On Mon, 13 Jul 2020 11:24:23 -0400 Phil M Perry <philpe...@hvc.rr.com> wrote:
> (my first digest copy arrived moments after posting my previous > update) > > Richard, > > "Top To Bottom" means that the characters (glyphs) are upright (top > uppermost), as they would be written horizontally, but stacked in a > column one-at-a-time and reading from the top to the bottom. BTT > (Bottom To Top) would be the same, except reading from bottom to top. > > I noted that with a cursive script such as Arabic, when written > horizontally, connects letters (also there are a lot of ligatures). > When written vertically, the individual "standalone" forms of letters > are used, so no connections. I would presume that Mongolian and > Phags-pa would do something similar. Latin text (and CJK) are > normally non-cursive (unconnected), as you note. Jonathan Kew's post spelled out the complexity - one needs to specify the orientation of the glyphs and the ordering of the lines. Mongolian is a TTB cursive script. When it is written horizontally, the glyphs are normally rotated. Apparently users learn it as a CV syllabary, so separating consonants and vowels is quite unnatural. Phags-pa appears to be treated similarly. Now, Ogham is reported to be a BTT script. I wonder if we should get bidi in mixed script contexts? When Ogham is written horizontally, it appears as left-to-right and 'cursive'. I don't think the issue has been solved for spacing marks in Indic scripts. I think vowels stay next to their consonants in Thai despite being letters, but examples of vertical Thai with upright text are vanishingly rare. Richard. _______________________________________________ HarfBuzz mailing list HarfBuzz@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/harfbuzz
