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Support the once option, when registering EventBus listeners

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This follows the same principle as the `once` option that exists in the native `addEventListener` method, and will thus automatically remove an `EventBus` listener when it's invoked; see https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener#Parameters

Finally, this patch also tweaks some the existing `EventBus`-code to use modern features such as optional chaining and logical assignment operators.
This commit is contained in:
Jonas Jenwald 2020-12-29 16:36:58 +01:00
parent 3e34281e3b
commit 739d7c6d77
4 changed files with 60 additions and 26 deletions
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38
web/ui_utils.js
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@ -804,24 +804,32 @@ class EventBus {
this._listeners = Object.create(null);
if (typeof PDFJSDev === "undefined" || PDFJSDev.test("MOZCENTRAL")) {
this._isInAutomation = (options && options.isInAutomation) === true;
this._isInAutomation = options?.isInAutomation === true;
}
}
/**
* @param {string} eventName
* @param {function} listener
* @param {Object} [options]
*/
on(eventName, listener) {
this._on(eventName, listener, { external: true });
on(eventName, listener, options = null) {
this._on(eventName, listener, {
external: true,
once: options?.once,
});
}
/**
* @param {string} eventName
* @param {function} listener
* @param {Object} [options]
*/
off(eventName, listener) {
this._off(eventName, listener, { external: true });
off(eventName, listener, options = null) {
this._off(eventName, listener, {
external: true,
once: options?.once,
});
}
dispatch(eventName) {
@ -841,12 +849,12 @@ class EventBus {
let externalListeners;
// Making copy of the listeners array in case if it will be modified
// during dispatch.
eventListeners.slice(0).forEach(function ({ listener, external }) {
eventListeners.slice(0).forEach(({ listener, external, once }) => {
if (once) {
this._off(eventName, listener);
}
if (external) {
if (!externalListeners) {
externalListeners = [];
}
externalListeners.push(listener);
(externalListeners ||= []).push(listener);
return;
}
listener.apply(null, args);
@ -854,7 +862,7 @@ class EventBus {
// Dispatch any "external" listeners *after* the internal ones, to give the
// viewer components time to handle events and update their state first.
if (externalListeners) {
externalListeners.forEach(function (listener) {
externalListeners.forEach(listener => {
listener.apply(null, args);
});
externalListeners = null;
@ -871,13 +879,11 @@ class EventBus {
* @ignore
*/
_on(eventName, listener, options = null) {
let eventListeners = this._listeners[eventName];
if (!eventListeners) {
this._listeners[eventName] = eventListeners = [];
}
const eventListeners = (this._listeners[eventName] ||= []);
eventListeners.push({
listener,
external: (options && options.external) === true,
external: options?.external === true,
once: options?.once === true,
});
}