GNU bug report logs - #57150
29.0.50; [PATCH] Add test coverage for overlay modification hooks

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From: Eli Zaretskii <eliz <at> gnu.org>
To: rms <at> gnu.org
Cc: matt <at> rfc20.org, yantar92 <at> gmail.com, 57150 <at> debbugs.gnu.org
Subject: bug#57150: 29.0.50; [PATCH] Add test coverage for overlay modification hooks
Date: Wed, 17 Aug 2022 14:51:26 +0300

> From: Richard Stallman <rms <at> gnu.org>
> Cc: yantar92 <at> gmail.com, matt <at> rfc20.org, 57150 <at> debbugs.gnu.org
> Date: Tue, 16 Aug 2022 22:50:38 -0400
> 
>   > The problems with overlays in Emacs are much wider than just Org.  Our
>   > performance sucks in many cases because of that.  Just two examples
>   > that were mentioned lately in the "long-line optimizations"
>   > discussion: show-paren-mode and isearch-lazy-highlight -- each one of
>   > these two is capable of literally bringing Emacs to its knees,
>   > response-time wise.
> 
> The first question is, should these use text properties instead of
> overlays?

Text properties are less convenient when used for ephemeral
highlighting.

> Are they using many overlays to highlight many potential matches in a
> long buffer?

isearch-lazy-highlight does.

> If so, would it make sense to show, at any time, only those
> that are near point?  When you move to a far-away part of the buffer,
> it could add highlighting to the matches near there.  But maybe it
> can avoid ever trying to highlight more than a few parts of the buffer.

isearch.el already attempts to do that, but its method of detecting
what's out of the window doesn't work under truncate-lines.

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