From eb381459b2fac570f17b944455262e6426397b8f Mon Sep 17 00:00:00 2001 From: Eli Zaretskii Date: Sat, 11 Apr 2009 08:54:08 +0000 Subject: [PATCH] (Overlays): Overlays don't scale well. See http://lists.gnu.org/archive/html/emacs-devel/2009-04/msg00243.html. --- doc/lispref/display.texi | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi index b017ce70704..a6c09cd0e30 100644 --- a/doc/lispref/display.texi +++ b/doc/lispref/display.texi @@ -1148,6 +1148,14 @@ object that belongs to a particular buffer, and has a specified 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 +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 +take a time that is proportional to the number of overlays in the +buffer). If you need to affect the visual appearance of many portions +in the buffer, we recommend to use text properties. + An overlay uses markers to record its beginning and end; thus, editing the text of the buffer adjusts the beginning and end of each overlay so that it stays with the text. When you create the overlay, -- 2.30.2