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Re: [csswg-drafts] [css-inline-3] About the central baseline (#5177)

From: Nat McCully via GitHub <sysbot+gh@w3.org>
Date: Tue, 16 Jun 2020 16:23:50 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-644869244-1592324628-sysbot+gh@w3.org>
I think the existing "text-top", "text-bottom" and "center" should not be used for CJK, but rather use specific baselines "ideo", "idtp" and "ideographic-central" (or "ideo-center"). My reason being that existing implementations that depend on how they were defined as related to font ascent and descent should probably remain, but for CJK we try to get away from such ambiguous practices using Latin metrics or overriding them conditionally by font script.

As to what should happen when composing text in a CJK manner with fonts that lack these metrics, the heuristics would be to try to center a given height within the ideographic embox or within a height that equals the point size. For Latin scripts, the cap height is such a metric. For Thai, perhaps a derived cap height can be computed to serve the same purpose, or use a different metric that achieves the same (CJK oriented) balance in the mixed-script line.

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Received on Tuesday, 16 June 2020 16:23:51 UTC

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