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Explain about conventioal use of t as `invisible' property

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and how `add-to-invisibility-spec' protects that.
This commit is contained in:
Richard M. Stallman 2002-12-23 18:13:17 +00:00
parent 175e9712b7
commit 31b0520f82
1 changed files with 15 additions and 9 deletions
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24
lispref/display.texi
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@ -339,7 +339,9 @@ text property (@pxref{Text Properties}) or a property of an overlay
In the simplest case, any non-@code{nil} @code{invisible} property makes
a character invisible. This is the default case---if you don't alter
the default value of @code{buffer-invisibility-spec}, this is how the
@code{invisible} property works.
@code{invisible} property works. You should normally use @code{t}
as the value of the @code{invisible} property if you don't plan
to set @code{buffer-invisibility-spec} yourself.
More generally, you can use the variable @code{buffer-invisibility-spec}
to control which values of the @code{invisible} property make text
@ -387,19 +389,23 @@ by a visible newline, it displays an ellipsis.
@code{buffer-invisibility-spec} and removing elements from it.
@defun add-to-invisibility-spec element
Add the element @var{element} to @code{buffer-invisibility-spec}
(if it is not already present in that list).
This function adds the element @var{element} to
@code{buffer-invisibility-spec} (if it is not already present in that
list). If @code{buffer-invisibility-spec} was @code{t}, it changes to
a list, @code{(t)}, so that text whose @code{invisible} property
is @code{t} remains invisible.
@end defun
@defun remove-from-invisibility-spec element
Remove the element @var{element} from @code{buffer-invisibility-spec}.
This does nothing if @var{element} is not in the list.
This removeds the element @var{element} from
@code{buffer-invisibility-spec}. This does nothing if @var{element}
is not in the list.
@end defun
One convention about the use of @code{buffer-invisibility-spec} is
that a major mode should use the mode's own name as an element of
@code{buffer-invisibility-spec} and as the value of the @code{invisible}
property:
A convention for use of @code{buffer-invisibility-spec} is that a
major mode should use the mode's own name as an element of
@code{buffer-invisibility-spec} and as the value of the
@code{invisible} property:
@example
;; @r{If you want to display an ellipsis:}