38.21.1 Display Table Format

A display table is actually a char-table (see Char-Tables) with display-table as its subtype.

The ordinary elements of the display table are indexed by character codes; the element at index c says how to display the character code c. The value should be nil or a vector of the glyphs to be output (see Glyphs). nil says to display the character c according to the usual display conventions (see Usual Display).

Warning: if you use the display table to change the display of newline characters, the whole buffer will be displayed as one long “line.”

The display table also has six “extra slots” which serve special purposes. Here is a table of their meanings; nil in any slot means to use the default for that slot, as stated below.

0

The glyph for the end of a truncated screen line (the default for this is ‘$’). See Glyphs. On graphical terminals, Emacs uses arrows in the fringes to indicate truncation, so the display table has no effect.

1

The glyph for the end of a continued line (the default is ‘\’). On graphical terminals, Emacs uses curved arrows in the fringes to indicate continuation, so the display table has no effect.

2

The glyph for indicating a character displayed as an octal character code (the default is ‘\’).

3

The glyph for indicating a control character (the default is ‘^’).

4

A vector of glyphs for indicating the presence of invisible lines (the default is ‘...’). See Selective Display.

5

The glyph used to draw the border between side-by-side windows (the default is ‘|’). See Splitting Windows. This takes effect only when there are no scroll bars; if scroll bars are supported and in use, a scroll bar separates the two windows.

For example, here is how to construct a display table that mimics the effect of setting ctl-arrow to a non-nil value:

     (setq disptab (make-display-table))
     (let ((i 0))
       (while (< i 32)
         (or (= i ?\t) (= i ?\n)
             (aset disptab i (vector ?^ (+ i 64))))
         (setq i (1+ i)))
       (aset disptab 127 (vector ?^ ??)))