From: Doug Ewell <>
Date: Fri, 19 Aug 2011 09:12:53 -0700

Michael Everson <everson at evertype dot com> wrote:

>> It's part of the private agreement. I can't personally tell an OS or
>> application (unless I write it) how to interpret those properties,
>> but they are out there, and it would be theoretically possible for an
>> OS or app to accept those properties in some format and honor them.
> Since your invented script is LTR, you don't have any problem with
> directionality. The same is not true for RTL invented scripts.

Yes, I was lucky that the script I invented (on paper, 30 years ago) was
LTR rather than RTL, or TTB or boustro. But that wasn't my point.

Section 16.5 says the bidi property of the PUA, like all other such
properties of the PUA, is a *default* that can be overridden. It isn't
an absolute, unlike the case for assigned code points. Whether software
exists to implement the overridable behavior is another matter.
Remember the bad old days of the early to mid '90s, when practically no
Unicode-aware applications or OS's existed, and everything about Unicode
had the "this works in theory" nature? The PUA is still like that.

I guess your point is that if a given area were designated *by default*
as RTL, then rendering engines could assume that, just as they assume
all the existing *default* properties (or at least the ones they care
about, i.e. not numeric value). I can live with that, and I hereby
volunteer Plane 16.

Doug Ewell | Thornton, Colorado, USA | RFC 5645, 4645, UTN #14 | | @DougEwell ­
Received on Fri Aug 19 2011 - 11:16:16 CDT

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