mediawiki-extensions-Visual.../modules/ve/ve.EventSequencer.js
David Chan 793172e41e ve.EventSequencer: Post-event listening
modules/ve/ve.EventSequencer.js
* Class to sequence pre-event and post-event listening correctly

demos/ve/eventSequencer.html
* Plain HTML example page for testing EventSequencer and event sequences

Change-Id: I4ddb10a30c2f44015136a7978a185d0b13f0690b
2013-09-04 11:20:46 -07:00

134 lines
4.9 KiB
JavaScript

/*!
* VisualEditor EventSequencer class.
*
* @copyright 2013 VisualEditor Team and others; see AUTHORS.txt
* @license The MIT License (MIT); see LICENSE.txt
*/
/**
* EventSequencer class with pre-event and post-event listeners.
*
* Post-event listeners are fired as soon as possible after the
* corresponding native event. They are similar to the setTimeout(f, 0)
* idiom, except that they are guaranteed to execute before any subsequent
* pre-event listener. Therefore, events are executed in the 'right order'.
*
* This matters when many events are added to the event 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.
*
* @constructor
* @param {HTMLElement} node Node to which listeners should be attached
* @param {string[]} eventNames List of event Names to listen to
* @param {Function} [boundLogFunc] Logging function, pre-bound with ve.bind
*/
ve.EventSequencer = function ( node, eventNames, boundLogFunc ) {
var i, len, eventName, $node = $( node );
this.node = node;
this.preListenersForEvent = {};
this.postListenersForEvent = {};
this.log = boundLogFunc || function () {};
/**
* @property {Object[]}
* - id {number} Id for setTimeout
* - func {Function} Post-event listener
* - ev {jQuery.Event} Browser event
* - eventName {string} Name, such as keydown
*/
this.pendingCalls = [];
for ( i = 0, len = eventNames.length; i < len; i++ ) {
eventName = eventNames[i];
$node.on( eventName, ve.bind( this.onEvent, this, eventName ) );
this.preListenersForEvent[eventName] = [];
this.postListenersForEvent[eventName] = [];
}
};
/**
* Add a listener to be fired just before the browser native action
* @method
* @param {string} eventName Javascript name of the event, e.g. 'keydown'
* @param {Function} listener Listener accepting a single argument 'event'
*/
ve.EventSequencer.prototype.addPreListener = function( eventName, listener ) {
this.preListenersForEvent[eventName].push( listener );
};
/**
* Add a listener to be fired as soon as possible after the native action
* @method
* @param {string} eventName Javascript name of the event, e.g. 'keydown'
* @param {Function} listener Listener accepting a single argument 'event'
*/
ve.EventSequencer.prototype.addPostListener = function( eventName, listener ) {
this.postListenersForEvent[eventName].push( listener );
};
/**
* Generic listener method which does the sequencing
* @method
* @param {string} eventName Javascript name of the event, e.g. 'keydown'
* @param {jQuery.Event} ev The browser event
*/
ve.EventSequencer.prototype.onEvent = function( eventName, ev ) {
var i, len, preListener, postListener, pendingCall;
this.log( '(EventSequencer: onEvent', eventName, ev, ')' );
this.runAllPendingCallsNow();
for ( i = 0, len = this.preListenersForEvent[eventName].length; i < len; i++ ) {
// Length cache is required, as a preListener could add another preListener
preListener = this.preListenersForEvent[eventName][i];
this.log( '(EventSequencer: preListener', eventName, ev, ')' );
preListener( ev );
}
for ( i = 0, len = this.postListenersForEvent[eventName].length; i < len; i++ ) {
// Length cache for style
postListener = this.postListenersForEvent[eventName][i];
// 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': postListener, 'id': null, 'ev': ev, 'eventName': eventName };
/*jshint loopfunc:true */
( function ( pendingCall, ev, log ) {
var id = setTimeout( function () {
if ( pendingCall.id === null ) {
return; // Seems to be necessary in Chromium
}
pendingCall.id = null;
log( '(EventSequencer: reached postListener', eventName, ev, ')' );
pendingCall.func( ev );
} );
pendingCall.id = id;
} )( pendingCall, ev, this.log );
/*jshint loopfunc:false */
this.pendingCalls.push( pendingCall );
}
};
/**
* Run any pending listeners, and clear the pending queue
* @method
*/
ve.EventSequencer.prototype.runAllPendingCallsNow = function () {
var i, pendingCall;
this.log( '(EventSequencer: runAllPendingCallsNow', this.pendingCalls, ')' );
for ( i = 0; i < this.pendingCalls.length; i++ ) {
// Length cache not possible, as a pending call appends another pending call.
pendingCall = this.pendingCalls[i];
if ( pendingCall.id === null ) {
continue; // already run
}
clearTimeout( pendingCall.id );
pendingCall.id = null;
this.log( '(EventSequencer: reached postListener', pendingCall, ')' );
// Force to run now
pendingCall.func( pendingCall.ev );
}
this.pendingCalls = [];
};