/**
* @fileoverview VisibilityListener is a utility class that listens for changes in
* document visibility and fullscreen state, invoking a callback when these states change.
*/
/**
* Class to listen for visibility and fullscreen changes in the document.
* It triggers a callback when the document becomes visible or enters fullscreen mode.
*/
export default class VisibilityListener {
/**
* @param {Function} callback The callback function to invoke on visibility or fullscreen changes.
*/
constructor(callback) {
/**
* @type {Function} The callback function to execute when the state changes.
*/
this.callback = callback;
// Bind methods to the instance.
this.handleVisibilityChange = this.handleVisibilityChange.bind(this);
this.handleFullscreenChange = this.handleFullscreenChange.bind(this);
this._addListeners();
}
/**
* Adds event listeners for visibility and fullscreen changes.
* @private
*/
_addListeners() {
document.addEventListener("visibilitychange", this.handleVisibilityChange);
document.addEventListener("fullscreenchange", this.handleFullscreenChange);
}
/**
* Handles the `visibilitychange` event.
* Invokes the callback if the document is visible.
*/
handleVisibilityChange() {
if (document.visibilityState === "visible") {
this.callback();
}
}
/**
* Handles the `fullscreenchange` event.
* Invokes the callback if the document enters fullscreen mode.
*/
handleFullscreenChange() {
if (document.fullscreenElement) {
this.callback();
}
}
/**
* Removes the event listeners for visibility and fullscreen changes.
*/
removeListeners() {
document.removeEventListener("visibilitychange", this.handleVisibilityChange);
document.removeEventListener("fullscreenchange", this.handleFullscreenChange);
}
}