Re: How to debug emacs repaint problems?

[Eli Zaretskii <eliz@gnu.org>]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  emacs-devel@gnu.org
> Date: Sun, 15 Oct 2023 09:02:00 +0800
> 
> joakim@verona.se writes:
> 
> > If so, it appears to me that my build of emacs redraws a lot of regions
> > unecessarily. So the my question is if its possible to make Emacs show
> > some hints of which areas its redrawing. Then I would know if the
> > problem is in emacs, or elsewhere.
> >
> > The emacs 28 in my distro doesnt flicker, nor does apps such as gedit.
> 
> This is consequent upon double buffering.  Being incapable of recording
> individual damage to window back buffers, the X server uniformly damages
> the whole front buffer whenever buffers are swapped.
> 
> Should flicker be preferable to slow redisplay, disabling double
> buffering is the correct solution.  But if not, use an X connection in
> place of VNC, enabling the transfer of only drawing commands.

Since double-buffering was introduced in Emacs 26, it still cannot
fully explain why Emacs 28 doesn't show this behavior.

However, as I explained in my other message, what Joakim sees is
definitely not the result of Emacs redisplay redrawing too large
portions of the screen, because Emacs doesn't do that.  Some other
factor or software is at work here.