37.16.4 Other Display Specifications
Here are the other sorts of display specifications that you can use
display text property.
- Display string instead of the text that has this property.
Recursive display specifications are not supported—string's
display properties, if any, are not used.
(image . image-props
- This kind of display specification is an image descriptor (see Images).
When used as a display specification, it means to display the image
instead of the text that has the display specification.
(slice x y width height
- This specification together with
image specifies a slice
(a partial area) of the image to display. The elements y and
x specify the top left corner of the slice, within the image;
width and height specify the width and height of the
slice. Integers are numbers of pixels. A floating-point number
in the range 0.0–1.0 stands for that fraction of the width or height
of the entire image.
((margin nil) 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. It is equivalent to using just string,
but it is done as a special case of marginal display (see Display Margins).
(left-fringe bitmap [face]
(right-fringe bitmap [face]
- This display specification on any character of a line of text causes
the specified bitmap be displayed in the left or right fringes
for that line, instead of the characters that have the display
specification. The optional face specifies the colors to be
used for the bitmap. See Fringe Bitmaps, for the details.
- 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.
- This display specification makes the text taller or shorter.
Here are the possibilities for height:
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.
- 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.
- 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
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.
You can make any display specification conditional. To do that,
package it in another list of the form
Then the specification spec applies only when
condition evaluates to a non-
nil value. During the
object is bound to the string or buffer having the
buffer-position are bound to the position within
and the buffer position where the
display property was found,
respectively. Both positions can be different when
object is a