Support braille dot or chorded typing conversions to standard keyboard keys

chrome/browser/resources/chromeos/chromevox/braille/braille_key_event_sequence_reducer.js

+// Copyright 2017 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 Manages a sequence of braille key events.
+ */
+
+goog.provide('BrailleKeyEventSequenceReducer');
+
+goog.require('Output');
+goog.require('cvox.BrailleKeyEvent');
+
+/**
+ * A class that transforms a sequence of braille key events into a standard key
+ * event.
+ * @constructor
+ */
+BrailleKeyEventSequenceReducer = function() {
+  /** @private {Object} */

[dmazzoni, 2017/04/17 04:53:25]

Use a more specific type. Looks like a nullable record with fields altKey,
ctrlKey, shiftKey.

+  this.incrementalKey_ = null;
+};
+
+BrailleKeyEventSequenceReducer.prototype = {
+  /**
+   * Accumulates and optionally modifies in-coming braille key events.
+   * @param {cvox.BrailleKeyEvent} evt
+   * @return {boolean} False to continue event propagation.
+   */
+  onBrailleKeyEvent: function(evt) {
+    var standardKeyCode;
+    var dots = evt.brailleDots;
+    if (!dots) {
+      this.incrementalKey_ = {};
+      return false;
+    }
+
+    if (evt.command == cvox.BrailleKeyCommand.CHORD) {
+      Output.forceModeForNextSpeechUtterance(cvox.QueueMode.CATEGORY_FLUSH);
+      var modifiers = cvox.BrailleKeyEvent.brailleDotsToModifiers[dots];
+
+      // Check for a modifier mapping.
+      if (modifiers) {
+        this.incrementalKey_ = this.incrementalKey_ || {};
+        for (var key in modifiers) {
+          this.incrementalKey_[key] = true;
+        }
+
+        return true;
+      }
+
+      // Check for a chord to standard key mapping.
+      standardKeyCode =
+          cvox.BrailleKeyEvent.brailleChordsToStandardKeyCode[dots];
+    }
+
+    // Check for a 'dots' command, which is typed on the keyboard with a
+    // previous incremental key press.
+    if (evt.command == cvox.BrailleKeyCommand.DOTS && this.incrementalKey_) {
+      // Check if this braille pattern has a standard key mapping.
+      standardKeyCode =
+          cvox.BrailleKeyEvent.brailleDotsToStandardKeyCode[dots];
+    }
+
+    if (standardKeyCode) {
+      evt.command = cvox.BrailleKeyCommand.STANDARD_KEY;
+      evt.standardKeyCode = standardKeyCode;
+      if (this.incrementalKey_) {
+        // Apply all modifiers seen so far to the outgoing event as a standard
+        // keyboard command.
+        evt.altKey = this.incrementalKey_.altKey;
+        evt.ctrlKey = this.incrementalKey_.ctrlKey;
+        evt.shiftKey = this.incrementalKey_.shiftKey;

[dmazzoni, 2017/04/17 04:53:24]

Would be nice to support Search too in a future change; I'm thinking mainly for
non-ChromeVox shortcuts

+        this.incrementalKey_ = null;

[dmazzoni, 2017/04/17 04:53:25]

Why not just set it to {} here and then you don't need line 44:
this.incrementalKey_ = this.incrementalKey_ || {};

Or have a helper method reset_() that sets altKey, ctrlKey, and shiftKey to
false.

[David Tseng, 2017/04/17 16:10:51]

Actually, the null state is important.

I've:
- renamed the class to BrailleKeyEventRewriter
- made the first "reste" of the incremental key set to null

The issue is that we sometimes don't want to make any changes to the incoming
braille key event if it doesn't meet any of the criteria for re-mapping (i.e.
having a dot or chord pattern we want to remap). In those cases, we should clear
the incremental key and not rewrite the event (even to our own defaults, which
might interfere).

+      }
+      return false;
+    }
+
+    this.incrementalKey_ = null;
+    return false;
+  }
+};