- From: MURATA Makoto <eb2m-mrt@asahi-net.or.jp>
- Date: Thu, 12 Dec 2019 13:47:52 +0900
- To: www-archive@w3.org
- Message-ID: <CALvn5EBupPoNOB9NvYTNzYXwi4nRvHQMNiyks-ZZzdEU6po+sw@mail.gmail.com>
---------- Forwarded message --------- From: Taro Yamamoto <tyamamot@adobe.com> Date: 2019年12月2日(月) 17:04 Subject: RE: UAX#50 conformance: Is it possible to update existing fonts without causing damage to existing non-CSS applications? To: MURATA Makoto <eb2m-mrt@asahi-net.or.jp>, Nat McCully < nmccully@adobe.com> Cc: Florian Rivoal <florian@rivoal.net>, fantasai <fantasai@inkedblade.net> Murata-san, Nat might have different ideas, but I would like to make some comments. > It appears that some fonts specify the vert feature in a way inconsistent with CSS WM and UAX#50. It becomes impossible to use the glyph as specified in the Unicode chart, since the vert feature always provide a different glyph. I learned this from Murakami-san. In Japan, proprietary digital fonts for Japanese have been used since the late 1960s. Japanese fonts for the PostScript interpreter appeared in 1989. There have been Adobe's Type 1-based Original Composite Fonts, naked CIDFonts, sfnt-wrapped CIDFonts on PostScript interpreters and the Macintosh, and TrueType fonts and OpenType fonts on PCs, the Macintosh, and some other operating systems. Today's fonts are based on the long history. Also, there can be vendor-specific or typeface-dependent elements in today's fonts, and many of them had been decided, before UTR #50 was written. This historical nature applies also to how layout software handles vertical postures. As I have repeated, the switching of glyph postures in Japanese typesetting are ruled mainly by application software. The area that the 'vert' feature really can control is relatively small. So, what you wrote in the "Document" is only half the domain of the possible problems of vertical glyph posture inconsistency with UTR #50. For example, If you type a COPYRIGHT SIGN U+00A9 character in a vertical line on some page layout application software, the result posture will be often different from that defined by UTR #50. These applications treat it as an R-vertical-posture character, and rotate it 90 degrees, but the character must have the vertical posture of U according to UTR #50. This is only ONE example of the inconsistency problems that you are concerned about, but the 'vert' feature in font is NOT responsible for this problem that occurs to the U+00A9 character at all, because the character is NOT included in the 'vert' feature. This problem of U+00A9 is not a 'vert' problem at all. Still, I know everyone cannot deny that as you wrote, if the 'vert' feature of a font instructs the vertical posture of an upright glyph in the font mapped to a character whose vertical posture is defined to be U or Tu by UTR #50, to be changed and to produce a rotated version of the glyph instead, it is clear the result will be incompatible with the definition of UTR #50, I agree that this is an incompatibility problem caused by the 'vert' feature. (On the other hand, this also means that as long as the 'vert' produces a variant glyph shape whose vertical posture is still Upright, there will be no problem, even if the vertical glyph design has some difference from the original Upright shape with the effect of the 'vert' feature, usually the vertical glyph shape is what is expected by the type designer. This kind of glyph substitution by the 'vert' feature must be allowed.) In your 'Document', some 'vert' related problems are reported, such as U+2016, etc. Although I do not yet check every glyph listed in the "Document", some of them seem to have been traditionally included in the 'vert' table in Adobe's and other Japanese font vendors' fonts, and such fonts may be producing the incompatibility problems with UTR #50 that you have described. In the sense, the 'vert' table needs to be modified in some way toward the future, but as mentioned above, updating the 'vert' table won't solve every incompatibility problems with UTR #50. Furthermore, any changes will cause backward compatibility problems which can damage the reproducibility of legacy documents and printed matters. This is my current, personal, view on the issue. Nat may have some different views. Regards, --Taro -- Regards, Makoto
Received on Thursday, 12 December 2019 04:48:34 UTC