// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
/**
* @fileoverview If the braille captions feature is enabled, sends
* braille content to the Panel on Chrome OS, or a content script on
* other platforms.
*/
import {LocalStorage} from '/common/local_storage.js';
import {TestImportManager} from '/common/testing/test_import_manager.js';
import {BrailleDisplayState} from '../../common/braille/braille_key_types.js';
import {NavBraille} from '../../common/braille/nav_braille.js';
import {Msgs} from '../../common/msgs.js';
import {PanelCommand, PanelCommandType} from '../../common/panel_command.js';
import {SettingsManager} from '../../common/settings_manager.js';
import {QueueMode} from '../../common/tts_types.js';
import {ChromeVox} from '../chromevox.js';
import {ChromeVoxPrefs} from '../prefs.js';
interface Offsets {
brailleOffset: number;
textOffset: number;
}
type TextToDisplay = [text: string, braille: string];
/**
* Interface that allows clients to listen for changes to the braille captions.
*/
export interface BrailleCaptionsListener {
/** Called when the braille captions state changes. */
onBrailleCaptionsStateChanged(): void;
}
export class BrailleCaptionsBackground {
static instance: BrailleCaptionsBackground;
private listener_: BrailleCaptionsListener;
constructor(listener: BrailleCaptionsListener) {
this.listener_ = listener;
}
/** Called once to initialize the class. */
static init(listener: BrailleCaptionsListener): void {
BrailleCaptionsBackground.instance =
new BrailleCaptionsBackground(listener);
}
/** Returns whether the braille captions feature is enabled. */
static isEnabled(): boolean {
return Boolean(LocalStorage.get(PREF_KEY));
}
/**
* @param text Text of the shown braille.
* @param cells Braille cells shown on the display.
* @param brailleToText Map of Braille letters to the first
* index of corresponding text letter.
* @param offsetsForSlices
* Offsets to use for calculating indices. The element is the braille
* offset, the second is the text offset.
* @param rows Number of rows to display.
* @param columns Number of columns to display.
*/
static setContent(
text: string, cells: ArrayBuffer, brailleToText: number[],
offsetsForSlices: Offsets, rows: number, columns: number): void {
// Convert the cells to Unicode braille pattern characters.
const byteBuf = new Uint8Array(cells);
let brailleChars = '';
for (const byteVal of byteBuf) {
brailleChars +=
String.fromCharCode(BRAILLE_UNICODE_BLOCK_START | byteVal);
}
const groups = BrailleCaptionsBackground.groupBrailleAndText(
brailleChars, text, brailleToText, offsetsForSlices);
const data = {groups, rows, cols: columns};
(new PanelCommand(PanelCommandType.UPDATE_BRAILLE, data)).send();
}
/**
* @param cells Braille cells shown on the display.
* @param rows Number of rows to display.
* @param columns Number of columns to display.
*/
static setImageContent(
cells: ArrayBuffer, rows: number, columns: number): void {
// Convert the cells to Unicode braille pattern characters.
const byteBuf = new Uint8Array(cells);
let brailleChars = '';
for (const byteVal of byteBuf) {
brailleChars +=
String.fromCharCode(BRAILLE_UNICODE_BLOCK_START | byteVal);
}
const groups = [['Image', brailleChars]];
const data = {groups, rows, cols: columns};
(new PanelCommand(PanelCommandType.UPDATE_BRAILLE, data)).send();
}
/**
* @param brailleChars Braille characters shown on the display.
* @param text Text of the shown braille.
* @param brailleToText Map of Braille cells to the first index of
* corresponding text letter.
* @param offsets Offsets to use for calculating indices. The element is the
* braille offset, the second is the text offset.
* @return The groups of braille and texts to be displayed.
*/
static groupBrailleAndText(
brailleChars: string, text: string, brailleToText: number[],
offsets: Offsets): TextToDisplay[] {
let brailleBuf = '';
const groups: TextToDisplay[] = [];
let textIndex = 0;
const brailleOffset = offsets.brailleOffset;
const textOffset = offsets.textOffset;
const calculateTextIndex = (index: number): number =>
brailleToText[index + brailleOffset] - textOffset;
for (let i = 0; i < brailleChars.length; ++i) {
const textSliceIndex = calculateTextIndex(i);
if (i !== 0 && textSliceIndex !== textIndex) {
groups.push(
[text.substr(textIndex, textSliceIndex - textIndex), brailleBuf]);
brailleBuf = '';
textIndex = textSliceIndex;
}
brailleBuf += brailleChars.charAt(i);
}
// Puts the rest of the text into the last group.
if (brailleBuf.length > 0 && text.charAt(textIndex) !== ' ') {
groups.push([text.substr(textIndex), brailleBuf]);
}
return groups;
}
/**
* Sets whether the overlay should be active.
* @param newValue The new value of the active flag.
*/
static setActive(newValue: boolean): void {
const oldValue = BrailleCaptionsBackground.isEnabled();
// TODO(b/314203187): Not null asserted, check that this is correct.
ChromeVoxPrefs.instance!.setPref(PREF_KEY, newValue);
if (oldValue !== newValue) {
BrailleCaptionsBackground.instance.listener_
.onBrailleCaptionsStateChanged();
const msg = newValue ? Msgs.getMsg('braille_captions_enabled') :
Msgs.getMsg('braille_captions_disabled');
ChromeVox.tts.speak(msg, QueueMode.QUEUE);
ChromeVox.braille.write(NavBraille.fromText(msg));
}
}
/**
* Asynchronously returns a display state representing the state of the
* captions feature. This is used when no actual hardware display is
* connected.
*/
static getVirtualDisplayState(): BrailleDisplayState {
if (BrailleCaptionsBackground.isEnabled()) {
const rows = SettingsManager.getNumber('virtualBrailleRows');
const columns = SettingsManager.getNumber('virtualBrailleColumns');
// TODO(accessibility) make `cellSize` customizable.
return {
available: true,
textRowCount: rows,
textColumnCount: columns,
cellSize: 8,
};
} else {
return {
available: false,
textRowCount: 0,
textColumnCount: 0,
cellSize: 0,
};
}
}
}
// Local to module.
/** Key set in local storage when this feature is enabled. */
const PREF_KEY = 'brailleCaptions';
/**
* Unicode block of braille pattern characters. A braille pattern is formed
* from this value with the low order 8 bits set to the bits representing
* the dots as per the ISO 11548-1 standard.
*/
const BRAILLE_UNICODE_BLOCK_START = 0x2800;
TestImportManager.exportForTesting(BrailleCaptionsBackground);
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