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Re: [csswg-drafts] [css-text] shaping breaks and typographic characters (#699)

From: Florian Rivoal via GitHub <sysbot+gh@w3.org>
Date: Tue, 23 Apr 2019 05:10:54 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-485645939-1555996253-sysbot+gh@w3.org>
@r12a We're waiting on your confirmation to be able to close this issue. Can you please confirm that this is now ok, or if it is not, say what you wish to see changed?

In your comment https://github.com/w3c/csswg-drafts/issues/699#issuecomment-446546503, you say you'd like to be able to do sub-grapheme cluster styling. As @fantasai  pointed out, the spec text leaves that possibility open (and encourages it), but falls short of requiring it because as far as we can tell **in the general case** it is not possible. Fonts can map a group of code points to a single glyph, and there's nothing that can be done in that case to style part of the glyph. Moreover, css is largely independent of the font technology used, so this is not a good spec to assume that certain things can be done just because they are possible in open type.

I don't disagree that the various things you wish to achieve are desirable, but if we want to elevate the requirement to a MUST, we're going to need to:
* narrow it down to the cases where it is actually possible (e.g. not the cases where `n` code points map to `m` glyphs)
* define the behavior precisely, which I believe will only be possible with explicit references to how the font substystem work, therefore taking on a normative dependency onto open type

This seems like it would be a significant expansion of scope for css-text Level 3 to cope with this, and we're trying to wrap it up, so I'd rather keep the spec as it is for now (i.e. allowing and recommending but not requiring the behavior you want), and leaving it up to future levels / modules to define the details so that this becomes interoperable in the cases where it is possible to do so.

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Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/699#issuecomment-485645939 using your GitHub account
Received on Tuesday, 23 April 2019 05:10:55 UTC

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