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ISSUE-283 (Deterministic Presentation): Deterministic text wrapping and presentation [TTML2]

From: Timed Text Working Group Issue Tracker <sysbot+tracker@w3.org>
Date: Thu, 10 Oct 2013 17:31:39 +0000
Message-Id: <E1VUK5L-0007BQ-JZ@shauna.w3.org>
To: public-tt@w3.org
ISSUE-283 (Deterministic Presentation): Deterministic text wrapping and presentation [TTML2]

http://www.w3.org/AudioVideo/TT/tracker/issues/283

Raised by: Nigel Megitt
On product: TTML2

There's a complex interaction between lineHeight, fontSize, overflow and wrapOption that determines, for the font that the display processor chooses, how much text will fit on a line and whether any text that doesn't fit overflows or is truncated. This creates a problem for document authors if they can not be certain of the metrics of the font used to present their content.

The goal from an audience perspective is that the on-screen text is readable and complete. Nobody wants missing words (that could change the editorial meaning) or text that is visible but unreadable.

TTML offers little by way of solution to this real world problem at the moment. The IMSC submission presents a 'reference font' mechanism, which should be considered. Is there anything more that we can do natively in TTML to allow deterministic rendering to be defined at the point of authoring?

Raising this issue for discussion at TPAC.

Note that there are related issues (to be filed separately) around lineHeight=normal being related to the height of the text actually flowed onto a line (is it? or is it related to the descendent elements of the <p>?) and being set to a percentage of the font size - should it be 100%, 120%, 125% etc. for compatibility with CSS etc.
Received on Thursday, 10 October 2013 17:31:40 UTC

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