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Bug 22114 - WebVTT: Regions scrolling mechanism should be better specified
Summary: WebVTT: Regions scrolling mechanism should be better specified
Alias: None
Product: TextTracks CG
Classification: Unclassified
Component: WebVTT (show other bugs)
Version: unspecified
Hardware: All All
: P2 normal
Target Milestone: ---
Assignee: This bug has no owner yet - up for the taking
QA Contact: This bug has no owner yet - up for the taking
Whiteboard: v1
Depends on:
Reported: 2013-05-21 10:14 UTC by vcarbune
Modified: 2014-03-03 07:45 UTC (History)
3 users (show)

See Also:


Description vcarbune 2013-05-21 10:14:39 UTC
The current form of the specification describes the functionality that should be achieved through several notes, but technically this can be achieved in multiple ways.

Currently, both CSS rules "overflow:hidden" and "transition-property: top" are set on the region node. Thus, moving the whole region node with cues as children upwards doesn't achieve the scrolling effect.

There are some alternatives for specifying it:
i) The current intent of the specification seems to be to have an extra container for all the cues that belong to the region, such that it scrolls upwards as cues are added (achieved by setting "transition-property: top" on this container).

ii) Set the "transition-property: top" on each cue and handle them individually out of the region.

iii) Since the same effect can be achieved for browsers using the above, and non-browser players won't even use CSS, the precise mechanism could be left as an implementation detail of the player displaying regions.

The current on-going implementation we're working at in Blink uses option i), as that seemed the initial intent of the spec and uses a single transition for all cues.
Comment 1 Silvia Pfeiffer 2013-12-16 10:49:00 UTC
scroll="none" settings have to be clarified, too
Comment 2 Silvia Pfeiffer 2014-03-03 07:45:44 UTC
Fixed in
by applying i).

I'm going to leave the scroll="none" issue to the current discussion on list.