From: James Kass (firstname.lastname@example.org)
Date: Wed Jan 09 2008 - 05:52:30 CST
AndrÃ© Szabolcs Szelp wrote,
> Concerning MUFI,
> I also see (alike J.K.) that assigning PUA codes to the precomposed glyphs
> is the correct way to go for font designers. Of course the use of the PUA
> codepoints for composable glyphs by anyone writing/editing a text is not
> encouraged, however due to limitations of some (even quite common
> software) I think the option should be given to the user to have the glyphs
> displayed in a typographic aesthetic way.
There are pros and cons.
I neither condone nor condemn the P.U.A. schemes of groups like MUFI,
but I do understand the reasoning behind this practice. So, I thought
I might help to explain this reasoning.
On the one hand, a font developer places precomposed glyphs in the P.U.A.
in order to accomodate users with older systems. On the other hand, the
developer is assigning code points to precomposed glyphs while telling
users that they really shouldn't use those code points.
On the one hand, a font developer supports a kind of backwards
compatibility with existing P.U.A. schemes. Such schemes have been
around for a while. On the other hand, the continuing existence of
all those lovely glyphs in the P.U.A. may tend to contribute to the
creation of new data which uses those code points.
In my own case, when designing glyphs for Devanagari, the only way
that I could display Devanagari presentation forms on my system was
to assign P.U.A. code points to them. I was happy to follow the P.U.A.
scheme devised by Mark Leisher for Devanagari presentation forms.
When I worked on Tamil, I didn't find any P.U.A. schemes for Tamil,
so I made one up.
Now, years later, when those P.U.A. code assignments really are no
longer needed, I still maintain those schemes. I will probably maintain
those schemes as long as I continue to produce the fonts.
But, I'm not assigning any more P.U.A. code points in my fonts for
items which should be represented by valid Unicode sequences.
It was Michael Everson who finally persuaded me to discontinue this
practice. He pointed out that a font like mine might be considered
useful, except that in many cases my P.U.A. assignations conflicted
with the configuration of his own system, resulting in unexpected
and undesirable displays. His comments caused me to consider that
many potential users of my font might well be dissuaded from using
it because of those P.U.A. conflicts.
Using the P.U.A. to enable precomposed glyph display on older systems
is a decision that each developer should make after carefully weighing
the pros and cons.
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