-/*!
- * An interface for scheduling background tasks.
- *
- * Loosely based on https://w3c.github.io/requestidlecallback/
- */
-( function ( mw, $ ) {
- var tasks = [],
- maxIdleDuration = 50,
- timeout = null;
-
- function schedule( trigger ) {
- clearTimeout( timeout );
- timeout = setTimeout( trigger, 700 );
- }
-
- function triggerIdle() {
- var elapsed,
- start = mw.now();
-
- while ( tasks.length ) {
- elapsed = mw.now() - start;
- if ( elapsed < maxIdleDuration ) {
- tasks.shift().callback();
- } else {
- // Idle moment expired, try again later
- schedule( triggerIdle );
- break;
- }
- }
- }
+( function ( mw ) {
+ var maxBusy = 50;
mw.requestIdleCallbackInternal = function ( callback ) {
- var task = { callback: callback };
- tasks.push( task );
-
- $( function () { schedule( triggerIdle ); } );
+ setTimeout( function () {
+ var start = mw.now();
+ callback( {
+ didTimeout: false,
+ timeRemaining: function () {
+ return Math.max( 0, maxBusy - ( mw.now() - start ) );
+ }
+ } );
+ }, 1 );
};
/**
* Schedule a deferred task to run in the background.
*
+ * This allows code to perform tasks in the main thread without impacting
+ * time-critical operations such as animations and response to input events.
+ *
+ * Basic logic is as follows:
+ *
+ * - User input event should be acknowledged within 100ms per [RAIL].
+ * - Idle work should be grouped in blocks of upto 50ms so that enough time
+ * remains for the event handler to execute and any rendering to take place.
+ * - Whenever a native event happens (e.g. user input), the deadline for any
+ * running idle callback drops to 0.
+ * - As long as the deadline is non-zero, other callbacks pending may be
+ * executed in the same idle period.
+ *
+ * See also:
+ *
+ * - <https://developer.mozilla.org/en-US/docs/Web/API/Window/requestIdleCallback>
+ * - <https://w3c.github.io/requestidlecallback/>
+ * - <https://developers.google.com/web/updates/2015/08/using-requestidlecallback>
+ * [RAIL]: https://developers.google.com/web/fundamentals/performance/rail
+ *
* @member mw
* @param {Function} callback
+ * @param {Object} [options]
+ * @param {number} [options.timeout] If set, the callback will be scheduled for
+ * immediate execution after this amount of time (in milliseconds) if it didn't run
+ * by that time.
*/
- mw.requestIdleCallback = window.requestIdleCallback
- ? function ( callback ) {
- window.requestIdleCallback( callback );
- }
- : mw.requestIdleCallbackInternal;
-}( mediaWiki, jQuery ) );
+ mw.requestIdleCallback = window.requestIdleCallback ?
+ // Bind because it throws TypeError if context is not window
+ window.requestIdleCallback.bind( window ) :
+ mw.requestIdleCallbackInternal;
+ // Note: Polyfill was previously disabled due to
+ // https://bugs.chromium.org/p/chromium/issues/detail?id=647870
+ // See also <http://codepen.io/Krinkle/full/XNGEvv>
+}( mediaWiki ) );