From: Mark E. Shoulson <>
Date: Fri, 19 Aug 2011 11:38:45 -0400

On 08/19/2011 11:21 AM, Michael Everson wrote:
> Directionality is a very deep property. A CSUR LTR script works fine out of the box on all platforms at least as far as directionality goes. A CSUR RTL script simply can't, and do you really think that "defining the properties" will effectively override the system-level expectations for LTR PUA on multiple platforms?
> Very very very unlikely.
Pretty sure it can't. I remember a discussion about the directionality
of the PUA some time ago, and I thought it was here, but looking back it
may have been on another mailing list. Here it is, from the
Fontforge-users mailing list (fontforge is an open-source font-design
program). Back in March:

Khaled Hosny ( wrote:

> On Tue, Mar 01, 2011 at 07:43:13PM +0100, Pocok Előd wrote:
> Could you tell me if there is a solution for changing the writing direction to
> > RTL while using the Latin area?
> Not in the font itself, OpenType engines relay on character's Unicode
> properties for directionality (using Unicode BiDi algorithm). But you
> can force a string of text to be RTL by surrounding it with U+202E
> (right to left override mark) and U+202C (pop directional formatting
> mark).

It's pretty disingenuous to say "Well, if you want a private-use RTL
script, you should be prepared to write an engine that can render it,"
ignoring the fact that LTR people can get by with just a font. Why
should it be so much harder to write RTL?

Received on Fri Aug 19 2011 - 10:39:39 CDT

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