109 lines
3.4 KiB
JavaScript
109 lines
3.4 KiB
JavaScript
/**
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* @module ol/events
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*/
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import {clear} from './obj.js';
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/**
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* Key to use with {@link module:ol/Observable~Observable#unByKey}.
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* @typedef {Object} EventsKey
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* @property {ListenerFunction} listener
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* @property {import("./events/Target.js").EventTargetLike} target
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* @property {string} type
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* @api
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*/
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/**
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* Listener function. This function is called with an event object as argument.
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* When the function returns `false`, event propagation will stop.
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*
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* @typedef {function((Event|import("./events/Event.js").default)): (void|boolean)} ListenerFunction
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* @api
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*/
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/**
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* @typedef {Object} ListenerObject
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* @property {ListenerFunction} handleEvent
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*/
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/**
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* @typedef {ListenerFunction|ListenerObject} Listener
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*/
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/**
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* Registers an event listener on an event target. Inspired by
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* https://google.github.io/closure-library/api/source/closure/goog/events/events.js.src.html
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*
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* This function efficiently binds a `listener` to a `this` object, and returns
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* a key for use with {@link module:ol/events~unlistenByKey}.
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*
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* @param {import("./events/Target.js").EventTargetLike} target Event target.
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* @param {string} type Event type.
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* @param {ListenerFunction} listener Listener.
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* @param {Object=} opt_this Object referenced by the `this` keyword in the
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* listener. Default is the `target`.
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* @param {boolean=} opt_once If true, add the listener as one-off listener.
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* @return {EventsKey} Unique key for the listener.
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*/
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export function listen(target, type, listener, opt_this, opt_once) {
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if (opt_this && opt_this !== target) {
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listener = listener.bind(opt_this);
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}
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if (opt_once) {
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const originalListener = listener;
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listener = function() {
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target.removeEventListener(type, listener);
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originalListener.apply(this, arguments);
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};
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}
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const eventsKey = {
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target: target,
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type: type,
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listener: listener
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};
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target.addEventListener(type, listener);
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return eventsKey;
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}
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/**
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* Registers a one-off event listener on an event target. Inspired by
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* https://google.github.io/closure-library/api/source/closure/goog/events/events.js.src.html
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*
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* This function efficiently binds a `listener` as self-unregistering listener
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* to a `this` object, and returns a key for use with
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* {@link module:ol/events~unlistenByKey} in case the listener needs to be
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* unregistered before it is called.
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*
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* When {@link module:ol/events~listen} is called with the same arguments after this
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* function, the self-unregistering listener will be turned into a permanent
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* listener.
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*
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* @param {import("./events/Target.js").EventTargetLike} target Event target.
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* @param {string} type Event type.
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* @param {ListenerFunction} listener Listener.
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* @param {Object=} opt_this Object referenced by the `this` keyword in the
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* listener. Default is the `target`.
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* @return {EventsKey} Key for unlistenByKey.
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*/
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export function listenOnce(target, type, listener, opt_this) {
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return listen(target, type, listener, opt_this, true);
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}
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/**
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* Unregisters event listeners on an event target. Inspired by
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* https://google.github.io/closure-library/api/source/closure/goog/events/events.js.src.html
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*
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* The argument passed to this function is the key returned from
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* {@link module:ol/events~listen} or {@link module:ol/events~listenOnce}.
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*
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* @param {EventsKey} key The key.
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*/
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export function unlistenByKey(key) {
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if (key && key.target) {
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key.target.removeEventListener(key.type, key.listener);
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clear(key);
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}
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}
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