Fontsets
A font for X typically defines shapes for a single alphabet or script.
Therefore, displaying the entire range of scripts that Emacs supports
requires a collection of many fonts. In Emacs, such a collection is
called a fontset. A fontset is defined by a list of fonts, each
assigned to handle a range of character codes.
Each fontset has a name, like a font. The available X fonts are
defined by the X server; fontsets, however, are defined within Emacs
itself. Once you have defined a fontset, you can use it within Emacs by
specifying its name, anywhere that you could use a single font. Of
course, Emacs fontsets can use only the fonts that the X server
supports; if certain characters appear on the screen as hollow boxes,
this means that the fontset in use for them has no font for those
characters.1
Emacs creates two fontsets automatically: the standard fontset
and the startup fontset. The standard fontset is most likely to
have fonts for a wide variety of non-ASCII characters; however, this is
not the default for Emacs to use. (By default, Emacs tries to find a
font that has bold and italic variants.) You can specify use of the
standard fontset with the -fn option, or with the Font X
resource (see Font X). For example,
emacs -fn fontset-standard
A fontset does not necessarily specify a font for every character
code. If a fontset specifies no font for a certain character, or if it
specifies a font that does not exist on your system, then it cannot
display that character properly. It will display that character as an
empty box instead.
The fontset height and width are determined by the ASCII characters
(that is, by the font used for ASCII characters in that fontset). If
another font in the fontset has a different height, or a different
width, then characters assigned to that font are clipped to the
fontset's size. If highlight-wrong-size-font is non-nil,
a box is displayed around these wrong-size characters as well.
Footnotes
-
The Emacs installation instructions have information on
additional font support.
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