/* 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/. */
// Maximum time into paragraph when pressing "skip previous" will go
// to previous paragraph and not the start of current one.
const PREV_THRESHOLD = 2000;
// All text-related style rules that we should copy over to the highlight node.
const kTextStylesRules = [
"font-family",
"font-kerning",
"font-size",
"font-size-adjust",
"font-stretch",
"font-variant",
"font-weight",
"line-height",
"letter-spacing",
"text-orientation",
"text-transform",
"word-spacing",
];
export function Narrator(win, languagePromise) {
this._winRef = Cu.getWeakReference(win);
this._languagePromise = languagePromise;
this._inTest = Services.prefs.getBoolPref("narrate.test");
this._speechOptions = {};
this._startTime = 0;
this._stopped = false;
}
Narrator.prototype = {
get _doc() {
return this._winRef.get().document;
},
get _win() {
return this._winRef.get();
},
get _treeWalker() {
if (!this._treeWalkerRef) {
let wu = this._win.windowUtils;
let nf = this._win.NodeFilter;
let filter = {
_matches: new Set(),
// We want high-level elements that have non-empty text nodes.
// For example, paragraphs. But nested anchors and other elements
// are not interesting since their text already appears in their
// parent's textContent.
acceptNode(node) {
if (this._matches.has(node.parentNode)) {
// Reject sub-trees of accepted nodes.
return nf.FILTER_REJECT;
}
if (!/\S/.test(node.textContent)) {
// Reject nodes with no text.
return nf.FILTER_REJECT;
}
let bb = wu.getBoundsWithoutFlushing(node);
if (!bb.width || !bb.height) {
// Skip non-rendered nodes. We don't reject because a zero-sized
// container can still have visible, "overflowed", content.
return nf.FILTER_SKIP;
}
for (let c = node.firstChild; c; c = c.nextSibling) {
if (c.nodeType == c.TEXT_NODE && /\S/.test(c.textContent)) {
// If node has a non-empty text child accept it.
this._matches.add(node);
return nf.FILTER_ACCEPT;
}
}
return nf.FILTER_SKIP;
},
};
this._treeWalkerRef = new WeakMap();
// We can't hold a weak reference on the treewalker, because there
// are no other strong references, and it will be GC'ed. Instead,
// we rely on the window's lifetime and use it as a weak reference.
this._treeWalkerRef.set(
this._win,
this._doc.createTreeWalker(
this._doc.querySelector(".container"),
nf.SHOW_ELEMENT,
filter,
false
)
);
}
return this._treeWalkerRef.get(this._win);
},
get _timeIntoParagraph() {
let rv = Date.now() - this._startTime;
return rv;
},
get speaking() {
return (
this._win.speechSynthesis.speaking || this._win.speechSynthesis.pending
);
},
_getVoice(voiceURI) {
if (!this._voiceMap || !this._voiceMap.has(voiceURI)) {
this._voiceMap = new Map(
this._win.speechSynthesis.getVoices().map(v => [v.voiceURI, v])
);
}
return this._voiceMap.get(voiceURI);
},
_isParagraphInView(paragraph) {
if (!paragraph) {
return false;
}
let bb = paragraph.getBoundingClientRect();
return bb.top >= 0 && bb.top < this._win.innerHeight;
},
_sendTestEvent(eventType, detail) {
let win = this._win;
win.dispatchEvent(
new win.CustomEvent(eventType, {
detail: Cu.cloneInto(detail, win.document),
})
);
},
_speakInner() {
this._win.speechSynthesis.cancel();
let tw = this._treeWalker;
let paragraph = tw.currentNode;
if (paragraph == tw.root) {
this._sendTestEvent("paragraphsdone", {});
return Promise.resolve();
}
let utterance = new this._win.SpeechSynthesisUtterance(
paragraph.textContent.replace(/\r?\n/g, " ")
);
utterance.rate = this._speechOptions.rate;
if (this._speechOptions.voice) {
utterance.voice = this._speechOptions.voice;
} else {
utterance.lang = this._speechOptions.lang;
}
this._startTime = Date.now();
let highlighter = new Highlighter(paragraph);
if (this._inTest) {
let onTestSynthEvent = e => {
if (e.detail.type == "boundary") {
let args = Object.assign({ utterance }, e.detail.args);
let evt = new this._win.SpeechSynthesisEvent(e.detail.type, args);
utterance.dispatchEvent(evt);
}
};
let removeListeners = () => {
this._win.removeEventListener("testsynthevent", onTestSynthEvent);
};
this._win.addEventListener("testsynthevent", onTestSynthEvent);
utterance.addEventListener("end", removeListeners);
utterance.addEventListener("error", removeListeners);
}
return new Promise((resolve, reject) => {
utterance.addEventListener("start", () => {
paragraph.classList.add("narrating");
let bb = paragraph.getBoundingClientRect();
if (bb.top < 0 || bb.bottom > this._win.innerHeight) {
paragraph.scrollIntoView({ behavior: "smooth", block: "start" });
}
if (this._inTest) {
this._sendTestEvent("paragraphstart", {
voice: utterance.chosenVoiceURI,
rate: utterance.rate,
paragraph: paragraph.textContent,
tag: paragraph.localName,
});
}
});
utterance.addEventListener("end", () => {
if (!this._win) {
// page got unloaded, don't do anything.
return;
}
highlighter.remove();
paragraph.classList.remove("narrating");
this._startTime = 0;
if (this._inTest) {
this._sendTestEvent("paragraphend", {});
}
if (this._stopped) {
// User pressed stopped.
resolve();
} else {
tw.currentNode = tw.nextNode() || tw.root;
this._speakInner().then(resolve, reject);
}
});
utterance.addEventListener("error", () => {
reject("speech synthesis failed");
});
utterance.addEventListener("boundary", e => {
if (e.name != "word") {
// We are only interested in word boundaries for now.
return;
}
if (e.charLength) {
highlighter.highlight(e.charIndex, e.charLength);
if (this._inTest) {
this._sendTestEvent("wordhighlight", {
start: e.charIndex,
end: e.charIndex + e.charLength,
});
}
}
});
this._win.speechSynthesis.speak(utterance);
});
},
start(speechOptions) {
this._speechOptions = {
rate: speechOptions.rate,
voice: this._getVoice(speechOptions.voice),
};
this._stopped = false;
return this._languagePromise.then(language => {
if (!this._speechOptions.voice) {
this._speechOptions.lang = language;
}
let tw = this._treeWalker;
if (!this._isParagraphInView(tw.currentNode)) {
tw.currentNode = tw.root;
while (tw.nextNode()) {
if (this._isParagraphInView(tw.currentNode)) {
break;
}
}
}
if (tw.currentNode == tw.root) {
tw.nextNode();
}
return this._speakInner();
});
},
stop() {
this._stopped = true;
this._win.speechSynthesis.cancel();
},
skipNext() {
this._win.speechSynthesis.cancel();
},
skipPrevious() {
this._goBackParagraphs(this._timeIntoParagraph < PREV_THRESHOLD ? 2 : 1);
},
setRate(rate) {
this._speechOptions.rate = rate;
/* repeat current paragraph */
this._goBackParagraphs(1);
},
setVoice(voice) {
this._speechOptions.voice = this._getVoice(voice);
/* repeat current paragraph */
this._goBackParagraphs(1);
},
_goBackParagraphs(count) {
let tw = this._treeWalker;
for (let i = 0; i < count; i++) {
if (!tw.previousNode()) {
tw.currentNode = tw.root;
}
}
this._win.speechSynthesis.cancel();
},
};
/**
* The Highlighter class is used to highlight a range of text in a container.
*
* @param {Element} container a text container
*/
function Highlighter(container) {
this.container = container;
}
Highlighter.prototype = {
/**
* Highlight the range within offsets relative to the container.
*
* @param {number} startOffset the start offset
* @param {number} length the length in characters of the range
*/
highlight(startOffset, length) {
let containerRect = this.container.getBoundingClientRect();
let range = this._getRange(startOffset, startOffset + length);
let rangeRects = range.getClientRects();
let win = this.container.ownerGlobal;
let computedStyle = win.getComputedStyle(range.endContainer.parentNode);
let nodes = this._getFreshHighlightNodes(rangeRects.length);
let textStyle = {};
for (let textStyleRule of kTextStylesRules) {
textStyle[textStyleRule] = computedStyle[textStyleRule];
}
for (let i = 0; i < rangeRects.length; i++) {
let r = rangeRects[i];
let node = nodes[i];
let style = Object.assign(
{
top: `${r.top - containerRect.top + r.height / 2}px`,
left: `${r.left - containerRect.left + r.width / 2}px`,
width: `${r.width}px`,
height: `${r.height}px`,
},
textStyle
);
// Enables us to vary the CSS transition on a line change.
node.classList.toggle("newline", style.top != node.dataset.top);
node.dataset.top = style.top;
// Enables CSS animations.
node.classList.remove("animate");
win.requestAnimationFrame(() => {
node.classList.add("animate");
});
// Enables alternative word display with a CSS pseudo-element.
node.dataset.word = range.toString();
// Apply style
node.style = Object.entries(style)
.map(s => `${s[0]}: ${s[1]};`)
.join(" ");
}
},
/**
* Releases reference to container and removes all highlight nodes.
*/
remove() {
for (let node of this._nodes) {
node.remove();
}
this.container = null;
},
/**
* Returns specified amount of highlight nodes. Creates new ones if necessary
* and purges any additional nodes that are not needed.
*
* @param {number} count number of nodes needed
*/
_getFreshHighlightNodes(count) {
let doc = this.container.ownerDocument;
let nodes = Array.from(this._nodes);
// Remove nodes we don't need anymore (nodes.length - count > 0).
for (let toRemove = 0; toRemove < nodes.length - count; toRemove++) {
nodes.shift().remove();
}
// Add additional nodes if we need them (count - nodes.length > 0).
for (let toAdd = 0; toAdd < count - nodes.length; toAdd++) {
let node = doc.createElement("div");
node.className = "narrate-word-highlight";
this.container.appendChild(node);
nodes.push(node);
}
return nodes;
},
/**
* Create and return a range object with the start and end offsets relative
* to the container node.
*
* @param {number} startOffset the start offset
* @param {number} endOffset the end offset
*/
_getRange(startOffset, endOffset) {
let doc = this.container.ownerDocument;
let i = 0;
let treeWalker = doc.createTreeWalker(
this.container,
doc.defaultView.NodeFilter.SHOW_TEXT
);
let node = treeWalker.nextNode();
function _findNodeAndOffset(offset) {
do {
let length = node.data.length;
if (offset >= i && offset <= i + length) {
return [node, offset - i];
}
i += length;
} while ((node = treeWalker.nextNode()));
// Offset is out of bounds, return last offset of last node.
node = treeWalker.lastChild();
return [node, node.data.length];
}
let range = doc.createRange();
range.setStart(..._findNodeAndOffset(startOffset));
range.setEnd(..._findNodeAndOffset(endOffset));
return range;
},
/*
* Get all existing highlight nodes for container.
*/
get _nodes() {
return this.container.querySelectorAll(".narrate-word-highlight");
},
};
