[webkit-help] Background PNG decoding in WebKit

[Stephen Mattison]

Hey Zoltan thanks for the input! Is there anything I can do to make sure
that the decoding always happens in the WebThread? Ie not adding to the DOM
or creating a dom fragment or something?


On Wed, Oct 12, 2011 at 3:01 AM, Zoltan Horvath <zoltan at webkit.org> wrote:

> On Wed, 12 Oct 2011 03:39:19 +0200, Stephen Mattison <
> stephenmattison at gmail.com> wrote:
>
>  The problem I'm having is that it does not appear that PNGs are decoded in
>> the background in Webkit on iOS. Right now what I have is essentially a
>> ScrollView. I have a div the size of the viewport with another div that
>> scales with the content. I am scrolling the content div using a transition
>> and translate3d to achieve GPU acceleration. The scrolling looks great.
>> However the content is composed of images and they cannot all fit in
>> memory
>> at once so I am loading them on demand. The problem arises when I set the
>> background-image css property to a locally stored PNG image and then
>> attempt
>> to scroll. I get a noticeable delay/jerkiness/hiccup as the image is
>> decoded. Is there something I should be doing differently?
>>
>
> Hey!
>
> WebKit is decoding images in the mainthread when there is new chunk of
> image and it hasn't decoded yet, thus it is imaginable that it blocks your
> main thread for 'longer' time.
>
> I have a sketchy implementation for Qt to support imagedecoding in a
> (currently 1) separate thread.
> If you are interested check: https://bugs.webkit.org/show_**
> bug.cgi?id=69515 <https://bugs.webkit.org/show_bug.cgi?id=69515>
>
> Regards,
> Zoltan
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-- 
Stephen Mattison
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