Intent to ship: CSS Scroll Snapping on B2G / Firefox OS

[Kearwood "Kip" Gilbert]

As of March 3, 2014 I intend to turn on by default CSS Scroll Snapping
on B2G. It has been developed behind the layout.css.scroll-snap.enabled
preference. Firefox is the first UA to ship this feature.

Platform coverage: Initially, this will be enabled only on B2G (Firefox
OS). Desktop platforms will be enabled once scroll bar support for CSS
scroll snapping lands (Bug 969250). Fennec will be enabled once the C++
based APZC implementation ships for Fennec (Bug 1138668).

This feature was previous discussed in this "intent to implement" thread:
https://groups.google.com/forum/#!topic/mozilla.dev.platform/HX9lwWZ250o/discussion

Feedback during the draft updates on the css-snappoints specification
took place on the w3.org www-style mailing list.

Bug to turn on by default:

Bug 1138651 - Enable CSS Scroll Snapping by Default on B2G

Link to standard:
http://dev.w3.org/csswg/css-snappoints/

The entirety of the W3 specification is implemented, with one
exception. In section 4 (Scroll Snap Types: the 'scroll-snap-type'
property), the specification reads, "If the content changes such that
the visual viewport would no longer rest on a snap point (e.g. content
is added, moved, deleted, resized), the scroll offset must be modified
to maintain this guarantee.". Support for this is tracked in Bug
1124324 (Perform instant and smooth scrolls to maintain guarantees set
by scroll snapping CSS attributes when content changes) and will be
landed separately.

- Kearwood "Kip" Gilbert