Re: Defined Private Use was: SSP default ignorable characters

From: Doug Ewell (
Date: Sun May 02 2004 - 13:32:13 CDT

C J Fynn <cfynn at gmx dot net> wrote:

> "Philippe Verdy" <> wrote:
>> Certainly, but what is the distinction between downloading/
>> distributing a font or downloading/ditributing a XML file containing
>> the PUA conventions?
> One file not two - and some assurance that the custom properties
> haven't been altered since the font and the document that uses it were
> created.

I didn't see Philippe's original post, of course, for reasons that many
list members will remember. But this response from Chris piqued my
curiosity. So I went digging into my "Deleted Items" folder, found the
relevant post from Philippe, and guess what? A miracle happened.


That is, if there is ever to be a mechanism for specifying properties of
PUA characters at the user level (Mark Davis' expectation
notwithstanding), I agree that it should live in an external file or
table or other data structure, not within a font. And XML would be a
perfectly suitable format for distributing such a property file.

Not all font formats, not even all "smart" font formats, can contain all
of the property information for every character the font supports.
OpenType/Uniscribe was mentioned as an example where the rendering
engine does work that would be done by the font in other systems. The
division of labor between font and engine isn't the same across systems.
And even if you can tell the font about the directionality and
default-ignorability of your characters, there are still issues like
line breaking and mirroring (and maybe others, or maybe those are bad
examples) that have to be handled outside the font anyway.

Putting all the property information inside the font forces the user to
use *only that font* for his PUA needs. There might be a choice of
fonts that support a particular PUA usage (such as for Klingon -- Mark
Shoulson, is this true?) and it would not make sense to require all of
these fonts to be updated to include property information (if that is
even possible). Better to store the property information separately and
make it work for any old font the user chooses.

Storing the custom properties in the font doesn't really provide any
assurance that they haven't been altered.

If astonishing events like this continue, I may have to consider taking
Philippe off my "Blocked Senders" list and re-evaluating the
signal-to-noise ratio of his posts. (Of course, all is not perfect
here -- we need to be careful to use U+100001 for our PUA examples, not
U+10001, which is an assigned Linear B character. Count your zeros

-Doug Ewell
 Fullerton, California

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