chrome/renderer/resources/extensions/automation/automation_node.js

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 var AutomationEvent = require('automationEvent').AutomationEvent;
   6 var automationInternal =
   7     require('binding').Binding.create('automationInternal').generate();
   8 var IsInteractPermitted =
   9     requireNative('automationInternal').IsInteractPermitted;
  10
  11 /**
  12  * @param {number} axTreeID The id of the accessibility tree.
  13  * @return {?number} The id of the root node.
  14  */
  15 var GetRootID = requireNative('automationInternal').GetRootID;
  16
  17 /**
  18  * @param {number} axTreeID The id of the accessibility tree.
  19  * @param {number} nodeID The id of a node.
  20  * @return {?number} The id of the node's parent, or undefined if it's the
  21  *    root of its tree or if the tree or node wasn't found.
  22  */
  23 var GetParentID = requireNative('automationInternal').GetParentID;
  24
  25 /**
  26  * @param {number} axTreeID The id of the accessibility tree.
  27  * @param {number} nodeID The id of a node.
  28  * @return {?number} The number of children of the node, or undefined if
  29  *     the tree or node wasn't found.
  30  */
  31 var GetChildCount = requireNative('automationInternal').GetChildCount;
  32
  33 /**
  34  * @param {number} axTreeID The id of the accessibility tree.
  35  * @param {number} nodeID The id of a node.
  36  * @param {number} childIndex An index of a child of this node.
  37  * @return {?number} The id of the child at the given index, or undefined
  38  *     if the tree or node or child at that index wasn't found.
  39  */
  40 var GetChildIDAtIndex = requireNative('automationInternal').GetChildIDAtIndex;
  41
  42 /**
  43  * @param {number} axTreeID The id of the accessibility tree.
  44  * @param {number} nodeID The id of a node.
  45  * @return {?number} The index of this node in its parent, or undefined if
  46  *     the tree or node or node parent wasn't found.
  47  */
  48 var GetIndexInParent = requireNative('automationInternal').GetIndexInParent;
  49
  50 /**
  51  * @param {number} axTreeID The id of the accessibility tree.
  52  * @param {number} nodeID The id of a node.
  53  * @return {?Object} An object with a string key for every state flag set,
  54  *     or undefined if the tree or node or node parent wasn't found.
  55  */
  56 var GetState = requireNative('automationInternal').GetState;
  57
  58 /**
  59  * @param {number} axTreeID The id of the accessibility tree.
  60  * @param {number} nodeID The id of a node.
  61  * @return {string} The role of the node, or undefined if the tree or
  62  *     node wasn't found.
  63  */
  64 var GetRole = requireNative('automationInternal').GetRole;
  65
  66 /**
  67  * @param {number} axTreeID The id of the accessibility tree.
  68  * @param {number} nodeID The id of a node.
  69  * @return {?automation.Rect} The location of the node, or undefined if
  70  *     the tree or node wasn't found.
  71  */
  72 var GetLocation = requireNative('automationInternal').GetLocation;
  73
  74 /**
  75  * @param {number} axTreeID The id of the accessibility tree.
  76  * @param {number} nodeID The id of a node.
  77  * @param {string} attr The name of a string attribute.
  78  * @return {?string} The value of this attribute, or undefined if the tree,
  79  *     node, or attribute wasn't found.
  80  */
  81 var GetStringAttribute = requireNative('automationInternal').GetStringAttribute;
  82
  83 /**
  84  * @param {number} axTreeID The id of the accessibility tree.
  85  * @param {number} nodeID The id of a node.
  86  * @param {string} attr The name of an attribute.
  87  * @return {?boolean} The value of this attribute, or undefined if the tree,
  88  *     node, or attribute wasn't found.
  89  */
  90 var GetBoolAttribute = requireNative('automationInternal').GetBoolAttribute;
  91
  92 /**
  93  * @param {number} axTreeID The id of the accessibility tree.
  94  * @param {number} nodeID The id of a node.
  95  * @param {string} attr The name of an attribute.
  96  * @return {?number} The value of this attribute, or undefined if the tree,
  97  *     node, or attribute wasn't found.
  98  */
  99 var GetIntAttribute = requireNative('automationInternal').GetIntAttribute;
 100
 101 /**
 102  * @param {number} axTreeID The id of the accessibility tree.
 103  * @param {number} nodeID The id of a node.
 104  * @param {string} attr The name of an attribute.
 105  * @return {?number} The value of this attribute, or undefined if the tree,
 106  *     node, or attribute wasn't found.
 107  */
 108 var GetFloatAttribute = requireNative('automationInternal').GetFloatAttribute;
 109
 110 /**
 111  * @param {number} axTreeID The id of the accessibility tree.
 112  * @param {number} nodeID The id of a node.
 113  * @param {string} attr The name of an attribute.
 114  * @return {?Array.<number>} The value of this attribute, or undefined
 115  *     if the tree, node, or attribute wasn't found.
 116  */
 117 var GetIntListAttribute =
 118     requireNative('automationInternal').GetIntListAttribute;
 119
 120 /**
 121  * @param {number} axTreeID The id of the accessibility tree.
 122  * @param {number} nodeID The id of a node.
 123  * @param {string} attr The name of an HTML attribute.
 124  * @return {?string} The value of this attribute, or undefined if the tree,
 125  *     node, or attribute wasn't found.
 126  */
 127 var GetHtmlAttribute = requireNative('automationInternal').GetHtmlAttribute;
 128
 129 var lastError = require('lastError');
 130 var logging = requireNative('logging');
 131 var schema = requireNative('automationInternal').GetSchemaAdditions();
 132 var utils = require('utils');
 133
 134 /**
 135  * A single node in the Automation tree.
 136  * @param {AutomationRootNodeImpl} root The root of the tree.
 137  * @constructor
 138  */
 139 function AutomationNodeImpl(root) {
 140   this.rootImpl = root;
 141   // Public attributes. No actual data gets set on this object.
 142   this.listeners = {};
 143 }
 144
 145 AutomationNodeImpl.prototype = {
 146   treeID: -1,
 147   id: -1,
 148   role: '',
 149   state: { busy: true },
 150   isRootNode: false,
 151
 152   get root() {
 153     return this.rootImpl.wrapper;
 154   },
 155
 156   get parent() {
 157     if (this.hostNode_)
 158       return this.hostNode_;
 159     var parentID = GetParentID(this.treeID, this.id);
 160     return this.rootImpl.get(parentID);
 161   },
 162
 163   get state() {
 164     return GetState(this.treeID, this.id);
 165   },
 166
 167   get role() {
 168     return GetRole(this.treeID, this.id);
 169   },
 170
 171   get location() {
 172     return GetLocation(this.treeID, this.id);
 173   },
 174
 175   get indexInParent() {
 176     return GetIndexInParent(this.treeID, this.id);
 177   },
 178
 179   get childTree() {
 180     var childTreeID = GetIntAttribute(this.treeID, this.id, 'childTreeId');
 181     if (childTreeID)
 182       return AutomationRootNodeImpl.get(childTreeID);
 183   },
 184
 185   get firstChild() {
 186     if (this.childTree)
 187       return this.childTree;
 188     if (!GetChildCount(this.treeID, this.id))
 189       return undefined;
 190     var firstChildID = GetChildIDAtIndex(this.treeID, this.id, 0);
 191     return this.rootImpl.get(firstChildID);
 192   },
 193
 194   get lastChild() {
 195     if (this.childTree)
 196       return this.childTree;
 197     var count = GetChildCount(this.treeID, this.id);
 198     if (!count)
 199       return undefined;
 200     var lastChildID = GetChildIDAtIndex(this.treeID, this.id, count - 1);
 201     return this.rootImpl.get(lastChildID);
 202   },
 203
 204   get children() {
 205     if (this.childTree)
 206       return [this.childTree];
 207
 208     var children = [];
 209     var count = GetChildCount(this.treeID, this.id);
 210     for (var i = 0; i < count; ++i) {
 211       var childID = GetChildIDAtIndex(this.treeID, this.id, i);
 212       var child = this.rootImpl.get(childID);
 213       children.push(child);
 214     }
 215     return children;
 216   },
 217
 218   get previousSibling() {
 219     var parent = this.parent;
 220     var indexInParent = GetIndexInParent(this.treeID, this.id);
 221     if (parent && indexInParent > 0)
 222       return parent.children[indexInParent - 1];
 223     return undefined;
 224   },
 225
 226   get nextSibling() {
 227     var parent = this.parent;
 228     var indexInParent = GetIndexInParent(this.treeID, this.id);
 229     if (parent && indexInParent < parent.children.length)
 230       return parent.children[indexInParent + 1];
 231     return undefined;
 232   },
 233
 234   doDefault: function() {
 235     this.performAction_('doDefault');
 236   },
 237
 238   focus: function() {
 239     this.performAction_('focus');
 240   },
 241
 242   makeVisible: function() {
 243     this.performAction_('makeVisible');
 244   },
 245
 246   setSelection: function(startIndex, endIndex) {
 247     this.performAction_('setSelection',
 248                         { startIndex: startIndex,
 249                           endIndex: endIndex });
 250   },
 251
 252   showContextMenu: function() {
 253     this.performAction_('showContextMenu');
 254   },
 255
 256   domQuerySelector: function(selector, callback) {
 257     automationInternal.querySelector(
 258       { treeID: this.rootImpl.treeID,
 259         automationNodeID: this.id,
 260         selector: selector },
 261       this.domQuerySelectorCallback_.bind(this, callback));
 262   },
 263
 264   find: function(params) {
 265     return this.findInternal_(params);
 266   },
 267
 268   findAll: function(params) {
 269     return this.findInternal_(params, []);
 270   },
 271
 272   matches: function(params) {
 273     return this.matchInternal_(params);
 274   },
 275
 276   addEventListener: function(eventType, callback, capture) {
 277     this.removeEventListener(eventType, callback);
 278     if (!this.listeners[eventType])
 279       this.listeners[eventType] = [];
 280     this.listeners[eventType].push({callback: callback, capture: !!capture});
 281   },
 282
 283   // TODO(dtseng/aboxhall): Check this impl against spec.
 284   removeEventListener: function(eventType, callback) {
 285     if (this.listeners[eventType]) {
 286       var listeners = this.listeners[eventType];
 287       for (var i = 0; i < listeners.length; i++) {
 288         if (callback === listeners[i].callback)
 289           listeners.splice(i, 1);
 290       }
 291     }
 292   },
 293
 294   toJSON: function() {
 295     return { treeID: this.treeID,
 296              id: this.id,
 297              role: this.role,
 298              attributes: this.attributes };
 299   },
 300
 301   dispatchEvent: function(eventType) {
 302     var path = [];
 303     var parent = this.parent;
 304     while (parent) {
 305       path.push(parent);
 306       parent = parent.parent;
 307     }
 308     var event = new AutomationEvent(eventType, this.wrapper);
 309
 310     // Dispatch the event through the propagation path in three phases:
 311     // - capturing: starting from the root and going down to the target's parent
 312     // - targeting: dispatching the event on the target itself
 313     // - bubbling: starting from the target's parent, going back up to the root.
 314     // At any stage, a listener may call stopPropagation() on the event, which
 315     // will immediately stop event propagation through this path.
 316     if (this.dispatchEventAtCapturing_(event, path)) {
 317       if (this.dispatchEventAtTargeting_(event, path))
 318         this.dispatchEventAtBubbling_(event, path);
 319     }
 320   },
 321
 322   toString: function() {
 323     var parentID = GetParentID(this.treeID, this.id);
 324     var childTreeID = GetIntAttribute(this.treeID, this.id, 'childTreeId');
 325     var count = GetChildCount(this.treeID, this.id);
 326     var childIDs = [];
 327     for (var i = 0; i < count; ++i) {
 328       var childID = GetChildIDAtIndex(this.treeID, this.id, i);
 329       childIDs.push(childID);
 330     }
 331
 332     var result = 'node id=' + this.id +
 333         ' role=' + this.role +
 334         ' state=' + $JSON.stringify(this.state) +
 335         ' parentID=' + parentID +
 336         ' childIds=' + $JSON.stringify(childIDs);
 337     if (this.hostNode_) {
 338       var hostNodeImpl = privates(this.hostNode_).impl;
 339       result += ' host treeID=' + hostNodeImpl.treeID +
 340           ' host nodeID=' + hostNodeImpl.id;
 341     }
 342     if (childTreeID)
 343       result += ' childTreeID=' + childTreeID;
 344     return result;
 345   },
 346
 347   dispatchEventAtCapturing_: function(event, path) {
 348     privates(event).impl.eventPhase = Event.CAPTURING_PHASE;
 349     for (var i = path.length - 1; i >= 0; i--) {
 350       this.fireEventListeners_(path[i], event);
 351       if (privates(event).impl.propagationStopped)
 352         return false;
 353     }
 354     return true;
 355   },
 356
 357   dispatchEventAtTargeting_: function(event) {
 358     privates(event).impl.eventPhase = Event.AT_TARGET;
 359     this.fireEventListeners_(this.wrapper, event);
 360     return !privates(event).impl.propagationStopped;
 361   },
 362
 363   dispatchEventAtBubbling_: function(event, path) {
 364     privates(event).impl.eventPhase = Event.BUBBLING_PHASE;
 365     for (var i = 0; i < path.length; i++) {
 366       this.fireEventListeners_(path[i], event);
 367       if (privates(event).impl.propagationStopped)
 368         return false;
 369     }
 370     return true;
 371   },
 372
 373   fireEventListeners_: function(node, event) {
 374     var nodeImpl = privates(node).impl;
 375     var listeners = nodeImpl.listeners[event.type];
 376     if (!listeners)
 377       return;
 378     var eventPhase = event.eventPhase;
 379     for (var i = 0; i < listeners.length; i++) {
 380       if (eventPhase == Event.CAPTURING_PHASE && !listeners[i].capture)
 381         continue;
 382       if (eventPhase == Event.BUBBLING_PHASE && listeners[i].capture)
 383         continue;
 384
 385       try {
 386         listeners[i].callback(event);
 387       } catch (e) {
 388         logging.WARNING('Error in event handler for ' + event.type +
 389                         ' during phase ' + eventPhase + ': ' +
 390                         e.message + '\nStack trace: ' + e.stack);
 391       }
 392     }
 393   },
 394
 395   performAction_: function(actionType, opt_args) {
 396     // Not yet initialized.
 397     if (this.rootImpl.treeID === undefined ||
 398         this.id === undefined) {
 399       return;
 400     }
 401
 402     // Check permissions.
 403     if (!IsInteractPermitted()) {
 404       throw new Error(actionType + ' requires {"desktop": true} or' +
 405           ' {"interact": true} in the "automation" manifest key.');
 406     }
 407
 408     automationInternal.performAction({ treeID: this.rootImpl.treeID,
 409                                        automationNodeID: this.id,
 410                                        actionType: actionType },
 411                                      opt_args || {});
 412   },
 413
 414   domQuerySelectorCallback_: function(userCallback, resultAutomationNodeID) {
 415     // resultAutomationNodeID could be zero or undefined or (unlikely) null;
 416     // they all amount to the same thing here, which is that no node was
 417     // returned.
 418     if (!resultAutomationNodeID) {
 419       userCallback(null);
 420       return;
 421     }
 422     var resultNode = this.rootImpl.get(resultAutomationNodeID);
 423     if (!resultNode) {
 424       logging.WARNING('Query selector result not in tree: ' +
 425                       resultAutomationNodeID);
 426       userCallback(null);
 427     }
 428     userCallback(resultNode);
 429   },
 430
 431   findInternal_: function(params, opt_results) {
 432     var result = null;
 433     this.forAllDescendants_(function(node) {
 434       if (privates(node).impl.matchInternal_(params)) {
 435         if (opt_results)
 436           opt_results.push(node);
 437         else
 438           result = node;
 439         return !opt_results;
 440       }
 441     });
 442     if (opt_results)
 443       return opt_results;
 444     return result;
 445   },
 446
 447   /**
 448    * Executes a closure for all of this node's descendants, in pre-order.
 449    * Early-outs if the closure returns true.
 450    * @param {Function(AutomationNode):boolean} closure Closure to be executed
 451    *     for each node. Return true to early-out the traversal.
 452    */
 453   forAllDescendants_: function(closure) {
 454     var stack = this.wrapper.children.reverse();
 455     while (stack.length > 0) {
 456       var node = stack.pop();
 457       if (closure(node))
 458         return;
 459
 460       var children = node.children;
 461       for (var i = children.length - 1; i >= 0; i--)
 462         stack.push(children[i]);
 463     }
 464   },
 465
 466   matchInternal_: function(params) {
 467     if (Object.keys(params).length == 0)
 468       return false;
 469
 470     if ('role' in params && this.role != params.role)
 471         return false;
 472
 473     if ('state' in params) {
 474       for (var state in params.state) {
 475         if (params.state[state] != (state in this.state))
 476           return false;
 477       }
 478     }
 479     if ('attributes' in params) {
 480       for (var attribute in params.attributes) {
 481         var attrValue = params.attributes[attribute];
 482         if (typeof attrValue != 'object') {
 483           if (this[attribute] !== attrValue)
 484             return false;
 485         } else if (attrValue instanceof RegExp) {
 486           if (typeof this[attribute] != 'string')
 487             return false;
 488           if (!attrValue.test(this[attribute]))
 489             return false;
 490         } else {
 491           // TODO(aboxhall): handle intlist case.
 492           return false;
 493         }
 494       }
 495     }
 496     return true;
 497   }
 498 };
 499
 500 var stringAttributes = [
 501     'accessKey',
 502     'action',
 503     'ariaInvalidValue',
 504     'autoComplete',
 505     'containerLiveRelevant',
 506     'containerLiveStatus',
 507     'description',
 508     'display',
 509     'docDoctype',
 510     'docMimetype',
 511     'docTitle',
 512     'docUrl',
 513     'dropeffect',
 514     'help',
 515     'htmlTag',
 516     'liveRelevant',
 517     'liveStatus',
 518     'name',
 519     'placeholder',
 520     'shortcut',
 521     'textInputType',
 522     'url',
 523     'value'];
 524
 525 var boolAttributes = [
 526     'ariaReadonly',
 527     'buttonMixed',
 528     'canSetValue',
 529     'canvasHasFallback',
 530     'containerLiveAtomic',
 531     'containerLiveBusy',
 532     'docLoaded',
 533     'grabbed',
 534     'isAxTreeHost',
 535     'liveAtomic',
 536     'liveBusy',
 537     'updateLocationOnly'];
 538
 539 var intAttributes = [
 540     'anchorOffset',
 541     'backgroundColor',
 542     'color',
 543     'colorValue',
 544     'focusOffset',
 545     'hierarchicalLevel',
 546     'invalidState',
 547     'posInSet',
 548     'scrollX',
 549     'scrollXMax',
 550     'scrollXMin',
 551     'scrollY',
 552     'scrollYMax',
 553     'scrollYMin',
 554     'setSize',
 555     'sortDirection',
 556     'tableCellColumnIndex',
 557     'tableCellColumnSpan',
 558     'tableCellRowIndex',
 559     'tableCellRowSpan',
 560     'tableColumnCount',
 561     'tableColumnIndex',
 562     'tableRowCount',
 563     'tableRowIndex',
 564     'textDirection',
 565     'textSelEnd',
 566     'textSelStart',
 567     'textStyle'];
 568
 569 var nodeRefAttributes = [
 570     ['activedescendantId', 'activedescendant'],
 571     ['anchorObjectId', 'anchorObject'],
 572     ['focusObjectId', 'focusObject'],
 573     ['tableColumnHeaderId', 'tableColumnHeader'],
 574     ['tableHeaderId', 'tableHeader'],
 575     ['tableRowHeaderId', 'tableRowHeader'],
 576     ['titleUiElement', 'titleUIElement']];
 577
 578 var intListAttributes = [
 579     'characterOffsets',
 580     'lineBreaks',
 581     'wordEnds',
 582     'wordStarts'];
 583
 584 var nodeRefListAttributes = [
 585     ['cellIds', 'cells'],
 586     ['controlsIds', 'controls'],
 587     ['describedbyIds', 'describedBy'],
 588     ['flowtoIds', 'flowTo'],
 589     ['labelledbyIds', 'labelledBy'],
 590     ['uniqueCellIds', 'uniqueCells']];
 591
 592 var floatAttributes = [
 593     'docLoadingProgress',
 594     'valueForRange',
 595     'minValueForRange',
 596     'maxValueForRange',
 597     'fontSize'];
 598
 599 var htmlAttributes = [
 600     ['type', 'inputType']];
 601
 602 var publicAttributes = [];
 603
 604 stringAttributes.forEach(function (attributeName) {
 605   publicAttributes.push(attributeName);
 606   Object.defineProperty(AutomationNodeImpl.prototype, attributeName, {
 607     get: function() {
 608       return GetStringAttribute(this.treeID, this.id, attributeName);
 609     }
 610   });
 611 });
 612
 613 boolAttributes.forEach(function (attributeName) {
 614   publicAttributes.push(attributeName);
 615   Object.defineProperty(AutomationNodeImpl.prototype, attributeName, {
 616     get: function() {
 617       return GetBoolAttribute(this.treeID, this.id, attributeName);
 618     }
 619   });
 620 });
 621
 622 intAttributes.forEach(function (attributeName) {
 623   publicAttributes.push(attributeName);
 624   Object.defineProperty(AutomationNodeImpl.prototype, attributeName, {
 625     get: function() {
 626       return GetIntAttribute(this.treeID, this.id, attributeName);
 627     }
 628   });
 629 });
 630
 631 nodeRefAttributes.forEach(function (params) {
 632   var srcAttributeName = params[0];
 633   var dstAttributeName = params[1];
 634   publicAttributes.push(dstAttributeName);
 635   Object.defineProperty(AutomationNodeImpl.prototype, dstAttributeName, {
 636     get: function() {
 637       var id = GetIntAttribute(this.treeID, this.id, srcAttributeName);
 638       if (id)
 639         return this.rootImpl.get(id);
 640       else
 641         return undefined;
 642     }
 643   });
 644 });
 645
 646 intListAttributes.forEach(function (attributeName) {
 647   publicAttributes.push(attributeName);
 648   Object.defineProperty(AutomationNodeImpl.prototype, attributeName, {
 649     get: function() {
 650       return GetIntListAttribute(this.treeID, this.id, attributeName);
 651     }
 652   });
 653 });
 654
 655 nodeRefListAttributes.forEach(function (params) {
 656   var srcAttributeName = params[0];
 657   var dstAttributeName = params[1];
 658   publicAttributes.push(dstAttributeName);
 659   Object.defineProperty(AutomationNodeImpl.prototype, dstAttributeName, {
 660     get: function() {
 661       var ids = GetIntListAttribute(this.treeID, this.id, srcAttributeName);
 662       if (!ids)
 663         return undefined;
 664       var result = [];
 665       for (var i = 0; i < ids.length; ++i) {
 666         var node = this.rootImpl.get(ids[i]);
 667         if (node)
 668           result.push(node);
 669       }
 670       return result;
 671     }
 672   });
 673 });
 674
 675 floatAttributes.forEach(function (attributeName) {
 676   publicAttributes.push(attributeName);
 677   Object.defineProperty(AutomationNodeImpl.prototype, attributeName, {
 678     get: function() {
 679       return GetFloatAttribute(this.treeID, this.id, attributeName);
 680     }
 681   });
 682 });
 683
 684 htmlAttributes.forEach(function (params) {
 685   var srcAttributeName = params[0];
 686   var dstAttributeName = params[1];
 687   publicAttributes.push(dstAttributeName);
 688   Object.defineProperty(AutomationNodeImpl.prototype, dstAttributeName, {
 689     get: function() {
 690       return GetHtmlAttribute(this.treeID, this.id, srcAttributeName);
 691     }
 692   });
 693 });
 694
 695 /**
 696  * AutomationRootNode.
 697  *
 698  * An AutomationRootNode is the javascript end of an AXTree living in the
 699  * browser. AutomationRootNode handles unserializing incremental updates from
 700  * the source AXTree. Each update contains node data that form a complete tree
 701  * after applying the update.
 702  *
 703  * A brief note about ids used through this class. The source AXTree assigns
 704  * unique ids per node and we use these ids to build a hash to the actual
 705  * AutomationNode object.
 706  * Thus, tree traversals amount to a lookup in our hash.
 707  *
 708  * The tree itself is identified by the accessibility tree id of the
 709  * renderer widget host.
 710  * @constructor
 711  */
 712 function AutomationRootNodeImpl(treeID) {
 713   AutomationNodeImpl.call(this, this);
 714   this.treeID = treeID;
 715   this.axNodeDataCache_ = {};
 716 }
 717
 718 AutomationRootNodeImpl.idToAutomationRootNode_ = {};
 719
 720 AutomationRootNodeImpl.get = function(treeID) {
 721   var result = AutomationRootNodeImpl.idToAutomationRootNode_[treeID];
 722   return result || undefined;
 723 }
 724
 725 AutomationRootNodeImpl.getOrCreate = function(treeID) {
 726   if (AutomationRootNodeImpl.idToAutomationRootNode_[treeID])
 727     return AutomationRootNodeImpl.idToAutomationRootNode_[treeID];
 728   var result = new AutomationRootNode(treeID);
 729   AutomationRootNodeImpl.idToAutomationRootNode_[treeID] = result;
 730   return result;
 731 }
 732
 733 AutomationRootNodeImpl.destroy = function(treeID) {
 734   delete AutomationRootNodeImpl.idToAutomationRootNode_[treeID];
 735 }
 736
 737 AutomationRootNodeImpl.prototype = {
 738   __proto__: AutomationNodeImpl.prototype,
 739
 740   /**
 741    * @type {boolean}
 742    */
 743   isRootNode: true,
 744
 745   /**
 746    * @type {number}
 747    */
 748   treeID: -1,
 749
 750   /**
 751    * The parent of this node from a different tree.
 752    * @type {?AutomationNode}
 753    * @private
 754    */
 755   hostNode_: null,
 756
 757   /**
 758    * A map from id to AutomationNode.
 759    * @type {Object.<number, AutomationNode>}
 760    * @private
 761    */
 762   axNodeDataCache_: null,
 763
 764   get id() {
 765     var result = GetRootID(this.treeID);
 766
 767     // Don't return undefined, because the id is often passed directly
 768     // as an argument to a native binding that expects only a valid number.
 769     if (result === undefined)
 770       return -1;
 771
 772     return result;
 773   },
 774
 775   get: function(id) {
 776     if (id == undefined)
 777       return undefined;
 778
 779     if (id == this.id)
 780       return this.wrapper;
 781
 782     var obj = this.axNodeDataCache_[id];
 783     if (obj)
 784       return obj;
 785
 786     obj = new AutomationNode(this);
 787     privates(obj).impl.treeID = this.treeID;
 788     privates(obj).impl.id = id;
 789     this.axNodeDataCache_[id] = obj;
 790
 791     return obj;
 792   },
 793
 794   remove: function(id) {
 795     delete this.axNodeDataCache_[id];
 796   },
 797
 798   destroy: function() {
 799     this.dispatchEvent(schema.EventType.destroyed);
 800   },
 801
 802   setHostNode(hostNode) {
 803     this.hostNode_ = hostNode;
 804   },
 805
 806   onAccessibilityEvent: function(eventParams) {
 807     var targetNode = this.get(eventParams.targetID);
 808     if (targetNode) {
 809       var targetNodeImpl = privates(targetNode).impl;
 810       targetNodeImpl.dispatchEvent(eventParams.eventType);
 811     } else {
 812       logging.WARNING('Got ' + eventParams.eventType +
 813                       ' event on unknown node: ' + eventParams.targetID +
 814                       '; this: ' + this.id);
 815     }
 816     return true;
 817   },
 818
 819   toString: function() {
 820     function toStringInternal(nodeImpl, indent) {
 821       if (!nodeImpl)
 822         return '';
 823       var output = '';
 824       if (nodeImpl.isRootNode)
 825         output += indent + 'tree id=' + nodeImpl.treeID + '\n';
 826       output += indent +
 827           AutomationNodeImpl.prototype.toString.call(nodeImpl) +
 828           '\n';
 829       indent += '  ';
 830       var children = nodeImpl.children;
 831       for (var i = 0; i < children.length; ++i)
 832         output += toStringInternal(privates(children[i]).impl, indent);
 833       return output;
 834     }
 835     return toStringInternal(this, '');
 836   },
 837 };
 838
 839 var AutomationNode = utils.expose('AutomationNode',
 840                                   AutomationNodeImpl,
 841                                   { functions: ['doDefault',
 842                                                 'find',
 843                                                 'findAll',
 844                                                 'focus',
 845                                                 'makeVisible',
 846                                                 'matches',
 847                                                 'setSelection',
 848                                                 'showContextMenu',
 849                                                 'addEventListener',
 850                                                 'removeEventListener',
 851                                                 'domQuerySelector',
 852                                                 'toString' ],
 853                                     readonly: publicAttributes.concat(
 854                                               ['parent',
 855                                                'firstChild',
 856                                                'lastChild',
 857                                                'children',
 858                                                'previousSibling',
 859                                                'nextSibling',
 860                                                'isRootNode',
 861                                                'role',
 862                                                'state',
 863                                                'location',
 864                                                'indexInParent',
 865                                                'root']) });
 866
 867 var AutomationRootNode = utils.expose('AutomationRootNode',
 868                                       AutomationRootNodeImpl,
 869                                       { superclass: AutomationNode });
 870
 871 AutomationRootNode.get = function(treeID) {
 872   return AutomationRootNodeImpl.get(treeID);
 873 }
 874
 875 AutomationRootNode.getOrCreate = function(treeID) {
 876   return AutomationRootNodeImpl.getOrCreate(treeID);
 877 }
 878
 879 AutomationRootNode.destroy = function(treeID) {
 880   AutomationRootNodeImpl.destroy(treeID);
 881 }
 882
 883 exports.AutomationNode = AutomationNode;
 884 exports.AutomationRootNode = AutomationRootNode;