display text property (or overlay property) is used to
insert images into text, and to control other aspects of how text
displays. The value of the
display property should be a
display specification, or a list or vector containing several display
specifications. Display specifications in the same
property value generally apply in parallel to the text they cover.
If several sources (overlays and/or a text property) specify values
display property, only one of the values takes effect,
following the rules of
get-char-property. See Examining Properties.
Some of the display specifications allow inclusion of Lisp forms,
which are evaluated at display time. This could be unsafe in certain
situations, e.g., when the display specification was generated by some
external program/agent. Wrapping a display specification in a list
that begins with the special symbol
disable-eval, as in
), will disable evaluation of any
Lisp in spec, while still supporting all the other display
The rest of this section describes several kinds of display specifications and what they mean.