38.17.3 Glyphs

A glyph is a generalization of a character; it stands for an image that takes up a single character position on the screen. Glyphs are represented in Lisp as integers, just as characters are.

The meaning of each integer, as a glyph, is defined by the glyph table, which is the value of the variable glyph-table.

Variable: glyph-table

The value of this variable is the current glyph table. It should be a vector; the gth element defines glyph code g. If the value is nil instead of a vector, then all glyphs are simple (see below). The glyph table is not used on windowed displays.

Here are the possible types of elements in the glyph table:

string

Send the characters in string to the terminal to output this glyph. This alternative is available on character terminals, but not under a window system.

integer

Define this glyph code as an alias for glyph code integer. You can use an alias to specify a face code for the glyph; see below.

nil

This glyph is simple. The glyph code mod 524288 is the character to output, and the glyph code divided by 524288 specifies the face number (see section 38.11.7 Functions for Working with Faces) to use while outputting it. (524288 is 2**19.) See section 38.11 Faces.

If a glyph code is greater than or equal to the length of the glyph table, that code is automatically simple.

Function: create-glyph string

This function returns a newly-allocated glyph code which is set up to display by sending string to the terminal.