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visibleTimeout.js
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visibleTimeout.js
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let doc, HIDDEN, VISIBILITY_CHANGE,
nextId = 1;
const clearHandles = Object.create( null );
function init( overrideDoc ) {
doc = overrideDoc || document;
if ( doc.hidden !== undefined ) {
HIDDEN = 'hidden';
VISIBILITY_CHANGE = 'visibilitychange';
} else if ( doc.mozHidden !== undefined ) {
HIDDEN = 'mozHidden';
VISIBILITY_CHANGE = 'mozvisibilitychange';
} else if ( doc.webkitHidden !== undefined ) {
HIDDEN = 'webkitHidden';
VISIBILITY_CHANGE = 'webkitvisibilitychange';
}
}
init();
/**
* A library similar to similar to setTimeout and clearTimeout,
* that pauses the time when page visibility is hidden.
*
* @exports mediawiki.visibleTimeout
* @singleton
*/
module.exports = {
/**
* Generally similar to setTimeout, but pauses the time when page visibility is hidden.
*
* The provided function is invoked after the page has been cumulatively visible for the
* specified number of milliseconds.
*
* @param {Function} fn Callback
* @param {number} delay Time left, in milliseconds.
* @return {number} A positive integer value which identifies the timer. This
* value can be passed to clear() to cancel the timeout.
*/
set: function ( fn, delay ) {
let nativeId = null,
lastStartedAt = mw.now();
const visibleId = nextId++;
function clearHandle() {
if ( nativeId !== null ) {
clearTimeout( nativeId );
nativeId = null;
}
delete clearHandles[ visibleId ];
if ( VISIBILITY_CHANGE ) {
// Circular reference is intentional, chain starts after last definition.
doc.removeEventListener( VISIBILITY_CHANGE, visibilityCheck, false );
}
}
function onComplete() {
clearHandle();
fn();
}
function visibilityCheck() {
const now = mw.now();
if ( HIDDEN && doc[ HIDDEN ] ) {
if ( nativeId !== null ) {
// Calculate how long we were visible, and update the time left.
delay = Math.max( 0, delay - Math.max( 0, now - lastStartedAt ) );
if ( delay === 0 ) {
onComplete();
} else {
// Unschedule the native timeout, will restart when visible again.
clearTimeout( nativeId );
nativeId = null;
}
}
} else {
// If we're visible, or if HIDDEN is not supported, then start
// (or resume) the timeout, which runs the user callback after one
// delay, unless the page becomes hidden first.
if ( nativeId === null ) {
lastStartedAt = now;
nativeId = setTimeout( onComplete, delay );
}
}
}
clearHandles[ visibleId ] = clearHandle;
if ( VISIBILITY_CHANGE ) {
doc.addEventListener( VISIBILITY_CHANGE, visibilityCheck, false );
}
visibilityCheck();
return visibleId;
},
/**
* Cancel a visible timeout previously established by calling set.
*
* Passing an invalid ID silently does nothing.
*
* @param {number} visibleId The identifier of the visible timeout you
* want to cancel. This ID was returned by the corresponding call to set().
*/
clear: function ( visibleId ) {
if ( visibleId in clearHandles ) {
clearHandles[ visibleId ]();
}
}
};
if ( window.QUnit ) {
module.exports.init = init;
}

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Sat, Oct 3, 20:15 (3 d, 13 h ago)
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Default Alt Text
visibleTimeout.js (3 KB)

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