The Tor Browser: accessible/src/jsat/Utils.jsm@141e0f1194b1 (annotated)

accessible/src/jsat/Utils.jsm@141e0f1194b1 (annotated)

accessible/src/jsat/Utils.jsm

Wed, 31 Dec 2014 07:16:47 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 07:16:47 +0100
branch: TOR_BUG_9701
changeset 3: 141e0f1194b1
permissions: -rw-r--r--

Revert simplistic fix pending revisit of Mozilla integration attempt.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 'use strict';
 const Cu = Components.utils;
 const Cc = Components.classes;
 const Ci = Components.interfaces;
 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');
 XPCOMUtils.defineLazyModuleGetter(this, 'Roles',
   'resource://gre/modules/accessibility/Constants.jsm');
 XPCOMUtils.defineLazyModuleGetter(this, 'Events',
   'resource://gre/modules/accessibility/Constants.jsm');
 XPCOMUtils.defineLazyModuleGetter(this, 'Relations',
   'resource://gre/modules/accessibility/Constants.jsm');
 XPCOMUtils.defineLazyModuleGetter(this, 'States',
   'resource://gre/modules/accessibility/Constants.jsm');
 this.EXPORTED_SYMBOLS = ['Utils', 'Logger', 'PivotContext', 'PrefCache', 'SettingCache'];
 this.Utils = {
   _buildAppMap: {
     '{3c2e2abc-06d4-11e1-ac3b-374f68613e61}': 'b2g',
     '{ec8030f7-c20a-464f-9b0e-13a3a9e97384}': 'browser',
     '{aa3c5121-dab2-40e2-81ca-7ea25febc110}': 'mobile/android',
     '{a23983c0-fd0e-11dc-95ff-0800200c9a66}': 'mobile/xul'
   },
   init: function Utils_init(aWindow) {
     if (this._win)
       // XXX: only supports attaching to one window now.
       throw new Error('Only one top-level window could used with AccessFu');
     this._win = Cu.getWeakReference(aWindow);
   },
   uninit: function Utils_uninit() {
     if (!this._win) {
       return;
     }
     delete this._win;
   },
   get win() {
     if (!this._win) {
       return null;
     }
     return this._win.get();
   },
   get AccRetrieval() {
     if (!this._AccRetrieval) {
       this._AccRetrieval = Cc['@mozilla.org/accessibleRetrieval;1'].
         getService(Ci.nsIAccessibleRetrieval);
     }
     return this._AccRetrieval;
   },
   set MozBuildApp(value) {
     this._buildApp = value;
   },
   get MozBuildApp() {
     if (!this._buildApp)
       this._buildApp = this._buildAppMap[Services.appinfo.ID];
     return this._buildApp;
   },
   get OS() {
     if (!this._OS)
       this._OS = Services.appinfo.OS;
     return this._OS;
   },
   get widgetToolkit() {
     if (!this._widgetToolkit)
       this._widgetToolkit = Services.appinfo.widgetToolkit;
     return this._widgetToolkit;
   },
   get ScriptName() {
     if (!this._ScriptName)
       this._ScriptName =
         (Services.appinfo.processType == 2) ? 'AccessFuContent' : 'AccessFu';
     return this._ScriptName;
   },
   get AndroidSdkVersion() {
     if (!this._AndroidSdkVersion) {
       if (Services.appinfo.OS == 'Android') {
         this._AndroidSdkVersion = Services.sysinfo.getPropertyAsInt32('version');
       } else {
         // Most useful in desktop debugging.
         this._AndroidSdkVersion = 16;
       }
     }
     return this._AndroidSdkVersion;
   },
   set AndroidSdkVersion(value) {
     // When we want to mimic another version.
     this._AndroidSdkVersion = value;
   },
   get BrowserApp() {
     if (!this.win) {
       return null;
     }
     switch (this.MozBuildApp) {
       case 'mobile/android':
         return this.win.BrowserApp;
       case 'browser':
         return this.win.gBrowser;
       case 'b2g':
         return this.win.shell;
       default:
         return null;
     }
   },
   get CurrentBrowser() {
     if (!this.BrowserApp) {
       return null;
     }
     if (this.MozBuildApp == 'b2g')
       return this.BrowserApp.contentBrowser;
     return this.BrowserApp.selectedBrowser;
   },
   get CurrentContentDoc() {
     let browser = this.CurrentBrowser;
     return browser ? browser.contentDocument : null;
   },
   get AllMessageManagers() {
     let messageManagers = [];
     for (let i = 0; i < this.win.messageManager.childCount; i++)
       messageManagers.push(this.win.messageManager.getChildAt(i));
     let document = this.CurrentContentDoc;
     if (document) {
       let remoteframes = document.querySelectorAll('iframe');
       for (let i = 0; i < remoteframes.length; ++i) {
         let mm = this.getMessageManager(remoteframes[i]);
         if (mm) {
           messageManagers.push(mm);
         }
       }
     }
     return messageManagers;
   },
   get isContentProcess() {
     delete this.isContentProcess;
     this.isContentProcess =
       Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT;
     return this.isContentProcess;
   },
   get stringBundle() {
     delete this.stringBundle;
     this.stringBundle = Services.strings.createBundle(
       'chrome://global/locale/AccessFu.properties');
     return this.stringBundle;
   },
   getMessageManager: function getMessageManager(aBrowser) {
     try {
       return aBrowser.QueryInterface(Ci.nsIFrameLoaderOwner).
          frameLoader.messageManager;
     } catch (x) {
       Logger.logException(x);
       return null;
     }
   },
   getViewport: function getViewport(aWindow) {
     switch (this.MozBuildApp) {
       case 'mobile/android':
         return aWindow.BrowserApp.selectedTab.getViewport();
       default:
         return null;
     }
   },
   getState: function getState(aAccessibleOrEvent) {
     if (aAccessibleOrEvent instanceof Ci.nsIAccessibleStateChangeEvent) {
       return new State(
         aAccessibleOrEvent.isExtraState ? 0 : aAccessibleOrEvent.state,
         aAccessibleOrEvent.isExtraState ? aAccessibleOrEvent.state : 0);
     } else {
       let state = {};
       let extState = {};
       aAccessibleOrEvent.getState(state, extState);
       return new State(state.value, extState.value);
     }
   },
   getAttributes: function getAttributes(aAccessible) {
     let attributes = {};
     if (aAccessible && aAccessible.attributes) {
       let attributesEnum = aAccessible.attributes.enumerate();
       // Populate |attributes| object with |aAccessible|'s attribute key-value
       // pairs.
       while (attributesEnum.hasMoreElements()) {
         let attribute = attributesEnum.getNext().QueryInterface(
           Ci.nsIPropertyElement);
         attributes[attribute.key] = attribute.value;
       }
     }
     return attributes;
   },
   getVirtualCursor: function getVirtualCursor(aDocument) {
     let doc = (aDocument instanceof Ci.nsIAccessible) ? aDocument :
       this.AccRetrieval.getAccessibleFor(aDocument);
     return doc.QueryInterface(Ci.nsIAccessibleDocument).virtualCursor;
   },
   getBounds: function getBounds(aAccessible) {
       let objX = {}, objY = {}, objW = {}, objH = {};
       aAccessible.getBounds(objX, objY, objW, objH);
       return new Rect(objX.value, objY.value, objW.value, objH.value);
   },
   getTextBounds: function getTextBounds(aAccessible, aStart, aEnd) {
       let accText = aAccessible.QueryInterface(Ci.nsIAccessibleText);
       let objX = {}, objY = {}, objW = {}, objH = {};
       accText.getRangeExtents(aStart, aEnd, objX, objY, objW, objH,
                               Ci.nsIAccessibleCoordinateType.COORDTYPE_SCREEN_RELATIVE);
       return new Rect(objX.value, objY.value, objW.value, objH.value);
   },
   /**
    * Get current display DPI.
    */
   get dpi() {
     delete this.dpi;
     this.dpi = this.win.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(
       Ci.nsIDOMWindowUtils).displayDPI;
     return this.dpi;
   },
   isInSubtree: function isInSubtree(aAccessible, aSubTreeRoot) {
     let acc = aAccessible;
     while (acc) {
       if (acc == aSubTreeRoot) {
         return true;
       }
       try {
         acc = acc.parent;
       } catch (x) {
         Logger.debug('Failed to get parent:', x);
         acc = null;
       }
     }
     return false;
   },
   inHiddenSubtree: function inHiddenSubtree(aAccessible) {
     for (let acc=aAccessible; acc; acc=acc.parent) {
       let hidden = Utils.getAttributes(acc).hidden;
       if (hidden && JSON.parse(hidden)) {
         return true;
       }
     }
     return false;
   },
   isAliveAndVisible: function isAliveAndVisible(aAccessible, aIsOnScreen) {
     if (!aAccessible) {
       return false;
     }
     try {
       let state = this.getState(aAccessible);
       if (state.contains(States.DEFUNCT) || state.contains(States.INVISIBLE) ||
           (aIsOnScreen && state.contains(States.OFFSCREEN)) ||
           Utils.inHiddenSubtree(aAccessible)) {
         return false;
       }
     } catch (x) {
       return false;
     }
     return true;
   },
   matchAttributeValue: function matchAttributeValue(aAttributeValue, values) {
     let attrSet = new Set(aAttributeValue.split(' '));
     for (let value of values) {
       if (attrSet.has(value)) {
         return value;
       }
     }
   },
   getLandmarkName: function getLandmarkName(aAccessible) {
     const landmarks = [
       'banner',
       'complementary',
       'contentinfo',
       'main',
       'navigation',
       'search'
     ];
     let roles = this.getAttributes(aAccessible)['xml-roles'];
     if (!roles) {
       return;
     }
     // Looking up a role that would match a landmark.
     return this.matchAttributeValue(roles, landmarks);
   },
   getEmbeddedControl: function getEmbeddedControl(aLabel) {
     if (aLabel) {
       let relation = aLabel.getRelationByType(Relations.LABEL_FOR);
       for (let i = 0; i < relation.targetsCount; i++) {
         let target = relation.getTarget(i);
         if (target.parent === aLabel) {
           return target;
         }
       }
     }
     return null;
   }
 };
 /**
  * State object used internally to process accessible's states.
  * @param {Number} aBase     Base state.
  * @param {Number} aExtended Extended state.
  */
 function State(aBase, aExtended) {
   this.base = aBase;
   this.extended = aExtended;
 }
 State.prototype = {
   contains: function State_contains(other) {
     return !!(this.base & other.base || this.extended & other.extended);
   },
   toString: function State_toString() {
     let stateStrings = Utils.AccRetrieval.
       getStringStates(this.base, this.extended);
     let statesArray = new Array(stateStrings.length);
     for (let i = 0; i < statesArray.length; i++) {
       statesArray[i] = stateStrings.item(i);
     }
     return '[' + statesArray.join(', ') + ']';
   }
 };
 this.Logger = {
   DEBUG: 0,
   INFO: 1,
   WARNING: 2,
   ERROR: 3,
   _LEVEL_NAMES: ['DEBUG', 'INFO', 'WARNING', 'ERROR'],
   logLevel: 1, // INFO;
   test: false,
   log: function log(aLogLevel) {
     if (aLogLevel < this.logLevel)
       return;
     let args = Array.prototype.slice.call(arguments, 1);
     let message = (typeof(args[0]) === 'function' ? args[0]() : args).join(' ');
     message = '[' + Utils.ScriptName + '] ' + this._LEVEL_NAMES[aLogLevel] +
       ' ' + message + '\n';
     dump(message);
     // Note: used for testing purposes. If |this.test| is true, also log to
     // the console service.
     if (this.test) {
       try {
         Services.console.logStringMessage(message);
       } catch (ex) {
         // There was an exception logging to the console service.
       }
     }
   },
   info: function info() {
     this.log.apply(
       this, [this.INFO].concat(Array.prototype.slice.call(arguments)));
   },
   debug: function debug() {
     this.log.apply(
       this, [this.DEBUG].concat(Array.prototype.slice.call(arguments)));
   },
   warning: function warning() {
     this.log.apply(
       this, [this.WARNING].concat(Array.prototype.slice.call(arguments)));
   },
   error: function error() {
     this.log.apply(
       this, [this.ERROR].concat(Array.prototype.slice.call(arguments)));
   },
   logException: function logException(
     aException, aErrorMessage = 'An exception has occured') {
     try {
       let stackMessage = '';
       if (aException.stack) {
         stackMessage = '  ' + aException.stack.replace(/\n/g, '\n  ');
       } else if (aException.location) {
         let frame = aException.location;
         let stackLines = [];
         while (frame && frame.lineNumber) {
           stackLines.push(
             '  ' + frame.name + '@' + frame.filename + ':' + frame.lineNumber);
           frame = frame.caller;
         }
         stackMessage = stackLines.join('\n');
       } else {
         stackMessage = '(' + aException.fileName + ':' + aException.lineNumber + ')';
       }
       this.error(aErrorMessage + ':\n ' +
                  aException.message + '\n' +
                  stackMessage);
     } catch (x) {
       this.error(x);
     }
   },
   accessibleToString: function accessibleToString(aAccessible) {
     let str = '[ defunct ]';
     try {
       str = '[ ' + Utils.AccRetrieval.getStringRole(aAccessible.role) +
         ' | ' + aAccessible.name + ' ]';
     } catch (x) {
     }
     return str;
   },
   eventToString: function eventToString(aEvent) {
     let str = Utils.AccRetrieval.getStringEventType(aEvent.eventType);
     if (aEvent.eventType == Events.STATE_CHANGE) {
       let event = aEvent.QueryInterface(Ci.nsIAccessibleStateChangeEvent);
       let stateStrings = event.isExtraState ?
         Utils.AccRetrieval.getStringStates(0, event.state) :
         Utils.AccRetrieval.getStringStates(event.state, 0);
       str += ' (' + stateStrings.item(0) + ')';
     }
     if (aEvent.eventType == Events.VIRTUALCURSOR_CHANGED) {
       let event = aEvent.QueryInterface(
         Ci.nsIAccessibleVirtualCursorChangeEvent);
       let pivot = aEvent.accessible.QueryInterface(
         Ci.nsIAccessibleDocument).virtualCursor;
       str += ' (' + this.accessibleToString(event.oldAccessible) + ' -> ' +
 	this.accessibleToString(pivot.position) + ')';
     }
     return str;
   },
   statesToString: function statesToString(aAccessible) {
     return Utils.getState(aAccessible).toString();
   },
   dumpTree: function dumpTree(aLogLevel, aRootAccessible) {
     if (aLogLevel < this.logLevel)
       return;
     this._dumpTreeInternal(aLogLevel, aRootAccessible, 0);
   },
   _dumpTreeInternal: function _dumpTreeInternal(aLogLevel, aAccessible, aIndent) {
     let indentStr = '';
     for (var i=0; i < aIndent; i++)
       indentStr += ' ';
     this.log(aLogLevel, indentStr,
              this.accessibleToString(aAccessible),
              '(' + this.statesToString(aAccessible) + ')');
     for (var i=0; i < aAccessible.childCount; i++)
       this._dumpTreeInternal(aLogLevel, aAccessible.getChildAt(i), aIndent + 1);
     }
 };
 /**
  * PivotContext: An object that generates and caches context information
  * for a given accessible and its relationship with another accessible.
  *
  * If the given accessible is a label for a nested control, then this
  * context will represent the nested control instead of the label.
  * With the exception of bounds calculation, which will use the containing
  * label. In this case the |accessible| field would be the embedded control,
  * and the |accessibleForBounds| field would be the label.
  */
 this.PivotContext = function PivotContext(aAccessible, aOldAccessible,
   aStartOffset, aEndOffset, aIgnoreAncestry = false,
   aIncludeInvisible = false) {
   this._accessible = aAccessible;
   this._nestedControl = Utils.getEmbeddedControl(aAccessible);
   this._oldAccessible =
     this._isDefunct(aOldAccessible) ? null : aOldAccessible;
   this.startOffset = aStartOffset;
   this.endOffset = aEndOffset;
   this._ignoreAncestry = aIgnoreAncestry;
   this._includeInvisible = aIncludeInvisible;
 }
 PivotContext.prototype = {
   get accessible() {
     // If the current pivot accessible has a nested control,
     // make this context use it publicly.
     return this._nestedControl || this._accessible;
   },
   get oldAccessible() {
     return this._oldAccessible;
   },
   get isNestedControl() {
     return !!this._nestedControl;
   },
   get accessibleForBounds() {
     return this._accessible;
   },
   get textAndAdjustedOffsets() {
     if (this.startOffset === -1 && this.endOffset === -1) {
       return null;
     }
     if (!this._textAndAdjustedOffsets) {
       let result = {startOffset: this.startOffset,
                     endOffset: this.endOffset,
                     text: this._accessible.QueryInterface(Ci.nsIAccessibleText).
                           getText(0, Ci.nsIAccessibleText.TEXT_OFFSET_END_OF_TEXT)};
       let hypertextAcc = this._accessible.QueryInterface(Ci.nsIAccessibleHyperText);
       // Iterate through the links in backwards order so text replacements don't
       // affect the offsets of links yet to be processed.
       for (let i = hypertextAcc.linkCount - 1; i >= 0; i--) {
         let link = hypertextAcc.getLinkAt(i);
         let linkText = '';
         if (link instanceof Ci.nsIAccessibleText) {
           linkText = link.QueryInterface(Ci.nsIAccessibleText).
                           getText(0, Ci.nsIAccessibleText.TEXT_OFFSET_END_OF_TEXT);
         }
         let start = link.startIndex;
         let end = link.endIndex;
         for (let offset of ['startOffset', 'endOffset']) {
           if (this[offset] >= end) {
             result[offset] += linkText.length - (end - start);
           }
         }
         result.text = result.text.substring(0, start) + linkText +
                       result.text.substring(end);
       }
       this._textAndAdjustedOffsets = result;
     }
     return this._textAndAdjustedOffsets;
   },
   /**
    * Get a list of |aAccessible|'s ancestry up to the root.
    * @param  {nsIAccessible} aAccessible.
    * @return {Array} Ancestry list.
    */
   _getAncestry: function _getAncestry(aAccessible) {
     let ancestry = [];
     let parent = aAccessible;
     try {
       while (parent && (parent = parent.parent)) {
        ancestry.push(parent);
       }
     } catch (x) {
       // A defunct accessible will raise an exception geting parent.
       Logger.debug('Failed to get parent:', x);
     }
     return ancestry.reverse();
   },
   /**
    * A list of the old accessible's ancestry.
    */
   get oldAncestry() {
     if (!this._oldAncestry) {
       if (!this._oldAccessible || this._ignoreAncestry) {
         this._oldAncestry = [];
       } else {
         this._oldAncestry = this._getAncestry(this._oldAccessible);
         this._oldAncestry.push(this._oldAccessible);
       }
     }
     return this._oldAncestry;
   },
   /**
    * A list of the current accessible's ancestry.
    */
   get currentAncestry() {
     if (!this._currentAncestry) {
       this._currentAncestry = this._ignoreAncestry ? [] :
         this._getAncestry(this.accessible);
     }
     return this._currentAncestry;
   },
   /*
    * This is a list of the accessible's ancestry up to the common ancestor
    * of the accessible and the old accessible. It is useful for giving the
    * user context as to where they are in the heirarchy.
    */
   get newAncestry() {
     if (!this._newAncestry) {
       this._newAncestry = this._ignoreAncestry ? [] : [currentAncestor for (
         [index, currentAncestor] of Iterator(this.currentAncestry)) if (
           currentAncestor !== this.oldAncestry[index])];
     }
     return this._newAncestry;
   },
   /*
    * Traverse the accessible's subtree in pre or post order.
    * It only includes the accessible's visible chidren.
    * Note: needSubtree is a function argument that can be used to determine
    * whether aAccessible's subtree is required.
    */
   _traverse: function _traverse(aAccessible, aPreorder, aStop) {
     if (aStop && aStop(aAccessible)) {
       return;
     }
     let child = aAccessible.firstChild;
     while (child) {
       let include;
       if (this._includeInvisible) {
         include = true;
       } else {
         include = !(Utils.getState(child).contains(States.INVISIBLE));
       }
       if (include) {
         if (aPreorder) {
           yield child;
           [yield node for (node of this._traverse(child, aPreorder, aStop))];
         } else {
           [yield node for (node of this._traverse(child, aPreorder, aStop))];
           yield child;
         }
       }
       child = child.nextSibling;
     }
   },
   /*
    * A subtree generator function, used to generate a flattened
    * list of the accessible's subtree in pre or post order.
    * It only includes the accessible's visible chidren.
    * @param {boolean} aPreorder A flag for traversal order. If true, traverse
    * in preorder; if false, traverse in postorder.
    * @param {function} aStop An optional function, indicating whether subtree
    * traversal should stop.
    */
   subtreeGenerator: function subtreeGenerator(aPreorder, aStop) {
     return this._traverse(this.accessible, aPreorder, aStop);
   },
   getCellInfo: function getCellInfo(aAccessible) {
     if (!this._cells) {
       this._cells = new WeakMap();
     }
     let domNode = aAccessible.DOMNode;
     if (this._cells.has(domNode)) {
       return this._cells.get(domNode);
     }
     let cellInfo = {};
     let getAccessibleCell = function getAccessibleCell(aAccessible) {
       if (!aAccessible) {
         return null;
       }
       if ([Roles.CELL, Roles.COLUMNHEADER, Roles.ROWHEADER].indexOf(
         aAccessible.role) < 0) {
           return null;
       }
       try {
         return aAccessible.QueryInterface(Ci.nsIAccessibleTableCell);
       } catch (x) {
         Logger.logException(x);
         return null;
       }
     };
     let getHeaders = function getHeaders(aHeaderCells) {
       let enumerator = aHeaderCells.enumerate();
       while (enumerator.hasMoreElements()) {
         yield enumerator.getNext().QueryInterface(Ci.nsIAccessible).name;
       }
     };
     cellInfo.current = getAccessibleCell(aAccessible);
     if (!cellInfo.current) {
       Logger.warning(aAccessible,
         'does not support nsIAccessibleTableCell interface.');
       this._cells.set(domNode, null);
       return null;
     }
     let table = cellInfo.current.table;
     if (table.isProbablyForLayout()) {
       this._cells.set(domNode, null);
       return null;
     }
     cellInfo.previous = null;
     let oldAncestry = this.oldAncestry.reverse();
     let ancestor = oldAncestry.shift();
     while (!cellInfo.previous && ancestor) {
       let cell = getAccessibleCell(ancestor);
       if (cell && cell.table === table) {
         cellInfo.previous = cell;
       }
       ancestor = oldAncestry.shift();
     }
     if (cellInfo.previous) {
       cellInfo.rowChanged = cellInfo.current.rowIndex !==
         cellInfo.previous.rowIndex;
       cellInfo.columnChanged = cellInfo.current.columnIndex !==
         cellInfo.previous.columnIndex;
     } else {
       cellInfo.rowChanged = true;
       cellInfo.columnChanged = true;
     }
     cellInfo.rowExtent = cellInfo.current.rowExtent;
     cellInfo.columnExtent = cellInfo.current.columnExtent;
     cellInfo.columnIndex = cellInfo.current.columnIndex;
     cellInfo.rowIndex = cellInfo.current.rowIndex;
     cellInfo.columnHeaders = [];
     if (cellInfo.columnChanged && cellInfo.current.role !==
       Roles.COLUMNHEADER) {
       cellInfo.columnHeaders = [headers for (headers of getHeaders(
         cellInfo.current.columnHeaderCells))];
     }
     cellInfo.rowHeaders = [];
     if (cellInfo.rowChanged && cellInfo.current.role === Roles.CELL) {
       cellInfo.rowHeaders = [headers for (headers of getHeaders(
         cellInfo.current.rowHeaderCells))];
     }
     this._cells.set(domNode, cellInfo);
     return cellInfo;
   },
   get bounds() {
     if (!this._bounds) {
       this._bounds = Utils.getBounds(this.accessibleForBounds);
     }
     return this._bounds.clone();
   },
   _isDefunct: function _isDefunct(aAccessible) {
     try {
       return Utils.getState(aAccessible).contains(States.DEFUNCT);
     } catch (x) {
       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) {
     try {
       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;
       }
     } catch (x) {
       // Pref does not exist.
       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])
 };
 this.SettingCache = function SettingCache(aName, aCallback, aOptions = {}) {
   this.value = aOptions.defaultValue;
   let runCallback = () => {
     if (aCallback) {
       aCallback(aName, this.value);
       if (aOptions.callbackOnce) {
         runCallback = () => {};
       }
     }
   };
   let settings = Utils.win.navigator.mozSettings;
   if (!settings) {
     if (aOptions.callbackNow) {
       runCallback();
     }
     return;
   }
   let lock = settings.createLock();
   let req = lock.get(aName);
   req.addEventListener('success', () => {
     this.value = req.result[aName] == undefined ? aOptions.defaultValue : req.result[aName];
     if (aOptions.callbackNow) {
       runCallback();
     }
   });
   settings.addObserver(aName,
                        (evt) => {
                          this.value = evt.settingValue;
                          runCallback();
                        });
 };

The Tor Browser / annotate

accessible/src/jsat/Utils.jsm@141e0f1194b1 (annotated)

accessible/src/jsat/Utils.jsm