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Re: Request for Comments: Proposal for Touch-Based Animation Scrubbing

From: François REMY <francois.remy.dev@outlook.com>
Date: Fri, 30 Nov 2012 17:47:55 +0100
Message-ID: <DUB120-DS877B24568229539E5FA70A5430@phx.gbl>
To: "Tobie Langel" <tobie@fb.com>, "Dean Jackson" <dino@apple.com>, "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: "Simon Fraser" <smfr@me.com>, "Rik Cabanier" <cabanier@gmail.com>, "www-style list" <www-style@w3.org>
|  From: Tobie Langel
|  Currently, the lack of events on which to prefetch and append new content
|  while scrolling makes it impossible to implement infinite scrolling
|  without re-implementing everything in JavaScript. Other UI refinements
|  (pull to refresh, etc.) suffer from similar issues. Re-implementing
|  scrolling in JavaScript prevents the browsers from carrying adequate perf
|  optimization, yields sub-optimal experiences for the users and is
|  extremely costly in engineering resources.

Unfortunately, this proposal is not aimed at all at solving the 'normal' 
scrolling performance, but rather at solving a popular hack around scrolling 
where you want to run 'scrolling animations' (for example a cartoon bullet 
enters the page from the left as you scroll further). Implementing this 
specification will do nothing to improve general scrolling performance 
(however, I don't understand either why people think it could degrade the 
normal case performance, this is simply not true: in the worst case the 
scrolling performance will stay the same (the feature will be disabled and 
will not trigger any slow down) and in the best it will become way better 
(it's enabled and replace traditionnal scroll behavior with a slower one, 
but which is way faster than using some JavaScript code).

Tab Atkins and I (and probably other people at Google) already discussed 
solutions to improve the scrolling experience in the general case using 
staged layout and (display: viewport). I think there are maybe cases where 
using a staged layout and a scrolling animation may make sense to optimize 
the scrolling even further, but I'm not completely convinced (any algorithm 
implementable by a CSS-scrolling-animation-hook, like "display: none when 
not in range" or "reuse/cycle through elements and modify their content via 
scripting later" could be implemeted in an even faster way by the UA itself 
as a fast path).

BTW, I've a few remarks on this proposal (a generalization from Florian's 
analysis) but I'll leave this for another mail.

Best regards,
Received on Friday, 30 November 2012 16:48:25 UTC

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