TAKAHASHI Naoto <ntakahas@etl.go.jp> and Ken'ichi Handa <handa@etl.go.jp> write:
Mule creates a window whose size is based on the width of ASCII
font. If the width of ASCII font and that of other fonts do not
match, some characters are not displayed completely. The width of
Japanese, Chinese, and Korean fonts must be exactly twice as wide
as that of ASCII fonts; the width of other fonts must be same as
that of ASCII fonts.
If you see dirty characters on your screen, it may be caused by
the auto-scaling function of X. If an X server receives a request
of a font which does not exist but whose specification is LFD
compliant, it tries to expand of reduce what is available. For
example, a specification
"-*-fixed-medium-r-*--*-*-*-*-*-*-jisx0208.1983-*"
is LFD compliant, so it may be resized. On the other hand, a
specification in mule-init.el:
"-*-fixed-medium-r-*--*-*-jisx0208.1983-*"
is not LFD compliant (the number of columns are less than it
should to be), so auto-scaling is inhibited. (What is described
here is what we have learned from experience, not from documents
of X.