bug#10179: 24.0.91; enforcing double-width CJK character display

[Kan-Ru Chen]

Discussion was started by Werner LEMBERG in this thread:

https://lists.gnu.org/archive/html/emacs-devel/2011-07/msg00938.html

Currently Emacs chooses fonts that has width close to the width of
the default font. But the font may have smaller advance width so a
double width character will not be rendered as wide as twice of a latin
character.

I set `face-font-rescale-alist' for every font that might be used as a
workaround:

  (setq face-font-rescale-alist
        '(("WenQuanYi Micro Hei" . 1.2)
          ("cwTexYen" . 1.35)
          ("AR Heiti Light B5" . 1.2)))

Ideally this should be calculated and applied automatically (I believe
the information has been exported to lisp but haven't find a good way to
manipulate the font-object) or the display engine should add padding to
double-width font so they are rendered nicely.

-- 
Kanru