DevTools: introduce external service client (behind experiment).

third_party/WebKit/Source/devtools/front_end/terminal/xterm.js/src/Viewport.js

+/**
+ * xterm.js: xterm, in the browser
+ * Copyright (c) 2016, SourceLair Limited <www.sourcelair.com> (MIT License)
+ */
+
+/**
+ * Represents the viewport of a terminal, the visible area within the larger buffer of output.
+ * Logic for the virtual scroll bar is included in this object.
+ * @param {Terminal} terminal The Terminal object.
+ * @param {HTMLElement} viewportElement The DOM element acting as the viewport
+ * @param {HTMLElement} charMeasureElement A DOM element used to measure the character size of
+ *   the terminal.
+ */
+function Viewport(terminal, viewportElement, scrollArea, charMeasureElement) {
+  this.terminal = terminal;
+  this.viewportElement = viewportElement;
+  this.scrollArea = scrollArea;
+  this.charMeasureElement = charMeasureElement;
+  this.currentRowHeight = 0;
+  this.lastRecordedBufferLength = 0;
+  this.lastRecordedViewportHeight = 0;
+
+  this.terminal.on('scroll', this.syncScrollArea.bind(this));
+  this.terminal.on('resize', this.syncScrollArea.bind(this));
+  this.viewportElement.addEventListener('scroll', this.onScroll.bind(this));
+
+  this.syncScrollArea();
+}
+
+/**
+ * Refreshes row height, setting line-height, viewport height and scroll area height if
+ * necessary.
+ * @param {number|undefined} charSize A character size measurement bounding rect object, if it
+ *   doesn't exist it will be created.
+ */
+Viewport.prototype.refresh = function(charSize) {
+  var size = charSize || this.charMeasureElement.getBoundingClientRect();
+  if (size.height > 0) {
+    var rowHeightChanged = size.height !== this.currentRowHeight;
+    if (rowHeightChanged) {
+      this.currentRowHeight = size.height;
+      this.viewportElement.style.lineHeight = size.height + 'px';
+      this.terminal.rowContainer.style.lineHeight = size.height + 'px';
+    }
+    var viewportHeightChanged = this.lastRecordedViewportHeight !== this.terminal.rows;
+    if (rowHeightChanged || viewportHeightChanged) {
+      this.lastRecordedViewportHeight = this.terminal.rows;
+      this.viewportElement.style.height = size.height * this.terminal.rows + 'px';
+    }
+    this.scrollArea.style.height = (size.height * this.lastRecordedBufferLength) + 'px';
+  }
+};
+
+/**
+ * Updates dimensions and synchronizes the scroll area if necessary.
+ */
+Viewport.prototype.syncScrollArea = function() {
+  if (this.lastRecordedBufferLength !== this.terminal.lines.length) {
+    // If buffer height changed
+    this.lastRecordedBufferLength = this.terminal.lines.length;
+    this.refresh();
+  } else if (this.lastRecordedViewportHeight !== this.terminal.rows) {
+    // If viewport height changed
+    this.refresh();
+  } else {
+    // If size has changed, refresh viewport
+    var size = this.charMeasureElement.getBoundingClientRect();
+    if (size.height !== this.currentRowHeight) {
+      this.refresh(size);
+    }
+  }
+
+  // Sync scrollTop
+  var scrollTop = this.terminal.ydisp * this.currentRowHeight;
+  if (this.viewportElement.scrollTop !== scrollTop) {
+    this.viewportElement.scrollTop = scrollTop;
+  }
+};
+
+/**
+ * Handles scroll events on the viewport, calculating the new viewport and requesting the
+ * terminal to scroll to it.
+ * @param {Event} ev The scroll event.
+ */
+Viewport.prototype.onScroll = function(ev) {
+  var newRow = Math.round(this.viewportElement.scrollTop / this.currentRowHeight);
+  var diff = newRow - this.terminal.ydisp;
+  this.terminal.scrollDisp(diff, true);
+};
+
+/**
+ * Handles mouse wheel events by adjusting the viewport's scrollTop and delegating the actual
+ * scrolling to `onScroll`, this event needs to be attached manually by the consumer of
+ * `Viewport`.
+ * @param {WheelEvent} ev The mouse wheel event.
+ */
+Viewport.prototype.onWheel = function(ev) {
+  if (ev.deltaY === 0) {
+    // Do nothing if it's not a vertical scroll event
+    return;
+  }
+  // Fallback to WheelEvent.DOM_DELTA_PIXEL
+  var multiplier = 1;
+  if (ev.deltaMode === WheelEvent.DOM_DELTA_LINE) {
+    multiplier = this.currentRowHeight;
+  } else if (ev.deltaMode === WheelEvent.DOM_DELTA_PAGE) {
+    multiplier = this.currentRowHeight * this.terminal.rows;
+  }
+  this.viewportElement.scrollTop += ev.deltaY * multiplier;
+  // Prevent the page from scrolling when the terminal scrolls
+  ev.preventDefault();
+};
+
+export { Viewport };