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[Bug 11342] TextMetrics should include distance from textBaseline to each of the baselines in the text

From: <bugzilla@jessica.w3.org>
Date: Thu, 03 Feb 2011 22:20:10 +0000
To: public-html-bugzilla@w3.org
Message-Id: <E1Pl7X8-0000YY-Lg@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=11342

--- Comment #8 from Charles Pritchard <chuck@jumis.com> 2011-02-03 22:20:10 UTC ---
(In reply to comment #7)
> Aah, so basically you need the distance from the current textBaseline to each
> of the possible baselines, for a particular span of text.
> Hmm.
> That's actually somewhat non-trivial to define, since a single string can have
> multiple distances for each baseline (that's why we need to provide a way to
> align to each baseline to start with).

You've got it.

When you say "non-trivial to define", are you referring to defining it in the
specs, or are you talking about actual implementation?

As for the specs, I think it's self-contained. It'd return the calculated
baseline for the content passed through measureText given the current
textBaseline.

For implementation, you're absolutely correct: a single string may rely upon
multiple fonts; especially a multilingual string. I'm all-but-certain, though,
that those cases are handled by underlying font layout engines.

If the font engine is inaccurate/strange, that's perfectly fine... we don't
need to define what "bottom" means in the spec, merely that the measureText
baseline attribute returns whatever the font engine has calculated.

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Received on Thursday, 3 February 2011 22:20:12 GMT

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