On Sat, 7 Sep 2002, Keith Packard wrote:
> Around 9 o'clock on Sep 7, Jungshik Shin wrote:
>
> > I'm not sure adding U+115F/U+1160 to the blank glyph list is the best
> > way, but it works. Keith, could you consider this?
>
> The blank glyph list is supposed to be filled with all of the Unicode
> values which have an empty visual representation. It's a hack to work
...
> I adapted the data I found in Mozilla for this purpose, hence the similar
> issues you found in the two programs.
Thank you for going through the Unicode tables to
come up with a more extensive list. I've just posted your list to bugzilla
bug 167136 mentioned previously.
> I'm reading through the Unicode tables looking for other blank values,
> so far I've found:
>
> Unicode range added? comments
>
> U+180B - U+180E no (but I don't have a Mongolian font to check against)
> U+200C - U+200F yes (the Unicode description isn't clear)
> U+2028 - U+2029 no (these seem like they're supposed to be drawn)
> U+202A - U+202F yes (these also appear blank from the description)
> U+3164 yes (HANGUL FILLER, similar to U+1160)
> U+FEFF yes (byte order detector (ZERO WIDTH NO-BREAK SPACE))
> U+FFA0 yes HALFWIDTH HANGUL FILLER (similar to U+3164)
> U+FFF9 - U+FFFB yes INTERLINEAR ANNOTATION marks for furigana
> Rules for inclusion -- if a font could reasonably draw these as blank,
> they should be included in the list. The idea is to ignore empty glyphs
> which should always have some visual representation.
I think that U+200C/U+200D(ZWNJ, ZWJ) are meant to be used mainly(
though not exclusively. Latin ligature formation may also be controlled
by them.) with Indic scripts and fonts for Indic scripts are supposed to
have some OT tables built-in to map a sequence of characters including
ZWNJ/ZWJ to appropriate glyph(s). As for U+200E/U+200F and U+202A -
U+202F, I guess a lower-level layer like fontconfig is never supposed to
see them because they have to be taken care of at a higher level(layout.
e.g. Pango?). Nonetheless, it seems like it's harmless(except for a
little performance hit, if any) to include them in the blank glyph list.
The same appears true of U+FFF9 - U+FFFB.
BTW, although depcecated, U+206A - U+206D seem to have to be included
as well. U+206E and U+206F may or may not have to be added. I'm not
sure what they're for.
Jungshik
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