playwright/src/firefox/ffAccessibility.ts

/**
 * Copyright 2018 Google Inc. All rights reserved.
 * Modifications copyright (c) Microsoft Corporation.
 *
 * Licensed under the Apache License, Version 2.0 (the 'License');
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an 'AS IS' BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import * as accessibility from '../accessibility';
import { FFSession } from './ffConnection';
import { Protocol } from './protocol';

export async function getAccessibilityTree(session: FFSession) : Promise<accessibility.AXNode> {
  const { tree } = await session.send('Accessibility.getFullAXTree');
  return new FFAXNode(tree);
}

class FFAXNode implements accessibility.AXNode {
  _children: FFAXNode[];
  private _payload: any;
  private _editable: boolean;
  private _richlyEditable: boolean;
  private _focusable: boolean;
  private _expanded: boolean;
  private _name: string;
  private _role: string;
  private _cachedHasFocusableChild: boolean|undefined;

  constructor(payload: Protocol.AXTree) {
    this._payload = payload;
    this._children = (payload.children || []).map(x => new FFAXNode(x));
    this._editable = !!payload.editable;
    this._richlyEditable = this._editable && (payload.tag !== 'textarea' && payload.tag !== 'input');
    this._focusable = !!payload.focusable;
    this._expanded = !!payload.expanded;
    this._name = this._payload.name;
    this._role = this._payload.role;
    this._cachedHasFocusableChild;
  }

  _isPlainTextField(): boolean {
    if (this._richlyEditable)
      return false;
    if (this._editable)
      return true;
    return this._role === 'entry';
  }

  _isTextOnlyObject(): boolean {
    const role = this._role;
    return (role === 'text leaf' || role === 'text' || role === 'statictext');
  }

  _hasFocusableChild(): boolean {
    if (this._cachedHasFocusableChild === undefined) {
      this._cachedHasFocusableChild = false;
      for (const child of this._children) {
        if (child._focusable || child._hasFocusableChild()) {
          this._cachedHasFocusableChild = true;
          break;
        }
      }
    }
    return this._cachedHasFocusableChild;
  }

  children() {
    return this._children;
  }

  async findElement(): Promise<FFAXNode | null> {
    throw new Error('Not implimented');
  }

  isLeafNode(): boolean {
    if (!this._children.length)
      return true;
      // These types of objects may have children that we use as internal
      // implementation details, but we want to expose them as leaves to platform
      // accessibility APIs because screen readers might be confused if they find
      // any children.
    if (this._isPlainTextField() || this._isTextOnlyObject())
      return true;
      // Roles whose children are only presentational according to the ARIA and
      // HTML5 Specs should be hidden from screen readers.
      // (Note that whilst ARIA buttons can have only presentational children, HTML5
      // buttons are allowed to have content.)
    switch (this._role) {
      case 'graphic':
      case 'scrollbar':
      case 'slider':
      case 'separator':
      case 'progressbar':
        return true;
      default:
        break;
    }
    // Here and below: Android heuristics
    if (this._hasFocusableChild())
      return false;
    if (this._focusable && this._name)
      return true;
    if (this._role === 'heading' && this._name)
      return true;
    return false;
  }

  isControl(): boolean {
    switch (this._role) {
      case 'checkbutton':
      case 'check menu item':
      case 'check rich option':
      case 'combobox':
      case 'combobox option':
      case 'color chooser':
      case 'listbox':
      case 'listbox option':
      case 'listbox rich option':
      case 'popup menu':
      case 'menupopup':
      case 'menuitem':
      case 'menubar':
      case 'button':
      case 'pushbutton':
      case 'radiobutton':
      case 'radio menuitem':
      case 'scrollbar':
      case 'slider':
      case 'spinbutton':
      case 'switch':
      case 'pagetab':
      case 'entry':
      case 'tree table':
        return true;
      default:
        return false;
    }
  }

  isInteresting(insideControl: boolean): boolean {
    if (this._focusable || this._richlyEditable)
      return true;
      // If it's not focusable but has a control role, then it's interesting.
    if (this.isControl())
      return true;
      // A non focusable child of a control is not interesting
    if (insideControl)
      return false;
    return this.isLeafNode() && !!this._name.trim();
  }

  serialize(): accessibility.SerializedAXNode {
    const node: {[x in keyof accessibility.SerializedAXNode]: any} = {
      role: this._role,
      name: this._name || ''
    };
    const userStringProperties: Array<keyof accessibility.SerializedAXNode> = [
      'name',
      'value',
      'description',
      'roledescription',
      'valuetext',
      'keyshortcuts',
    ];
    for (const userStringProperty of userStringProperties) {
      if (!(userStringProperty in this._payload))
        continue;
      node[userStringProperty] = this._payload[userStringProperty];
    }
    const booleanProperties: Array<keyof accessibility.SerializedAXNode> = [
      'disabled',
      'expanded',
      'focused',
      'modal',
      'multiline',
      'multiselectable',
      'readonly',
      'required',
      'selected',
    ];
    for (const booleanProperty of booleanProperties) {
      if (this._role === 'document' && booleanProperty === 'focused')
        continue; // document focusing is strange
      const value = this._payload[booleanProperty];
      if (!value)
        continue;
      node[booleanProperty] = value;
    }
    const tristateProperties: Array<keyof accessibility.SerializedAXNode> = [
      'checked',
      'pressed',
    ];
    for (const tristateProperty of tristateProperties) {
      if (!(tristateProperty in this._payload))
        continue;
      const value = this._payload[tristateProperty];
      node[tristateProperty] = value;
    }
    const numericalProperties: Array<keyof accessibility.SerializedAXNode> = [
      'level'
    ];
    for (const numericalProperty of numericalProperties) {
      if (!(numericalProperty in this._payload))
        continue;
      node[numericalProperty] = this._payload[numericalProperty];
    }
    const tokenProperties: Array<keyof accessibility.SerializedAXNode> = [
      'autocomplete',
      'haspopup',
      'invalid',
      'orientation',
    ];
    for (const tokenProperty of tokenProperties) {
      const value = this._payload[tokenProperty];
      if (!value || value === 'false')
        continue;
      node[tokenProperty] = value;
    }
    return node;
  }
}