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

bugzilla-daemon at opendarwin.org bugzilla-daemon at opendarwin.org
Mon Feb 6 10:23:43 PST 2006


http://bugzilla.opendarwin.org/show_bug.cgi?id=6626





------- Comment #6 from ahmad.moshref at gmail.com  2006-02-06 10:23 PDT -------
(In reply to comment #5)

Dear Mitz;

The problem of broken cursive connectivity is not limited to these "bad" fonts
(Tahoma, Arial, TimeNewRoman). It is rather a problem in ATS/AAT technology and
OSX text engine. For example all of these fonts works properly in Mellel and
Indesign ME, that because this two program uses their own text engine rather
than the one built into OSX.  As I have mentioned in my previous post OSX has
problem in dealing with ALL non Apple (the one without AAT table)
Arabic/Persian/Urdu fonts no matter if they are TTF or OT. To prove this I can
send you privately some TTF&OT fonts so that you can test and see by yourself.
Although the Arabic OT and TTF I have has designed by professional and has all
the necessary resources that they should have, they displayed broken by
TextEdit or any other application which is dependent on OSX ATS/AAT to handle
the text. As to "mort/morx, OpenType GSUB/GPOS" because I do not know about
these I will ask a friend who is an expert to comment on these issues. 


As to the workaround you suggested using the style sheet, I have tried this but
neither in Safari nor in WEbkit it is properly functional. Beside for a user to
load an style sheet just to be able to set other fonts than the default fonts
is not a good solution. It should be possible for user to define fonts for
different script system as it is done (and works) in Mozilla. Webkit should
respect the user choice of other fonts and it should override the default
fonts, something than it is not possible in Webkits current version. 


best regards, Ahmad



> (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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