W3C home > Mailing lists > Public > www-style@w3.org > November 2012

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

From: Simon Fraser <smfr@me.com>
Date: Fri, 30 Nov 2012 10:53:38 -0800
Cc: Dean Jackson <dino@apple.com>, "Tab Atkins Jr." <jackalmage@gmail.com>, Rik Cabanier <cabanier@gmail.com>, www-style list <www-style@w3.org>
Message-id: <CFCE42BE-68EC-4F5E-AFA5-E16C17CE375B@me.com>
To: Tobie Langel <tobie@fb.com>
On Nov 30, 2012, at 9:55 AM, Tobie Langel <tobie@fb.com> wrote:

> On 11/30/12 6:41 PM, "Dean Jackson" <dino@apple.com> wrote:
>> 
>> Without going into details of the iOS implementation, the main reason your
>> scrolling performance improved when you went to a native app is because
>> it's more deterministic that the anything-goes Web scrolling, even though
>> it may not seem that way.
> 
> Yes, I'm aware some of the constraints enforced by UITableViews are key to
> its perf.
> 
>> Tab's proposal attempts to make some things more deterministic, but not
>> the types of things you needed for the Facebook app.
> 
> Understood.
> 
>> What you need is some way to do some (quite advanced) layout during scroll
>> without interrupting the main UI thread. Also, that layout should be
>> constrained
>> to some parts of the tree, and not affect other parts. That's the magic
>> behind the fast scrolling in a native app.
> 
> Thanks for these insights. Can we bring this to the web? (Pretty please.)

Yes, but we're going to need your help!

It's painfully obvious the the current user experience on desktop facebook
pages when you hit the end is just terrible. In Safari, at least, the right sidebar
jiggles up and down as you try to implement a sticky-like behavior in JS
while the page is rubber-banding, and the experience of hitting the bounce
at the bottom quickly followed by new content loading is very jarring.

First, I don't think this is a CSS problem; it should probably be brought up
in WebApps or something. But there is a clear need for some web-exposed
way to do smooth infinite scrolling.

It probably involves some combination of "near the end" scrolling-related
events, and a way for the page to provide content that gets appended to
the page with some guarantee that only the page height will change, and
smoothly enough to not interfere with scrolling.

I think it's a tricky problem, but someone needs to make a stab
at a straw-man proposal, and then get feedback from implementors.
You are the best people to write up such a proposal.

Simon
Received on Friday, 30 November 2012 18:54:11 GMT

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