[Webkit-unassigned] [Bug 6626] Arabic & Farsi rendered with no shaping (all glyphs separate, unreadable!)

bugzilla-daemon at opendarwin.org bugzilla-daemon at opendarwin.org
Fri Feb 3 03:02:08 PST 2006


------- Comment #5 from opendarwin.org at mitzpettel.com  2006-02-03 03:02 PDT -------
(In reply to comment #4)
> But the problem is that text engine/AAT on OSX dose not support the fonts which
> is dependent on cursive connectivity (Arabic Script) if they do not contain AAT
> table. You see, OSX has problem with all TTF and OpenType fonts ONLY and ONLY
> when it comes to Arabic Script. All other script like Hebrew, CJK etc are not
> affected.

Actually, Hebrew Niqqud placement is also broken with these fonts. I have
looked at one of them (Arial), and as far as I could see, the font file itself
doesn't contain the information needed for shaping (or positioning) in any
format, neither TrueType mort/morx nor OpenType GSUB/GPOS. In fact, I don't see
how these fonts render properly in Windows unless the system applies to them
some private knowledge (perhaps a default set of tables, based on hard-coded
glyph IDs).

I'm not sure if and how ATS can identify these fonts as "broken" and "fix"
them. On the WebKit level, it may be possible to have a heuristic that checks
if a font doesn't have any (or sufficiently rich) shaping information, and in
that case avoid it entirely for characters in the Arabic range. This will not
work for Hebrew, though.

As a workaround, maybe a user style sheet can be used to override Arial even
when it is specified by the page and replace it with another font.

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