RE: ZWJ as a Ligature Suppressor

From: Andrew Glass (WINDOWS) <>
Date: Mon, 10 Aug 2015 17:58:24 +0000

Hi Richard,

To ligate or not to ligate is up to the font designer. Normally, GSUB lookups that perform ligation will be broken by the presence of ZWJ or ZWNJ. If a font designer wishes to ligate in the presence of a ZWJ or ZWNJ then they could choose to include appropriate glyph sequences in their ligation lookups. For example:

glyphA glyphB -> glyphC
glyphA ZWJ glyphB -> glyphC



Andrew Glass Ph.D.
Program Manager
Shell Text Input Group | Windows | Microsoft

-----Original Message-----
From: Unicode [] On Behalf Of Richard Wordingham
Sent: Sunday, August 9, 2015 3:58 AM
Subject: ZWJ as a Ligature Suppressor

According to the text just after TUS 7.0.0 Figure 23-3 (, ZWJ suppresses ligatures in Arabic script. Does this rule apply to other normally cursive joined scripts, e.g. Syriac and Mongolian?

Am I right in thinking that for an OpenType font for other scripts, the font writer must take precautions to prevent ZWJ accidentally suppressing ligatures that would be better suppressed by ZWNJ or <ZWJ ZWNJ ZWJ>?
Received on Mon Aug 10 2015 - 12:58:53 CDT

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