Implement isVoiceOverRunning and isClosedCaptioningEnabled methods for iOS

Also implement VoiceOverStatusChanged and
ClosedCaptioningStatusDidChange notifications

www/mobile-accessibility.js

@@ -22,12 +22,74 @@
 var argscheck = require('cordova/argscheck'),
     utils = require('cordova/utils'),
     exec = require('cordova/exec');
-   
+
 var MobileAccessibility = function() {
+    this._isVoiceOverRunning = false;
+    this._isClosedCaptioningEnabled = false;
+    // Create new event handlers on the window (returns a channel instance)
+    this.channels = {
+        voiceoverstatuschanged:cordova.addWindowEventHandler("voiceoverstatuschanged"),
+        closedcaptioningstatusdidchange:cordova.addWindowEventHandler("closedcaptioningstatusdidchange")
+    };
+    for (var key in this.channels) {
+        this.channels[key].onHasSubscribersChange = MobileAccessibility.onHasSubscribersChange;
+    }
 };
 
-MobileAccessibility.isVoiceOverRunning = function() {
-    exec(null, null, "MobileAccessibility", "isVoiceOverRunning", []);
+function handlers() {
+    return mobileAccessibility.channels.voiceoverstatuschanged.numHandlers +
+           mobileAccessibility.channels.closedcaptioningstatusdidchange.numHandlers;
 };
 
-module.exports = MobileAccessibility;
+/**
+ * Event handlers for when callbacks get registered for mobileAccessibility.
+ * Keep track of how many handlers we have so we can start and stop the native MobileAccessibility listener
+ * appropriately.
+ */
+MobileAccessibility.onHasSubscribersChange = function() {
+    // If we just registered the first handler, make sure native listener is started.
+    if (this.numHandlers === 1 && handlers() === 1) {
+        exec(mobileAccessibility._status, mobileAccessibility._error, "MobileAccessibility", "start", []);
+    } else if (handlers() === 0) {
+        exec(null, null, "MobileAccessibility", "stop", []);
+    }
+};
+
+MobileAccessibility.prototype.isVoiceOverRunning = function(callback) {
+    exec(callback, null, "MobileAccessibility", "isVoiceOverRunning", []);
+};
+
+MobileAccessibility.prototype.isClosedCaptioningEnabled = function(callback) {
+    exec(callback, null, "MobileAccessibility", "isClosedCaptioningEnabled", []);
+};
+
+/**
+ * Callback for mobileAccessibility status
+ *
+ * @param {Object} info keys: isVoiceOverRunning, isClosedCaptioningEnabled
+ */
+MobileAccessibility.prototype._status = function(info) {
+    if (info) {
+        var me = mobileAccessibility;
+        if (me._isVoiceOverRunning !== info.isVoiceOverRunning) {
+            cordova.fireWindowEvent("voiceoverstatuschanged", info);
+            me._isVoiceOverRunning = info.isVoiceOverRunning;
+        }
+        if (me._isClosedCaptioningEnabled !== info.isClosedCaptioningEnabled) {
+            cordova.fireWindowEvent("closedcaptioningstatusdidchange", info);
+            me._isClosedCaptioningEnabled = info.isClosedCaptioningEnabled;
+        }
+    }
+};
+
+/**
+ * Error callback for MobileAccessibility start
+ */
+MobileAccessibility.prototype._error = function(e) {
+    console.log("Error initializing MobileAccessibility: " + e);
+};
+
+var mobileAccessibility = new MobileAccessibility();
+               
+module.exports = mobileAccessibility;
+start