27.10 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.