зеркало из https://github.com/mozilla/gecko-dev.git
103 строки
3.0 KiB
JavaScript
103 строки
3.0 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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"use strict";
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var EXPORTED_SYMBOLS = [
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"DOMContentLoadedPromise",
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"EventPromise",
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"MessagePromise",
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];
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const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");
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/**
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* Wait for a single event to be fired on a specific EventListener.
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*
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* The returned promise is guaranteed to not be called before the
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* next event tick after the event listener is called, so that all
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* other event listeners for the element are executed before the
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* handler is executed. For example:
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*
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* const promise = new EventPromise(element, "myEvent");
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* // same event tick here
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* await promise;
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* // next event tick here
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*
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* @param {EventListener} listener
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* Object which receives a notification (an object that implements
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* the Event interface) when an event of the specificed type occurs.
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* @param {string} type
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* Case-sensitive string representing the event type to listen for.
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* @param {boolean?} [false] options.capture
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* Indicates the event will be despatched to this subject,
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* before it bubbles down to any EventTarget beneath it in the
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* DOM tree.
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* @param {boolean?} [false] options.wantsUntrusted
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* Receive synthetic events despatched by web content.
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* @param {boolean?} [false] options.mozSystemGroup
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* Determines whether to add listener to the system group.
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*
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* @return {Promise.<Event>}
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*
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* @throws {TypeError}
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*/
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function EventPromise(listener, type, options = {
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capture: false,
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wantsUntrusted: false,
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mozSystemGroup: false,
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}) {
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if (!listener || !("addEventListener" in listener)) {
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throw new TypeError();
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}
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if (typeof type != "string") {
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throw new TypeError();
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}
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if (("capture" in options && typeof options.capture != "boolean") ||
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("wantsUntrusted" in options && typeof options.wantsUntrusted != "boolean") ||
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("mozSystemGroup" in options && typeof options.mozSystemGroup != "boolean")) {
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throw new TypeError();
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}
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options.once = true;
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return new Promise(resolve => {
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listener.addEventListener(type, event => {
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Services.tm.dispatchToMainThread(() => resolve(event));
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}, options);
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});
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}
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function DOMContentLoadedPromise(window, options = {mozSystemGroup: true}) {
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if (window.document.readyState == "complete") {
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return Promise.resolve();
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}
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return new EventPromise(window, "DOMContentLoaded", options);
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}
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/**
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* Awaits a single IPC message.
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*
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* @param {nsIMessageSender} target
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* @param {string} name
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*
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* @return {Promise}
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*
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* @throws {TypeError}
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* If target is not an nsIMessageSender.
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*/
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function MessagePromise(target, name) {
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if (!(target instanceof Ci.nsIMessageSender)) {
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throw new TypeError();
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}
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return new Promise(resolve => {
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const onMessage = (...args) => {
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target.removeMessageListener(name, onMessage);
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resolve(...args);
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};
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target.addMessageListener(name, onMessage);
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});
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}
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