composition -- combining accent alignment off for variable-width fonts

[Miles Bader]

The alignment of unicode combining accents seems reasonable in a
fixed-width font, but is clearly off for a variable-width font.

For instance, the following string:

xyz: ç̄̓ö̈ó̀l̗̈

Looks OK with font "DejaVu Sans Mono", but messed up with font "DejaVu
Sans".  [As far as I can tell, these fonts have roughly the same
coverage, so I'm guessing that's not a problem.]

With the cursor positioned over the "c", for instance, I can use `C-u
C-x =' to see:

Composed with the following character(s) "̧̄" using this font:
  xft:-unknown-DejaVu Sans-normal-normal-normal-*-12-*-*-*-*-0-iso10646-1
by these glyphs:
  [0 2 99 70 7 -2 6 8 2 nil]
  [0 2 807 728 0 -4 -2 0 2 [-4 0 0]]
  [0 2 772 693 0 -5 -1 9 -8 [-4 0 0]]


-Miles

-- 
"I distrust a research person who is always obviously busy on a task."
   --Robert Frosch, VP, GM Research