Display images in multiline Braille

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

 // Copyright 2016 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 ChromeVox commands.
  */
 
 goog.provide('CommandHandler');
 
 goog.require('ChromeVoxState');
 goog.require('Output');
 goog.require('cvox.ChromeVoxBackground');
 
 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;
 
 /**
  * Handles ChromeVox Next commands.
  * @param {string} command
  * @return {boolean} True if the command should propagate.
  */
@@ skipping 545 matching lines @@
         ChromeVoxState.instance.pageSel_ = null;
         return false;
       }
       break;
     case 'fullyDescribe':
       var o = new Output();
       o.withContextFirst()
           .withRichSpeechAndBraille(current, null, Output.EventType.NAVIGATE)
           .go();
       return false;
-
+    case 'viewGraphicAsBraille':
+      CommandHandler.viewGraphicAsBraille_(current);
+      return false;
     // Table commands.
     case 'previousRow':
       dir = Dir.BACKWARD;
       var tableOpts = {row: true, dir: dir};
       pred = AutomationPredicate.makeTableCellPredicate(
           current.start.node, tableOpts);
       predErrorMsg = 'no_cell_above';
       rootPred = AutomationPredicate.table;
       break;
     case 'previousCol':
@@ skipping 175 matching lines @@
       announcement = Msgs.getMsg('announce_volume', [valueAsPercent]);
       break;
   }
   if (announcement) {
     cvox.ChromeVox.tts.speak(
         announcement, cvox.QueueMode.FLUSH,
         cvox.AbstractTts.PERSONALITY_ANNOTATION);
   }
 };
 
+/**
+ * To support viewGraphicAsBraille_(), the current image node and its
+ * associated event listener that listens for the image frame updated
+ * event.
+ * @type {{node: AutomationNode, listener: function(AutomationEvent)}?};
+ */
+CommandHandler.imageNode_;
+
+/**
+ * Handle the command to view the first graphic within the current range
+ * as braille.
+ * @param {!AutomationNode} current The current range.
+ * @private
+ */
+CommandHandler.viewGraphicAsBraille_ = function(current) {
+  if (CommandHandler.imageNode_) {

[David Tseng, 2017/02/27 16:27:13]

I don't think you need to track the image node (and this won't catch the case
where someone navigates away from the node).

[dmazzoni, 2017/02/28 05:08:23]

Fixed as discussed offline. Tracking the image node but not
the listener. Cleans up the listener if we get a callback
and it's not within the range anymore.

+    CommandHandler.imageNode_.node.removeEventListener(
+        EventType.IMAGE_FRAME_UPDATED, CommandHandler.imageNode_.listener,
+        false);
+    CommandHandler.imageNode_ = null;
+  }
+
+  // Find the first node within the current range that supports image data.
+  var imageNode = AutomationUtil.findNodePost(
+      current.start.node, Dir.FORWARD,
+      AutomationPredicate.supportsImageData);
+  if (!imageNode)

[David Tseng, 2017/02/27 16:27:13]

If the current range already has our event listener added, skip the code.

+    return;
+
+  var listener = function(event) {
+    var target = event.target;
+    if (target != CommandHandler.imageNode_.node)
+      return;
+    if (target.imageDataUrl) {

[David Tseng, 2017/02/27 16:15:50]

If the current range is no longer the image node, remove th elistener

[dmazzoni, 2017/02/28 05:08:23]

Done.

+      cvox.ChromeVox.braille.writeRawImage(target.imageDataUrl);
+      cvox.ChromeVox.braille.freeze();
+    }
+  }
+
+  imageNode.addEventListener(EventType.IMAGE_FRAME_UPDATED, listener, false);
+  CommandHandler.imageNode_ = {node: imageNode, listener: listener};

[David Tseng, 2017/02/27 16:27:13]

Set current range to the image node and don't keep the image node as state..

[dmazzoni, 2017/02/28 05:08:23]

As discussed, this would leak too many listeners.

+  if (imageNode.imageDataUrl) {
+    listener({target: imageNode});
+  } else {
+    imageNode.getImageData(0, 0);
+  }
+};
+
 }); //  goog.scope