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Re: Utility of background-composite and background-blend-mode?

From: Dirk Schulze <dschulze@adobe.com>
Date: Thu, 14 Mar 2013 05:44:03 -0700
To: "robert@ocallahan.org" <robert@ocallahan.org>
CC: Rik Cabanier <cabanier@gmail.com>, "public-fx@w3.org" <public-fx@w3.org>
Message-ID: <DD671D17-6BBB-44FF-AB81-6DA49A2F3D64@adobe.com>

On Mar 14, 2013, at 3:53 AM, Robert O'Callahan <robert@ocallahan.org> wrote:

> On Thu, Mar 14, 2013 at 5:00 PM, Rik Cabanier <cabanier@gmail.com> wrote:
> I create a jsfiddle testcase: http://jsfiddle.net/vSjXM/5/
> and attached the rendering of WebKit and Firefox that has the blending patch. (https://bugzilla.mozilla.org/show_bug.cgi?id=841601)
> 
> The behavior you described indeed happens. As soon as an element is scrolled, it goes to an offscreen bitmap (ffox_scrolling vs ffox_no_scrolling).
> Webkit does not seems to suffer from this.
> 
> You mean "Webkit doesn't do this optimization" :-).
>  
> Is this something we can detect and disable if we detect blending in the element?
> Another difference is that 'position: fixed' didn't create a buffer in Firefox, but it did in WebKit.
> It does create a buffer is the scrollable div goes under it; just like you said :-)
> 
> These differences should all be fixed so blending and filter chains that access the background can work.
> 
> I'm not sure what you're suggesting. Are you suggesting we write Webkit's buffer-creation rules into a spec and modify other browsers to follow those rules if blending is detected in the page?

No, not WebKit's rules. And I do not think that we want to specify buffering. A behavior in situations like scrolling for blending should be specified and browser need to follow. I see that this can be challenging but would be most desireabale. After all, scrolling should not affect the browser experience of the user on the visual side - especially for blending.

Greetings,
Dirk

> 
> Rob
> -- 
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Received on Thursday, 14 March 2013 12:44:37 GMT

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