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Re: cannot understand Elisp manual node Glyphs

From: Kim F. Storm
Subject: Re: cannot understand Elisp manual node Glyphs
Date: Fri, 09 Feb 2007 12:12:46 +0100
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.0.93 (gnu/linux)

Richard Stallman <address@hidden> writes:

> Please do NOT add a function make-glyph-code now.
> This is not the time for new features.

The initial reason behind this change was to improve _documentation_,
for an _existing_ feature which is definitely non-obvious, and
basically has no clean API (or an API at all).

In fact, I have code which I wrote for Emacs 19 / Emacs 20, which
stopped working in Emacs 21 because the encoding of faces in 
glyph codes changed ...  

IMO, it is a very bad API design to force Lisp code to relying on
internal numeric constants, which have already changed once between
Emacs releases.

AND IT WILL CHANGE AGAIN IN EMACS 23 (using 22 bits instead of 19).

So if _this_ is not the right time for cleaning up this mess, I don't
know when is!!

BTW, the unicode-2 branch seems to have bugs in this area, exactly
because the changes to this encoding at the C-leve are not reflected in
the Lisp code.  My patch would fix those bugs too (with the obvious
changes to the new functions) in Emacs 23 too.  

Furthermore, the unicode branch only allows the first 511 faces
defined to be used in glyph-code (vs. 4088 in Emacs 22) ... so maybe
the whole implementation of glyph-codes need to be revised in Emacs 23
-- yet another reason for making a clean interface for this NOW.


Kim F. Storm <address@hidden> http://www.cua.dk

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