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Re: [csswg-drafts] [css-inline-3] sTypoAscender / sTypoDescender should not be recommended (#5485)

From: Chris Lilley via GitHub <sysbot+gh@w3.org>
Date: Fri, 04 Sep 2020 16:31:33 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-687254780-1599237092-sysbot+gh@w3.org>
Recommending `sTypoAscender`/`Descender` has a long history, see the 1997 Web Fonts specification:

> **9.11. Maximum unaccented height**

> For Type 1 fonts, this value may be obtained from the 'Ascender' value in the AFM file. For TrueType and OpenType fonts, this value may be obtained from the 'Ascender' entry in the 'hhea' table or (preferably) from the 'sTypoAscender' value in the 'OS/2' table. For TrueType GX fonts, the 'horizontalBefore' entry in the 'fmtx' table is used, over-riding Ascender values in the 'hhea' table. 
> https://www.w3.org/TR/WD-font-970721#typoascent

My hazy recollection is that Windows had a broken way of measuring ascender and descender, Mac had a broken way to measure them, and `sTypo*` was supposed to be the platform-neutral fix (although putting it in the OS/2 table is an odd historical curiosity)

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