Other Display Specifications
----------------------------
`(image . IMAGE-PROPS)'
This is in fact an image descriptor (Note:Images). When used
as a display specification, it means to display the image instead
of the text that has the display specification.
`((margin nil) STRING)'
`STRING'
A display specification of this form means to display STRING
instead of the text that has the display specification, at the same
position as that text. This is a special case of marginal display
(Note:Display Margins).
Recursive display specifications are not supported, i.e. string
display specifications that have a display specification property
themselves.
`(space-width FACTOR)'
This display specification affects all the space characters within
the text that has the specification. It displays all of these
spaces FACTOR times as wide as normal. The element FACTOR should
be an integer or float. Characters other than spaces are not
affected at all; in particular, this has no effect on tab
characters.
`(height HEIGHT)'
This display specification makes the text taller or shorter. Here
are the possibilities for HEIGHT:
`(+ N)'
This means to use a font that is N steps larger. A "step" is
defined by the set of available fonts--specifically, those
that match what was otherwise specified for this text, in all
attributes except height. Each size for which a suitable
font is available counts as another step. N should be an
integer.
`(- N)'
This means to use a font that is N steps smaller.
a number, FACTOR
A number, FACTOR, means to use a font that is FACTOR times as
tall as the default font.
a symbol, FUNCTION
A symbol is a function to compute the height. It is called
with the current height as argument, and should return the
new height to use.
anything else, FORM
If the HEIGHT value doesn't fit the previous possibilities,
it is a form. Emacs evaluates it to get the new height, with
the symbol `height' bound to the current specified font
height.
`(raise FACTOR)'
This kind of display specification raises or lowers the text it
applies to, relative to the baseline of the line.
FACTOR must be a number, which is interpreted as a multiple of the
height of the affected text. If it is positive, that means to
display the characters raised. If it is negative, that means to
display them lower down.
If the text also has a `height' display specification, that does
not affect the amount of raising or lowering, which is based on the
faces used for the text.