Commit c0f5a3b3 authored by Eli Zaretskii's avatar Eli Zaretskii
Browse files

Describe and index "empty overlays".

* doc/lispref/display.texi (Overlays): Improve indexing.
(Managing Overlays): Describe "empty" overlays.
(Overlay Properties, Finding Overlays): Add cross-reference to
where empty overlays are described.
parent 8f1eda7a
......@@ -1310,6 +1310,7 @@ beginning and end. It also has properties that you can examine and set;
these affect the display of the text within the overlay.
@cindex scalability of overlays
@cindex overlays, scalability
The visual effect of an overlay is the same as of the corresponding
text property (@pxref{Text Properties}). However, due to a different
implementation, overlays generally don't scale well (many operations
......@@ -1351,6 +1352,15 @@ and @var{end} must specify buffer positions; they may be integers or
markers. If @var{buffer} is omitted, the overlay is created in the
current buffer.
@cindex empty overlay
@cindex overlay, empty
An overlay whose @var{start} and @var{end} specify the same buffer
position is known as @dfn{empty}. A non-empty overlay can become
empty if the text between its @var{start} and @var{end} is deleted.
When that happens, the overlay is by default not deleted, but you can
cause it to be deleted by giving it the @samp{evaporate} property
(@pxref{Overlay Properties, evaporate property}).
The arguments @var{front-advance} and @var{rear-advance} specify the
marker insertion type for the start of the overlay and for the end of
the overlay, respectively. @xref{Marker Insertion Types}. If they
......@@ -1720,8 +1730,11 @@ line at display-time. @xref{Truncation}.
@kindex evaporate @r{(overlay property)}
If this property is non-@code{nil}, the overlay is deleted automatically
if it becomes empty (i.e., if its length becomes zero). If you give
an empty overlay a non-@code{nil} @code{evaporate} property, that deletes
it immediately.
an empty overlay (@pxref{Managing Overlays, empty overlay}) a
non-@code{nil} @code{evaporate} property, that deletes it immediately.
Note that, unless an overlay has this property, it will not be deleted
when the text between its starting and ending positions is deleted
from the buffer.
@item keymap
@cindex keymap of character (and overlays)
......@@ -1777,10 +1790,10 @@ overlays that specify property @var{prop} for the character at point:
This function returns a list of the overlays that overlap the region
@var{beg} through @var{end}. ``Overlap'' means that at least one
character is contained within the overlay and also contained within the
specified region; however, empty overlays are included in the result if
they are located at @var{beg}, strictly between @var{beg} and @var{end},
or at @var{end} when @var{end} denotes the position at the end of the
buffer.
specified region; however, empty overlays (@pxref{Managing Overlays,
empty overlay}) are included in the result if they are located at
@var{beg}, strictly between @var{beg} and @var{end}, or at @var{end}
when @var{end} denotes the position at the end of the buffer.
@end defun
@defun next-overlay-change pos
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment