Initial landing of Screen, Terminal, and VT100 classes.

chrome/browser/resources/hterm/js/terminal.js

Index: chrome/browser/resources/hterm/js/terminal.js
diff --git a/chrome/browser/resources/hterm/js/terminal.js b/chrome/browser/resources/hterm/js/terminal.js
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+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * Constructor for the Terminal class.
+ *
+ * A Terminal pulls together the hterm.ScrollPort, hterm.Screen and hterm.VT100
+ * classes to provide the complete terminal functionality.
+ *
+ * There are a number of lower-level Terminal methods that can be called
+ * directly to manipulate the cursor, text, scroll region, and other terminal
+ * attributes.  However, the primary method is interpret(), which parses VT
+ * escape sequences and invokes the appropriate Terminal methods.
+ *
+ * This class was heavily influenced by Cory Maccarrone's Framebuffer class.
+ *
+ * TODO(rginda): Eventually we're going to need to support characters which are
+ * displayed twice as wide as standard latin characters.  This is to support
+ * CJK (and possibly other character sets).
+ */
+hterm.Terminal = function() {
+  // Two screen instances.
+  this.primaryScreen_ = new hterm.Screen();
+  this.alternateScreen_ = new hterm.Screen();
+
+  // The "current" screen.
+  this.screen_ = this.primaryScreen_;
+
+  // The VT escape sequence interpreter.
+  this.vt100_ = new hterm.VT100(this);
+
+  // The local notion of the screen size.  ScreenBuffers also have a size which
+  // indicates their present size.  During size changes, the two may disagree.
+  // Also, the inactive screen's size is not altered until it is made the active
+  // screen.
+  this.screenSize = new hterm.Size(0, 0);
+
+  // The pixel dimensions of a single character on the screen.
+  this.characterSize_ = new hterm.Size(0, 0);
+
+  // The scroll port we'll be using to display the visible rows.
+  this.scrollPort_ = new hterm.ScrollPort(this, 15);
+  this.scrollPort_.subscribe('resize', this.onResize_.bind(this));
+  this.scrollPort_.subscribe('scroll', this.onScroll_.bind(this));
+
+  // The rows that have scrolled off screen and are no longer addressable.
+  this.scrollbackRows_ = [];
+
+  // The VT's notion of the top and bottom rows.  Used during some VT
+  // cursor positioning and scrolling commands.
+  this.vtScrollTop_ = null;
+  this.vtScrollBottom_ = null;
+
+  // The DIV element for the visible cursor.
+  this.cursorNode_ = null;
+
+  // The default colors for text with no other color attributes.
+  this.backgroundColor = 'black';
+  this.foregroundColor = 'white';
+
+  // The color of the cursor.
+  this.cursorColor = 'rgba(255,0,0,0.5)';
+
+  // The current mode bits for the terminal.
+  this.options_ = new hterm.Options();
+
+  // Timeouts we might need to clear.
+  this.timeouts_ = {};
+};
+
+/**
+ * Methods called by Cory's vt100 interpreter which we haven't implemented yet.
+ */
+hterm.Terminal.prototype.reset =
+hterm.Terminal.prototype.clearColorAndAttributes =
+hterm.Terminal.prototype.setForegroundColor256 =
+hterm.Terminal.prototype.setBackgroundColor256 =
+hterm.Terminal.prototype.setForegroundColor =
+hterm.Terminal.prototype.setBackgroundColor =
+hterm.Terminal.prototype.setAttributes =
+hterm.Terminal.prototype.resize =
+hterm.Terminal.prototype.setSpecialCharactersEnabled =
+hterm.Terminal.prototype.setTabStopAtCursor =
+hterm.Terminal.prototype.clearTabStops =
+hterm.Terminal.prototype.saveCursor =
+hterm.Terminal.prototype.restoreCursor =
+hterm.Terminal.prototype.reverseLineFeed = function() {
+  throw 'NOT IMPLEMENTED';
+};
+
+/**
+ * Interpret a sequence of characters.
+ *
+ * Incomplete escape sequences are buffered until the next call.
+ *
+ * @param {string} str Sequence of characters to interpret or pass through.
+ */
+hterm.Terminal.prototype.interpret = function(str) {
+  this.vt100_.interpretString(str);
+  this.scheduleSyncCursorPosition_();
+};
+
+/**
+ * Take over the given DIV for use as the terminal display.
+ *
+ * @param {HTMLDivElement} div The div to use as the terminal display.
+ */
+hterm.Terminal.prototype.decorate = function(div) {
+  this.scrollPort_.decorate(div);
+  this.document_ = this.scrollPort_.getDocument();
+
+  // Get character dimensions from the scrollPort.
+  this.characterSize_.height = this.scrollPort_.getRowHeight();
+  this.characterSize_.width = this.scrollPort_.getCharacterWidth();
+
+  this.cursorNode_ = this.document_.createElement('div');
+  this.cursorNode_.style.cssText =
+      ('position: absolute;' +
+       'display: none;' +
+       'width: ' + this.characterSize_.width + 'px;' +
+       'height: ' + this.characterSize_.height + 'px;' +
+       'background-color: ' + this.cursorColor);
+  this.document_.body.appendChild(this.cursorNode_);
+
+  this.setReverseVideo(false);
+};
+
+/**
+ * Return the HTML Element for a given row index.
+ *
+ * This is a method from the RowProvider interface.  The ScrollPort uses
+ * it to fetch rows on demand as they are scrolled into view.
+ *
+ * TODO(rginda): Consider saving scrollback rows as (HTML source, text content)
+ * pairs to conserve memory.
+ *
+ * @param {integer} index The zero-based row index, measured relative to the
+ *     start of the scrollback buffer.  On-screen rows will always have the
+ *     largest indicies.
+ * @return {HTMLElement} The 'x-row' element containing for the requested row.
+ */
+hterm.Terminal.prototype.getRowNode = function(index) {
+  if (index < this.scrollbackRows_.length)
+    return this.scrollbackRows_[index];
+
+  var screenIndex = index - this.scrollbackRows_.length;
+  return this.screen_.rowsArray[screenIndex];
+};
+
+/**
+ * Return the text content for a given range of rows.
+ *
+ * This is a method from the RowProvider interface.  The ScrollPort uses
+ * it to fetch text content on demand when the user attempts to copy their
+ * selection to the clipboard.
+ *
+ * @param {integer} start The zero-based row index to start from, measured
+ *     relative to the start of the scrollback buffer.  On-screen rows will
+ *     always have the largest indicies.
+ * @param {integer} end The zero-based row index to end on, measured
+ *     relative to the start of the scrollback buffer.
+ * @return {string} A single string containing the text value of the range of
+ *     rows.  Lines will be newline delimited, with no trailing newline.
+ */
+hterm.Terminal.prototype.getRowsText = function(start, end) {
+  var ary = [];
+  for (var i = start; i < end; i++) {
+    var node = this.getRowNode(i);
+    ary.push(node.textContent);
+  }
+
+  return ary.join('\n');
+};
+
+/**
+ * Return the text content for a given row.
+ *
+ * This is a method from the RowProvider interface.  The ScrollPort uses
+ * it to fetch text content on demand when the user attempts to copy their
+ * selection to the clipboard.
+ *
+ * @param {integer} index The zero-based row index to return, measured
+ *     relative to the start of the scrollback buffer.  On-screen rows will
+ *     always have the largest indicies.
+ * @return {string} A string containing the text value of the selected row.
+ */
+hterm.Terminal.prototype.getRowText = function(index) {
+  var node = this.getRowNode(index);
+  return row.textContent;
+};
+
+/**
+ * Return the total number of rows in the addressable screen and in the
+ * scrollback buffer of this terminal.
+ *
+ * This is a method from the RowProvider interface.  The ScrollPort uses
+ * it to compute the size of the scrollbar.
+ *
+ * @return {integer} The number of rows in this terminal.
+ */
+hterm.Terminal.prototype.getRowCount = function() {
+  return this.scrollbackRows_.length + this.screen_.rowsArray.length;
+};
+
+/**
+ * Create DOM nodes for new rows and append them to the end of the terminal.
+ *
+ * This is the only correct way to add a new DOM node for a row.  Notice that
+ * the new row is appended to the bottom of the list of rows, and does not
+ * require renumbering (of the rowIndex property) of previous rows.
+ *
+ * If you think you want a new blank row somewhere in the middle of the
+ * terminal, look into moveRows_().
+ *
+ * This method does not pay attention to vtScrollTop/Bottom, since you should
+ * be using moveRows() in cases where they would matter.
+ *
+ * The cursor will be positioned at column 0 of the first inserted line.
+ */
+hterm.Terminal.prototype.appendRows_ = function(count) {
+  var cursorRow = this.screen_.rowsArray.length;
+  var offset = this.scrollbackRows_.length + cursorRow;
+  for (var i = 0; i < count; i++) {
+    var row = this.document_.createElement('x-row');
+    row.appendChild(this.document_.createTextNode(''));
+    row.rowIndex = offset + i;
+    this.screen_.pushRow(row);
+  }
+
+  var extraRows = this.screen_.rowsArray.length - this.screenSize.height;
+  if (extraRows > 0) {
+    var ary = this.screen_.shiftRows(extraRows);
+    Array.prototype.push.apply(this.scrollbackRows_, ary);
+    this.scheduleScrollDown_();
+  }
+
+  if (cursorRow >= this.screen_.rowsArray.length)
+    cursorRow = this.screen_.rowsArray.length - 1;
+
+  this.screen_.setCursorPosition(cursorRow, 0);
+};
+
+/**
+ * Relocate rows from one part of the addressable screen to another.
+ *
+ * This is used to recycle rows during VT scrolls (those which are driven
+ * by VT commands, rather than by the user manipulating the scrollbar.)
+ *
+ * In this case, the blank lines scrolled into the scroll region are made of
+ * the nodes we scrolled off.  These have their rowIndex properties carefully
+ * renumbered so as not to confuse the ScrollPort.
+ *
+ * TODO(rginda): I'm not sure why this doesn't require a scrollport repaint.
+ * It may just be luck.  I wouldn't be surprised if we actually needed to call
+ * scrollPort_.invalidateRowRange, but I'm going to wait for evidence before
+ * adding it.
+ */
+hterm.Terminal.prototype.moveRows_ = function(fromIndex, count, toIndex) {
+  var ary = this.screen_.removeRows(fromIndex, count);
+  this.screen_.insertRows(toIndex, ary);
+
+  var start, end;
+  if (fromIndex < toIndex) {
+    start = fromIndex;
+    end = fromIndex + count;
+  } else {
+    start = toIndex;
+    end = toIndex + count;
+  }
+
+  this.renumberRows_(start, end);
+};
+
+/**
+ * Renumber the rowIndex property of the given range of rows.
+ *
+ * The start and end indicies are relative to the screen, not the scrollback.
+ * Rows in the scrollback buffer cannot be renumbered.  Since they are not
+ * addressable (you cant delete them, scroll them, etc), you should have
+ * no need to renumber scrollback rows.
+ */
+hterm.Terminal.prototype.renumberRows_ = function(start, end) {
+  var offset = this.scrollbackRows_.length;
+  for (var i = start; i < end; i++) {
+    this.screen_.rowsArray[i].rowIndex = offset + i;
+  }
+};
+
+/**
+ * Print a string to the terminal.
+ *
+ * This respects the current insert and wraparound modes.  It will add new lines
+ * to the end of the terminal, scrolling off the top into the scrollback buffer
+ * if necessary.
+ *
+ * The string is *not* parsed for escape codes.  Use the interpret() method if
+ * that's what you're after.
+ *
+ * @param{string} str The string to print.
+ */
+hterm.Terminal.prototype.print = function(str) {
+  do {
+    if (this.options_.insertMode) {
+      str = this.screen_.insertString(str);
+    } else {
+      str = this.screen_.overwriteString(str);
+    }
+
+    if (this.options_.wraparound && str) {
+      this.newLine();
+    } else {
+      break;
+    }
+  } while (str);
+
+  this.scheduleSyncCursorPosition_();
+};
+
+/**
+ * Return the top row index according to the VT.
+ *
+ * This will return 0 unless the terminal has been told to restrict scrolling
+ * to some lower row.  It is used for some VT cursor positioning and scrolling
+ * commands.
+ *
+ * @return {integer} The topmost row in the terminal's scroll region.
+ */
+hterm.Terminal.prototype.getVTScrollTop = function() {
+  if (this.vtScrollTop_ != null)
+    return this.vtScrollTop_;
+
+  return 0;
+}
+
+/**
+ * Return the bottom row index according to the VT.
+ *
+ * This will return the height of the terminal unless the it has been told to
+ * restrict scrolling to some higher row.  It is used for some VT cursor
+ * positioning and scrolling commands.
+ *
+ * @return {integer} The bottommost row in the terminal's scroll region.
+ */
+hterm.Terminal.prototype.getVTScrollBottom = function() {
+  if (this.vtScrollBottom_ != null)
+    return this.vtScrollBottom_;
+
+  return this.screenSize.height;
+}
+
+/**
+ * Process a '\n' character.
+ *
+ * If the cursor is on the final row of the terminal this will append a new
+ * blank row to the screen and scroll the topmost row into the scrollback
+ * buffer.
+ *
+ * Otherwise, this moves the cursor to column zero of the next row.
+ */
+hterm.Terminal.prototype.newLine = function() {
+  if (this.screen_.cursorPosition.row == this.screen_.rowsArray.length - 1) {
+    this.appendRows_(1);
+  } else {
+    this.screen_.setCursorPosition(this.screen_.cursorPosition.row + 1, 0);
+  }
+};
+
+/**
+ * Like newLine(), except maintain the cursor column.
+ */
+hterm.Terminal.prototype.lineFeed = function() {
+  var column = this.screen_.cursorPosition.column;
+  this.newLine();
+  this.setCursorColumn(column);
+};
+
+/**
+ * Replace all characters to the left of the current cursor with the space
+ * character.
+ *
+ * TODO(rginda): This should probably *remove* the characters (not just replace
+ * with a space) if there are no characters at or beyond the current cursor
+ * position.  Once it does that, it'll have the same text-attribute related
+ * issues as hterm.Screen.prototype.clearCursorRow :/
+ */
+hterm.Terminal.prototype.eraseToLeft = function() {
+  var currentColumn = this.screen_.cursorPosition.column;
+  this.setCursorColumn(0);
+  this.screen_.overwriteString(hterm.getWhitespace(currentColumn + 1));
+  this.setCursorColumn(currentColumn);
+};
+
+/**
+ * Erase a given number of characters to the right of the cursor, shifting
+ * remaining characters to the left.
+ *
+ * The cursor position is unchanged.
+ *
+ * TODO(rginda): Test that this works even when the cursor is positioned beyond
+ * the end of the text.
+ *
+ * TODO(rginda): This likely has text-attribute related troubles similar to the
+ * todo on hterm.Screen.prototype.clearCursorRow.
+ */
+hterm.Terminal.prototype.eraseToRight = function(opt_count) {
+  var currentColumn = this.screen_.cursorPosition.column;
+
+  var maxCount = this.screenSize.width - currentColumn;
+  var count = (opt_count && opt_count < maxCount) ? opt_count : maxCount;
+  this.screen_.deleteChars(count);
+  this.setCursorColumn(currentColumn);
+};
+
+/**
+ * Erase the current line.
+ *
+ * The cursor position is unchanged.
+ *
+ * TODO(rginda): This relies on hterm.Screen.prototype.clearCursorRow, which
+ * has a text-attribute related TODO.
+ */
+hterm.Terminal.prototype.eraseLine = function() {
+  var currentColumn = this.screen_.cursorPosition.column;
+  this.screen_.clearCursorRow();
+  this.setCursorColumn(currentColumn);
+};
+
+/**
+ * Erase all characters from the start of the scroll region to the current
+ * cursor position.
+ *
+ * The cursor position is unchanged.
+ *
+ * TODO(rginda): This relies on hterm.Screen.prototype.clearCursorRow, which
+ * has a text-attribute related TODO.
+ */
+hterm.Terminal.prototype.eraseAbove = function() {
+  var currentRow = this.screen_.cursorPosition.row;
+  var currentColumn = this.screen_.cursorPosition.column;
+
+  var top = this.getVTScrollTop();
+  for (var i = top; i < currentRow; i++) {
+    this.screen_.setCursorPosition(i, 0);
+    this.screen_.clearCursorRow();
+  }
+
+  this.screen_.setCursorPosition(currentRow, currentColumn);
+};
+
+/**
+ * Erase all characters from the current cursor position to the end of the
+ * scroll region.
+ *
+ * The cursor position is unchanged.
+ *
+ * TODO(rginda): This relies on hterm.Screen.prototype.clearCursorRow, which
+ * has a text-attribute related TODO.
+ */
+hterm.Terminal.prototype.eraseBelow = function() {
+  var currentRow = this.screen_.cursorPosition.row;
+  var currentColumn = this.screen_.cursorPosition.column;
+
+  var bottom = this.getVTScrollBottom();
+  for (var i = currentRow + 1; i < bottom; i++) {
+    this.screen_.setCursorPosition(i, 0);
+    this.screen_.clearCursorRow();
+  }
+
+  this.screen_.setCursorPosition(currentRow, currentColumn);
+};
+
+/**
+ * Erase the entire scroll region.
+ *
+ * The cursor position is unchanged.
+ *
+ * TODO(rginda): This relies on hterm.Screen.prototype.clearCursorRow, which
+ * has a text-attribute related TODO.
+ */
+hterm.Terminal.prototype.clear = function() {
+  var currentRow = this.screen_.cursorPosition.row;
+  var currentColumn = this.screen_.cursorPosition.column;
+
+  var top = this.getVTScrollTop();
+  var bottom = this.getVTScrollBottom();
+
+  for (var i = top; i < bottom; i++) {
+    this.screen_.setCursorPosition(i, 0);
+    this.screen_.clearCursorRow();
+  }
+
+  this.screen_.setCursorPosition(currentRow, currentColumn);
+};
+
+/**
+ * VT command to insert lines at the current cursor row.
+ *
+ * This respects the current scroll region.  Rows pushed off the bottom are
+ * lost (they won't show up in the scrollback buffer).
+ *
+ * TODO(rginda): This relies on hterm.Screen.prototype.clearCursorRow, which
+ * has a text-attribute related TODO.
+ *
+ * @param {integer} count The number of lines to insert.
+ */
+hterm.Terminal.prototype.insertLines = function(count) {
+  var currentRow = this.screen_.cursorPosition.row;
+
+  var bottom = this.getVTScrollBottom();
+  count = Math.min(count, bottom - currentRow);
+
+  var start = bottom - count;
+  if (start != currentRow)
+    this.moveRows_(start, count, currentRow);
+
+  for (var i = 0; i < count; i++) {
+    this.screen_.setCursorPosition(currentRow + i, 0);
+    this.screen_.clearCursorRow();
+  }
+
+  this.screen_.setCursorPosition(currentRow, 0);
+};
+
+/**
+ * VT command to delete lines at the current cursor row.
+ *
+ * New rows are added to the bottom of scroll region to take their place.  New
+ * rows are strictly there to take up space and have no content or style.
+ */
+hterm.Terminal.prototype.deleteLines = function(count) {
+  var currentRow = this.screen_.cursorPosition.row;
+  var currentColumn = this.screen_.cursorPosition.column;
+
+  var top = currentRow;
+  var bottom = this.getVTScrollBottom();
+
+  var maxCount = bottom - top;
+  count = Math.min(count, maxCount);
+
+  var moveStart = bottom - count;
+  if (count != maxCount)
+    this.moveRows_(top, count, moveStart);
+
+  for (var i = 0; i < count; i++) {
+    this.screen_.setCursorPosition(moveStart + i, 0);
+    this.screen_.clearCursorRow();
+  }
+
+  this.screen_.setCursorPosition(currentRow, currentColumn);
+};
+
+/**
+ * Inserts the given number of spaces at the current cursor position.
+ *
+ * The cursor is left at the end of the inserted spaces.
+ */
+hterm.Terminal.prototype.insertSpace = function(count) {
+  var ws = hterm.getWhitespace(count);
+  this.screen_.insertString(ws);
+};
+
+/**
+ * Forward-delete the specified number of characters starting at the cursor
+ * position.
+ *
+ * @param {integer} count The number of characters to delete.
+ */
+hterm.Terminal.prototype.deleteChars = function(count) {
+  this.screen_.deleteChars(count);
+};
+
+/**
+ * Shift rows in the scroll region upwards by a given number of lines.
+ *
+ * New rows are inserted at the bottom of the scroll region to fill the
+ * vacated rows.  The new rows not filled out with the current text attributes.
+ *
+ * This function does not affect the scrollback rows at all.  Rows shifted
+ * off the top are lost.
+ *
+ * @param {integer} count The number of rows to scroll.
+ */
+hterm.Terminal.prototype.vtScrollUp = function(count) {
+  var currentRow = this.screen_.cursorPosition.row;
+  var currentColumn = this.screen_.cursorPosition.column;
+
+  this.setCursorRow(this.getVTScrollTop());
+  this.deleteLines(count);
+
+  this.screen_.setCursorPosition(currentRow, currentColumn);
+};
+
+/**
+ * Shift rows below the cursor down by a given number of lines.
+ *
+ * This function respects the current scroll region.
+ *
+ * New rows are inserted at the top of the scroll region to fill the
+ * vacated rows.  The new rows not filled out with the current text attributes.
+ *
+ * This function does not affect the scrollback rows at all.  Rows shifted
+ * off the bottom are lost.
+ *
+ * @param {integer} count The number of rows to scroll.
+ */
+hterm.Terminal.prototype.vtScrollDown = function(opt_count) {
+  var currentRow = this.screen_.cursorPosition.row;
+  var currentColumn = this.screen_.cursorPosition.column;
+
+  this.setCursorRow(this.getVTScrollTop());
+  this.insertLines(opt_count);
+
+  this.screen_.setCursorPosition(currentRow, currentColumn);
+};
+
+/**
+ * Set the cursor position.
+ *
+ * The cursor row is relative to the scroll region if the terminal has
+ * 'origin mode' enabled, or relative to the addressable screen otherwise.
+ *
+ * @param {integer} row The new zero-based cursor row.
+ * @param {integer} row The new zero-based cursor column.
+ */
+hterm.Terminal.prototype.setCursorPosition = function(row, column) {
+  if (this.options_.originMode) {
+    var scrollTop = this.getScrollTop();
+    row = hterm.clamp(row + scrollTop, scrollTop, this.getScrollBottom());
+  } else {
+    row = hterm.clamp(row, 0, this.screenSize.height);
+  }
+
+  this.screen_.setCursorPosition(row, column);
+};
+
+/**
+ * Set the cursor column.
+ *
+ * @param {integer} column The new zero-based cursor column.
+ */
+hterm.Terminal.prototype.setCursorColumn = function(column) {
+  this.screen_.setCursorPosition(this.screen_.cursorPosition.row, column);
+};
+
+/**
+ * Return the cursor column.
+ *
+ * @return {integer} The zero-based cursor column.
+ */
+hterm.Terminal.prototype.getCursorColumn = function() {
+  return this.screen_.cursorPosition.column;
+};
+
+/**
+ * Set the cursor row.
+ *
+ * The cursor row is relative to the scroll region if the terminal has
+ * 'origin mode' enabled, or relative to the addressable screen otherwise.
+ *
+ * @param {integer} row The new cursor row.
+ */
+hterm.Terminal.prototype.setCursorRow = function(row) {
+  this.setCursorPosition(row, this.screen_.cursorPosition.column);
+};
+
+/**
+ * Return the cursor row.
+ *
+ * @return {integer} The zero-based cursor row.
+ */
+hterm.Terminal.prototype.getCursorRow = function(row) {
+  return this.screen_.cursorPosition.row;
+};
+
+/**
+ * Request that the ScrollPort redraw itself soon.
+ *
+ * The redraw will happen asynchronously, soon after the call stack winds down.
+ * Multiple calls will be coalesced into a single redraw.
+ */
+hterm.Terminal.prototype.scheduleRedraw_ = function() {
+  if (this.redrawTimeout_)
+    clearTimeout(this.redrawTimeout_);
+
+  var self = this;
+  setTimeout(function() {
+      self.redrawTimeout_ = null;
+      self.scrollPort_.redraw_();
+    }, 0);
+};
+
+/**
+ * Request that the ScrollPort be scrolled to the bottom.
+ *
+ * The scroll will happen asynchronously, soon after the call stack winds down.
+ * Multiple calls will be coalesced into a single scroll.
+ *
+ * This affects the scrollbar position of the ScrollPort, and has nothing to
+ * do with the VT scroll commands.
+ */
+hterm.Terminal.prototype.scheduleScrollDown_ = function() {
+  if (this.timeouts_.scrollDown)
+    clearTimeout(this.timeouts_.scrollDown);
+
+  var self = this;
+  this.timeouts_.scrollDown = setTimeout(function() {
+      delete self.timeouts_.scrollDown;
+      self.scrollPort_.scrollRowToBottom(self.getRowCount());
+    }, 10);
+};
+
+/**
+ * Move the cursor up a specified number of rows.
+ *
+ * @param {integer} count The number of rows to move the cursor.
+ */
+hterm.Terminal.prototype.cursorUp = function(count) {
+  return this.cursorDown(-count);
+};
+
+/**
+ * Move the cursor down a specified number of rows.
+ *
+ * @param {integer} count The number of rows to move the cursor.
+ */
+hterm.Terminal.prototype.cursorDown = function(count) {
+  var minHeight = (this.options_.originMode ? this.getVTScrollTop() : 0);
+  var maxHeight = (this.options_.originMode ? this.getVTScrollBottom() :
+                   this.screenSize.height - 1);
+
+  var row = hterm.clamp(this.screen_.cursorPosition.row + count,
+                        minHeight, maxHeight);
+  this.setCursorRow(row);
+};
+
+/**
+ * Move the cursor left a specified number of columns.
+ *
+ * @param {integer} count The number of columns to move the cursor.
+ */
+hterm.Terminal.prototype.cursorLeft = function(count) {
+  return this.cursorRight(-count);
+};
+
+/**
+ * Move the cursor right a specified number of columns.
+ *
+ * @param {integer} count The number of columns to move the cursor.
+ */
+hterm.Terminal.prototype.cursorRight = function(count) {
+  var column = hterm.clamp(this.screen_.cursorPosition.column + count,
+                           0, this.screenSize.width);
+  this.setCursorColumn(column);
+};
+
+/**
+ * Reverse the foreground and background colors of the terminal.
+ *
+ * This only affects text that was drawn with no attributes.
+ *
+ * TODO(rginda): Test xterm to see if reverse is respected for text that has
+ * been drawn with attributes that happen to coincide with the default
+ * 'no-attribute' colors.  My guess is probably not.
+ */
+hterm.Terminal.prototype.setReverseVideo = function(state) {
+  if (state) {
+    this.scrollPort_.setForegroundColor(this.backgroundColor);
+    this.scrollPort_.setBackgroundColor(this.foregroundColor);
+  } else {
+    this.scrollPort_.setForegroundColor(this.foregroundColor);
+    this.scrollPort_.setBackgroundColor(this.backgroundColor);
+  }
+};
+
+/**
+ * Set the origin mode bit.
+ *
+ * If origin mode is on, certain VT cursor and scrolling commands measure their
+ * row parameter relative to the VT scroll region.  Otherwise, row 0 corresponds
+ * to the top of the addressable screen.
+ *
+ * Defaults to off.
+ *
+ * @param {boolean} state True to set origin mode, false to unset.
+ */
+hterm.Terminal.prototype.setOriginMode = function(state) {
+  this.options_.originMode = state;
+};
+
+/**
+ * Set the insert mode bit.
+ *
+ * If insert mode is on, existing text beyond the cursor position will be
+ * shifted right to make room for new text.  Otherwise, new text overwrites
+ * any existing text.
+ *
+ * Defaults to off.
+ *
+ * @param {boolean} state True to set insert mode, false to unset.
+ */
+hterm.Terminal.prototype.setInsertMode = function(state) {
+  this.options_.insertMode = state;
+};
+
+/**
+ * Set the wraparound mode bit.
+ *
+ * If wraparound mode is on, certain VT commands will allow the cursor to wrap
+ * to the start of the following row.  Otherwise, the cursor is clamped to the
+ * end of the screen and attempts to write past it are ignored.
+ *
+ * Defaults to on.
+ *
+ * @param {boolean} state True to set wraparound mode, false to unset.
+ */
+hterm.Terminal.prototype.setWraparound = function(state) {
+  this.options_.wraparound = state;
+};
+
+/**
+ * Set the reverse-wraparound mode bit.
+ *
+ * If wraparound mode is off, certain VT commands will allow the cursor to wrap
+ * to the end of the previous row.  Otherwise, the cursor is clamped to column
+ * 0.
+ *
+ * Defaults to off.
+ *
+ * @param {boolean} state True to set reverse-wraparound mode, false to unset.
+ */
+hterm.Terminal.prototype.setReverseWraparound = function(state) {
+  this.options_.reverseWraparound = state;
+};
+
+/**
+ * Selects between the primary and alternate screens.
+ *
+ * If alternate mode is on, the alternate screen is active.  Otherwise the
+ * primary screen is active.
+ *
+ * Swapping screens has no effect on the scrollback buffer.
+ *
+ * Each screen maintains its own cursor position.
+ *
+ * Defaults to off.
+ *
+ * @param {boolean} state True to set alternate mode, false to unset.
+ */
+hterm.Terminal.prototype.setAlternateMode = function(state) {
+  this.screen_ = state ? this.alternateScreen_ : this.primaryScreen_;
+
+  this.screen_.setColumnCount(this.screenSize.width);
+
+  var rowDelta = this.screenSize.height - this.screen_.getHeight();
+  if (rowDelta > 0)
+    this.appendRows_(rowDelta);
+
+  this.scrollPort_.invalidateRowRange(
+      this.scrollbackRows_.length,
+      this.scrollbackRows_.length + this.screenSize.height);
+
+  if (this.screen_.cursorPosition.row == -1)
+    this.screen_.setCursorPosition(0, 0);
+
+  this.syncCursorPosition_();
+};
+
+/**
+ * Set the cursor-blink mode bit.
+ *
+ * If cursor-blink is on, the cursor will blink when it is visible.  Otherwise
+ * a visible cursor does not blink.
+ *
+ * You should make sure to turn blinking off if you're going to dispose of a
+ * terminal, otherwise you'll leak a timeout.
+ *
+ * Defaults to on.
+ *
+ * @param {boolean} state True to set cursor-blink mode, false to unset.
+ */
+hterm.Terminal.prototype.setCursorBlink = function(state) {
+  this.options_.cursorBlink = state;
+
+  if (!state && this.timeouts_.cursorBlink) {
+    clearTimeout(this.timeouts_.cursorBlink);
+    delete this.timeouts_.cursorBlink;
+  }
+
+  if (this.options_.cursorVisible)
+    this.setCursorVisible(true);
+};
+
+/**
+ * Set the cursor-visible mode bit.
+ *
+ * If cursor-visible is on, the cursor will be visible.  Otherwise it will not.
+ *
+ * Defaults to on.
+ *
+ * @param {boolean} state True to set cursor-visible mode, false to unset.
+ */
+hterm.Terminal.prototype.setCursorVisible = function(state) {
+  this.options_.cursorVisible = state;
+
+  if (!state) {
+    this.cursorNode_.style.display = 'none';
+    return;
+  }
+
+  this.cursorNode_.style.display = 'block';
+
+  if (this.options_.cursorBlink) {
+    if (this.timeouts_.cursorBlink)
+      return;
+
+    this.timeouts_.cursorBlink = setInterval(this.onCursorBlink_.bind(this),
+                                             500);
+  } else {
+    if (this.timeouts_.cursorBlink) {
+      clearTimeout(this.timeouts_.cursorBlink);
+      delete this.timeouts_.cursorBlink;
+    }
+  }
+};
+
+/**
+ * Synchronizes the visible cursor with the current cursor coordinates.
+ */
+hterm.Terminal.prototype.syncCursorPosition_ = function() {
+  var topRowIndex = this.scrollPort_.getTopRowIndex();
+  var bottomRowIndex = this.scrollPort_.getBottomRowIndex(topRowIndex);
+  var cursorRowIndex = this.scrollbackRows_.length +
+      this.screen_.cursorPosition.row;
+
+  if (cursorRowIndex > bottomRowIndex) {
+    // Cursor is scrolled off screen, move it outside of the visible area.
+    this.cursorNode_.style.top = -this.characterSize_.height;
+    return;
+  }
+
+  this.cursorNode_.style.top = this.scrollPort_.visibleRowTopMargin +
+      this.characterSize_.height * (cursorRowIndex - topRowIndex);
+  this.cursorNode_.style.left = this.characterSize_.width *
+      this.screen_.cursorPosition.column;
+};
+
+/**
+ * Synchronizes the visible cursor with the current cursor coordinates.
+ *
+ * The sync will happen asynchronously, soon after the call stack winds down.
+ * Multiple calls will be coalesced into a single sync.
+ */
+hterm.Terminal.prototype.scheduleSyncCursorPosition_ = function() {
+  if (this.timeouts_.syncCursor)
+    clearTimeout(this.timeouts_.syncCursor);
+
+  var self = this;
+  this.timeouts_.syncCursor = setTimeout(function() {
+      self.syncCursorPosition_();
+      delete self.timeouts_.syncCursor;
+    }, 100);
+};
+
+/**
+ * React when the ScrollPort is scrolled.
+ */
+hterm.Terminal.prototype.onScroll_ = function() {
+  this.scheduleSyncCursorPosition_();
+};
+
+/**
+ * React when the ScrollPort is resized.
+ */
+hterm.Terminal.prototype.onResize_ = function() {
+  var width = Math.floor(this.scrollPort_.getScreenWidth() /
+                         this.characterSize_.width);
+  var height = this.scrollPort_.visibleRowCount;
+
+  if (width == this.screenSize.width && height == this.screenSize.height)
+    return;
+
+  this.screenSize.resize(width, height);
+
+  var screenHeight = this.screen_.getHeight();
+
+  var deltaRows = this.screenSize.height - screenHeight;
+
+  if (deltaRows < 0) {
+    // Screen got smaller.
+    var ary = this.screen_.shiftRows(-deltaRows);
+    this.scrollbackRows_.push.apply(this.scrollbackRows_, ary);
+  } else if (deltaRows > 0) {
+    // Screen got larger.
+
+    if (deltaRows <= this.scrollbackRows_.length) {
+      var scrollbackCount = Math.min(deltaRows, this.scrollbackRows_.length);
+      var rows = this.scrollbackRows_.splice(
+          0, this.scrollbackRows_.length - scrollbackCount);
+      this.screen_.unshiftRows(rows);
+      deltaRows -= scrollbackCount;
+    }
+
+    if (deltaRows)
+      this.appendRows_(deltaRows);
+  }
+
+  this.screen_.setColumnCount(this.screenSize.width);
+
+  if (this.screen_.cursorPosition.row == -1)
+    this.screen_.setCursorPosition(0, 0);
+};
+
+/**
+ * Service the cursor blink timeout.
+ */
+hterm.Terminal.prototype.onCursorBlink_ = function() {
+  if (this.cursorNode_.style.display == 'block') {
+    this.cursorNode_.style.display = 'none';
+  } else {
+    this.cursorNode_.style.display = 'block';
+  }
+};