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/* 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/. */
"use strict";
var EXPORTED_SYMBOLS = [
"AnimationFramePromise",
"Deferred",
"EventPromise",
"executeSoon",
"PollPromise",
];
const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
const { XPCOMUtils } = ChromeUtils.import(
);
const lazy = {};
XPCOMUtils.defineLazyModuleGetters(lazy, {
});
const { TYPE_ONE_SHOT, TYPE_REPEATING_SLACK } = Ci.nsITimer;
XPCOMUtils.defineLazyGetter(lazy, "logger", () =>
lazy.Log.get(lazy.Log.TYPES.REMOTE_AGENT)
);
/**
* Throttle until the `window` has performed an animation frame.
*
* @param {ChromeWindow} win
* Window to request the animation frame from.
*
* @return {Promise}
*/
function AnimationFramePromise(win) {
const animationFramePromise = new Promise(resolve => {
win.requestAnimationFrame(resolve);
});
// Abort if the underlying window gets closed
const windowClosedPromise = new PollPromise(resolve => {
if (win.closed) {
resolve();
}
});
return Promise.race([animationFramePromise, windowClosedPromise]);
}
/**
* Create a helper object to defer a promise.
*
* @returns {Object}
* An object that returns the following properties:
* - fulfilled Flag that indicates that the promise got resolved
* - pending Flag that indicates a not yet fulfilled/rejected promise
* - promise The actual promise
* - reject Callback to reject the promise
* - rejected Flag that indicates that the promise got rejected
* - resolve Callback to resolve the promise
*/
function Deferred() {
const deferred = {};
deferred.promise = new Promise((resolve, reject) => {
deferred.fulfilled = false;
deferred.pending = true;
deferred.rejected = false;
deferred.resolve = (...args) => {
deferred.fulfilled = true;
deferred.pending = false;
resolve(...args);
};
deferred.reject = (...args) => {
deferred.pending = false;
deferred.rejected = true;
reject(...args);
};
});
return deferred;
}
/**
* Wait for an event to be fired on a specified element.
*
* The returned promise is guaranteed to not resolve before the
* next event tick after the event listener is called, so that all
* other event listeners for the element are executed before the
* handler is executed. For example:
*
* const promise = new EventPromise(element, "myEvent");
* // same event tick here
* await promise;
* // next event tick here
*
* @param {Element} subject
* The element that should receive the event.
* @param {string} eventName
* Case-sensitive string representing the event name to listen for.
* @param {Object=} options
* @param {boolean=} [false] options.capture
* Indicates the event will be despatched to this subject,
* before it bubbles down to any EventTarget beneath it in the
* DOM tree.
* @param {function=} [null] options.checkFn
* Called with the Event object as argument, should return true if the
* event is the expected one, or false if it should be ignored and
* listening should continue. If not specified, the first event with
* the specified name resolves the returned promise.
* @param {number=} [null] options.timeout
* Timeout duration in milliseconds, if provided.
* If specified, then the returned promise will be rejected with
* TimeoutError, if not already resolved, after this duration has elapsed.
* If not specified, then no timeout is used.
* @param {boolean=} [false] options.mozSystemGroup
* Determines whether to add listener to the system group.
* @param {boolean=} [false] options.wantUntrusted
* Receive synthetic events despatched by web content.
*
* @return {Promise<Event>}
* Either fulfilled with the first described event, satisfying
* options.checkFn if specified, or rejected with TimeoutError after
* options.timeout milliseconds if specified.
*
* @throws {TypeError}
* @throws {RangeError}
*/
function EventPromise(subject, eventName, options = {}) {
const {
capture = false,
checkFn = null,
timeout = null,
mozSystemGroup = false,
wantUntrusted = false,
} = options;
if (
!subject ||
!("addEventListener" in subject) ||
typeof eventName != "string" ||
typeof capture != "boolean" ||
(checkFn && typeof checkFn != "function") ||
(timeout !== null && typeof timeout != "number") ||
typeof mozSystemGroup != "boolean" ||
typeof wantUntrusted != "boolean"
) {
throw new TypeError();
}
if (timeout < 0) {
throw new RangeError();
}
return new Promise((resolve, reject) => {
let timer;
function cleanUp() {
subject.removeEventListener(eventName, listener, capture);
timer?.cancel();
}
function listener(event) {
lazy.logger.trace(`Received DOM event ${event.type} for ${event.target}`);
try {
if (checkFn && !checkFn(event)) {
return;
}
} catch (e) {
// Treat an exception in the callback as a falsy value
lazy.logger.warn(`Event check failed: ${e.message}`);
}
cleanUp();
executeSoon(() => resolve(event));
}
subject.addEventListener(eventName, listener, {
capture,
mozSystemGroup,
wantUntrusted,
});
if (timeout !== null) {
timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
timer.init(
() => {
cleanUp();
reject(
new lazy.error.TimeoutError(
`EventPromise timed out after ${timeout} ms`
)
);
},
timeout,
TYPE_ONE_SHOT
);
}
});
}
/**
* Wait for the next tick in the event loop to execute a callback.
*
* @param {function} fn
* Function to be executed.
*/
function executeSoon(fn) {
if (typeof fn != "function") {
throw new TypeError();
}
Services.tm.dispatchToMainThread(fn);
}
/**
* Runs a Promise-like function off the main thread until it is resolved
* through ``resolve`` or ``rejected`` callbacks. The function is
* guaranteed to be run at least once, irregardless of the timeout.
*
* The ``func`` is evaluated every ``interval`` for as long as its
* runtime duration does not exceed ``interval``. Evaluations occur
* sequentially, meaning that evaluations of ``func`` are queued if
* the runtime evaluation duration of ``func`` is greater than ``interval``.
*
* ``func`` is given two arguments, ``resolve`` and ``reject``,
* of which one must be called for the evaluation to complete.
* Calling ``resolve`` with an argument indicates that the expected
* wait condition was met and will return the passed value to the
* caller. Conversely, calling ``reject`` will evaluate ``func``
* again until the ``timeout`` duration has elapsed or ``func`` throws.
* The passed value to ``reject`` will also be returned to the caller
* once the wait has expired.
*
* Usage::
*
* let els = new PollPromise((resolve, reject) => {
* let res = document.querySelectorAll("p");
* if (res.length > 0) {
* resolve(Array.from(res));
* } else {
* reject([]);
* }
* }, {timeout: 1000});
*
* @param {Condition} func
* Function to run off the main thread.
* @param {number=} [timeout] timeout
* Desired timeout if wanted. If 0 or less than the runtime evaluation
* time of ``func``, ``func`` is guaranteed to run at least once.
* Defaults to using no timeout.
* @param {number=} [interval=10] interval
* Duration between each poll of ``func`` in milliseconds.
* Defaults to 10 milliseconds.
*
* @return {Promise.<*>}
* Yields the value passed to ``func``'s
* ``resolve`` or ``reject`` callbacks.
*
* @throws {*}
* If ``func`` throws, its error is propagated.
* @throws {TypeError}
* If `timeout` or `interval`` are not numbers.
* @throws {RangeError}
* If `timeout` or `interval` are not unsigned integers.
*/
function PollPromise(func, { timeout = null, interval = 10 } = {}) {
const timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
if (typeof func != "function") {
throw new TypeError();
}
if (timeout != null && typeof timeout != "number") {
throw new TypeError();
}
if (typeof interval != "number") {
throw new TypeError();
}
if (
(timeout && (!Number.isInteger(timeout) || timeout < 0)) ||
!Number.isInteger(interval) ||
interval < 0
) {
throw new RangeError();
}
return new Promise((resolve, reject) => {
let start, end;
if (Number.isInteger(timeout)) {
start = new Date().getTime();
end = start + timeout;
}
let evalFn = () => {
new Promise(func)
.then(resolve, rejected => {
if (typeof rejected != "undefined") {
throw rejected;
}
// return if there is a timeout and set to 0,
// allowing |func| to be evaluated at least once
if (
typeof end != "undefined" &&
(start == end || new Date().getTime() >= end)
) {
resolve(rejected);
}
})
.catch(reject);
};
// the repeating slack timer waits |interval|
// before invoking |evalFn|
evalFn();
timer.init(evalFn, interval, TYPE_REPEATING_SLACK);
}).then(
res => {
timer.cancel();
return res;
},
err => {
timer.cancel();
throw err;
}
);
}