Refactor event handler classes to make it easier to add new event type listeners.

chrome/browser/resources/chromeos/chromevox/cvox2/background/desktop_automation_handler.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 Handles automation from a desktop automation node.
  */
 
 goog.provide('DesktopAutomationHandler');
 
+goog.require('AutomationObjectInstaller');
 goog.require('BaseAutomationHandler');
 goog.require('ChromeVoxState');
 goog.require('editing.TextEditHandler');
 
 goog.scope(function() {
 var AutomationEvent = chrome.automation.AutomationEvent;
 var AutomationNode = chrome.automation.AutomationNode;
 var Dir = constants.Dir;
+var EventType = chrome.automation.EventType;
 var RoleType = chrome.automation.RoleType;
 
 /**
  * @param {!AutomationNode} node
  * @constructor
  * @extends {BaseAutomationHandler}
  */
 DesktopAutomationHandler = function(node) {
   BaseAutomationHandler.call(this, node);
 
   /**
    * The object that speaks changes to an editable text field.
    * @type {editing.TextEditHandler}
    */
   this.textEditHandler_ = null;
 
   /**
    * The last time we handled a value changed event.
    * @type {!Date}
    * @private
    */
   this.lastValueChanged_ = new Date(0);
 
+  var e = EventType;
+  this.addListener_(e.activedescendantchanged, this.onActiveDescendantChanged);
+  this.addListener_(e.alert, this.onAlert);
+  this.addListener_(e.ariaAttributeChanged, this.onEventIfInRange);
+  this.addListener_(e.checkedStateChanged, this.onEventIfInRange);
+  this.addListener_(e.focus, this.onFocus);
+  this.addListener_(e.hover, this.onEventWithFlushedOutput);
+  this.addListener_(e.loadComplete, this.onLoadComplete);
+  this.addListener_(e.menuEnd, this.onMenuEnd);
+  this.addListener_(e.menuListItemSelected, this.onEventDefault);
+  this.addListener_(e.menuStart, this.onMenuStart);
+  this.addListener_(e.scrollPositionChanged, this.onScrollPositionChanged);
+  this.addListener_(e.selection, this.onEventWithFlushedOutput);
+  this.addListener_(e.textChanged, this.onTextChanged);
+  this.addListener_(e.textSelectionChanged, this.onTextSelectionChanged);
+  this.addListener_(e.valueChanged, this.onValueChanged);
+
   // The focused state gets set on the containing webView node.
   var webView = node.find({role: RoleType.webView, state: {focused: true}});
   if (webView) {
     var root = webView.find({role: RoleType.rootWebArea});
     if (root) {
       this.onLoadComplete(
-          {target: root,
-           type: chrome.automation.EventType.loadComplete});
+          new chrome.automation.AutomationEvent(EventType.loadComplete, root));

[dmazzoni, 2016/05/02 22:15:48]

Is there a possible race condition if the chrome.automation.AutomationEvent
installer hasn't succeeded yet? Maybe check that
chrome.automation.AutomationEvent exists first?

[David Tseng, 2016/05/03 20:18:27]

Went with a callback as suggested below.

     }
   }
 
   chrome.automation.getFocus((function(focus) {
     if (focus)
-      this.onFocus({target: focus, type: 'focus'});
+    this.onFocus(new chrome.automation.AutomationEvent(EventType.focus, focus));

[dmazzoni, 2016/05/02 22:15:48]

nit: indentation

[David Tseng, 2016/05/03 20:18:27]

Done.

   }).bind(this));
+
+  AutomationObjectInstaller.init(node);

[dmazzoni, 2016/05/02 22:15:48]

Perhaps this init should just take a callback argument and that can trigger
actually doing the rest of the registration.

[David Tseng, 2016/05/03 20:18:27]

Done.

 };
 
 /**
  * Time to wait until processing more value changed events.
  * @const {number}
  */
 DesktopAutomationHandler.VMIN_VALUE_CHANGE_DELAY_MS = 500;
 
 DesktopAutomationHandler.prototype = {
   __proto__: BaseAutomationHandler.prototype,
@@ skipping 44 matching lines @@
       output.withBraille(
           ChromeVoxState.instance.currentRange, prevRange, evt.type);
     } else {
       // Delegate event handling to the text edit handler for braille.
       this.textEditHandler_.onEvent(evt);
     }
     output.go();
   },
 
   /**
+   * @param {!AutomationEvent} evt
+   */
+  onEventIfInRange: function(evt) {
+    // TODO(dtseng): Consider the end of the current range as well.
+    if (AutomationUtil.isDescendantOf(
+        global.backgroundObj.currentRange.start.node, evt.target) ||
+            evt.target.state.focused)
+      this.onEventDefault(evt);
+  },
+
+  /**
+   * @param {!AutomationEvent} evt
+   */
+  onEventWithFlushedOutput: function(evt) {
+    Output.flushNextSpeechUtterance();
+    this.onEventDefault(evt);
+  },
+
+  /**
    * Makes an announcement without changing focus.
-   * @param {Object} evt
+   * @param {!AutomationEvent} evt
+   */
+  onActiveDescendantChanged: function(evt) {
+    if (!evt.target.activeDescendant)
+      return;
+    this.onEventDefault(new chrome.automation.AutomationEvent(
+        EventType.focus, evt.target.activeDescendant));
+  },
+
+  /**
+   * Makes an announcement without changing focus.
+   * @param {!AutomationEvent} evt
    */
   onAlert: function(evt) {
     var node = evt.target;
     if (!node)
       return;
 
     // Don't process nodes inside of web content if ChromeVox Next is inactive.
     if (node.root.role != RoleType.desktop &&
         ChromeVoxState.instance.mode === ChromeVoxMode.CLASSIC) {
       return;
     }
 
     var range = cursors.Range.fromNode(node);
 
     new Output().withSpeechAndBraille(range, null, evt.type).go();
   },
 
   /**
    * Provides all feedback once a focus event fires.
-   * @param {Object} evt
+   * @param {!AutomationEvent} evt
    */
   onFocus: function(evt) {
     // Invalidate any previous editable text handler state.
     this.textEditHandler_ = null;
 
     var node = evt.target;
 
     // Discard focus events on embeddedObject and client nodes.
     if (node.role == RoleType.embeddedObject || node.role == RoleType.client)
       return;
 
     this.createTextEditHandlerIfNeeded_(evt.target);
 
     // Since we queue output mostly for live regions support and there isn't a
     // reliable way to know if this focus event resulted from a user's explicit
     // action, only flush when the focused node is not web content.
     if (node.root.role == RoleType.desktop)
       Output.flushNextSpeechUtterance();
 
     this.onEventDefault(
-        /** @type {!AutomationEvent} */
-        ({target: node, type: chrome.automation.EventType.focus}));
+        new chrome.automation.AutomationEvent(EventType.focus, node));
   },
 
   /**
    * Provides all feedback once a load complete event fires.
-   * @param {Object} evt
+   * @param {!AutomationEvent} evt
    */
   onLoadComplete: function(evt) {
     ChromeVoxState.instance.refreshMode(evt.target.docUrl);
 
     // Don't process nodes inside of web content if ChromeVox Next is inactive.
     if (evt.target.root.role != RoleType.desktop &&
         ChromeVoxState.instance.mode === ChromeVoxMode.CLASSIC)
       return;
 
     chrome.automation.getFocus((function(focus) {
       if (!focus)
         return;
 
       // If initial focus was already placed on this page (e.g. if a user starts
       // tabbing before load complete), then don't move ChromeVox's position on
       // the page.
       if (ChromeVoxState.instance.currentRange &&
           ChromeVoxState.instance.currentRange.start.node.root == focus.root)
         return;
 
       ChromeVoxState.instance.setCurrentRange(cursors.Range.fromNode(focus));
       new Output().withRichSpeechAndBraille(
           ChromeVoxState.instance.currentRange, null, evt.type).go();
     }).bind(this));
   },
 
-  /** @override */
+
+    /**
+   * Provides all feedback once a text changed event fires.
+   * @param {!AutomationEvent} evt
+   */
   onTextChanged: function(evt) {
     if (evt.target.state.editable)
       this.onEditableChanged_(evt);
   },
 
-  /** @override */
+  /**
+   * Provides all feedback once a text selection changed event fires.
+   * @param {!AutomationEvent} evt
+   */
   onTextSelectionChanged: function(evt) {
     if (evt.target.state.editable)
       this.onEditableChanged_(evt);
   },
 
   /**
    * Provides all feedback once a change event in a text field fires.
    * @param {!AutomationEvent} evt
    * @private
    */
@@ skipping 46 matching lines @@
 
       this.lastValueChanged_ = new Date();
 
       new Output().format('$value', evt.target)
           .go();
     }
   },
 
   /**
    * Handle updating the active indicator when the document scrolls.
-   * @override
+   * @param {!AutomationEvent} evt
    */
   onScrollPositionChanged: function(evt) {
     if (ChromeVoxState.instance.mode === ChromeVoxMode.CLASSIC)
       return;
 
     var currentRange = ChromeVoxState.instance.currentRange;
     if (currentRange)
       new Output().withLocation(currentRange, null, evt.type).go();
   },
 
-  /** @override */
+  /**
+   * Provides all feedback once a menu start event fires.
+   * @param {!AutomationEvent} evt
+   */
   onMenuStart: function(evt) {
     global.backgroundObj.startExcursion();
     this.onEventDefault(evt);
   },
 
-  /** @override */
+  /**
+   * Provides all feedback once a menu end event fires.
+   * @param {!AutomationEvent} evt
+   */
   onMenuEnd: function(evt) {
     this.onEventDefault(evt);
     global.backgroundObj.endExcursion();
   },
 
   /**
    * Create an editable text handler for the given node if needed.
    * @param {!AutomationNode} node
    */
   createTextEditHandlerIfNeeded_: function(node) {
@@ skipping 12 matching lines @@
   if (cvox.ChromeVox.isMac)
     return;
   chrome.automation.getDesktop(function(desktop) {
     global.desktopAutomationHandler = new DesktopAutomationHandler(desktop);
   });
 };
 
 DesktopAutomationHandler.init_();
 
 });  // goog.scope