Complete live region support in ChromeVox Next.

chrome/browser/resources/chromeos/chromevox/cvox2/background/live_regions.js

+// Copyright 2015 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.
+
+/**
+ * @fileoverview Implements support for live regions in ChromeVox Next.
+ */
+
+goog.provide('LiveRegions');
+
+goog.require('ChromeVoxState');
+
+goog.scope(function() {
+var AutomationNode = chrome.automation.AutomationNode;
+var TreeChange = chrome.automation.TreeChange;
+
+/**
+ * ChromeVox2 live region handler.
+ * @param {!ChromeVoxState} chromeVoxState The ChromeVox state object,
+ *     keeping track of the current mode and current range.
+ * @constructor
+ */
+LiveRegions = function(chromeVoxState) {
+  /**
+   * @type {!ChromeVoxState}
+   * @private
+   */
+  this.chromeVoxState_ = chromeVoxState;
+
+  /**
+   * The time the last live region event was output.
+   * @type {!Date}
+   * @private
+   */
+  this.lastLiveRegionTime_ = new Date(0);
+
+  /**
+   * Set of nodes that have been announced as part of a live region since
+   *     |this.lastLiveRegionTime_|, to prevent duplicate announcements.
+   * @type {!WeakSet<AutomationNode>}
+   * @private
+   */
+  this.liveRegionNodeSet_ = new WeakSet();
+
+  chrome.automation.addTreeChangeObserver(
+      'liveRegionTreeChanges', this.onTreeChange.bind(this));
+};
+
+/**
+ * Live region events received in fewer than this many milliseconds will
+ * queue, otherwise they'll be output with a category flush.
+ * @type {number}
+ * @const
+ */
+LiveRegions.LIVE_REGION_QUEUE_TIME_MS = 500;
+
+/**
+ * Whether live regions from background tabs should be announced or not.
+ * @type {boolean}
+ * @private
+ */
+LiveRegions.announceLiveRegionsFromBackgroundTabs_ = true;
+
+LiveRegions.prototype = {
+  /**
+   * Called when the automation tree is changed.
+   * @param {TreeChange} treeChange
+   */
+  onTreeChange: function(treeChange) {
+    var node = treeChange.target;
+    if (!node.containerLiveStatus)
+      return;
+
+    var mode = this.chromeVoxState_.mode;
+    var currentRange = this.chromeVoxState_.currentRange;
+
+    if (mode === ChromeVoxMode.CLASSIC || !cvox.ChromeVox.isActive)
+      return;
+
+    if (!currentRange)
+      return;
+
+    if (!LiveRegions.announceLiveRegionsFromBackgroundTabs_ &&
+        !AutomationUtil.isInSameWebpage(node, currentRange.start.node)) {
+      return;
+    }
+
+    var type = treeChange.type;
+    var relevant = node.containerLiveRelevant;
+    if (relevant.indexOf('additions') >= 0 &&
+        (type == 'nodeCreated' || type == 'subtreeCreated')) {
+      this.outputLiveRegionChange_(node, null);
+    }
+
+    if (relevant.indexOf('text') >= 0 && type == 'nodeChanged')
+      this.outputLiveRegionChange_(node, null);
+
+    if (relevant.indexOf('removals') >= 0 && type == 'nodeRemoved')
+      this.outputLiveRegionChange_(node, '@live_regions_removed');
+  },
+
+  /**
+   * Given a node that needs to be spoken as part of a live region
+   * change and an additional optional format string, output the
+   * live region description.
+   * @param {!AutomationNode} node The changed node.
+   * @param {?string=} opt_prependFormatStr If set, a format string for
+   *     cvox2.Output to prepend to the output.
+   * @private
+   */
+  outputLiveRegionChange_: function(node, opt_prependFormatStr) {
+    if (node.containerLiveBusy)
+      return;
+
+    if (node.containerLiveAtomic && !node.liveAtomic) {
+      if (node.parent)
+        this.outputLiveRegionChange_(node.parent, opt_prependFormatStr);
+      return;
+    }
+
+    var range = cursors.Range.fromNode(node);
+    var output = new Output();
+    if (opt_prependFormatStr)
+      output.format(opt_prependFormatStr);
+    output.withSpeech(range, range, Output.EventType.NAVIGATE);
+
+    if (!output.hasSpeech && node.liveAtomic)
+      output.format('$descendants', node);
+
+    output.withSpeechCategory(cvox.TtsCategory.LIVE);
+
+    if (!output.hasSpeech)
+      return;
+
+    // Enqueue live region updates that were received at approximately
+    // the same time, otherwise flush previous live region updates.
+    var currentTime = new Date();
+    var queueTime = LiveRegions.LIVE_REGION_QUEUE_TIME_MS;
+    if (currentTime - this.lastLiveRegionTime_ > queueTime) {
+      this.liveRegionNodeSet_ = new WeakSet();
+      output.withQueueMode(cvox.QueueMode.CATEGORY_FLUSH);
+      this.lastLiveRegionTime_ = currentTime;
+    } else {
+      output.withQueueMode(cvox.QueueMode.QUEUE);
+    }
+
+    var parent = node;
+    while (parent) {
+      if (this.liveRegionNodeSet_.has(parent))
+        return;
+      parent = parent.parent;
+    }
+
+    this.liveRegionNodeSet_.add(node);
+    output.go();
+  },
+};
+
+});  // goog.scope