Glyphless characters are characters which are displayed in a special way, e.g., as a box containing a hexadecimal code, instead of being displayed literally. These include characters which are explicitly defined to be glyphless, as well as characters for which there is no available font (on a graphical display), and characters which cannot be encoded by the terminal’s coding system (on a text terminal).
The value of this variable is a char-table which defines glyphless characters and how they are displayed. Each entry must be one of the following display methods:
Display the character in the usual way.
Don’t display the character.
Display a thin space, 1-pixel wide on graphical displays, or 1-character wide on text terminals.
Display an empty box.
Display a box containing the Unicode codepoint of the character, in hexadecimal notation.
Display a box containing that string. The string should contain at most 6 ASCII characters.
(graphical . text)
Display with graphical on graphical displays, and with text on text terminals. Both graphical and text must be one of the display methods described above.
ASCII string display methods are drawn with the
glyphless-char face. On text terminals, a box is emulated by
square brackets, ‘’.
The char-table has one extra slot, which determines how to display any
character that cannot be displayed with any available font, or cannot
be encoded by the terminal’s coding system. Its value should be one
of the above display methods, except
zero-width or a cons cell.
If a character has a non-
nil entry in an active display table,
the display table takes effect; in this case, Emacs does not consult
glyphless-char-display at all.
This user option provides a convenient way to set
glyphless-char-display for groups of similar characters. Do
not set its value directly from Lisp code; the value takes effect only
via a custom
:set function (see Variable Definitions),
which updates glyphless-char-display.
Its value should be an alist of elements
. method), where group is a symbol specifying a group of
characters, and method is a symbol specifying how to display
group should be one of the following:
ASCII control characters
excluding the newline and tab characters (normally displayed as escape
sequences like ‘^A’; see How Text Is Displayed in The GNU Emacs Manual).
Non-ASCII, non-printing characters
U+009F (normally displayed as octal escape sequences like
Characters of Unicode General Category [Cf], such as ‘U+200E’ (Left-to-Right Mark), but excluding characters that have graphic images, such as ‘U+00AD’ (Soft Hyphen).
Characters for there is no suitable font, or which cannot be encoded by the terminal’s coding system.
The method symbol should be one of
hex-code. These have
the same meanings as in glyphless-char-display, above.