[webkit-dev] Status of multithreaded image decoding

Peter Kasting pkasting at chromium.org
Sun Aug 12 17:34:08 PDT 2012

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.

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