Re: Zero-width joiner won't join

From: Philippe Verdy <>
Date: Thu, 8 Mar 2012 05:35:26 +0100

There's another similar subject:

Chome will not join all Arabic characters as it should.

Simply because it assumes that fonts are mapping the compatibility
characters for the joining forms, when there are such compatibility
character encoded. But some fonts for Arabic don't map these caracters
(those at end of the BMP), but instead map the contextual forms utdng
the mandatory OpenType features on the standard Arabic characters. If
Chrome cannot find those compatibility characters, no joining will be
attempted, and the isolated forms will be displayed instead (without
even trying to fnd a matching font that has those compatibility
characters mapped, such as "Arial" instead "of Arabic Typesetting").

I found the case on some rare Arabic characters that normally have 4
contextual forms, only 2 were rendered (the isolated and initial
forms, not the medial and final forms). I think this is a bug of the
layout engine that does not use the FULL set of joining types (despite
they are defined since many years for most characters that Chrome
still do not fully join), notably of the Arabic letter follows a
TATWEEN (in that case it should not be using the isolated or final
form for the letter): Chrome or its renderer (tested on Windows 7)
does not implement apparently one of the standard joining types (the
*forced*" joining).
Received on Wed Mar 07 2012 - 22:39:43 CST

This archive was generated by hypermail 2.2.0 : Wed Mar 07 2012 - 22:39:44 CST