W3C home > Mailing lists > Public > www-style@w3.org > May 2013

Re: [css-display]? Compositing, expensive things, and laziness

From: Robert O'Callahan <robert@ocallahan.org>
Date: Fri, 31 May 2013 11:40:11 +1200
Message-ID: <CAOp6jLbjb13FY0kK2SajXT94KOAmWE7q9XamjBB_ee1Z5Y7wjw@mail.gmail.com>
To: Ali Juma <ajuma@chromium.org>
Cc: Simon Fraser <smfr@me.com>, "Tab Atkins Jr." <jackalmage@gmail.com>, www-style <www-style@w3.org>, Jon Rimmer <jon.rimmer@gmail.com>, Ian Vollick <vollick@chromium.org>
I'm unenthusiastic about adding a feature with a very narrow range of
utility. In this case the range is very narrow: a page with complex content
coming into view, running on an implementation that supports
off-main-thread-painting but not enough parallelism to paint the content
quickly, where there is other content on the page that the user is
interacting with, where the content coming into view is not animated in a
way that requires it to be repainted, and this page is authored by very
sophisticated Web developers who know about and can effectively use this
esoteric feature. Furthermore in this case the range of utility a sliding
window over time, since we're going to get increasingly fast drawing over
time thanks to increasing parallelism, and the complexity of the content
will have to scale appropriately for the feature to be useful.

While this feature may be essential to give some important site optimal UX
today or tomorrow, I don't think we can or should add every feature that
meets that criterion at some point in time.

Here are some alternatives that you've probably considered but I'd like to
hear more about:
-- If you use a heuristic to suppress rendering at the beginning of an
opacity transition when the opacity values are small, does that look bad?
-- What if you just fudge the shape of the opacity transition function in
the compositor so the painting of expensive content can be automatically
delayed a little with the rest of the transition sped up to compensate? I
don't know what is expensive about the content in the cases you have in
mind, but I presume some heuristics could detect it.
-- What about other techniques to speed up the initial rendering of the
content in exchange for reduced quality when the opacity values are low
enough the content is barely visible anyway? It would help if we knew
exactly what this expensive content is.

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Received on Thursday, 30 May 2013 23:40:38 UTC

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