Re: face-variable-width-p?

[Kevin Rodgers]

David Reitter wrote:
> I'm trying to figure out whether a given face (the default face in a 
> frame, to be precise) uses a variable width font, but I can't find an 
> appropriate function in Emacs.
> One could compare the pixel widths of 'w' and 'i', but I can't find a 
> function that would give me the pixel width of a (propertized) string, 
> either.

How about parsing the XLFD font name:

(let ((font (frame-parameter (selected-frame) 'font)))
  (string-match xlfd-tight-regexp font)
  (match-string xlfd-regexp-spacing-subnum font))

On my machine, font is 
"-apple-monaco-medium-r-normal--12-120-72-72-m-120-iso10646-1",
but match-string returns "72" instead of "m".  So perhaps there's
a bug in xlfd-tight-regexp that can be worked around:

(let ((font (frame-parameter (selected-frame) 'font)))
  (string-match xlfd-tight-regexp font)
  (match-string (1+ xlfd-regexp-spacing-subnum) font))

A variable-width font (aka proportional pitch) should return "p"
-- see section 3.1.2.10 (SPACING Field) in 
http://ftp.xfree.org/pub/XFree86/4.5.0/doc/xlfd.txt

--
Kevin Rodgers
Denver, Colorado, USA