W3C home > Mailing lists > Public > www-style@w3.org > November 2011

Paged UIs a la Mobile Navigation

From: Yehuda Katz <wycats@gmail.com>
Date: Thu, 3 Nov 2011 12:06:01 -0700
Message-ID: <CAMFeDTU0j1d5DeGz5-G1gV9hwjwZ9JMBPHp3gBybE6MYqkaA_g@mail.gmail.com>
To: www-style@w3.org
I'd like to get some feedback on whether we could have explicit way in CSS
to describe the type of UI that mobile devices use for navigation or
hierarchy, but which also figure into popovers on tablet or desktop devices.

The basic idea is:

   - A container element of this type could have several child elements,
   only one of which could be presented on screen at once.
   - When a child element is on screen, it can scroll using the normal
   scrolling mechanism, but the container element never scrolls.
   - The container can transition to an element to its left or right. After
   transitioning, the new element retains its last scroll position (the
   initial scroll position is top).
   - Transitions should be regular CSS transitions, and possibly some
   additional conveniently defined transitions, like "pan" or "fold"

It is possible to get close to this on some browsers, but because hardware
acceleration figured prominently into making this experience performant,
and because hardware acceleration is only indirectly exposed to the author,
making this work reliably across all browsers is, at present, impossible.

This is partially addressed on iOS via -webkit-overflow-scrolling.

One major area of remaining concern is that, in general, it is inadvisable
to make scrolling elements hardware accelerated (using one of the transform
hacks) because it creates a worse scrolling experience (significantly more
tiling), but horizontal transitioning is only performant on mobile devices
when working against an accelerated element. Transitioning an element to
accelerated (by beginning a 3d transform, for instance), reliably produces
an undesirable flicker.

In short, the browsers are in a much better position to make this
interaction performant than authors, who need to devine performance
characteristics on a per-release, per-browser basis, and a performant,
flicker-free solution is often not possible at all.

Yehuda Katz
(ph) 718.877.1325
Received on Thursday, 3 November 2011 19:06:56 GMT

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