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EventSequencer: New hooks for useful moments

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ve.EventSequencer.js - Implement new types of event listener:
* onLoop( f ) to set a listener for the start of the event loop
* afterLoop( f ) to set a listener for the end of the event loop
* afterOne( f ) to set a one-time listener for after an event
* afterLoopOne( f ) to set a one-time listener for the end of the event loop

Change-Id: Ie388e0e9edcfccaa20e04c649a8b85d028ddde9c
This commit is contained in:
David Chan 2013-09-19 17:57:30 +01:00 committed by Krinkle
parent 9dc33e38f7
commit e515017827
1 changed files with 185 additions and 26 deletions
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211
modules/ve/ve.EventSequencer.js
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@ -13,16 +13,23 @@
* idiom, except that they are guaranteed to execute before any subsequent
* on-event listener. Therefore, events are executed in the 'right order'.
*
* This matters when many events are added to the event queue in one go.
* This matters when many events are added to the task queue in one go.
* For instance, browsers often queue 'keydown' and 'keypress' in immediate
* sequence, so a setTimeout(f, 0) defined in the keydown listener will run
* *after* the keypress listener (i.e. in the 'wrong' order). EventSequencer
* ensures that this does not happen.
*
* All listeners receive the jQuery event as an argument. If an on-event
* All these listeners receive the jQuery event as an argument. If an on-event
* listener needs to pass information to a corresponding after-event listener,
* it can do so by adding properties into the jQuery event itself.
*
* There are also 'onLoop' and 'afterLoop' listeners, which only fire once per
* Javascript event loop iteration, respectively before and after all the
* other listeners fire.
*
* For further event loop / task queue information, see:
* http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#event-loops
*
* @class ve.EventSequencer
*/
@ -66,21 +73,51 @@ ve.EventSequencer = function VeEventSequencer( eventNames ) {
this.pendingCalls = [];
/**
* @property {Object.<string,Function>}
* @property {Object.<string,Function[]>}
*/
this.onListenersForEvent = {};
/**
* @property {Object.<string,Function>}
* @property {Object.<string,Function[]>}
*/
this.afterListenersForEvent = {};
/**
* @property {Object.<string,Function[]>}
*/
this.afterOneListenersForEvent = {};
for ( i = 0, len = eventNames.length; i < len; i++ ) {
eventName = eventNames[i];
this.onListenersForEvent[eventName] = [];
this.afterListenersForEvent[eventName] = [];
this.eventHandlers[eventName] = makeEventHandler( eventName );
}
/**
* @property {Function[]}
*/
this.onLoopListeners = [];
/**
* @property {Function[]}
*/
this.afterLoopListeners = [];
/**
* @property {Function[]}
*/
this.afterLoopOneListeners = [];
/**
* @property {boolean}
*/
this.doneOnLoop = false;
/**
* @property {number}
*/
this.afterLoopTimeoutId = null;
};
/**
@ -109,6 +146,15 @@ ve.EventSequencer.prototype.detach = function () {
};
/**
* Add listeners to be fired at the start of the Javascript event loop iteration
* @method
* @param {Function[]} listeners Listeners that take no arguments
*/
ve.EventSequencer.prototype.onLoop = function ( listeners ) {
this.onLoopListeners.push.apply( this.onLoopListeners, listeners );
};
/**
* Add listeners to be fired just before the browser native action
* @method
@ -121,7 +167,6 @@ ve.EventSequencer.prototype.on = function ( listeners ) {
}
};
/**
* Add listeners to be fired as soon as possible after the native action
* @method
@ -134,6 +179,36 @@ ve.EventSequencer.prototype.after = function ( listeners ) {
}
};
/**
* Add listeners to be fired once, as soon as possible after the native action
* @method
* @param {Object.<string,Function[]>} listeners Function for each event
*/
ve.EventSequencer.prototype.afterOne = function ( listeners ) {
var eventName;
for ( eventName in listeners ) {
this.afterOneListenersForEvent[eventName].push( listeners[eventName] );
}
};
/**
* Add listeners to be fired at the end of the Javascript event loop iteration
* @method
* @param {Function[]} listeners Listeners that take no arguments
*/
ve.EventSequencer.prototype.afterLoop = function ( listeners ) {
Array.prototype.push.apply( this.afterLoopListeners, listeners );
};
/**
* Add listeners to be fired once, at the end of the Javascript event loop iteration
* @method
* @param {Function[]} listeners Listeners that take no arguments
*/
ve.EventSequencer.prototype.afterLoopOne = function ( listeners ) {
Array.prototype.push.apply( this.afterLoopOneListeners, listeners );
};
/**
* Generic listener method which does the sequencing
* @private
@ -142,40 +217,124 @@ ve.EventSequencer.prototype.after = function ( listeners ) {
* @param {jQuery.Event} ev The browser event
*/
ve.EventSequencer.prototype.onEvent = function ( eventName, ev ) {
var i, len, onListener, afterListener, pendingCall;
var i, len, onListener, pendingCall, me, id;
this.runPendingCalls();
if ( !this.doneOnLoop ) {
this.doneOnLoop = true;
this.doOnLoop();
}
// Length cache 'len' is required, as an onListener could add another onListener
for ( i = 0, len = this.onListenersForEvent[eventName].length; i < len; i++ ) {
onListener = this.onListenersForEvent[eventName][i];
onListener( ev );
}
// Length cache 'len' for style only
for ( i = 0, len = this.afterListenersForEvent[eventName].length; i < len; i++ ) {
afterListener = this.afterListenersForEvent[eventName][i];
// Queue a call to afterEvent only if there are some afterListeners/afterOneListeners
if ( this.afterListenersForEvent[eventName].length > 0 ||
this.afterOneListenersForEvent[eventName].length > 0 ) {
// Create a cancellable pending call
// - Create the pendingCall object first
// - then create the setTimeout invocation to modify pendingCall.id
// - then set pendingCall.id to the setTimeout id, so the call can cancel itself
// Must wrap everything in a function call, to create the required closure.
pendingCall = { 'func': afterListener, 'id': null, 'ev': ev, 'eventName': eventName };
/*jshint loopfunc:true */
( function ( pendingCall, ev ) {
var id = setTimeout( function () {
if ( pendingCall.id === null ) {
// clearTimeout seems not always to work immediately
return;
}
pendingCall.id = null;
pendingCall.func( ev );
} );
pendingCall.id = id;
} )( pendingCall, ev );
/*jshint loopfunc:false */
pendingCall = { 'id': null, 'ev': ev, 'eventName': eventName };
me = this;
id = setTimeout( function () {
if ( pendingCall.id === null ) {
// clearTimeout seems not always to work immediately
return;
}
me.resetAfterLoopTimeout();
pendingCall.id = null;
me.afterEvent( eventName, ev );
} );
pendingCall.id = id;
this.pendingCalls.push( pendingCall );
}
};
/**
* Generic after listener method which gets queued
* @private
* @method
* @param {string} eventName Javascript name of the event, e.g. 'keydown'
* @param {jQuery.Event} ev The browser event
*/
ve.EventSequencer.prototype.afterEvent = function ( eventName, ev ) {
var i, len, afterListeners, afterOneListeners;
// Snapshot the listener lists, and blank *OneListener list.
// This ensures reasonable behaviour if a function called adds another listener.
afterListeners = this.afterListenersForEvent[eventName].slice();
afterOneListeners = this.afterOneListenersForEvent[eventName].slice();
this.afterOneListenersForEvent[eventName].length = 0;
for ( i = 0, len = afterListeners.length; i < len; i++ ) {
afterListeners[i]( ev );
}
for ( i = 0, len = afterOneListeners.length; i < len; i++ ) {
afterOneListeners[i]( ev );
}
};
/**
* Call each onLoopListener once
* @private
* @method
*/
ve.EventSequencer.prototype.doOnLoop = function () {
var i, len;
// Length cache 'len' is required, as the functions called may add another listener
for ( i = 0, len = this.onLoopListeners.length; i < len; i++ ) {
this.onLoopListeners[i]();
}
};
/**
* Call each afterLoopListener once, unless the setTimeout is already cancelled
* @private
* @method
* @param {number} myTimeoutId The calling setTimeout id
*/
ve.EventSequencer.prototype.doAfterLoop = function ( myTimeoutId ) {
var i, len, afterLoopListeners, afterOneLoopListeners;
if ( this.afterLoopTimeoutId !== myTimeoutId ) {
// cancelled; do nothing
return;
}
this.afterLoopTimeoutId = null;
// Snapshot the listener lists, and blank *OneListener list.
// This ensures reasonable behaviour if a function called adds another listener.
afterLoopListeners = this.afterLoopListeners.slice();
afterOneLoopListeners = this.afterOneLoopListeners.slice();
this.afterOneLoopListeners.length = 0;
for ( i = 0, len = this.afterLoopListeners.length; i < len; i++ ) {
this.afterLoopListeners[i]();
}
for ( i = 0, len = this.afterLoopOneListeners.length; i < len; i++ ) {
this.afterLoopOneListeners[i]();
}
};
/**
* Push any pending doAfterLoop to end of task queue (cancel, then re-set)
* @private
* @method
*/
ve.EventSequencer.prototype.resetAfterLoopTimeout = function () {
var timeoutId, me = this;
if ( this.afterLoopTimeoutId !== null ) {
clearTimeout( this.afterLoopTimeoutId );
}
timeoutId = setTimeout( function () {
me.doAfterLoop( timeoutId );
} );
this.afterLoopTimeoutId = timeoutId;
};
/**
* Run any pending listeners, and clear the pending queue
* @private
@ -196,7 +355,7 @@ ve.EventSequencer.prototype.runPendingCalls = function () {
pendingCall.id = null;
// Force to run now. It's important that we set id to null before running,
// so that there's no chance a recursive call will call the listener again.
pendingCall.func( pendingCall.ev );
this.afterEvent( pendingCall.eventName, pendingCall.ev );
}
// This is safe because we only ever appended to the list, so it's definitely exhausted
// now.