bug#11106: 24.0.94; enhancement request: have autoload treat faces like it does options

[Drew Adams]

Enhancement request:

Be able to add an autoload cookie before a `defface', and have
the face definition handled appropriately, similarly
to what is done for user options (variables).  And be able to
specify `face' as the TYPE arg for function `autoload'.  IOW,
have faces handled by autoloading in a way similar to user
options (variables).
 
For options, the cookie adds property `custom-autoload' to the symbol,
and that property is handled appropriately in code in custom.el etc.
 
It would be good if "function" `autoload' explicitly handled
both options and faces via its TYPE argument, just as it handles
functions and keymaps.
 
In particular, I would like to be able to do the following:
 
;;;###autoload (autoload 'someface "somelib" "Doc" nil 'face)
 
And then have the file somelib.el[c] be autoloaded whenever the face is
used (at least wrt some set of face-accessing functions).
 
An advantage of this is that a file of generated autoloads would not
contain the actual face definition, with its sexp that evals to the
face's default "value".  Instead, it would just contain that
`(autoload...)' form, which would DTRT.
 
This would obviate dealing with computing the default at the time that
the autoloads file is loaded.  And that would mean that any dependencies
within that default sexp would be handled normally, when the library
itself is loaded (not when the generated autoloads file is loaded).
 
If my use case is not clear, ignore it.  You can perhaps come up
with your own use case.  After all, faces are similar to user options
in other ways.  The purpose of this enhancement request is to extend
that similarity to autoloading.

(Just as for options, no one is required or necessarily encouraged
to autoload any faces.  This would just make it possible to do so,
without putting the entire face definition into the autoloads file.)
 

In GNU Emacs 24.0.94.1 (i386-mingw-nt5.1.2600)
 of 2012-03-19 on MARVIN
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.6) --no-opt --enable-checking --cflags
 -ID:/devel/emacs/libs/libXpm-3.5.8/include
 -ID:/devel/emacs/libs/libXpm-3.5.8/src
 -ID:/devel/emacs/libs/libpng-dev_1.4.3-1/include
 -ID:/devel/emacs/libs/zlib-dev_1.2.5-2/include
 -ID:/devel/emacs/libs/giflib-4.1.4-1/include
 -ID:/devel/emacs/libs/jpeg-6b-4/include
 -ID:/devel/emacs/libs/tiff-3.8.2-1/include
 -ID:/devel/emacs/libs/gnutls-3.0.9/include'