[webkit-dev] Status of multithreaded image decoding

Dong Seong Hwang luxtella at company100.net
Mon Aug 13 03:20:20 PDT 2012


In the above link, Hin-Chung shows how to determine whether an image
is actually painted.

2012/8/13 Maciej Stachowiak <mjs at apple.com>:
> I that case, starting async decoding at layout time makes sense if and only
> if at layout to e you can predict what you will paint. I don't know enough
> about our rendering to know of that is the case.
>  - Maciej
> On Aug 12, 2012, at 5:34 PM, Peter Kasting <pkasting at chromium.org> wrote:
> On Sun, Aug 12, 2012 at 1:24 PM, Maciej Stachowiak <mjs at apple.com> wrote:
>> Why not start asynchronous decoding immediately as the image is loading,
>> and synchronize at paint time? What is the benefit of waiting until layout
>> time to start decoding the image data?
> Uninformed guess (since I haven't touched the decoders in a while), but
> currently we don't decode unless the image is actually painted, which helps
> a ton on pages that are an enormous long string of images (common cases:
> Boston Big Picture blog, various porn sites), since most of the images can
> be decoded after initial layout, or not at all (if the user never scrolls
> down enough).  If we started decoding as images loaded I'd imagine we'd do
> (possibly a lot of) extra work compared to today.
> PK
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