Commit c1cbc25a authored by Kim F. Storm's avatar Kim F. Storm
Browse files

Document new :width and :align-to features.

parent ab24c127
......@@ -1850,6 +1850,65 @@ configuration files.
* Lisp Changes in Emacs 21.4
** The display space :width and :align-to text properties are now
supported on text terminals.
** Enhancements to stretch display properties
The display property stretch specification form `(space PROPS)', where
PROPS is a property list now allows pixel based width and height
specifications, as well as enhanced horisontal text alignment.
The value of these properties can now be a (primitive) expression
which is evaluated during redisplay. The following expressions
are supported:
EXPR ::= NUM | (NUM) | UNIT | ELEM | POS | IMAGE | FORM
NUM ::= INTEGER | FLOAT | SYMBOL
UNIT ::= in | mm | cm | width | height
ELEM ::= left-fringe | right-fringe | left-margin | right-margin
| scroll-bar | text
POS ::= left | center | right
FORM ::= (NUM . EXPR) | (OP EXPR ...)
OP ::= + | -
The form `NUM' specifies a fractional width or height of the default
frame font size. The form `(NUM)' specifies an absolute number of
pixels. If a symbol is specified, its buffer-local variable binding
is used. The `in', `mm', and `cm' units specifies the number of
pixels per inch, milli-meter, and centi-meter, resp. The `width' and
`height' units correspond to the width and height of the current face
font. An image specification corresponds to the width or height of
the image.
The `left-fringe', `right-fringe', `left-margin', `right-margin',
`scroll-bar', and `text' elements specify to the width of the
corresponding area of the window.
The `left', `center', and `right' positions can be used with :align-to
to specify a position relative to the left edge, center, or right edge
of the text area. One of the above window elements (except `text')
can also be used with :align-to to specify that the position is
relative to the left edge of the given area. Once the base offset for
a relative position has been set (by the first occurrence of one of
these symbols), further occurences of these symbols are interpreted as
the width of the area.
For example, to align to the center of the left-margin, use
:align-to (+ left-margin (0.5 . left-margin))
If no specific base offset is set for alignment, it is always relative
to the left edge of the text area. For example, :align-to 0 in a
header-line aligns with the first text column in the text area.
The value of the form `(NUM . EXPR)' is the value of NUM multiplied by
the value of the expression EXPR. For example, (2 . in) specifies a
width of 2 inches, while (0.5 . IMAGE) specifies half the width (or
height) of the specified image.
The form `(+ EXPR ...)' adds up the value of the expressions.
The form `(- EXPR ...)' negates or subtracts the value of the expressions.
** New macro with-local-quit temporarily sets inhibit-quit to nil for use
around potentially blocking or long-running code in timers
and post-command-hooks.
......
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