Ken Snyder wrote:
> Along with all this Event handling discussion, I'd like to throw in my
> ideas for a rewrite of Event.observe et al before I test and submit as a
> patch. My proposed changes allow the traditional Event.stopObserving()
> and simplify some of the current messaging ideas. Please provide feedback.
>
Colin, thanks for pointing out that my observer array will slow things
down in many cases. I really like your implementation, especially the
way you keep a different EventCache object. One thing I wonder, though,
if like you said your function returns an index--an array index could be
problematic, but why not use an object as a cache? Consider the draft
below.
--Ken
Object.extend(Event, {
//...
// the cache of observers
observers: {},
// the current position in our cache
cacheIdx: 0,
// added return of cacheIdx to allow Event.stopObserving(idx)
observe: function( element, event, observer, useCapture ) {
element = $(element);
useCapture = useCapture || false;
element[this._addFnName](this._eventName(event), observer, useCapture);
this.cacheIdx++;
this.observers[this.cacheIdx] = [element, event, observer, useCapture];
return cacheIdx;
},
stopObserving: function( element, event, observer, useCapture ) {
if( typeof arguments[0]=='number' ) {
this._cancel(arguments[0]);
} else {
element = $(element);
useCapture = useCapture || false;
element[this._removeFnName](this._eventName(event), observer,
useCapture);
//
// The current implementation seems not to clear the cache like this
//
for( idx in this.observers ) {
if( this.observers[idx][0]==element &&
this.observers[idx][1]==event &&
this.observers[idx][2]==observer &&
this.observers[idx][3]==useCapture) {
delete this.observers[idx];
break;
}
}
//
//
//
}
},
unloadCache: function() {
for( idx in this.observers ) {
this._cancel(idx);
}
},
//
// New methods
//
// function that actually detaches the event and clears from cache
_cancel: function(idx) {
var handle = this.observers[idx];
try {
handle.element[this._removeFnName](this._eventName(handle.event),
handle.observer, handle.useCapture);
delete this.observers[idx];
} catch(e) {}
},
// New method: cancel all the observers associated with a particular
element for a particular event
stopObservingElementEvent: function( element, event ) {
element = $(element);
for( idx in this.observers ) {
if( this.observers[idx][0]==element && this.observers[idx][1]==event )
this._cancel[idx];
}
},
// New method: cancel all the observers associated with a particular
element
stopObservingElement: function( element ) {
element = $(element);
for( idx in this.observers ) {
if( this.observers[idx][0]==element )
this._cancel[idx];
}
}
};
// cross-browser function and event naming
if( window.addEventListener ) {
Event._addFnName = 'addEventListener';
Event._removeFnName = 'removeEventListener';
if( navigator.appVersion.match(/Konqueror|Safari|KHTML/) )
Event._eventName = function(name) { return name=='keypress' ?
'keydown' : name; };
} else {
Event._eventName = function(name) { return name; };
}
} else if( window.attachEvent ) {
Event._addFnName = 'attachEvent';
Event._removeFnName = 'detachEvent';
Event._eventName = function(name) { return 'on'+name; };
// garbage collect for IE
window.attachEvent('onunload', Event.unloadCache);
}
Using an indexed object as a cache even opens up the possibility of
using my original API suggestion:
...
observe: function( element, event, observer, useCapture ) {
element = $(element);
useCapture = useCapture || false;
element[this._addFnName](this._eventName(event), observer, useCapture);
this.cacheIdx++;
this.observers[this.cacheIdx] = [element, event, observer, useCapture];
return { cancel: function() { Event._cancel(cacheIdx); } };
}
...
stopObserving: function( element, event, observer, useCapture ) {
if( typeof arguments[0]=='object' && arguments[0].cancel ) {
arguments[0].cancel();
} else {
...
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