Bug 865023 - Introduce a prefs cache and listener utility. r=yzen

accessible/src/jsat/AccessFu.jsm

@@ -28,10 +28,6 @@ this.AccessFu = {
   attach: function attach(aWindow) {
     Utils.init(aWindow);
 
-    this.prefsBranch = Cc['@mozilla.org/preferences-service;1']
-      .getService(Ci.nsIPrefService).getBranch('accessibility.accessfu.');
-    this.prefsBranch.addObserver('activate', this, false);
-
     try {
       Cc['@mozilla.org/android/bridge;1'].
         getService(Ci.nsIAndroidBridge).handleGeckoMessage(
@@ -44,21 +40,8 @@ this.AccessFu = {
       }
     }
 
-    try {
-      this._activatePref = this.prefsBranch.getIntPref('activate');
-    } catch (x) {
-      this._activatePref = ACCESSFU_DISABLE;
-    }
-
-    try {
-      this._notifyOutput = this.prefsBranch.getBoolPref('notify_output');
-    } catch (x) {
-      this._notifyOutput = false;
-    }
-
-    this.Input.quickNavMode.updateModes(this.prefsBranch);
-
-    this._enableOrDisable();
+    this._activatePref = new PrefCache(
+      'accessibility.accessfu.activate', this._enableOrDisable.bind(this), true);
   },
 
   /**
@@ -76,7 +59,7 @@ this.AccessFu = {
         'mozContentEvent', this);
       Utils.win.removeEventListener('ContentStart', this);
     }
-    this.prefsBranch.removeObserver('activate', this);
+    delete this._activatePref;
     Utils.uninit();
   },
 
@@ -107,6 +90,20 @@ this.AccessFu = {
     Utils.win.document.insertBefore(stylesheet, Utils.win.document.firstChild);
     this.stylesheet = Cu.getWeakReference(stylesheet);
 
+
+    // Populate quicknav modes
+    this._quicknavModesPref =
+      new PrefCache(
+        'accessibility.accessfu.quicknav_modes',
+        (aName, aValue) => {
+          this.Input.quickNavMode.updateModes(aValue);
+        }, true);
+
+    // Check for output notification
+    this._notifyOutputPref =
+      new PrefCache('accessibility.accessfu.notify_output');
+
+
     this.Input.start();
     Output.start();
     TouchAdapter.start();
@@ -168,8 +165,9 @@ this.AccessFu = {
 
   _enableOrDisable: function _enableOrDisable() {
     try {
-      if (this._activatePref == ACCESSFU_ENABLE ||
-          this._systemPref && this._activatePref == ACCESSFU_AUTO)
+      let activatePref = this._activatePref.value;
+      if (activatePref == ACCESSFU_ENABLE ||
+          this._systemPref && activatePref == ACCESSFU_AUTO)
         this._enable();
       else
         this._disable();
@@ -211,7 +209,7 @@ this.AccessFu = {
       }
     }
 
-    if (this._notifyOutput) {
+    if (this._notifyOutputPref.value) {
       Services.obs.notifyObservers(null, 'accessfu-output',
                                    JSON.stringify(aPresentationData));
     }
@@ -272,22 +270,6 @@ this.AccessFu = {
                               {action: 'whereIsIt', move: true});
         }
         break;
-      case 'nsPref:changed':
-        switch (aData) {
-          case 'activate':
-            this._activatePref = this.prefsBranch.getIntPref('activate');
-            this._enableOrDisable();
-            break;
-          case 'quicknav_modes':
-            this.Input.quickNavMode.updateModes(this.prefsBranch);
-            break;
-          case 'notify_output':
-            this._notifyOutput = this.prefsBranch.getBoolPref('notify_output');
-            break;
-          default:
-            break;
-        }
-        break;
       case 'remote-browser-frame-shown':
       case 'in-process-browser-or-app-frame-shown':
       {
@@ -738,11 +720,10 @@ var Input = {
         this._currentIndex = 0;
     },
 
-    updateModes: function updateModes(aPrefsBranch) {
-      try {
-        this.modes = aPrefsBranch.getCharPref('quicknav_modes').split(',');
-      } catch (x) {
-        // Fallback
+    updateModes: function updateModes(aModes) {
+      if (aModes) {
+        this.modes = aModes.split(',');
+      } else {
         this.modes = [];
       }
     },

accessible/src/jsat/Utils.jsm

@@ -8,10 +8,13 @@ const Cu = Components.utils;
 const Cc = Components.classes;
 const Ci = Components.interfaces;
 
-Cu.import('resource://gre/modules/Services.jsm');
-Cu.import('resource://gre/modules/Geometry.jsm');
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, 'Services',
+  'resource://gre/modules/Services.jsm');
+XPCOMUtils.defineLazyModuleGetter(this, 'Rect',
+  'resource://gre/modules/Geometry.jsm');
 
-this.EXPORTED_SYMBOLS = ['Utils', 'Logger', 'PivotContext'];
+this.EXPORTED_SYMBOLS = ['Utils', 'Logger', 'PivotContext', 'PrefCache'];
 
 this.Utils = {
   _buildAppMap: {
@@ -426,4 +429,55 @@ PivotContext.prototype = {
       return true;
     }
   }
+};
+
+this.PrefCache = function PrefCache(aName, aCallback, aRunCallbackNow) {
+  this.name = aName;
+  this.callback = aCallback;
+
+  let branch = Services.prefs;
+  this.value = this._getValue(branch);
+
+  if (this.callback && aRunCallbackNow) {
+    try {
+      this.callback(this.name, this.value);
+    } catch (x) {
+      Logger.logException(x);
+    }
+  }
+
+  branch.addObserver(aName, this, true);
+};
+
+PrefCache.prototype = {
+  _getValue: function _getValue(aBranch) {
+    if (!this.type) {
+      this.type = aBranch.getPrefType(this.name);
+    }
+
+    switch (this.type) {
+      case Ci.nsIPrefBranch.PREF_STRING:
+        return aBranch.getCharPref(this.name);
+      case Ci.nsIPrefBranch.PREF_INT:
+        return aBranch.getIntPref(this.name);
+      case Ci.nsIPrefBranch.PREF_BOOL:
+        return aBranch.getBoolPref(this.name);
+      default:
+        return null;
+    }
+  },
+
+  observe: function observe(aSubject, aTopic, aData) {
+    this.value = this._getValue(aSubject.QueryInterface(Ci.nsIPrefBranch));
+    if (this.callback) {
+      try {
+        this.callback(this.name, this.value);
+      } catch (x) {
+        Logger.logException(x);
+      }
+    }
+  },
+
+  QueryInterface : XPCOMUtils.generateQI([Ci.nsIObserver,
+                                          Ci.nsISupportsWeakReference])
 };

accessible/src/jsat/UtteranceGenerator.jsm

@@ -15,29 +15,16 @@ const INCLUDE_CUSTOM = 0x04;
 
 const UTTERANCE_DESC_FIRST = 0;
 
-// Read and observe changes to a setting for utterance order.
-let gUtteranceOrder;
-let prefsBranch = Cc['@mozilla.org/preferences-service;1']
-  .getService(Ci.nsIPrefService).getBranch('accessibility.accessfu.');
-let observeUtterance = function observeUtterance(aSubject, aTopic, aData) {
-  try {
-    gUtteranceOrder = prefsBranch.getIntPref('utterance');
-  } catch (x) {
-    gUtteranceOrder = UTTERANCE_DESC_FIRST;
-  }
-};
-// Set initial gUtteranceOrder.
-observeUtterance();
-prefsBranch.addObserver('utterance', observeUtterance, false);
+Cu.import('resource://gre/modules/accessibility/Utils.jsm');
+
+let gUtteranceOrder = new PrefCache('accessibility.accessfu.utterance');
 
 var gStringBundle = Cc['@mozilla.org/intl/stringbundle;1'].
   getService(Ci.nsIStringBundleService).
   createBundle('chrome://global/locale/AccessFu.properties');
 
-
 this.EXPORTED_SYMBOLS = ['UtteranceGenerator'];
 
-Cu.import('resource://gre/modules/accessibility/Utils.jsm');
 
 /**
  * Generates speech utterances from objects, actions and state changes.
@@ -88,7 +75,9 @@ this.UtteranceGenerator = {
         UtteranceGenerator.genForObject(aAccessible));
     };
 
-    if (gUtteranceOrder === UTTERANCE_DESC_FIRST) {
+    let utteranceOrder = gUtteranceOrder.value || UTTERANCE_DESC_FIRST;
+
+    if (utteranceOrder === UTTERANCE_DESC_FIRST) {
       aContext.newAncestry.forEach(addUtterance);
       addUtterance(aContext.accessible);
       aContext.subtreePreorder.forEach(addUtterance);
@@ -117,7 +106,7 @@ this.UtteranceGenerator = {
     let func = this.objectUtteranceFunctions[roleString] ||
       this.objectUtteranceFunctions.defaultFunc;
 
-    let flags = this.verbosityRoleMap[roleString] || 0;
+    let flags = this.verbosityRoleMap[roleString] || UTTERANCE_DESC_FIRST;
 
     if (aAccessible.childCount == 0)
       flags |= INCLUDE_NAME;
@@ -326,8 +315,10 @@ this.UtteranceGenerator = {
 
   _addName: function _addName(utterance, aAccessible, aFlags) {
     let name = (aFlags & INCLUDE_NAME) ? (aAccessible.name || '') : '';
+    let utteranceOrder = gUtteranceOrder.value || 0;
+
     if (name) {
-      utterance[gUtteranceOrder === UTTERANCE_DESC_FIRST ?
+      utterance[utteranceOrder === UTTERANCE_DESC_FIRST ?
         "push" : "unshift"](name);
     }
   },