resources/src/mediawiki.visibleTimeout.js

   1 ( function () {
   2         var hidden, visibilityChange,
   3                 nextVisibleTimeoutId = 0,
   4                 activeTimeouts = {},
   5                 document = window.document,
   6                 init = function ( overrideDoc ) {
   7                         if ( overrideDoc !== undefined ) {
   8                                 document = overrideDoc;
   9                         }
  10
  11                         if ( document.hidden !== undefined ) {
  12                                 hidden = 'hidden';
  13                                 visibilityChange = 'visibilitychange';
  14                         } else if ( document.mozHidden !== undefined ) {
  15                                 hidden = 'mozHidden';
  16                                 visibilityChange = 'mozvisibilitychange';
  17                         } else if ( document.msHidden !== undefined ) {
  18                                 hidden = 'msHidden';
  19                                 visibilityChange = 'msvisibilitychange';
  20                         } else if ( document.webkitHidden !== undefined ) {
  21                                 hidden = 'webkitHidden';
  22                                 visibilityChange = 'webkitvisibilitychange';
  23                         }
  24                 };
  25
  26         init();
  27
  28         /**
  29          * @class mw.visibleTimeout
  30          * @singleton
  31          */
  32         module.exports = {
  33                 /**
  34                  * Generally similar to setTimeout, but turns itself on/off on page
  35                  * visibility changes. The passed function fires after the page has been
  36                  * cumulatively visible for the specified number of ms.
  37                  *
  38                  * @param {Function} fn The action to execute after visible timeout has expired.
  39                  * @param {number} delay The number of ms the page should be visible before
  40                  *  calling fn.
  41                  * @return {number} A positive integer value which identifies the timer. This
  42                  *  value can be passed to clearVisibleTimeout() to cancel the timeout.
  43                  */
  44                 set: function ( fn, delay ) {
  45                         var handleVisibilityChange,
  46                                 timeoutId = null,
  47                                 visibleTimeoutId = nextVisibleTimeoutId++,
  48                                 lastStartedAt = mw.now(),
  49                                 clearVisibleTimeout = function () {
  50                                         if ( timeoutId !== null ) {
  51                                                 clearTimeout( timeoutId );
  52                                                 timeoutId = null;
  53                                         }
  54                                         delete activeTimeouts[ visibleTimeoutId ];
  55                                         if ( hidden !== undefined ) {
  56                                                 document.removeEventListener( visibilityChange, handleVisibilityChange, false );
  57                                         }
  58                                 },
  59                                 onComplete = function () {
  60                                         clearVisibleTimeout();
  61                                         fn();
  62                                 };
  63
  64                         handleVisibilityChange = function () {
  65                                 var now = mw.now();
  66
  67                                 if ( document[ hidden ] ) {
  68                                         // pause timeout if running
  69                                         if ( timeoutId !== null ) {
  70                                                 delay = Math.max( 0, delay - Math.max( 0, now - lastStartedAt ) );
  71                                                 if ( delay === 0 ) {
  72                                                         onComplete();
  73                                                 } else {
  74                                                         clearTimeout( timeoutId );
  75                                                         timeoutId = null;
  76                                                 }
  77                                         }
  78                                 } else {
  79                                         // resume timeout if not running
  80                                         if ( timeoutId === null ) {
  81                                                 lastStartedAt = now;
  82                                                 timeoutId = setTimeout( onComplete, delay );
  83                                         }
  84                                 }
  85                         };
  86
  87                         activeTimeouts[ visibleTimeoutId ] = clearVisibleTimeout;
  88                         if ( hidden !== undefined ) {
  89                                 document.addEventListener( visibilityChange, handleVisibilityChange, false );
  90                         }
  91                         handleVisibilityChange();
  92
  93                         return visibleTimeoutId;
  94                 },
  95
  96                 /**
  97                  * Cancel a visible timeout previously established by calling set.
  98                  * Passing an invalid ID silently does nothing.
  99                  *
 100                  * @param {number} visibleTimeoutId The identifier of the visible
 101                  *  timeout you want to cancel. This ID was returned by the
 102                  *  corresponding call to set().
 103                  */
 104                 clear: function ( visibleTimeoutId ) {
 105                         if ( Object.prototype.hasOwnProperty.call( activeTimeouts, visibleTimeoutId ) ) {
 106                                 activeTimeouts[ visibleTimeoutId ]();
 107                         }
 108                 }
 109         };
 110
 111         if ( window.QUnit ) {
 112                 module.exports.setDocument = init;
 113         }
 114
 115 }() );