A glyph is a generalization of a character; it stands for an image that takes up a single character position on the screen. Normally glyphs come from vectors in the display table (see Display Tables).
A glyph is represented in Lisp as a glyph code. A glyph code can be simple or it can be defined by the glyph table. A simple glyph code is just a way of specifying a character and a face to output it in. See Faces.
The following functions are used to manipulate simple glyph codes:
This function returns a simple glyph code representing char char with face face.
This function returns face of simple glyph code glyph, or
nilif glyph has the default face (face-id 0). See Face Functions.
On character terminals, you can set up a glyph table to define the meaning of glyph codes (represented as small integers).
The value of this variable is the current glyph table. It should be
nilor a vector whose gth element defines glyph code g.
If a glyph code is greater than or equal to the length of the glyph table, that code is automatically simple. If
nilthen all glyph codes are simple.
The glyph table is used only on character terminals. On graphical displays, all glyph codes are simple.
Here are the meaningful types of elements in the glyph table:
make-glyph-code. You can use such an alias to define a small-numbered glyph code which specifies a character with a face.
This function returns a newly-allocated glyph code which is set up to display by sending string to the terminal.