GNU bug report logs - #12956
24.2; Move hl-line-mode to display engine so performance reason.

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Oleksandr Gavenko <gavenkoa <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.2; Move hl-line-mode to display engine so performance reason.
Date: Thu, 22 Nov 2012 00:17:02 +0200

From http://debbugs.gnu.org/cgi/bugreport.cgi?bug=12927

> > Also I found that "(global-hl-line-mode 1)" slow down scrolling in CC-mode
> > enabled buffers in two or more times. Do I need report a bug?

> No, this is expected.  hl-line-mode adds itself to post-command-hook,
> and moves its overlay after each command that changes the current
> line.  What this does is completely disable the redisplay
> optimizations used when only the cursor moves without any other
> changes to the text, because moving an overlay requires a thorough
> redisplay of the window, which is more expensive.

> The only bug report that I can think of is a feature request to move
> hl-line-mode into the display engine, because the display engine
> knowns very well where's the current line (when it decides where to
> display the cursor), and can do this highlighting better and much more
> efficiently.

-- 
Best regards!

Message #12 received at 12956 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Oleksandr Gavenko <gavenkoa <at> gmail.com>
Cc: 12956 <at> debbugs.gnu.org
Subject: Re: bug#12956: 24.2;
	Move hl-line-mode to display engine so performance reason.
Date: Thu, 22 Nov 2012 05:45:42 +0200

> From: Oleksandr Gavenko <gavenkoa <at> gmail.com>
> Date: Thu, 22 Nov 2012 00:17:02 +0200
> 
> >From http://debbugs.gnu.org/cgi/bugreport.cgi?bug=12927
> 
> > > Also I found that "(global-hl-line-mode 1)" slow down scrolling in CC-mode
> > > enabled buffers in two or more times. Do I need report a bug?
> 
> > No, this is expected.  hl-line-mode adds itself to post-command-hook,
> > and moves its overlay after each command that changes the current
> > line.  What this does is completely disable the redisplay
> > optimizations used when only the cursor moves without any other
> > changes to the text, because moving an overlay requires a thorough
> > redisplay of the window, which is more expensive.
> 
> > The only bug report that I can think of is a feature request to move
> > hl-line-mode into the display engine, because the display engine
> > knowns very well where's the current line (when it decides where to
> > display the cursor), and can do this highlighting better and much more
> > efficiently.

This is a duplicate of 12953.

Message #17 received at 12956 <at> debbugs.gnu.org (full text, mbox):

From: Juanma Barranquero <lekktu <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 12956 <at> debbugs.gnu.org, Oleksandr Gavenko <gavenkoa <at> gmail.com>
Subject: Re: bug#12956: 24.2; Move hl-line-mode to display engine so
	performance reason.
Date: Thu, 22 Nov 2012 22:00:31 +0100

On Thu, Nov 22, 2012 at 4:45 AM, Eli Zaretskii <eliz <at> gnu.org> wrote:

> This is a duplicate of 12953.

It's already merged.

    Juanma

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