9ba3261571
This adds `page.accessibility.snapshot()`. It serializes and returns the accessibility tree for the page. By default, uninteresting nodes are filtered out of the snapshot. fixes #2033
394 lines
11 KiB
JavaScript
394 lines
11 KiB
JavaScript
/**
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* Copyright 2018 Google Inc. All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the 'License');
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an 'AS IS' BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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const {helper} = require('./helper');
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/**
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* @typedef {Object} SerializedAXNode
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* @property {string} role
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*
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* @property {string=} name
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* @property {string|number=} value
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* @property {string=} description
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*
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* @property {string=} keyshortcuts
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* @property {string=} roledescription
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* @property {string=} valuetext
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*
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* @property {boolean=} disabled
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* @property {boolean=} expanded
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* @property {boolean=} focused
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* @property {boolean=} modal
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* @property {boolean=} multiline
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* @property {boolean=} multiselectable
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* @property {boolean=} readonly
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* @property {boolean=} required
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* @property {boolean=} selected
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*
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* @property {boolean|"mixed"=} checked
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* @property {boolean|"mixed"=} pressed
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*
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* @property {number=} level
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* @property {number=} valuemin
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* @property {number=} valuemax
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*
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* @property {string=} autocomplete
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* @property {string=} haspopup
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* @property {string=} invalid
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* @property {string=} orientation
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*
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* @property {Array<SerializedAXNode>=} children
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*/
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class Accessibility {
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/**
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* @param {!Puppeteer.CDPSession} client
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*/
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constructor(client) {
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this._client = client;
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}
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/**
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* @param {{interestingOnly?: boolean}=} options
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* @return {!Promise<!SerializedAXNode>}
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*/
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async snapshot(options = {}) {
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const {interestingOnly = true} = options;
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const {nodes} = await this._client.send('Accessibility.getFullAXTree');
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const root = AXNode.createTree(nodes);
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if (!interestingOnly)
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return serializeTree(root)[0];
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/** @type {!Set<!AXNode>} */
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const interestingNodes = new Set();
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collectInterestingNodes(interestingNodes, root, false);
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return serializeTree(root, interestingNodes)[0];
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}
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}
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/**
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* @param {!Set<!AXNode>} collection
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* @param {!AXNode} node
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* @param {boolean} insideControl
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*/
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function collectInterestingNodes(collection, node, insideControl) {
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if (node.isInteresting(insideControl))
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collection.add(node);
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if (node.isLeafNode())
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return;
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insideControl = insideControl || node.isControl();
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for (const child of node._children)
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collectInterestingNodes(collection, child, insideControl);
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}
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/**
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* @param {!AXNode} node
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* @param {!Set<!AXNode>=} whitelistedNodes
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* @return {!Array<!SerializedAXNode>}
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*/
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function serializeTree(node, whitelistedNodes) {
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/** @type {!Array<!SerializedAXNode>} */
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const children = [];
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for (const child of node._children)
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children.push(...serializeTree(child, whitelistedNodes));
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if (whitelistedNodes && !whitelistedNodes.has(node))
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return children;
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const serializedNode = node.serialize();
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if (children.length)
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serializedNode.children = children;
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return [serializedNode];
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}
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class AXNode {
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/**
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* @param {!Protocol.Accessibility.AXNode} payload
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*/
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constructor(payload) {
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this._payload = payload;
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/** @type {!Array<!AXNode>} */
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this._children = [];
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this._richlyEditable = false;
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this._editable = false;
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this._focusable = false;
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this._expanded = false;
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this._name = this._payload.name ? this._payload.name.value : '';
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this._role = this._payload.role ? this._payload.role.value : 'Unknown';
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this._cachedHasFocusableChild;
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for (const property of this._payload.properties || []) {
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if (property.name === 'editable') {
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this._richlyEditable = property.value.value === 'richtext';
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this._editable = true;
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}
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if (property.name === 'focusable')
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this._focusable = property.value.value;
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if (property.name === 'expanded')
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this._expanded = property.value.value;
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}
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}
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/**
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* @return {boolean}
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*/
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_isPlainTextField() {
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if (this._richlyEditable)
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return false;
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if (this._editable)
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return true;
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return this._role === 'textbox' || this._role === 'ComboBox' || this._role === 'searchbox';
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}
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/**
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* @return {boolean}
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*/
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_isTextOnlyObject() {
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const role = this._role;
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return (role === 'LineBreak' || role === 'text' ||
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role === 'InlineTextBox');
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}
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/**
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* @return {boolean}
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*/
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_hasFocusableChild() {
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if (this._cachedHasFocusableChild === undefined) {
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this._cachedHasFocusableChild = false;
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for (const child of this._children) {
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if (child._focusable || child._hasFocusableChild()) {
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this._cachedHasFocusableChild = true;
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break;
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}
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}
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}
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return this._cachedHasFocusableChild;
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}
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/**
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* @return {boolean}
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*/
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isLeafNode() {
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if (!this._children.length)
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return true;
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// These types of objects may have children that we use as internal
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// implementation details, but we want to expose them as leaves to platform
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// accessibility APIs because screen readers might be confused if they find
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// any children.
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if (this._isPlainTextField() || this._isTextOnlyObject())
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return true;
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// Roles whose children are only presentational according to the ARIA and
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// HTML5 Specs should be hidden from screen readers.
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// (Note that whilst ARIA buttons can have only presentational children, HTML5
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// buttons are allowed to have content.)
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switch (this._role) {
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case 'doc-cover':
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case 'graphics-symbol':
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case 'img':
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case 'Meter':
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case 'scrollbar':
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case 'slider':
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case 'separator':
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case 'progressbar':
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return true;
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default:
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break;
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}
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// Here and below: Android heuristics
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if (this._hasFocusableChild())
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return false;
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if (this._focusable && this._name)
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return true;
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if (this._role === 'heading' && this._name)
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return true;
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return false;
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}
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/**
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* @return {boolean}
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*/
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isControl() {
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switch (this._role) {
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case 'button':
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case 'checkbox':
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case 'ColorWell':
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case 'combobox':
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case 'DisclosureTriangle':
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case 'listbox':
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case 'menu':
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case 'menubar':
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case 'menuitem':
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case 'menuitemcheckbox':
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case 'menuitemradio':
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case 'radio':
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case 'scrollbar':
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case 'searchbox':
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case 'slider':
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case 'spinbutton':
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case 'switch':
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case 'tab':
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case 'textbox':
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case 'tree':
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return true;
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default:
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return false;
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}
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}
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/**
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* @param {boolean} insideControl
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* @return {boolean}
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*/
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isInteresting(insideControl) {
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const role = this._role;
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if (role === 'Ignored')
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return false;
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if (this._focusable || this._richlyEditable)
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return true;
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// If it's not focusable but has a control role, then it's interesting.
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if (this.isControl())
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return true;
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// A non focusable child of a control is not interesting
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if (insideControl)
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return false;
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return this.isLeafNode() && !!this._name;
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}
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/**
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* @return {!SerializedAXNode}
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*/
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serialize() {
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/** @type {!Map<string, number|string|boolean>} */
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const properties = new Map();
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for (const property of this._payload.properties || [])
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properties.set(property.name.toLowerCase(), property.value.value);
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if (this._payload.name)
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properties.set('name', this._payload.name.value);
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if (this._payload.value)
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properties.set('value', this._payload.value.value);
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if (this._payload.description)
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properties.set('description', this._payload.description.value);
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/** @type {SerializedAXNode} */
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const node = {
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role: this._role
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};
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/** @type {!Array<keyof SerializedAXNode>} */
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const userStringProperties = [
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'name',
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'value',
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'description',
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'keyshortcuts',
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'roledescription',
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'valuetext',
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];
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for (const userStringProperty of userStringProperties) {
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if (!properties.has(userStringProperty))
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continue;
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node[userStringProperty] = properties.get(userStringProperty);
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}
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/** @type {!Array<keyof SerializedAXNode>} */
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const booleanProperties = [
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'disabled',
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'expanded',
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'focused',
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'modal',
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'multiline',
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'multiselectable',
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'readonly',
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'required',
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'selected',
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];
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for (const booleanProperty of booleanProperties) {
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// WebArea's treat focus differently than other nodes. They report whether their frame has focus,
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// not whether focus is specifically on the root node.
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if (booleanProperty === 'focused' && this._role === 'WebArea')
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continue;
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const value = properties.get(booleanProperty);
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if (!value)
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continue;
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node[booleanProperty] = value;
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}
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/** @type {!Array<keyof SerializedAXNode>} */
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const tristateProperties = [
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'checked',
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'pressed',
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];
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for (const tristateProperty of tristateProperties) {
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if (!properties.has(tristateProperty))
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continue;
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const value = properties.get(tristateProperty);
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node[tristateProperty] = value === 'mixed' ? 'mixed' : value === 'true' ? true : false;
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}
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/** @type {!Array<keyof SerializedAXNode>} */
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const numericalProperties = [
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'level',
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'valuemax',
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'valuemin',
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];
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for (const numericalProperty of numericalProperties) {
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if (!properties.has(numericalProperty))
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continue;
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node[numericalProperty] = properties.get(numericalProperty);
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}
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/** @type {!Array<keyof SerializedAXNode>} */
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const tokenProperties = [
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'autocomplete',
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'haspopup',
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'invalid',
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'orientation',
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];
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for (const tokenProperty of tokenProperties) {
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const value = properties.get(tokenProperty);
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if (!value || value === 'false')
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continue;
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node[tokenProperty] = value;
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}
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return node;
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}
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/**
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* @param {!Array<!Protocol.Accessibility.AXNode>} payloads
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* @return {!AXNode}
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*/
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static createTree(payloads) {
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/** @type {!Map<string, !AXNode>} */
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const nodeById = new Map();
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for (const payload of payloads)
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nodeById.set(payload.nodeId, new AXNode(payload));
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for (const node of nodeById.values()) {
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for (const childId of node._payload.childIds || [])
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node._children.push(nodeById.get(childId));
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}
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return nodeById.values().next().value;
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}
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}
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module.exports = {Accessibility};
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helper.tracePublicAPI(Accessibility);
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