[PATCH] Prevent a crash if the ASCII charset registries match nothing

[Aidan Kehoe]

 Ar an tri? l? d?ag de m? na Samhain, scr?obh stephen at xemacs.org: 

 > QUERY
 > 
 > What's the big hurry?

Where is everyone getting the impression I?m in a hurry? I mean, if you want
me to code less, sure, I?ve a stack of language textbooks that are being
super-slack about reading themselves. But if you want me to spend months
intermittently on every patch, I don?t know that that?s any more helpful
than a concentrated block of time; certainly I think that the docstring
error that Ilya pointed out was a consequence of that sort of wait. 

 > Aidan Kehoe writes:
 > 
 >  > Eh, still, XEmacs shouldn?t be crashable from Lisp. The below has a
 >  > bit more testing, with X11 and GTK; I intend committing it this
 >  > evening.
 > 
 > The crash you're describing is the well-known exit-via-X-handler on
 > startup, is it not? 

No, at least not to my knowledge. Reference? My crash is:

1. Start an XEmacs in a screen session.
   (unset DISPLAY && screen -d -m xemacs)

2. Open a gnuclient frame on the current X11 display. 
   gnuclient

3. Set the charset registries of ASCII to something that prevents any font
   matching. 
   (set-charset-registries 'ascii ["this is not-sensible"])

4. Watch XEmacs crash. But it shouldn?t crash, it should delete the X11
   frame and throw an error in the TTY. 

This didn?t happen previously and in 21.4 because of some special-casing
that optionally ignored charset registries for ASCII--this restores some
special-casing, but enforces more strictly that font names should be in XLFD
format, a requirement already documented in the manual. 

 > You really need to replace the X error handler to prevent that.
 > 
 > Making things a little bit better for people with misconfigured
 > systems at the expense of breaking Ilya's hacks is not a good tradeoff
 > IMO.

-- 
Santa Maradona, priez pour moi!