[webkit-dev] WebKit image rendering performance

Benjamin Poulain benjamin at webkit.org
Tue Sep 11 11:04:02 PDT 2012

On Tue, Sep 11, 2012 at 1:45 AM, Klemen Slavič <krof.drakula at gmail.com>wrote:

> First time poster. While I admit I haven't worked on WebKit code (yet),
> I'm very familiar with its workings across different implementations
> (desktop, mobile and otherwise).
> In my research regarding WebKit rendering performance, I've stumbled upon
> an interesting artefact while animating spritesheet-based image animations.
> I've written up a an article on the effects and metrics, including a
> minimal test case to help demonstrate the effects on various
> implementations:
> http://gist.io/3639830

The way decoded images is handled depends on great many things.
I suggest you to ask questions on webkit-help. The mailing list webkit-dev
is about the development of WebKit

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.

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

I remember reading somewhere in the WebKit archives (messages dated at
> least one year ago) about keeping render objects removed from the tree by
> caching them according to their URI, but have since been unable to locate
> that specific message. From what I understand, the effects described in the
> document seem to match up exactly with what I'm assuming is happening
> inside the engine and according to Levi Weintraub's high-level description
> of the rendering engine.
> I would greatly appreciate any feedback on the document, to help optimise
> my approach when dealing with graphically intensive games and applications.
> I wouldn't mind getting my hands dirty with the source if someone can point
> me in the right direction.

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.

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