From: Doug Ewell <>
Date: Fri, 19 Aug 2011 07:57:21 -0700

"Mark E. Shoulson" <mark at kli dot org> wrote:

>> So your private agreement, in addition to specifying the meaning of
>> your PUA characters and probably some sample glyphs, can also specify
>> their properties, overriding the default properties.
> I don't know if you can even do this. My understanding of the
> rendering process is very sketchy, but I seem to recall that things
> like directionality cannot be specified by a font or other easily
> transmissible piece of information, but has to be baked into the
> application or rendering engine itself. This severely limits the
> utility of the PUA, if applications that use it have to be written
> from scratch each time. At least with stuff that is font-dependent,
> you can use ordinary word-processors that honor OpenType or Graphite
> or whatever.

I didn't say that applications or rendering engines are able to accept
your overridden properties and apply them, right out of the box, at
least not today. Most applications don't care about the PUA, or assume
it's only for that particular vendor's custom Latin-script ligatures and
dictionary symbols. But you are certainly able to define the
properties, and doing so is the conformant thing to do.

Doug Ewell | Thornton, Colorado, USA | RFC 5645, 4645, UTN #14 | | @DougEwell ­
Received on Fri Aug 19 2011 - 09:58:05 CDT

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