> Date: Thu, 6 Jun 2019 01:31:19 +0100 > From: Richard Wordingham <richard.wording...@ntlworld.com> > > On Wed, 05 Jun 2019 20:26:41 +0300 > Eli Zaretskii <e...@gnu.org> wrote: > > > To make the question perhaps more concrete: the current code considers > > a font to be a match for shaping with HarfBuzz if it's either OTF or > > TTF, and covers at least one Unicode sub-range above u+00FF > > codepoint. Is this a reasonable test, or should the code consider > > additional font features? > > Even that's fraught. For example, my Tai Tham font Da Lekh includes > some Thai characters because they're used with Tai Tham text, but > doesn't include Thai script characters that aren't. I trust you're > allowing for the fact that a font for an Indian script will typically > use the dandas from the Devanagari block, without the font supporting > anything else from the Devanagari block.
That's another layer of matching in Emacs. The lower layer constructs a list of all fonts that could match, and then a higher layer tests which one of those actually match the requirements of the script. I was talking about the former one, you are talking about the latter. > 1) Some good old faces may lack punctuation characters and logograms. > This doesn't mean the fonts haven't been equipped with new, good GSUB > and GPOS tables. > > 2) There seems to be an implication that Lao usage only uses one set of > digits. > > 3) A Lao-based font would omit some consonants because they aren't used > in the Lao tradition. > > 4) Some of the consonant marks are alien to modern Northern Thai > habits, and may therefore be omitted from an old typeface. > > Some fonts omit explicit shaping for Tai Tham because they entirely > reasonably want to avoid the USE. (Rumour has it that Andrew Glass > wants to ban some words from being shaped properly.) They rely on the > shaping being done by other features as applied to the default script. > This doesn't work well on Windows, but could work well with HarfBuzz as > the renderer. It's only a heuristic that they have a restricted > repertoire - proper DIY Indic rearrangement is a pain, but even I can > achieve it. > > Restricted repertoire would be very reasonable for a Myanmar script > font - it's a more extreme version of the fact that Icelandic and > German don't have the same set of letters. If all else fails, Emacs offers a facility for specifying the fonts to be used, which could go down to individual codepoints. _______________________________________________ HarfBuzz mailing list HarfBuzz@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/harfbuzz