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Document :box attribute caveats when used on display strings

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* doc/lispref/display.texi (Replacing Specs, Face Attributes):
Mention special considerations when a display string has a
':box' face attribute identical to the surrounding buffer text.
Suggested by JD Smith <jdtsmith@gmail.com>.  (Bug#70637)
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Eli Zaretskii 2024-05-18 12:15:21 +03:00
parent ca17bc8dd0
commit df1a9e42ba
1 changed files with 33 additions and 0 deletions
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doc/lispref/display.texi
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@ -2747,6 +2747,11 @@ being pressed. If it is @code{pressed-button}, the box looks like a
@code{flat-button} or omitted, a plain 2D box is used. @code{flat-button} or omitted, a plain 2D box is used.
@end table @end table
If you use the @code{:box} face attribute on strings displayed instead
of buffer text via the @code{display} text property, special
considerations might apply if the surrounding buffer text also has the
@code{:box} face attribute. @xref{Replacing Specs}.
@item :inverse-video @item :inverse-video
Whether or not characters should be displayed in inverse video. The Whether or not characters should be displayed in inverse video. The
value should be @code{t} (yes) or @code{nil} (no). value should be @code{t} (yes) or @code{nil} (no).
@ -5266,6 +5271,34 @@ characters get a second string (@code{concat} creates a new string
object), so they are replaced with one @samp{A}; and so on. Thus, the object), so they are replaced with one @samp{A}; and so on. Thus, the
ten characters appear as five A's. ten characters appear as five A's.
@cindex box face attribute, and @code{display} properties
Note: Using @code{:box} face attribute (@pxref{Face Attributes}) on a
replacing @code{display} string that is adjacent to normal text with
the same @code{:box} style can lead to display artifacts when moving
the cursor across the text with this face attribute. These can be
avoided by applying the @code{:box} attribute directly to the text
being replaced, rather than (or in addition to) the @code{display}
string itself. Here's an example:
@smallexample
@group
;; Causes display artifacts when moving the cursor across text
(progn
(put-text-property 1 2 'display (propertize " [" 'face '(:box t)))
(put-text-property 2 3 'face '(:box t))
(put-text-property 3 4 'display (propertize "] " 'face '(:box t))))
@end group
@group
;; No display artifacts due to `:box'
(progn
(add-text-properties 1 2 '(face (:box t) display " ["))
(put-text-property 2 3 'face '(:box t))
(add-text-properties 3 4 '(face (:box t) display "] ")))
@end group
@end smallexample
@node Specified Space @node Specified Space
@subsection Specified Spaces @subsection Specified Spaces
@cindex spaces, specified height or width @cindex spaces, specified height or width