[Bug 22114] New: Regions scrolling mechanism should be better specified

https://www.w3.org/Bugs/Public/show_bug.cgi?id=22114

            Bug ID: 22114
           Summary: Regions scrolling mechanism should be better specified
    Classification: Unclassified
           Product: TextTracks CG
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: WebVTT Extension: Regions for rendering cue groups
          Assignee: silviapfeiffer1@gmail.com
          Reporter: victor.carbune@gmail.com
        QA Contact: dave.null@w3.org
                CC: public-texttracks@w3.org

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.

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Received on Tuesday, 21 May 2013 10:14:44 UTC