[webkit-dev] WebKit image rendering performance

Klemen Slavič krof.drakula at gmail.com
Tue Sep 11 11:59:33 PDT 2012

> I suggest you to ask questions on webkit-help. The mailing list webkit-dev
> is about the development of WebKit

Sorry about that, I didn't know which list to address this to, and -dev
seemed the appropriate place to pose such a question.

> A quick run in Instruments shows that, on my machine, blitting the images
> is the problem in this case. The hotspot has nothing to do with decoding
> the images.

What exactly do you mean by blitting? The way I understand it, doesn't
blitting mean every write to the screen buffer? I've only seen long-running
paint operations when new images came into view (identified using
console.timeStamp(frameNumber)), not on every frame. Even so, JPEGs
rendered consistently faster than PNGs when coming into view. I'm just
trying to understand what is done internally to avoid this behaviour.

> I would appreciate if you could update or remove the article to make sure
> we do not spread erroneous informations about WebKit through the mailing
> list.

Updating the article is exactly what I intended to do, to clear up any
errors due to my misinterpretation of the internal behaviour of WebKit.
Since I have only a high-level overview of the workings of the rendering
engine, I'd like to know more about what exactly the effects are so that I
may clear things up.

> I suggest you to use a profiler like Instruments' time profile. It will
> give you an idea of where the time is spent without making assumptions
> based on behaviors.

Sorry to sound completely uninformed, but what is Instruments? Bear in
mind, I don't have a Mac, I'm a Windows/Linux user. If you can point me in
the right direction, I can find my way around the documentation.

I'll refrain from posting any more messages regarding this on webkit-div
and instead divert any additional questions to -help.

Thanks for the pointers so far!

*    <http://about.me/klemen.slavic>
*It's who I am.*
*It's what I do.*
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