine && !builder.measuredSomething) {
-        measure[0] = builder.pre.appendChild(zeroWidthElement(cm.display.measure));
-        builder.measuredSomething = true;
-      }
-      if (next) line = getLine(cm.doc, next.to.line);
-    } while (next);
+      // Ensure at least a single node is present, for measuring.
+      if (builder.map.length == 0)
+        builder.map.push(0, 0, builder.content.appendChild(zeroWidthElement(cm.display.measure)));
 
-    if (measure && !builder.measuredSomething && !measure[0])
-      measure[0] = builder.pre.appendChild(empty ? elt("span", "\u00a0") : zeroWidthElement(cm.display.measure));
-    if (!builder.pre.firstChild && !lineIsHidden(cm.doc, realLine))
-      builder.pre.appendChild(document.createTextNode("\u00a0"));
-
-    var order;
-    // Work around problem with the reported dimensions of single-char
-    // direction spans on IE (issue #1129). See also the comment in
-    // cursorCoords.
-    if (measure && ie && (order = getOrder(line))) {
-      var l = order.length - 1;
-      if (order[l].from == order[l].to) --l;
-      var last = order[l], prev = order[l - 1];
-      if (last.from + 1 == last.to && prev && last.level < prev.level) {
-        var span = measure[builder.pos - 1];
-        if (span) span.parentNode.insertBefore(span.measureRight = zeroWidthElement(cm.display.measure),
-                                               span.nextSibling);
+      // Store the map and a cache object for the current logical line
+      if (i == 0) {
+        lineView.measure.map = builder.map;
+        lineView.measure.cache = {};
+      } else {
+        (lineView.measure.maps || (lineView.measure.maps = [])).push(builder.map);
+        (lineView.measure.caches || (lineView.measure.caches = [])).push({});
       }
     }
 
-    var textClass = builder.textClass ? builder.textClass + " " + (realLine.textClass || "") : realLine.textClass;
-    if (textClass) builder.pre.className = textClass;
-
-    signal(cm, "renderLine", cm, realLine, builder.pre);
+    signal(cm, "renderLine", cm, lineView.line, builder.pre);
     return builder;
   }
 
   function defaultSpecialCharPlaceholder(ch) {
     var token = elt("span", "\u2022", "cm-invalidchar");
     token.title = "\\u" + ch.charCodeAt(0).toString(16);
     return token;
   }
 
+  // Build up the DOM representation for a single token, and add it to
+  // the line map. Takes care to render special characters separately.
   function buildToken(builder, text, style, startStyle, endStyle, title) {
     if (!text) return;
-    var special = builder.cm.options.specialChars;
+    var special = builder.cm.options.specialChars, mustWrap = false;
     if (!special.test(text)) {
       builder.col += text.length;
       var content = document.createTextNode(text);
+      builder.map.push(builder.pos, builder.pos + text.length, content);
+      if (ie_upto8) mustWrap = true;
+      builder.pos += text.length;
     } else {
       var content = document.createDocumentFragment(), pos = 0;
       while (true) {
         special.lastIndex = pos;
         var m = special.exec(text);
         var skipped = m ? m.index - pos : text.length - pos;
         if (skipped) {
-          content.appendChild(document.createTextNode(text.slice(pos, pos + skipped)));
+          var txt = document.createTextNode(text.slice(pos, pos + skipped));
+          if (ie_upto8) content.appendChild(elt("span", [txt]));
+          else content.appendChild(txt);
+          builder.map.push(builder.pos, builder.pos + skipped, txt);
           builder.col += skipped;
+          builder.pos += skipped;
         }
         if (!m) break;
         pos += skipped + 1;
         if (m[0] == "\t") {
           var tabSize = builder.cm.options.tabSize, tabWidth = tabSize - builder.col % tabSize;
-          content.appendChild(elt("span", spaceStr(tabWidth), "cm-tab"));
+          var txt = content.appendChild(elt("span", spaceStr(tabWidth), "cm-tab"));
           builder.col += tabWidth;
         } else {
-          var token = builder.cm.options.specialCharPlaceholder(m[0]);
-          content.appendChild(token);
+          var txt = builder.cm.options.specialCharPlaceholder(m[0]);
+          if (ie_upto8) content.appendChild(elt("span", [txt]));
+          else content.appendChild(txt);
           builder.col += 1;
         }
+        builder.map.push(builder.pos, builder.pos + 1, txt);
+        builder.pos++;
       }
     }
-    if (style || startStyle || endStyle || builder.measure) {
+    if (style || startStyle || endStyle || mustWrap) {
       var fullStyle = style || "";
       if (startStyle) fullStyle += startStyle;
       if (endStyle) fullStyle += endStyle;
       var token = elt("span", [content], fullStyle);
       if (title) token.title = title;
-      return builder.pre.appendChild(token);
+      return builder.content.appendChild(token);
     }
-    builder.pre.appendChild(content);
-  }
-
-  function buildTokenMeasure(builder, text, style, startStyle, endStyle) {
-    var wrapping = builder.cm.options.lineWrapping;
-    for (var i = 0; i < text.length; ++i) {
-      var start = i == 0, to = i + 1;
-      while (to < text.length && isExtendingChar(text.charAt(to))) ++to;
-      var ch = text.slice(i, to);
-      i = to - 1;
-      if (i && wrapping && spanAffectsWrapping(text, i))
-        builder.pre.appendChild(elt("wbr"));
-      var old = builder.measure[builder.pos];
-      var span = builder.measure[builder.pos] =
-        buildToken(builder, ch, style,
-                   start && startStyle, i == text.length - 1 && endStyle);
-      if (old) span.leftSide = old.leftSide || old;
-      // In IE single-space nodes wrap differently than spaces
-      // embedded in larger text nodes, except when set to
-      // white-space: normal (issue #1268).
-      if (old_ie && wrapping && ch == " " && i && !/\s/.test(text.charAt(i - 1)) &&
-          i < text.length - 1 && !/\s/.test(text.charAt(i + 1)))
-        span.style.whiteSpace = "normal";
-      builder.pos += ch.length;
-    }
-    if (text.length) builder.measuredSomething = true;
+    builder.content.appendChild(content);
   }
 
   function buildTokenSplitSpaces(inner) {
     function split(old) {
       var out = " ";
       for (var i = 0; i < old.length - 2; ++i) out += i % 2 ? " " : "\u00a0";
       out += " ";
       return out;
     }
     return function(builder, text, style, startStyle, endStyle, title) {
-      return inner(builder, text.replace(/ {3,}/g, split), style, startStyle, endStyle, title);
+      inner(builder, text.replace(/ {3,}/g, split), style, startStyle, endStyle, title);
+    };
+  }
+
+  // Work around nonsense dimensions being reported for stretches of
+  // right-to-left text.
+  function buildTokenBadBidi(inner, order) {
+    return function(builder, text, style, startStyle, endStyle, title) {
+      style = style ? style + " cm-force-border" : "cm-force-border";
+      var start = builder.pos, end = start + text.length;
+      for (;;) {
+        // Find the part that overlaps with the start of this text
+        for (var i = 0; i < order.length; i++) {
+          var part = order[i];
+          if (part.to > start && part.from <= start) break;
+        }
+        if (part.to >= end) return inner(builder, text, style, startStyle, endStyle, title);
+        inner(builder, text.slice(0, part.to - start), style, startStyle, null, title);
+        startStyle = null;
+        text = text.slice(part.to - start);
+        start = part.to;
+      }
     };
   }
 
   function buildCollapsedSpan(builder, size, marker, ignoreWidget) {
-    var widget = !ignoreWidget && marker.replacedWith;
+    var widget = !ignoreWidget && marker.widgetNode;
     if (widget) {
-      if (builder.copyWidgets) widget = widget.cloneNode(true);
-      builder.pre.appendChild(widget);
-      if (builder.measure) {
-        if (size) {
-          builder.measure[builder.pos] = widget;
-        } else {
-          var elt = zeroWidthElement(builder.cm.display.measure);
-          if (marker.type == "bookmark" && !marker.insertLeft)
-            builder.measure[builder.pos] = builder.pre.appendChild(elt);
-          else if (builder.measure[builder.pos])
-            return;
-          else
-            builder.measure[builder.pos] = builder.pre.insertBefore(elt, widget);
-        }
-        builder.measuredSomething = true;
-      }
+      builder.map.push(builder.pos, builder.pos + size, widget);
+      builder.content.appendChild(widget);
     }
     builder.pos += size;
   }
 
   // Outputs a number of spans to make up a line, taking highlighting
   // and marked text into account.
   function insertLineContent(line, builder, styles) {
     var spans = line.markedSpans, allText = line.text, at = 0;
     if (!spans) {
       for (var i = 1; i < styles.length; i+=2)
@@ skipping 14 matching lines @@
             if (sp.to != null && nextChange > sp.to) { nextChange = sp.to; spanEndStyle = ""; }
             if (m.className) spanStyle += " " + m.className;
             if (m.startStyle && sp.from == pos) spanStartStyle += " " + m.startStyle;
             if (m.endStyle && sp.to == nextChange) spanEndStyle += " " + m.endStyle;
             if (m.title && !title) title = m.title;
             if (m.collapsed && (!collapsed || compareCollapsedMarkers(collapsed.marker, m) < 0))
               collapsed = sp;
           } else if (sp.from > pos && nextChange > sp.from) {
             nextChange = sp.from;
           }
-          if (m.type == "bookmark" && sp.from == pos && m.replacedWith) foundBookmarks.push(m);
+          if (m.type == "bookmark" && sp.from == pos && m.widgetNode) foundBookmarks.push(m);
         }
         if (collapsed && (collapsed.from || 0) == pos) {
-          buildCollapsedSpan(builder, (collapsed.to == null ? len : collapsed.to) - pos,
+          buildCollapsedSpan(builder, (collapsed.to == null ? len + 1 : collapsed.to) - pos,
                              collapsed.marker, collapsed.from == null);
-          if (collapsed.to == null) return collapsed.marker.find();
+          if (collapsed.to == null) return;
         }
         if (!collapsed && foundBookmarks.length) for (var j = 0; j < foundBookmarks.length; ++j)
           buildCollapsedSpan(builder, 0, foundBookmarks[j]);
       }
       if (pos >= len) break;
 
       var upto = Math.min(len, nextChange);
       while (true) {
         if (text) {
           var end = pos + text.length;
           if (!collapsed) {
             var tokenText = end > upto ? text.slice(0, upto - pos) : text;
             builder.addToken(builder, tokenText, style ? style + spanStyle : spanStyle,
                              spanStartStyle, pos + tokenText.length == nextChange ? spanEndStyle : "", title);
           }
           if (end >= upto) {text = text.slice(upto - pos); pos = upto; break;}
           pos = end;
           spanStartStyle = "";
         }
         text = allText.slice(at, at = styles[i++]);
         style = interpretTokenStyle(styles[i++], builder);
       }
     }
   }
 
   // DOCUMENT DATA STRUCTURE
 
-  function updateDoc(doc, change, markedSpans, selAfter, estimateHeight) {
+  // By default, updates that start and end at the beginning of a line
+  // are treated specially, in order to make the association of line
+  // widgets and marker elements with the text behave more intuitive.
+  function isWholeLineUpdate(doc, change) {
+    return change.from.ch == 0 && change.to.ch == 0 && lst(change.text) == "" &&
+      (!doc.cm || doc.cm.options.wholeLineUpdateBefore);
+  }
+
+  // Perform a change on the document data structure.
+  function updateDoc(doc, change, markedSpans, estimateHeight) {
     function spansFor(n) {return markedSpans ? markedSpans[n] : null;}
     function update(line, text, spans) {
       updateLine(line, text, spans, estimateHeight);
       signalLater(line, "change", line, change);
     }
 
     var from = change.from, to = change.to, text = change.text;
     var firstLine = getLine(doc, from.line), lastLine = getLine(doc, to.line);
     var lastText = lst(text), lastSpans = spansFor(text.length - 1), nlines = to.line - from.line;
 
-    // First adjust the line structure
-    if (from.ch == 0 && to.ch == 0 && lastText == "" &&
-        (!doc.cm || doc.cm.options.wholeLineUpdateBefore)) {
+    // Adjust the line structure
+    if (isWholeLineUpdate(doc, change)) {
       // This is a whole-line replace. Treated specially to make
       // sure line objects move the way they are supposed to.
-      for (var i = 0, e = text.length - 1, added = []; i < e; ++i)
+      for (var i = 0, added = []; i < text.length - 1; ++i)
         added.push(new Line(text[i], spansFor(i), estimateHeight));
       update(lastLine, lastLine.text, lastSpans);
       if (nlines) doc.remove(from.line, nlines);
       if (added.length) doc.insert(from.line, added);
     } else if (firstLine == lastLine) {
       if (text.length == 1) {
         update(firstLine, firstLine.text.slice(0, from.ch) + lastText + firstLine.text.slice(to.ch), lastSpans);
       } else {
-        for (var added = [], i = 1, e = text.length - 1; i < e; ++i)
+        for (var added = [], i = 1; i < text.length - 1; ++i)
           added.push(new Line(text[i], spansFor(i), estimateHeight));
         added.push(new Line(lastText + firstLine.text.slice(to.ch), lastSpans, estimateHeight));
         update(firstLine, firstLine.text.slice(0, from.ch) + text[0], spansFor(0));
         doc.insert(from.line + 1, added);
       }
     } else if (text.length == 1) {
       update(firstLine, firstLine.text.slice(0, from.ch) + text[0] + lastLine.text.slice(to.ch), spansFor(0));
       doc.remove(from.line + 1, nlines);
     } else {
       update(firstLine, firstLine.text.slice(0, from.ch) + text[0], spansFor(0));
       update(lastLine, lastText + lastLine.text.slice(to.ch), lastSpans);
-      for (var i = 1, e = text.length - 1, added = []; i < e; ++i)
+      for (var i = 1, added = []; i < text.length - 1; ++i)
         added.push(new Line(text[i], spansFor(i), estimateHeight));
       if (nlines > 1) doc.remove(from.line + 1, nlines - 1);
       doc.insert(from.line + 1, added);
     }
 
     signalLater(doc, "change", doc, change);
-    setSelection(doc, selAfter.anchor, selAfter.head, null, true);
   }
 
+  // The document is represented as a BTree consisting of leaves, with
+  // chunk of lines in them, and branches, with up to ten leaves or
+  // other branch nodes below them. The top node is always a branch
+  // node, and is the document object itself (meaning it has
+  // additional methods and properties).
+  //
+  // All nodes have parent links. The tree is used both to go from
+  // line numbers to line objects, and to go from objects to numbers.
+  // It also indexes by height, and is used to convert between height
+  // and line object, and to find the total height of the document.
+  //
+  // See also http://marijnhaverbeke.nl/blog/codemirror-line-tree.html
+
   function LeafChunk(lines) {
     this.lines = lines;
     this.parent = null;
-    for (var i = 0, e = lines.length, height = 0; i < e; ++i) {
+    for (var i = 0, height = 0; i < lines.length; ++i) {
       lines[i].parent = this;
       height += lines[i].height;
     }
     this.height = height;
   }
 
   LeafChunk.prototype = {
     chunkSize: function() { return this.lines.length; },
+    // Remove the n lines at offset 'at'.
     removeInner: function(at, n) {
       for (var i = at, e = at + n; i < e; ++i) {
         var line = this.lines[i];
         this.height -= line.height;
         cleanUpLine(line);
         signalLater(line, "delete");
       }
       this.lines.splice(at, n);
     },
+    // Helper used to collapse a small branch into a single leaf.
     collapse: function(lines) {
-      lines.splice.apply(lines, [lines.length, 0].concat(this.lines));
+      lines.push.apply(lines, this.lines);
     },
+    // Insert the given array of lines at offset 'at', count them as
+    // having the given height.
     insertInner: function(at, lines, height) {
       this.height += height;
       this.lines = this.lines.slice(0, at).concat(lines).concat(this.lines.slice(at));
-      for (var i = 0, e = lines.length; i < e; ++i) lines[i].parent = this;
+      for (var i = 0; i < lines.length; ++i) lines[i].parent = this;
     },
+    // Used to iterate over a part of the tree.
     iterN: function(at, n, op) {
       for (var e = at + n; at < e; ++at)
         if (op(this.lines[at])) return true;
     }
   };
 
   function BranchChunk(children) {
     this.children = children;
     var size = 0, height = 0;
-    for (var i = 0, e = children.length; i < e; ++i) {
+    for (var i = 0; i < children.length; ++i) {
       var ch = children[i];
       size += ch.chunkSize(); height += ch.height;
       ch.parent = this;
     }
     this.size = size;
     this.height = height;
     this.parent = null;
   }
 
   BranchChunk.prototype = {
     chunkSize: function() { return this.size; },
     removeInner: function(at, n) {
       this.size -= n;
       for (var i = 0; i < this.children.length; ++i) {
         var child = this.children[i], sz = child.chunkSize();
         if (at < sz) {
           var rm = Math.min(n, sz - at), oldHeight = child.height;
           child.removeInner(at, rm);
           this.height -= oldHeight - child.height;
           if (sz == rm) { this.children.splice(i--, 1); child.parent = null; }
           if ((n -= rm) == 0) break;
           at = 0;
         } else at -= sz;
       }
-      if (this.size - n < 25) {
+      // If the result is smaller than 25 lines, ensure that it is a
+      // single leaf node.
+      if (this.size - n < 25 &&
+          (this.children.length > 1 || !(this.children[0] instanceof LeafChunk))) {
         var lines = [];
         this.collapse(lines);
         this.children = [new LeafChunk(lines)];
         this.children[0].parent = this;
       }
     },
     collapse: function(lines) {
-      for (var i = 0, e = this.children.length; i < e; ++i) this.children[i].collapse(lines);
+      for (var i = 0; i < this.children.length; ++i) this.children[i].collapse(lines);
     },
     insertInner: function(at, lines, height) {
       this.size += lines.length;
       this.height += height;
-      for (var i = 0, e = this.children.length; i < e; ++i) {
+      for (var i = 0; i < this.children.length; ++i) {
         var child = this.children[i], sz = child.chunkSize();
         if (at <= sz) {
           child.insertInner(at, lines, height);
           if (child.lines && child.lines.length > 50) {
             while (child.lines.length > 50) {
               var spilled = child.lines.splice(child.lines.length - 25, 25);
               var newleaf = new LeafChunk(spilled);
               child.height -= newleaf.height;
               this.children.splice(i + 1, 0, newleaf);
               newleaf.parent = this;
             }
             this.maybeSpill();
           }
           break;
         }
         at -= sz;
       }
     },
+    // When a node has grown, check whether it should be split.
     maybeSpill: function() {
       if (this.children.length <= 10) return;
       var me = this;
       do {
         var spilled = me.children.splice(me.children.length - 5, 5);
         var sibling = new BranchChunk(spilled);
         if (!me.parent) { // Become the parent node
           var copy = new BranchChunk(me.children);
           copy.parent = me;
           me.children = [copy, sibling];
           me = copy;
         } else {
           me.size -= sibling.size;
           me.height -= sibling.height;
           var myIndex = indexOf(me.parent.children, me);
           me.parent.children.splice(myIndex + 1, 0, sibling);
         }
         sibling.parent = me.parent;
       } while (me.children.length > 10);
       me.parent.maybeSpill();
     },
     iterN: function(at, n, op) {
-      for (var i = 0, e = this.children.length; i < e; ++i) {
+      for (var i = 0; i < this.children.length; ++i) {
         var child = this.children[i], sz = child.chunkSize();
         if (at < sz) {
           var used = Math.min(n, sz - at);
           if (child.iterN(at, used, op)) return true;
           if ((n -= used) == 0) break;
           at = 0;
         } else at -= sz;
       }
     }
   };
 
   var nextDocId = 0;
   var Doc = CodeMirror.Doc = function(text, mode, firstLine) {
     if (!(this instanceof Doc)) return new Doc(text, mode, firstLine);
     if (firstLine == null) firstLine = 0;
 
     BranchChunk.call(this, [new LeafChunk([new Line("", null)])]);
     this.first = firstLine;
     this.scrollTop = this.scrollLeft = 0;
     this.cantEdit = false;
-    this.history = makeHistory();
     this.cleanGeneration = 1;
     this.frontier = firstLine;
     var start = Pos(firstLine, 0);
-    this.sel = {from: start, to: start, head: start, anchor: start, shift: false, extend: false, goalColumn: null};
+    this.sel = simpleSelection(start);
+    this.history = new History(null);
     this.id = ++nextDocId;
     this.modeOption = mode;
 
     if (typeof text == "string") text = splitLines(text);
-    updateDoc(this, {from: start, to: start, text: text}, null, {head: start, anchor: start});
+    updateDoc(this, {from: start, to: start, text: text});
+    setSelection(this, simpleSelection(start), sel_dontScroll);
   };
 
   Doc.prototype = createObj(BranchChunk.prototype, {
     constructor: Doc,
+    // Iterate over the document. Supports two forms -- with only one
+    // argument, it calls that for each line in the document. With
+    // three, it iterates over the range given by the first two (with
+    // the second being non-inclusive).
     iter: function(from, to, op) {
       if (op) this.iterN(from - this.first, to - from, op);
       else this.iterN(this.first, this.first + this.size, from);
     },
 
+    // Non-public interface for adding and removing lines.
     insert: function(at, lines) {
       var height = 0;
-      for (var i = 0, e = lines.length; i < e; ++i) height += lines[i].height;
+      for (var i = 0; i < lines.length; ++i) height += lines[i].height;
       this.insertInner(at - this.first, lines, height);
     },
     remove: function(at, n) { this.removeInner(at - this.first, n); },
 
+    // From here, the methods are part of the public interface. Most
+    // are also available from CodeMirror (editor) instances.
+
     getValue: function(lineSep) {
       var lines = getLines(this, this.first, this.first + this.size);
       if (lineSep === false) return lines;
       return lines.join(lineSep || "\n");
     },
-    setValue: function(code) {
+    setValue: docMethodOp(function(code) {
       var top = Pos(this.first, 0), last = this.first + this.size - 1;
       makeChange(this, {from: top, to: Pos(last, getLine(this, last).text.length),
-                        text: splitLines(code), origin: "setValue"},
-                 {head: top, anchor: top}, true);
-    },
+                        text: splitLines(code), origin: "setValue"}, true);
+      setSelection(this, simpleSelection(top));
+    }),
     replaceRange: function(code, from, to, origin) {
       from = clipPos(this, from);
       to = to ? clipPos(this, to) : from;
       replaceRange(this, code, from, to, origin);
     },
     getRange: function(from, to, lineSep) {
       var lines = getBetween(this, clipPos(this, from), clipPos(this, to));
       if (lineSep === false) return lines;
       return lines.join(lineSep || "\n");
     },
 
     getLine: function(line) {var l = this.getLineHandle(line); return l && l.text;},
-    setLine: function(line, text) {
-      if (isLine(this, line))
-        replaceRange(this, text, Pos(line, 0), clipPos(this, Pos(line)));
-    },
-    removeLine: function(line) {
-      if (line) replaceRange(this, "", clipPos(this, Pos(line - 1)), clipPos(this, Pos(line)));
-      else replaceRange(this, "", Pos(0, 0), clipPos(this, Pos(1, 0)));
-    },
 
     getLineHandle: function(line) {if (isLine(this, line)) return getLine(this, line);},
     getLineNumber: function(line) {return lineNo(line);},
 
     getLineHandleVisualStart: function(line) {
       if (typeof line == "number") line = getLine(this, line);
-      return visualLine(this, line);
+      return visualLine(line);
     },
 
     lineCount: function() {return this.size;},
     firstLine: function() {return this.first;},
     lastLine: function() {return this.first + this.size - 1;},
 
     clipPos: function(pos) {return clipPos(this, pos);},
 
     getCursor: function(start) {
-      var sel = this.sel, pos;
-      if (start == null || start == "head") pos = sel.head;
-      else if (start == "anchor") pos = sel.anchor;
-      else if (start == "end" || start === false) pos = sel.to;
-      else pos = sel.from;
-      return copyPos(pos);
+      var range = this.sel.primary(), pos;
+      if (start == null || start == "head") pos = range.head;
+      else if (start == "anchor") pos = range.anchor;
+      else if (start == "end" || start == "to" || start === false) pos = range.to();
+      else pos = range.from();
+      return pos;
     },
-    somethingSelected: function() {return !posEq(this.sel.head, this.sel.anchor);},
+    listSelections: function() { return this.sel.ranges; },
+    somethingSelected: function() {return this.sel.somethingSelected();},
 
-    setCursor: docOperation(function(line, ch, extend) {
-      var pos = clipPos(this, typeof line == "number" ? Pos(line, ch || 0) : line);
-      if (extend) extendSelection(this, pos);
-      else setSelection(this, pos, pos);
+    setCursor: docMethodOp(function(line, ch, options) {
+      setSimpleSelection(this, clipPos(this, typeof line == "number" ? Pos(line, ch || 0) : line), null, options);
     }),
-    setSelection: docOperation(function(anchor, head, bias) {
-      setSelection(this, clipPos(this, anchor), clipPos(this, head || anchor), bias);
+    setSelection: docMethodOp(function(anchor, head, options) {
+      setSimpleSelection(this, clipPos(this, anchor), clipPos(this, head || anchor), options);
     }),
-    extendSelection: docOperation(function(from, to, bias) {
-      extendSelection(this, clipPos(this, from), to && clipPos(this, to), bias);
+    extendSelection: docMethodOp(function(head, other, options) {
+      extendSelection(this, clipPos(this, head), other && clipPos(this, other), options);
+    }),
+    extendSelections: docMethodOp(function(heads, options) {
+      extendSelections(this, clipPosArray(this, heads, options));
+    }),
+    extendSelectionsBy: docMethodOp(function(f, options) {
+      extendSelections(this, map(this.sel.ranges, f), options);
+    }),
+    setSelections: docMethodOp(function(ranges, primary, options) {
+      if (!ranges.length) return;
+      for (var i = 0, out = []; i < ranges.length; i++)
+        out[i] = new Range(clipPos(this, ranges[i].anchor),
+                           clipPos(this, ranges[i].head));
+      if (primary == null) primary = Math.min(ranges.length - 1, this.sel.primIndex);
+      setSelection(this, normalizeSelection(out, primary), options);
+    }),
+    addSelection: docMethodOp(function(anchor, head, options) {
+      var ranges = this.sel.ranges.slice(0);
+      ranges.push(new Range(clipPos(this, anchor), clipPos(this, head || anchor)));
+      setSelection(this, normalizeSelection(ranges, ranges.length - 1), options);
     }),
 
-    getSelection: function(lineSep) {return this.getRange(this.sel.from, this.sel.to, lineSep);},
-    replaceSelection: function(code, collapse, origin) {
-      makeChange(this, {from: this.sel.from, to: this.sel.to, text: splitLines(code), origin: origin}, collapse || "around");
+    getSelection: function(lineSep) {
+      var ranges = this.sel.ranges, lines;
+      for (var i = 0; i < ranges.length; i++) {
+        var sel = getBetween(this, ranges[i].from(), ranges[i].to());
+        lines = lines ? lines.concat(sel) : sel;
+      }
+      if (lineSep === false) return lines;
+      else return lines.join(lineSep || "\n");
     },
-    undo: docOperation(function() {makeChangeFromHistory(this, "undo");}),
-    redo: docOperation(function() {makeChangeFromHistory(this, "redo");}),
+    getSelections: function(lineSep) {
+      var parts = [], ranges = this.sel.ranges;
+      for (var i = 0; i < ranges.length; i++) {
+        var sel = getBetween(this, ranges[i].from(), ranges[i].to());
+        if (lineSep !== false) sel = sel.join(lineSep || "\n");
+        parts[i] = sel;
+      }
+      return parts;
+    },
+    replaceSelection: docMethodOp(function(code, collapse, origin) {
+      var dup = [];
+      for (var i = 0; i < this.sel.ranges.length; i++)
+        dup[i] = code;
+      this.replaceSelections(dup, collapse, origin || "+input");
+    }),
+    replaceSelections: function(code, collapse, origin) {
+      var changes = [], sel = this.sel;
+      for (var i = 0; i < sel.ranges.length; i++) {
+        var range = sel.ranges[i];
+        changes[i] = {from: range.from(), to: range.to(), text: splitLines(code[i]), origin: origin};
+      }
+      var newSel = collapse && collapse != "end" && computeReplacedSel(this, changes, collapse);
+      for (var i = changes.length - 1; i >= 0; i--)
+        makeChange(this, changes[i]);
+      if (newSel) setSelectionReplaceHistory(this, newSel);
+      else if (this.cm) ensureCursorVisible(this.cm);
+    },
+    undo: docMethodOp(function() {makeChangeFromHistory(this, "undo");}),
+    redo: docMethodOp(function() {makeChangeFromHistory(this, "redo");}),
+    undoSelection: docMethodOp(function() {makeChangeFromHistory(this, "undo", true);}),
+    redoSelection: docMethodOp(function() {makeChangeFromHistory(this, "redo", true);}),
 
-    setExtending: function(val) {this.sel.extend = val;},
+    setExtending: function(val) {this.extend = val;},
+    getExtending: function() {return this.extend;},
 
     historySize: function() {
-      var hist = this.history;
-      return {undo: hist.done.length, redo: hist.undone.length};
+      var hist = this.history, done = 0, undone = 0;
+      for (var i = 0; i < hist.done.length; i++) if (!hist.done[i].ranges) ++done;
+      for (var i = 0; i < hist.undone.length; i++) if (!hist.undone[i].ranges) ++undone;
+      return {undo: done, redo: undone};
     },
-    clearHistory: function() {this.history = makeHistory(this.history.maxGeneration);},
+    clearHistory: function() {this.history = new History(this.history.maxGeneration);},
 
     markClean: function() {
       this.cleanGeneration = this.changeGeneration(true);
     },
     changeGeneration: function(forceSplit) {
       if (forceSplit)
         this.history.lastOp = this.history.lastOrigin = null;
       return this.history.generation;
     },
     isClean: function (gen) {
       return this.history.generation == (gen || this.cleanGeneration);
     },
 
     getHistory: function() {
       return {done: copyHistoryArray(this.history.done),
               undone: copyHistoryArray(this.history.undone)};
     },
     setHistory: function(histData) {
-      var hist = this.history = makeHistory(this.history.maxGeneration);
-      hist.done = histData.done.slice(0);
-      hist.undone = histData.undone.slice(0);
+      var hist = this.history = new History(this.history.maxGeneration);
+      hist.done = copyHistoryArray(histData.done.slice(0), null, true);
+      hist.undone = copyHistoryArray(histData.undone.slice(0), null, true);
     },
 
     markText: function(from, to, options) {
       return markText(this, clipPos(this, from), clipPos(this, to), options, "range");
     },
     setBookmark: function(pos, options) {
       var realOpts = {replacedWith: options && (options.nodeType == null ? options.widget : options),
                       insertLeft: options && options.insertLeft,
-                      clearWhenEmpty: false};
+                      clearWhenEmpty: false, shared: options && options.shared};
       pos = clipPos(this, pos);
       return markText(this, pos, pos, realOpts, "bookmark");
     },
     findMarksAt: function(pos) {
       pos = clipPos(this, pos);
       var markers = [], spans = getLine(this, pos.line).markedSpans;
       if (spans) for (var i = 0; i < spans.length; ++i) {
         var span = spans[i];
         if ((span.from == null || span.from <= pos.ch) &&
             (span.to == null || span.to >= pos.ch))
           markers.push(span.marker.parent || span.marker);
       }
       return markers;
     },
+    findMarks: function(from, to) {
+      from = clipPos(this, from); to = clipPos(this, to);
+      var found = [], lineNo = from.line;
+      this.iter(from.line, to.line + 1, function(line) {
+        var spans = line.markedSpans;
+        if (spans) for (var i = 0; i < spans.length; i++) {
+          var span = spans[i];
+          if (!(lineNo == from.line && from.ch > span.to ||
+                span.from == null && lineNo != from.line||
+                lineNo == to.line && span.from > to.ch))
+            found.push(span.marker.parent || span.marker);
+        }
+        ++lineNo;
+      });
+      return found;
+    },
     getAllMarks: function() {
       var markers = [];
       this.iter(function(line) {
         var sps = line.markedSpans;
         if (sps) for (var i = 0; i < sps.length; ++i)
           if (sps[i].from != null) markers.push(sps[i].marker);
       });
       return markers;
     },
 
@@ skipping 13 matching lines @@
       if (coords.line < this.first || coords.ch < 0) return 0;
       this.iter(this.first, coords.line, function (line) {
         index += line.text.length + 1;
       });
       return index;
     },
 
     copy: function(copyHistory) {
       var doc = new Doc(getLines(this, this.first, this.first + this.size), this.modeOption, this.first);
       doc.scrollTop = this.scrollTop; doc.scrollLeft = this.scrollLeft;
-      doc.sel = {from: this.sel.from, to: this.sel.to, head: this.sel.head, anchor: this.sel.anchor,
-                 shift: this.sel.shift, extend: false, goalColumn: this.sel.goalColumn};
+      doc.sel = this.sel;
+      doc.extend = false;
       if (copyHistory) {
         doc.history.undoDepth = this.history.undoDepth;
         doc.setHistory(this.getHistory());
       }
       return doc;
     },
 
     linkedDoc: function(options) {
       if (!options) options = {};
       var from = this.first, to = this.first + this.size;
@@ skipping 11 matching lines @@
         var link = this.linked[i];
         if (link.doc != other) continue;
         this.linked.splice(i, 1);
         other.unlinkDoc(this);
         break;
       }
       // If the histories were shared, split them again
       if (other.history == this.history) {
         var splitIds = [other.id];
         linkedDocs(other, function(doc) {splitIds.push(doc.id);}, true);
-        other.history = makeHistory();
+        other.history = new History(null);
         other.history.done = copyHistoryArray(this.history.done, splitIds);
         other.history.undone = copyHistoryArray(this.history.undone, splitIds);
       }
     },
     iterLinkedDocs: function(f) {linkedDocs(this, f);},
 
     getMode: function() {return this.mode;},
     getEditor: function() {return this.cm;}
   });
 
+  // Public alias.
   Doc.prototype.eachLine = Doc.prototype.iter;
 
-  // The Doc methods that should be available on CodeMirror instances
+  // Set up methods on CodeMirror's prototype to redirect to the editor's document.
   var dontDelegate = "iter insert remove copy getEditor".split(" ");
   for (var prop in Doc.prototype) if (Doc.prototype.hasOwnProperty(prop) && indexOf(dontDelegate, prop) < 0)
     CodeMirror.prototype[prop] = (function(method) {
       return function() {return method.apply(this.doc, arguments);};
     })(Doc.prototype[prop]);
 
   eventMixin(Doc);
 
+  // Call f for all linked documents.
   function linkedDocs(doc, f, sharedHistOnly) {
     function propagate(doc, skip, sharedHist) {
       if (doc.linked) for (var i = 0; i < doc.linked.length; ++i) {
         var rel = doc.linked[i];
         if (rel.doc == skip) continue;
         var shared = sharedHist && rel.sharedHist;
         if (sharedHistOnly && !shared) continue;
         f(rel.doc, shared);
         propagate(rel.doc, doc, shared);
       }
     }
     propagate(doc, null, true);
   }
 
+  // Attach a document to an editor.
   function attachDoc(cm, doc) {
     if (doc.cm) throw new Error("This document is already in use.");
     cm.doc = doc;
     doc.cm = cm;
     estimateLineHeights(cm);
     loadMode(cm);
-    if (!cm.options.lineWrapping) computeMaxLength(cm);
+    if (!cm.options.lineWrapping) findMaxLine(cm);
     cm.options.mode = doc.modeOption;
     regChange(cm);
   }
 
   // LINE UTILITIES
 
-  function getLine(chunk, n) {
-    n -= chunk.first;
-    while (!chunk.lines) {
+  // Find the line object corresponding to the given line number.
+  function getLine(doc, n) {
+    n -= doc.first;
+    if (n < 0 || n >= doc.size) throw new Error("There is no line " + (n + doc.first) + " in the document.");
+    for (var chunk = doc; !chunk.lines;) {
       for (var i = 0;; ++i) {
         var child = chunk.children[i], sz = child.chunkSize();
         if (n < sz) { chunk = child; break; }
         n -= sz;
       }
     }
     return chunk.lines[n];
   }
 
+  // Get the part of a document between two positions, as an array of
+  // strings.
   function getBetween(doc, start, end) {
     var out = [], n = start.line;
     doc.iter(start.line, end.line + 1, function(line) {
       var text = line.text;
       if (n == end.line) text = text.slice(0, end.ch);
       if (n == start.line) text = text.slice(start.ch);
       out.push(text);
       ++n;
     });
     return out;
   }
+  // Get the lines between from and to, as array of strings.
   function getLines(doc, from, to) {
     var out = [];
     doc.iter(from, to, function(line) { out.push(line.text); });
     return out;
   }
 
+  // Update the height of a line, propagating the height change
+  // upwards to parent nodes.
   function updateLineHeight(line, height) {
     var diff = height - line.height;
-    for (var n = line; n; n = n.parent) n.height += diff;
+    if (diff) for (var n = line; n; n = n.parent) n.height += diff;
   }
 
+  // Given a line object, find its line number by walking up through
+  // its parent links.
   function lineNo(line) {
     if (line.parent == null) return null;
     var cur = line.parent, no = indexOf(cur.lines, line);
     for (var chunk = cur.parent; chunk; cur = chunk, chunk = chunk.parent) {
       for (var i = 0;; ++i) {
         if (chunk.children[i] == cur) break;
         no += chunk.children[i].chunkSize();
       }
     }
     return no + cur.first;
   }
 
+  // Find the line at the given vertical position, using the height
+  // information in the document tree.
   function lineAtHeight(chunk, h) {
     var n = chunk.first;
     outer: do {
-      for (var i = 0, e = chunk.children.length; i < e; ++i) {
+      for (var i = 0; i < chunk.children.length; ++i) {
         var child = chunk.children[i], ch = child.height;
         if (h < ch) { chunk = child; continue outer; }
         h -= ch;
         n += child.chunkSize();
       }
       return n;
     } while (!chunk.lines);
-    for (var i = 0, e = chunk.lines.length; i < e; ++i) {
+    for (var i = 0; i < chunk.lines.length; ++i) {
       var line = chunk.lines[i], lh = line.height;
       if (h < lh) break;
       h -= lh;
     }
     return n + i;
   }
 
-  function heightAtLine(cm, lineObj) {
-    lineObj = visualLine(cm.doc, lineObj);
+
+  // Find the height above the given line.
+  function heightAtLine(lineObj) {
+    lineObj = visualLine(lineObj);
 
     var h = 0, chunk = lineObj.parent;
     for (var i = 0; i < chunk.lines.length; ++i) {
       var line = chunk.lines[i];
       if (line == lineObj) break;
       else h += line.height;
     }
     for (var p = chunk.parent; p; chunk = p, p = chunk.parent) {
       for (var i = 0; i < p.children.length; ++i) {
         var cur = p.children[i];
         if (cur == chunk) break;
         else h += cur.height;
       }
     }
     return h;
   }
 
+  // Get the bidi ordering for the given line (and cache it). Returns
+  // false for lines that are fully left-to-right, and an array of
+  // BidiSpan objects otherwise.
   function getOrder(line) {
     var order = line.order;
     if (order == null) order = line.order = bidiOrdering(line.text);
     return order;
   }
 
   // HISTORY
 
-  function makeHistory(startGen) {
-    return {
-      // Arrays of history events. Doing something adds an event to
-      // done and clears undo. Undoing moves events from done to
-      // undone, redoing moves them in the other direction.
-      done: [], undone: [], undoDepth: Infinity,
-      // Used to track when changes can be merged into a single undo
-      // event
-      lastTime: 0, lastOp: null, lastOrigin: null,
-      // Used by the isClean() method
-      generation: startGen || 1, maxGeneration: startGen || 1
-    };
+  function History(startGen) {
+    // Arrays of change events and selections. Doing something adds an
+    // event to done and clears undo. Undoing moves events from done
+    // to undone, redoing moves them in the other direction.
+    this.done = []; this.undone = [];
+    this.undoDepth = Infinity;
+    // Used to track when changes can be merged into a single undo
+    // event
+    this.lastModTime = this.lastSelTime = 0;
+    this.lastOp = null;
+    this.lastOrigin = this.lastSelOrigin = null;
+    // Used by the isClean() method
+    this.generation = this.maxGeneration = startGen || 1;
   }
 
-  function attachLocalSpans(doc, change, from, to) {
-    var existing = change["spans_" + doc.id], n = 0;
-    doc.iter(Math.max(doc.first, from), Math.min(doc.first + doc.size, to), function(line) {
-      if (line.markedSpans)
-        (existing || (existing = change["spans_" + doc.id] = {}))[n] = line.markedSpans;
-      ++n;
-    });
-  }
-
+  // Create a history change event from an updateDoc-style change
+  // object.
   function historyChangeFromChange(doc, change) {
-    var from = { line: change.from.line, ch: change.from.ch };
-    var histChange = {from: from, to: changeEnd(change), text: getBetween(doc, change.from, change.to)};
+    var histChange = {from: copyPos(change.from), to: changeEnd(change), text: getBetween(doc, change.from, change.to)};
     attachLocalSpans(doc, histChange, change.from.line, change.to.line + 1);
     linkedDocs(doc, function(doc) {attachLocalSpans(doc, histChange, change.from.line, change.to.line + 1);}, true);
     return histChange;
   }
 
-  function addToHistory(doc, change, selAfter, opId) {
+  // Pop all selection events off the end of a history array. Stop at
+  // a change event.
+  function clearSelectionEvents(array) {
+    while (array.length) {
+      var last = lst(array);
+      if (last.ranges) array.pop();
+      else break;
+    }
+  }
+
+  // Find the top change event in the history. Pop off selection
+  // events that are in the way.
+  function lastChangeEvent(hist, force) {
+    if (force) {
+      clearSelectionEvents(hist.done);
+      return lst(hist.done);
+    } else if (hist.done.length && !lst(hist.done).ranges) {
+      return lst(hist.done);
+    } else if (hist.done.length > 1 && !hist.done[hist.done.length - 2].ranges) {
+      hist.done.pop();
+      return lst(hist.done);
+    }
+  }
+
+  // Register a change in the history. Merges changes that are within
+  // a single operation, ore are close together with an origin that
+  // allows merging (starting with "+") into a single event.
+  function addChangeToHistory(doc, change, selAfter, opId) {
     var hist = doc.history;
     hist.undone.length = 0;
-    var time = +new Date, cur = lst(hist.done);
+    var time = +new Date, cur;
 
-    if (cur &&
-        (hist.lastOp == opId ||
+    if ((hist.lastOp == opId ||
          hist.lastOrigin == change.origin && change.origin &&
-         ((change.origin.charAt(0) == "+" && doc.cm && hist.lastTime > time - doc.cm.options.historyEventDelay) ||
-          change.origin.charAt(0) == "*"))) {
+         ((change.origin.charAt(0) == "+" && doc.cm && hist.lastModTime > time - doc.cm.options.historyEventDelay) ||
+          change.origin.charAt(0) == "*")) &&
+        (cur = lastChangeEvent(hist, hist.lastOp == opId))) {
       // Merge this change into the last event
       var last = lst(cur.changes);
-      if (posEq(change.from, change.to) && posEq(change.from, last.to)) {
+      if (cmp(change.from, change.to) == 0 && cmp(change.from, last.to) == 0) {
         // Optimized case for simple insertion -- don't want to add
         // new changesets for every character typed
         last.to = changeEnd(change);
       } else {
         // Add new sub-event
         cur.changes.push(historyChangeFromChange(doc, change));
       }
-      cur.anchorAfter = selAfter.anchor; cur.headAfter = selAfter.head;
     } else {
       // Can not be merged, start a new event.
+      var before = lst(hist.done);
+      if (!before || !before.ranges)
+        pushSelectionToHistory(doc.sel, hist.done);
       cur = {changes: [historyChangeFromChange(doc, change)],
-             generation: hist.generation,
-             anchorBefore: doc.sel.anchor, headBefore: doc.sel.head,
-             anchorAfter: selAfter.anchor, headAfter: selAfter.head};
+             generation: hist.generation};
       hist.done.push(cur);
-      while (hist.done.length > hist.undoDepth)
+      while (hist.done.length > hist.undoDepth) {
         hist.done.shift();
+        if (!hist.done[0].ranges) hist.done.shift();
+      }
     }
+    hist.done.push(selAfter);
     hist.generation = ++hist.maxGeneration;
-    hist.lastTime = time;
+    hist.lastModTime = hist.lastSelTime = time;
     hist.lastOp = opId;
-    hist.lastOrigin = change.origin;
+    hist.lastOrigin = hist.lastSelOrigin = change.origin;
+
+    if (!last) signal(doc, "historyAdded");
   }
 
+  function selectionEventCanBeMerged(doc, origin, prev, sel) {
+    var ch = origin.charAt(0);
+    return ch == "*" ||
+      ch == "+" &&
+      prev.ranges.length == sel.ranges.length &&
+      prev.somethingSelected() == sel.somethingSelected() &&
+      new Date - doc.history.lastSelTime <= (doc.cm ? doc.cm.options.historyEventDelay : 500);
+  }
+
+  // Called whenever the selection changes, sets the new selection as
+  // the pending selection in the history, and pushes the old pending
+  // selection into the 'done' array when it was significantly
+  // different (in number of selected ranges, emptiness, or time).
+  function addSelectionToHistory(doc, sel, opId, options) {
+    var hist = doc.history, origin = options && options.origin;
+
+    // A new event is started when the previous origin does not match
+    // the current, or the origins don't allow matching. Origins
+    // starting with * are always merged, those starting with + are
+    // merged when similar and close together in time.
+    if (opId == hist.lastOp ||
+        (origin && hist.lastSelOrigin == origin &&
+         (hist.lastModTime == hist.lastSelTime && hist.lastOrigin == origin ||
+          selectionEventCanBeMerged(doc, origin, lst(hist.done), sel))))
+      hist.done[hist.done.length - 1] = sel;
+    else
+      pushSelectionToHistory(sel, hist.done);
+
+    hist.lastSelTime = +new Date;
+    hist.lastSelOrigin = origin;
+    hist.lastOp = opId;
+    if (options && options.clearRedo !== false)
+      clearSelectionEvents(hist.undone);
+  }
+
+  function pushSelectionToHistory(sel, dest) {
+    var top = lst(dest);
+    if (!(top && top.ranges && top.equals(sel)))
+      dest.push(sel);
+  }
+
+  // Used to store marked span information in the history.
+  function attachLocalSpans(doc, change, from, to) {
+    var existing = change["spans_" + doc.id], n = 0;
+    doc.iter(Math.max(doc.first, from), Math.min(doc.first + doc.size, to), function(line) {
+      if (line.markedSpans)
+        (existing || (existing = change["spans_" + doc.id] = {}))[n] = line.markedSpans;
+      ++n;
+    });
+  }
+
+  // When un/re-doing restores text containing marked spans, those
+  // that have been explicitly cleared should not be restored.
   function removeClearedSpans(spans) {
     if (!spans) return null;
     for (var i = 0, out; i < spans.length; ++i) {
       if (spans[i].marker.explicitlyCleared) { if (!out) out = spans.slice(0, i); }
       else if (out) out.push(spans[i]);
     }
     return !out ? spans : out.length ? out : null;
   }
 
+  // Retrieve and filter the old marked spans stored in a change event.
   function getOldSpans(doc, change) {
     var found = change["spans_" + doc.id];
     if (!found) return null;
     for (var i = 0, nw = []; i < change.text.length; ++i)
       nw.push(removeClearedSpans(found[i]));
     return nw;
   }
 
   // Used both to provide a JSON-safe object in .getHistory, and, when
   // detaching a document, to split the history in two
-  function copyHistoryArray(events, newGroup) {
+  function copyHistoryArray(events, newGroup, instantiateSel) {
     for (var i = 0, copy = []; i < events.length; ++i) {
-      var event = events[i], changes = event.changes, newChanges = [];
-      copy.push({changes: newChanges, anchorBefore: event.anchorBefore, headBefore: event.headBefore,
-                 anchorAfter: event.anchorAfter, headAfter: event.headAfter});
+      var event = events[i];
+      if (event.ranges) {
+        copy.push(instantiateSel ? Selection.prototype.deepCopy.call(event) : event);
+        continue;
+      }
+      var changes = event.changes, newChanges = [];
+      copy.push({changes: newChanges});
       for (var j = 0; j < changes.length; ++j) {
         var change = changes[j], m;
         newChanges.push({from: change.from, to: change.to, text: change.text});
         if (newGroup) for (var prop in change) if (m = prop.match(/^spans_(\d+)$/)) {
           if (indexOf(newGroup, Number(m[1])) > -1) {
             lst(newChanges)[prop] = change[prop];
             delete change[prop];
           }
         }
       }
     }
     return copy;
   }
 
   // Rebasing/resetting history to deal with externally-sourced changes
 
-  function rebaseHistSel(pos, from, to, diff) {
+  function rebaseHistSelSingle(pos, from, to, diff) {
     if (to < pos.line) {
       pos.line += diff;
     } else if (from < pos.line) {
       pos.line = from;
       pos.ch = 0;
     }
   }
 
   // Tries to rebase an array of history events given a change in the
   // document. If the change touches the same lines as the event, the
   // event, and everything 'behind' it, is discarded. If the change is
   // before the event, the event's positions are updated. Uses a
   // copy-on-write scheme for the positions, to avoid having to
   // reallocate them all on every rebase, but also avoid problems with
   // shared position objects being unsafely updated.
   function rebaseHistArray(array, from, to, diff) {
     for (var i = 0; i < array.length; ++i) {
       var sub = array[i], ok = true;
+      if (sub.ranges) {
+        if (!sub.copied) { sub = array[i] = sub.deepCopy(); sub.copied = true; }
+        for (var j = 0; j < sub.ranges.length; j++) {
+          rebaseHistSelSingle(sub.ranges[j].anchor, from, to, diff);
+          rebaseHistSelSingle(sub.ranges[j].head, from, to, diff);
+        }
+        continue;
+      }
       for (var j = 0; j < sub.changes.length; ++j) {
         var cur = sub.changes[j];
-        if (!sub.copied) { cur.from = copyPos(cur.from); cur.to = copyPos(cur.to); }
         if (to < cur.from.line) {
-          cur.from.line += diff;
-          cur.to.line += diff;
+          cur.from = Pos(cur.from.line + diff, cur.from.ch);
+          cur.to = Pos(cur.to.line + diff, cur.to.ch);
         } else if (from <= cur.to.line) {
           ok = false;
           break;
         }
       }
-      if (!sub.copied) {
-        sub.anchorBefore = copyPos(sub.anchorBefore); sub.headBefore = copyPos(sub.headBefore);
-        sub.anchorAfter = copyPos(sub.anchorAfter); sub.readAfter = copyPos(sub.headAfter);
-        sub.copied = true;
-      }
       if (!ok) {
         array.splice(0, i + 1);
         i = 0;
-      } else {
-        rebaseHistSel(sub.anchorBefore); rebaseHistSel(sub.headBefore);
-        rebaseHistSel(sub.anchorAfter); rebaseHistSel(sub.headAfter);
       }
     }
   }
 
   function rebaseHist(hist, change) {
     var from = change.from.line, to = change.to.line, diff = change.text.length - (to - from) - 1;
     rebaseHistArray(hist.done, from, to, diff);
     rebaseHistArray(hist.undone, from, to, diff);
   }
 
-  // EVENT OPERATORS
+  // EVENT UTILITIES
 
-  function stopMethod() {e_stop(this);}
-  // Ensure an event has a stop method.
-  function addStop(event) {
-    if (!event.stop) event.stop = stopMethod;
-    return event;
-  }
+  // Due to the fact that we still support jurassic IE versions, some
+  // compatibility wrappers are needed.
 
-  function e_preventDefault(e) {
+  var e_preventDefault = CodeMirror.e_preventDefault = function(e) {
     if (e.preventDefault) e.preventDefault();
     else e.returnValue = false;
-  }
-  function e_stopPropagation(e) {
+  };
+  var e_stopPropagation = CodeMirror.e_stopPropagation = function(e) {
     if (e.stopPropagation) e.stopPropagation();
     else e.cancelBubble = true;
-  }
+  };
   function e_defaultPrevented(e) {
     return e.defaultPrevented != null ? e.defaultPrevented : e.returnValue == false;
   }
-  function e_stop(e) {e_preventDefault(e); e_stopPropagation(e);}
-  CodeMirror.e_stop = e_stop;
-  CodeMirror.e_preventDefault = e_preventDefault;
-  CodeMirror.e_stopPropagation = e_stopPropagation;
+  var e_stop = CodeMirror.e_stop = function(e) {e_preventDefault(e); e_stopPropagation(e);};
 
   function e_target(e) {return e.target || e.srcElement;}
   function e_button(e) {
     var b = e.which;
     if (b == null) {
       if (e.button & 1) b = 1;
       else if (e.button & 2) b = 3;
       else if (e.button & 4) b = 2;
     }
     if (mac && e.ctrlKey && b == 1) b = 3;
     return b;
   }
 
   // EVENT HANDLING
 
-  function on(emitter, type, f) {
+  // Lightweight event framework. on/off also work on DOM nodes,
+  // registering native DOM handlers.
+
+  var on = CodeMirror.on = function(emitter, type, f) {
     if (emitter.addEventListener)
       emitter.addEventListener(type, f, false);
     else if (emitter.attachEvent)
       emitter.attachEvent("on" + type, f);
     else {
       var map = emitter._handlers || (emitter._handlers = {});
       var arr = map[type] || (map[type] = []);
       arr.push(f);
     }
-  }
+  };
 
-  function off(emitter, type, f) {
+  var off = CodeMirror.off = function(emitter, type, f) {
     if (emitter.removeEventListener)
       emitter.removeEventListener(type, f, false);
     else if (emitter.detachEvent)
       emitter.detachEvent("on" + type, f);
     else {
       var arr = emitter._handlers && emitter._handlers[type];
       if (!arr) return;
       for (var i = 0; i < arr.length; ++i)
         if (arr[i] == f) { arr.splice(i, 1); break; }
     }
-  }
+  };
 
-  function signal(emitter, type /*, values...*/) {
+  var signal = CodeMirror.signal = function(emitter, type /*, values...*/) {
     var arr = emitter._handlers && emitter._handlers[type];
     if (!arr) return;
     var args = Array.prototype.slice.call(arguments, 2);
     for (var i = 0; i < arr.length; ++i) arr[i].apply(null, args);
-  }
+  };
 
+  // Often, we want to signal events at a point where we are in the
+  // middle of some work, but don't want the handler to start calling
+  // other methods on the editor, which might be in an inconsistent
+  // state or simply not expect any other events to happen.
+  // signalLater looks whether there are any handlers, and schedules
+  // them to be executed when the last operation ends, or, if no
+  // operation is active, when a timeout fires.
   var delayedCallbacks, delayedCallbackDepth = 0;
   function signalLater(emitter, type /*, values...*/) {
     var arr = emitter._handlers && emitter._handlers[type];
     if (!arr) return;
     var args = Array.prototype.slice.call(arguments, 2);
     if (!delayedCallbacks) {
       ++delayedCallbackDepth;
       delayedCallbacks = [];
       setTimeout(fireDelayed, 0);
     }
     function bnd(f) {return function(){f.apply(null, args);};};
     for (var i = 0; i < arr.length; ++i)
       delayedCallbacks.push(bnd(arr[i]));
   }
 
-  function signalDOMEvent(cm, e, override) {
-    signal(cm, override || e.type, cm, e);
-    return e_defaultPrevented(e) || e.codemirrorIgnore;
-  }
-
   function fireDelayed() {
     --delayedCallbackDepth;
     var delayed = delayedCallbacks;
     delayedCallbacks = null;
     for (var i = 0; i < delayed.length; ++i) delayed[i]();
   }
 
+  // The DOM events that CodeMirror handles can be overridden by
+  // registering a (non-DOM) handler on the editor for the event name,
+  // and preventDefault-ing the event in that handler.
+  function signalDOMEvent(cm, e, override) {
+    signal(cm, override || e.type, cm, e);
+    return e_defaultPrevented(e) || e.codemirrorIgnore;
+  }
+
   function hasHandler(emitter, type) {
     var arr = emitter._handlers && emitter._handlers[type];
     return arr && arr.length > 0;
   }
 
-  CodeMirror.on = on; CodeMirror.off = off; CodeMirror.signal = signal;
-
+  // Add on and off methods to a constructor's prototype, to make
+  // registering events on such objects more convenient.
   function eventMixin(ctor) {
     ctor.prototype.on = function(type, f) {on(this, type, f);};
     ctor.prototype.off = function(type, f) {off(this, type, f);};
   }
 
   // MISC UTILITIES
 
   // Number of pixels added to scroller and sizer to hide scrollbar
   var scrollerCutOff = 30;
 
   // Returned or thrown by various protocols to signal 'I'm not
   // handling this'.
   var Pass = CodeMirror.Pass = {toString: function(){return "CodeMirror.Pass";}};
 
+  // Reused option objects for setSelection & friends
+  var sel_dontScroll = {scroll: false}, sel_mouse = {origin: "*mouse"}, sel_move = {origin: "+move"};
+
   function Delayed() {this.id = null;}
-  Delayed.prototype = {set: function(ms, f) {clearTimeout(this.id); this.id = setTimeout(f, ms);}};
+  Delayed.prototype.set = function(ms, f) {
+    clearTimeout(this.id);
+    this.id = setTimeout(f, ms);
+  };
 
   // Counts the column offset in a string, taking tabs into account.
   // Used mostly to find indentation.
-  function countColumn(string, end, tabSize, startIndex, startValue) {
+  var countColumn = CodeMirror.countColumn = function(string, end, tabSize, startIndex, startValue) {
     if (end == null) {
       end = string.search(/[^\s\u00a0]/);
       if (end == -1) end = string.length;
     }
-    for (var i = startIndex || 0, n = startValue || 0; i < end; ++i) {
-      if (string.charAt(i) == "\t") n += tabSize - (n % tabSize);
-      else ++n;
+    for (var i = startIndex || 0, n = startValue || 0;;) {
+      var nextTab = string.indexOf("\t", i);
+      if (nextTab < 0 || nextTab >= end)
+        return n + (end - i);
+      n += nextTab - i;
+      n += tabSize - (n % tabSize);
+      i = nextTab + 1;
     }
-    return n;
+  };
+
+  // The inverse of countColumn -- find the offset that corresponds to
+  // a particular column.
+  function findColumn(string, goal, tabSize) {
+    for (var pos = 0, col = 0;;) {
+      var nextTab = string.indexOf("\t", pos);
+      if (nextTab == -1) nextTab = string.length;
+      var skipped = nextTab - pos;
+      if (nextTab == string.length || col + skipped >= goal)
+        return pos + Math.min(skipped, goal - col);
+      col += nextTab - pos;
+      col += tabSize - (col % tabSize);
+      pos = nextTab + 1;
+      if (col >= goal) return pos;
+    }
   }
-  CodeMirror.countColumn = countColumn;
 
   var spaceStrs = [""];
   function spaceStr(n) {
     while (spaceStrs.length <= n)
       spaceStrs.push(lst(spaceStrs) + " ");
     return spaceStrs[n];
   }
 
   function lst(arr) { return arr[arr.length-1]; }
 
-  function selectInput(node) {
-    if (ios) { // Mobile Safari apparently has a bug where select() is broken.
-      node.selectionStart = 0;
-      node.selectionEnd = node.value.length;
-    } else {
-      // Suppress mysterious IE10 errors
-      try { node.select(); }
-      catch(_e) {}
-    }
-  }
+  var selectInput = function(node) { node.select(); };
+  if (ios) // Mobile Safari apparently has a bug where select() is broken.
+    selectInput = function(node) { node.selectionStart = 0; node.selectionEnd = node.value.length; };
+  else if (ie) // Suppress mysterious IE10 errors
+    selectInput = function(node) { try { node.select(); } catch(_e) {} };
 
-  function indexOf(collection, elt) {
-    if (collection.indexOf) return collection.indexOf(elt);
-    for (var i = 0, e = collection.length; i < e; ++i)
-      if (collection[i] == elt) return i;
+  function indexOf(array, elt) {
+    for (var i = 0; i < array.length; ++i)
+      if (array[i] == elt) return i;
     return -1;
   }
+  if ([].indexOf) indexOf = function(array, elt) { return array.indexOf(elt); };
+  function map(array, f) {
+    var out = [];
+    for (var i = 0; i < array.length; i++) out[i] = f(array[i], i);
+    return out;
+  }
+  if ([].map) map = function(array, f) { return array.map(f); };
 
   function createObj(base, props) {
-    function Obj() {}
-    Obj.prototype = base;
-    var inst = new Obj();
+    var inst;
+    if (Object.create) {
+      inst = Object.create(base);
+    } else {
+      var ctor = function() {};
+      ctor.prototype = base;
+      inst = new ctor();
+    }
     if (props) copyObj(props, inst);
     return inst;
-  }
+  };
 
   function copyObj(obj, target) {
     if (!target) target = {};
     for (var prop in obj) if (obj.hasOwnProperty(prop)) target[prop] = obj[prop];
     return target;
   }
 
-  function emptyArray(size) {
-    for (var a = [], i = 0; i < size; ++i) a.push(undefined);
-    return a;
-  }
-
   function bind(f) {
     var args = Array.prototype.slice.call(arguments, 1);
     return function(){return f.apply(null, args);};
   }
 
-  var nonASCIISingleCaseWordChar = /[\u3040-\u309f\u30a0-\u30ff\u3400-\u4db5\u4e00-\u9fcc\uac00-\ud7af]/;
-  function isWordChar(ch) {
+  var nonASCIISingleCaseWordChar = /[\u00df\u3040-\u309f\u30a0-\u30ff\u3400-\u4db5\u4e00-\u9fcc\uac00-\ud7af]/;
+  var isWordChar = CodeMirror.isWordChar = function(ch) {
     return /\w/.test(ch) || ch > "\x80" &&
       (ch.toUpperCase() != ch.toLowerCase() || nonASCIISingleCaseWordChar.test(ch));
-  }
+  };
 
   function isEmpty(obj) {
     for (var n in obj) if (obj.hasOwnProperty(n) && obj[n]) return false;
     return true;
   }
 
+  // Extending unicode characters. A series of a non-extending char +
+  // any number of extending chars is treated as a single unit as far
+  // as editing and measuring is concerned. This is not fully correct,
+  // since some scripts/fonts/browsers also treat other configurations
+  // of code points as a group.
   var extendingChars = /[\u0300-\u036f\u0483-\u0489\u0591-\u05bd\u05bf\u05c1\u05c2\u05c4\u05c5\u05c7\u0610-\u061a\u064b-\u065e\u0670\u06d6-\u06dc\u06de-\u06e4\u06e7\u06e8\u06ea-\u06ed\u0711\u0730-\u074a\u07a6-\u07b0\u07eb-\u07f3\u0816-\u0819\u081b-\u0823\u0825-\u0827\u0829-\u082d\u0900-\u0902\u093c\u0941-\u0948\u094d\u0951-\u0955\u0962\u0963\u0981\u09bc\u09be\u09c1-\u09c4\u09cd\u09d7\u09e2\u09e3\u0a01\u0a02\u0a3c\u0a41\u0a42\u0a47\u0a48\u0a4b-\u0a4d\u0a51\u0a70\u0a71\u0a75\u0a81\u0a82\u0abc\u0ac1-\u0ac5\u0ac7\u0ac8\u0acd\u0ae2\u0ae3\u0b01\u0b3c\u0b3e\u0b3f\u0b41-\u0b44\u0b4d\u0b56\u0b57\u0b62\u0b63\u0b82\u0bbe\u0bc0\u0bcd\u0bd7\u0c3e-\u0c40\u0c46-\u0c48\u0c4a-\u0c4d\u0c55\u0c56\u0c62\u0c63\u0cbc\u0cbf\u0cc2\u0cc6\u0ccc\u0ccd\u0cd5\u0cd6\u0ce2\u0ce3\u0d3e\u0d41-\u0d44\u0d4d\u0d57\u0d62\u0d63\u0dca\u0dcf\u0dd2-\u0dd4\u0dd6\u0ddf\u0e31\u0e34-\u0e3a\u0e47-\u0e4e\u0eb1\u0eb4-\u0eb9\u0ebb\u0ebc\u0ec8-\u0ecd\u0f18\u0f19\u0f35\u0f37\u0f39\u0f71-\u0f7e\u0f80-\u0f84\u0f86\u0f87\u0f90-\u0f97\u0f99-\u0fbc\u0fc6\u102d-\u1030\u1032-\u1037\u1039\u103a\u103d\u103e\u1058\u1059\u105e-\u1060\u1071-\u1074\u1082\u1085\u1086\u108d\u109d\u135f\u1712-\u1714\u1732-\u1734\u1752\u1753\u1772\u1773\u17b7-\u17bd\u17c6\u17c9-\u17d3\u17dd\u180b-\u180d\u18a9\u1920-\u1922\u1927\u1928\u1932\u1939-\u193b\u1a17\u1a18\u1a56\u1a58-\u1a5e\u1a60\u1a62\u1a65-\u1a6c\u1a73-\u1a7c\u1a7f\u1b00-\u1b03\u1b34\u1b36-\u1b3a\u1b3c\u1b42\u1b6b-\u1b73\u1b80\u1b81\u1ba2-\u1ba5\u1ba8\u1ba9\u1c2c-\u1c33\u1c36\u1c37\u1cd0-\u1cd2\u1cd4-\u1ce0\u1ce2-\u1ce8\u1ced\u1dc0-\u1de6\u1dfd-\u1dff\u200c\u200d\u20d0-\u20f0\u2cef-\u2cf1\u2de0-\u2dff\u302a-\u302f\u3099\u309a\ua66f-\ua672\ua67c\ua67d\ua6f0\ua6f1\ua802\ua806\ua80b\ua825\ua826\ua8c4\ua8e0-\ua8f1\ua926-\ua92d\ua947-\ua951\ua980-\ua982\ua9b3\ua9b6-\ua9b9\ua9bc\uaa29-\uaa2e\uaa31\uaa32\uaa35\uaa36\uaa43\uaa4c\uaab0\uaab2-\uaab4\uaab7\uaab8\uaabe\uaabf\uaac1\uabe5\uabe8\uabed\udc00-\udfff\ufb1e\ufe00-\ufe0f\ufe20-\ufe26\uff9e\uff9f]/;
   function isExtendingChar(ch) { return ch.charCodeAt(0) >= 768 && extendingChars.test(ch); }
 
   // DOM UTILITIES
 
   function elt(tag, content, className, style) {
     var e = document.createElement(tag);
     if (className) e.className = className;
     if (style) e.style.cssText = style;
-    if (typeof content == "string") setTextContent(e, content);
+    if (typeof content == "string") e.appendChild(document.createTextNode(content));
     else if (content) for (var i = 0; i < content.length; ++i) e.appendChild(content[i]);
     return e;
   }
 
+  var range;
+  if (document.createRange) range = function(node, start, end) {
+    var r = document.createRange();
+    r.setEnd(node, end);
+    r.setStart(node, start);
+    return r;
+  };
+  else range = function(node, start, end) {
+    var r = document.body.createTextRange();
+    r.moveToElementText(node.parentNode);
+    r.collapse(true);
+    r.moveEnd("character", end);
+    r.moveStart("character", start);
+    return r;
+  };
+
   function removeChildren(e) {
     for (var count = e.childNodes.length; count > 0; --count)
       e.removeChild(e.firstChild);
     return e;
   }
 
   function removeChildrenAndAdd(parent, e) {
     return removeChildren(parent).appendChild(e);
   }
 
-  function setTextContent(e, str) {
-    if (ie_lt9) {
-      e.innerHTML = "";
-      e.appendChild(document.createTextNode(str));
-    } else e.textContent = str;
+  function contains(parent, child) {
+    if (parent.contains)
+      return parent.contains(child);
+    while (child = child.parentNode)
+      if (child == parent) return true;
   }
 
-  function getRect(node) {
-    return node.getBoundingClientRect();
-  }
-  CodeMirror.replaceGetRect = function(f) { getRect = f; };
+  function activeElt() { return document.activeElement; }
+  // Older versions of IE throws unspecified error when touching
+  // document.activeElement in some cases (during loading, in iframe)
+  if (ie_upto10) activeElt = function() {
+    try { return document.activeElement; }
+    catch(e) { return document.body; }
+  };
 
   // FEATURE DETECTION
 
   // Detect drag-and-drop
   var dragAndDrop = function() {
     // There is *some* kind of drag-and-drop support in IE6-8, but I
     // couldn't get it to work yet.
-    if (ie_lt9) return false;
+    if (ie_upto8) return false;
     var div = elt('div');
     return "draggable" in div || "dragDrop" in div;
   }();
 
-  // For a reason I have yet to figure out, some browsers disallow
-  // word wrapping between certain characters *only* if a new inline
-  // element is started between them. This makes it hard to reliably
-  // measure the position of things, since that requires inserting an
-  // extra span. This terribly fragile set of tests matches the
-  // character combinations that suffer from this phenomenon on the
-  // various browsers.
-  function spanAffectsWrapping() { return false; }
-  if (gecko) // Only for "$'"
-    spanAffectsWrapping = function(str, i) {
-      return str.charCodeAt(i - 1) == 36 && str.charCodeAt(i) == 39;
-    };
-  else if (safari && !/Version\/([6-9]|\d\d)\b/.test(navigator.userAgent))
-    spanAffectsWrapping = function(str, i) {
-      return /\-[^ \-?]|\?[^ !\'\"\),.\-\/:;\?\]\}]/.test(str.slice(i - 1, i + 1));
-    };
-  else if (webkit && /Chrome\/(?:29|[3-9]\d|\d\d\d)\./.test(navigator.userAgent))
-    spanAffectsWrapping = function(str, i) {
-      var code = str.charCodeAt(i - 1);
-      return code >= 8208 && code <= 8212;
-    };
-  else if (webkit)
-    spanAffectsWrapping = function(str, i) {
-      if (i > 1 && str.charCodeAt(i - 1) == 45) {
-        if (/\w/.test(str.charAt(i - 2)) && /[^\-?\.]/.test(str.charAt(i))) return true;
-        if (i > 2 && /[\d\.,]/.test(str.charAt(i - 2)) && /[\d\.,]/.test(str.charAt(i))) return false;
-      }
-      return /[~!#%&*)=+}\]\\|\"\.>,:;][({[<]|-[^\-?\.\u2010-\u201f\u2026]|\?[\w~`@#$%\^&*(_=+{[|><]|\u2026[\w~`@#$%\^&*(_=+{[><]/.test(str.slice(i - 1, i + 1));
-    };
-
   var knownScrollbarWidth;
   function scrollbarWidth(measure) {
     if (knownScrollbarWidth != null) return knownScrollbarWidth;
     var test = elt("div", null, null, "width: 50px; height: 50px; overflow-x: scroll");
     removeChildrenAndAdd(measure, test);
     if (test.offsetWidth)
       knownScrollbarWidth = test.offsetHeight - test.clientHeight;
     return knownScrollbarWidth || 0;
   }
 
   var zwspSupported;
   function zeroWidthElement(measure) {
     if (zwspSupported == null) {
       var test = elt("span", "\u200b");
       removeChildrenAndAdd(measure, elt("span", [test, document.createTextNode("x")]));
       if (measure.firstChild.offsetHeight != 0)
-        zwspSupported = test.offsetWidth <= 1 && test.offsetHeight > 2 && !ie_lt8;
+        zwspSupported = test.offsetWidth <= 1 && test.offsetHeight > 2 && !ie_upto7;
     }
     if (zwspSupported) return elt("span", "\u200b");
     else return elt("span", "\u00a0", null, "display: inline-block; width: 1px; margin-right: -1px");
   }
 
+  // Feature-detect IE's crummy client rect reporting for bidi text
+  var badBidiRects;
+  function hasBadBidiRects(measure) {
+    if (badBidiRects != null) return badBidiRects;
+    var txt = removeChildrenAndAdd(measure, document.createTextNode("A\u062eA"));
+    var r0 = range(txt, 0, 1).getBoundingClientRect();
+    if (r0.left == r0.right) return false;
+    var r1 = range(txt, 1, 2).getBoundingClientRect();
+    return badBidiRects = (r1.right - r0.right < 3);
+  }
+
   // See if "".split is the broken IE version, if so, provide an
   // alternative way to split lines.
-  var splitLines = "\n\nb".split(/\n/).length != 3 ? function(string) {
+  var splitLines = CodeMirror.splitLines = "\n\nb".split(/\n/).length != 3 ? function(string) {
     var pos = 0, result = [], l = string.length;
     while (pos <= l) {
       var nl = string.indexOf("\n", pos);
       if (nl == -1) nl = string.length;
       var line = string.slice(pos, string.charAt(nl - 1) == "\r" ? nl - 1 : nl);
       var rt = line.indexOf("\r");
       if (rt != -1) {
         result.push(line.slice(0, rt));
         pos += rt + 1;
       } else {
         result.push(line);
         pos = nl + 1;
       }
     }
     return result;
   } : function(string){return string.split(/\r\n?|\n/);};
-  CodeMirror.splitLines = splitLines;
 
   var hasSelection = window.getSelection ? function(te) {
     try { return te.selectionStart != te.selectionEnd; }
     catch(e) { return false; }
   } : function(te) {
     try {var range = te.ownerDocument.selection.createRange();}
     catch(e) {}
     if (!range || range.parentElement() != te) return false;
     return range.compareEndPoints("StartToEnd", range) != 0;
   };
 
   var hasCopyEvent = (function() {
     var e = elt("div");
     if ("oncopy" in e) return true;
     e.setAttribute("oncopy", "return;");
-    return typeof e.oncopy == 'function';
+    return typeof e.oncopy == "function";
   })();
 
-  // KEY NAMING
+  // KEY NAMES
 
   var keyNames = {3: "Enter", 8: "Backspace", 9: "Tab", 13: "Enter", 16: "Shift", 17: "Ctrl", 18: "Alt",
                   19: "Pause", 20: "CapsLock", 27: "Esc", 32: "Space", 33: "PageUp", 34: "PageDown", 35: "End",
                   36: "Home", 37: "Left", 38: "Up", 39: "Right", 40: "Down", 44: "PrintScrn", 45: "Insert",
                   46: "Delete", 59: ";", 61: "=", 91: "Mod", 92: "Mod", 93: "Mod", 107: "=", 109: "-", 127: "Delete",
                   173: "-", 186: ";", 187: "=", 188: ",", 189: "-", 190: ".", 191: "/", 192: "`", 219: "[", 220: "\\",
                   221: "]", 222: "'", 63232: "Up", 63233: "Down", 63234: "Left", 63235: "Right", 63272: "Delete",
                   63273: "Home", 63275: "End", 63276: "PageUp", 63277: "PageDown", 63302: "Insert"};
   CodeMirror.keyNames = keyNames;
   (function() {
@@ skipping 25 matching lines @@
 
   function lineLeft(line) { var order = getOrder(line); return order ? bidiLeft(order[0]) : 0; }
   function lineRight(line) {
     var order = getOrder(line);
     if (!order) return line.text.length;
     return bidiRight(lst(order));
   }
 
   function lineStart(cm, lineN) {
     var line = getLine(cm.doc, lineN);
-    var visual = visualLine(cm.doc, line);
+    var visual = visualLine(line);
     if (visual != line) lineN = lineNo(visual);
     var order = getOrder(visual);
     var ch = !order ? 0 : order[0].level % 2 ? lineRight(visual) : lineLeft(visual);
     return Pos(lineN, ch);
   }
   function lineEnd(cm, lineN) {
-    var merged, line;
-    while (merged = collapsedSpanAtEnd(line = getLine(cm.doc, lineN)))
-      lineN = merged.find().to.line;
+    var merged, line = getLine(cm.doc, lineN);
+    while (merged = collapsedSpanAtEnd(line)) {
+      line = merged.find(1, true).line;
+      lineN = null;
+    }
     var order = getOrder(line);
     var ch = !order ? line.text.length : order[0].level % 2 ? lineLeft(line) : lineRight(line);
-    return Pos(lineN, ch);
+    return Pos(lineN == null ? lineNo(line) : lineN, ch);
   }
 
   function compareBidiLevel(order, a, b) {
     var linedir = order[0].level;
     if (a == linedir) return true;
     if (b == linedir) return false;
     return a < b;
   }
   var bidiOther;
   function getBidiPartAt(order, pos) {
@@ skipping 16 matching lines @@
     return found;
   }
 
   function moveInLine(line, pos, dir, byUnit) {
     if (!byUnit) return pos + dir;
     do pos += dir;
     while (pos > 0 && isExtendingChar(line.text.charAt(pos)));
     return pos;
   }
 
-  // This is somewhat involved. It is needed in order to move
-  // 'visually' through bi-directional text -- i.e., pressing left
-  // should make the cursor go left, even when in RTL text. The
-  // tricky part is the 'jumps', where RTL and LTR text touch each
-  // other. This often requires the cursor offset to move more than
-  // one unit, in order to visually move one unit.
+  // This is needed in order to move 'visually' through bi-directional
+  // text -- i.e., pressing left should make the cursor go left, even
+  // when in RTL text. The tricky part is the 'jumps', where RTL and
+  // LTR text touch each other. This often requires the cursor offset
+  // to move more than one unit, in order to visually move one unit.
   function moveVisually(line, start, dir, byUnit) {
     var bidi = getOrder(line);
     if (!bidi) return moveLogically(line, start, dir, byUnit);
     var pos = getBidiPartAt(bidi, start), part = bidi[pos];
     var target = moveInLine(line, start, part.level % 2 ? -dir : dir, byUnit);
 
     for (;;) {
       if (target > part.from && target < part.to) return target;
       if (target == part.from || target == part.to) {
         if (getBidiPartAt(bidi, target) == pos) return target;
@@ skipping 34 matching lines @@
   // s (B):   Paragraph Separator
   // t (S):   Segment Separator
   // w (WS):  Whitespace
   // N (ON):  Other Neutrals
 
   // Returns null if characters are ordered as they appear
   // (left-to-right), or an array of sections ({from, to, level}
   // objects) in the order in which they occur visually.
   var bidiOrdering = (function() {
     // Character types for codepoints 0 to 0xff
-    var lowTypes = "bbbbbbbbbtstwsbbbbbbbbbbbbbbssstwNN%%%NNNNNN,N,N1111111111NNNNNNNLLLLLLLLLLLLLLLLLLLLLLLLLLNNNNNNLLLLLLLLLLLLLLLLLLLLLLLLLLNNNNbbbbbbsbbbbbbbbbbbbbbbbbbbbbbbbbb,N%%%%NNNNLNNNNN%%11NLNNN1LNNNNNLLLLLLLLLLLLLLLLLLLLLLLNLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLNLLLLLLLL";
+    var lowTypes = "bbbbbbbbbtstwsbbbbbbbbbbbbbbssstwNN%%%NNNNNN,N,N1111111111NNNNNNNLLLLLLLLLLLLLLLLLLLLLLLLLLNNNNNNLLLLLLLLLLLLLLLLLLLLLLLLLLNNNNbbbbbbsbbbbbbbbbbbbbbbbbbbbbbbbbb,N%%%%NNNNLNNNNN%%11NLNNN1LNNNNNLLLLLLLLLLLLLLLLLLLLLLLNLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLN";
     // Character types for codepoints 0x600 to 0x6ff
-    var arabicTypes = "rrrrrrrrrrrr,rNNmmmmmmrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrmmmmmmmmmmmmmmrrrrrrrnnnnnnnnnn%nnrrrmrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrmmmmmmmmmmmmmmmmmmmNmmmmrrrrrrrrrrrrrrrrrr";
+    var arabicTypes = "rrrrrrrrrrrr,rNNmmmmmmrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrmmmmmmmmmmmmmmrrrrrrrnnnnnnnnnn%nnrrrmrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrmmmmmmmmmmmmmmmmmmmNmmmm";
     function charType(code) {
-      if (code <= 0xff) return lowTypes.charAt(code);
+      if (code <= 0xf7) return lowTypes.charAt(code);
       else if (0x590 <= code && code <= 0x5f4) return "R";
-      else if (0x600 <= code && code <= 0x6ff) return arabicTypes.charAt(code - 0x600);
-      else if (0x700 <= code && code <= 0x8ac) return "r";
+      else if (0x600 <= code && code <= 0x6ed) return arabicTypes.charAt(code - 0x600);
+      else if (0x6ee <= code && code <= 0x8ac) return "r";
+      else if (0x2000 <= code && code <= 0x200b) return "w";
+      else if (code == 0x200c) return "b";
       else return "L";
     }
 
     var bidiRE = /[\u0590-\u05f4\u0600-\u06ff\u0700-\u08ac]/;
     var isNeutral = /[stwN]/, isStrong = /[LRr]/, countsAsLeft = /[Lb1n]/, countsAsNum = /[1n]/;
     // Browsers seem to always treat the boundaries of block elements as being L.
     var outerType = "L";
 
+    function BidiSpan(level, from, to) {
+      this.level = level;
+      this.from = from; this.to = to;
+    }
+
     return function(str) {
       if (!bidiRE.test(str)) return false;
       var len = str.length, types = [];
       for (var i = 0, type; i < len; ++i)
         types.push(type = charType(str.charCodeAt(i)));
 
       // W1. Examine each non-spacing mark (NSM) in the level run, and
       // change the type of the NSM to the type of the previous
       // character. If the NSM is at the start of the level run, it will
       // get the type of sor.
@@ skipping 69 matching lines @@
       // Here we depart from the documented algorithm, in order to avoid
       // building up an actual levels array. Since there are only three
       // levels (0, 1, 2) in an implementation that doesn't take
       // explicit embedding into account, we can build up the order on
       // the fly, without following the level-based algorithm.
       var order = [], m;
       for (var i = 0; i < len;) {
         if (countsAsLeft.test(types[i])) {
           var start = i;
           for (++i; i < len && countsAsLeft.test(types[i]); ++i) {}
-          order.push({from: start, to: i, level: 0});
+          order.push(new BidiSpan(0, start, i));
         } else {
           var pos = i, at = order.length;
           for (++i; i < len && types[i] != "L"; ++i) {}
           for (var j = pos; j < i;) {
             if (countsAsNum.test(types[j])) {
-              if (pos < j) order.splice(at, 0, {from: pos, to: j, level: 1});
+              if (pos < j) order.splice(at, 0, new BidiSpan(1, pos, j));
               var nstart = j;
               for (++j; j < i && countsAsNum.test(types[j]); ++j) {}
-              order.splice(at, 0, {from: nstart, to: j, level: 2});
+              order.splice(at, 0, new BidiSpan(2, nstart, j));
               pos = j;
             } else ++j;
           }
-          if (pos < i) order.splice(at, 0, {from: pos, to: i, level: 1});
+          if (pos < i) order.splice(at, 0, new BidiSpan(1, pos, i));
         }
       }
       if (order[0].level == 1 && (m = str.match(/^\s+/))) {
         order[0].from = m[0].length;
-        order.unshift({from: 0, to: m[0].length, level: 0});
+        order.unshift(new BidiSpan(0, 0, m[0].length));
       }
       if (lst(order).level == 1 && (m = str.match(/\s+$/))) {
         lst(order).to -= m[0].length;
-        order.push({from: len - m[0].length, to: len, level: 0});
+        order.push(new BidiSpan(0, len - m[0].length, len));
       }
       if (order[0].level != lst(order).level)
-        order.push({from: len, to: len, level: order[0].level});
+        order.push(new BidiSpan(order[0].level, len, len));
 
       return order;
     };
   })();
 
   // THE END
 
-  CodeMirror.version = "3.21.1";
+  CodeMirror.version = "4.0.3";
 
   return CodeMirror;
-})();
+});