W3C home > Mailing lists > Public > www-style@w3.org > December 2012

RE: [css-display-viewport] Enabling fast layout for web apps via isolation

From: François REMY <francois.remy.dev@outlook.com>
Date: Thu, 20 Dec 2012 22:06:33 +0100
Message-ID: <DUB002-W144836C830616B3635892CEA5370@phx.gbl>
To: Simon Fraser <smfr@me.com>
CC: CSS WG <www-style@w3.org>
> Transforms do affect layout, in that they affect overflow. Moving an element around inside an overflow:scroll element should update the scrollbars.

Indeed. I was told that before already, but I keep forgetting it :) However, in most cases, it's snappier than just modifying the position directly.

> Not necessarily. WebKit has a "layout positioned objects only" optimization that attempts to make moving out-of-flow positioned elements fast.

Granted, I should have said "in the general case", but most of the time this is just what's happening. Let's take the case of infinitely scrolling lists, most of them have to use non-positioned objects because they want a vertical flow.

> This is not true on many mobile platforms, which "flatten" iframes

I guess it only happens on scaled down websites, right? I do believe that if the Sencha team did use iframes to isolate their webcomponents and claim this was a very important performance improvement (despite memory and marshalling issue), they probably didn't face this issue.

BTW, seamless iframes are also doing content-size-retrofitting in Chrome, and it's possible that we may want that in the case of "height: auto" local viewports, too. 		 	   		  
Received on Thursday, 20 December 2012 21:07:00 UTC

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