DialogUnderlay: performance problem on IE6 w/CSS expressions

[nkolba]

CSS expressions on DialogUnderlay are causing performance issues in IE6. Proposed fix is to disable expressions when dialog is hidden.

[bill]

DialogUnderlay doesn't use any CSS expressions AFAIK. Maybe are you talking about the !BackgroundIFrame?

Can you attach a test case showing this performance issue?

Also, when you write a summary for a ticket try to write something more specific, like "Dialog: performance issue w/CSS expressions on IE6" Thanks.

[Sam Foster]

This came in as a sitepen support ticket originally, I asked Nick to file it here so we/he could track it. A test case would be good though...

Replying to bill:

DialogUnderlay doesn't use any CSS expressions AFAIK. Maybe are you talking about the !BackgroundIFrame?

Yes, the CSS expressions are actually in the BackgroundIframe? class, but as the iframes are recycled, and arent easily hook-able, the workaround we've tested (to the problem observed when using Dialog) adds some code to BackgroundIframe? to remove the expressions in the dijit.DialogUnderlay? class' hide method. This might be an issue elsewhere, best fixed somehow in the BackgroundIframe? itself, but I dont have any reports to go on for that.

[bill]

ISTM the BackgroundIframe code already removes the expressions when the iframes are put in the re-use queue:

this.push = function(iframe){
	iframe.style.display="none";
	if(dojo.isIE){
		iframe.style.removeExpression("width");
		iframe.style.removeExpression("height");
	}
	queue.push(iframe);
}

Isn't that code working for you (and if not, why not)?

[Sam Foster]

In the Dialog's fadeOut.onEnd method, you get dijit._underlay.hide(). This only does:

this.domNode.style.display = "none";
if(this.bgIframe.iframe){
	this.bgIframe.iframe.style.display = "none";
}

...It looks like it should be calling dijit._frames.push() there?

[bill]

Ah I see, OK fair enough, I'll check in a fix. Actually just call BackgroundIframe.destroy() will work, since that will save the <iframe> node (although destroying the BackgroundIframe object)

[bill]

(In [19119]) Destroy and recreate BackgroundIframe javascript object... it doesn't actually destroy the <iframe>, since that goes on a re-use stack, and it has the advantage of cleaning up the CSS expressions on the <iframe> to prevent IE6 performance problems.

Fixes #9208 !strict.