[IMSC] Thoughts re: issue-312 -- itts:forcedDisplay

Hi all,

During our last call, I noted two concerns with the itts:forcedDisplay
feature as currently drafted.

(a) the semantics of the itts:forcedDisplay feature are not
sufficiently specified
(b) the representation of itts:forcedDisplay as an attribute is not desirable

To address (a), below is proposed prose:

"""
The presentation processor SHALL accept an optional boolean parameter
called forcedDisplayModeParameter, whose value may be set by the
application. If not set, the value of forcedDisplayModeParameter shall
be assumed to be equal to "false".

If the value of forcedDisplayModeParameter is "true", a content
element with a itts:forcedDisplay computed value of "false" shall be
assumed to have a tts:visibility computed value equal to "hidden",
even if tts:visibility is otherwise set to "true".
"""

The idea is to essentially ignore the itts:forcedDisplay attribute
unless otherwise specifically requested by the application. This also
clarifies that itts:forcedDisplay has "no effect on content layout or
composition, but merely determines whether composed content is visible
or not." As next step, I plan to create examples.

Re: (b), I am not comfortable rejecting a solution that users have
devised and implemented based on actual use cases and in the absence
of specific guidance and/or prohibition in TTML 1.0.

Best,

-- Pierre

Received on Saturday, 21 June 2014 01:06:44 UTC