bug#65840: 29.1; desktop-load moves frames to the right and down

[Eli Zaretskii]

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> From: Christian Tanzer <tanzer@gg32.com>
> Date: Sat, 9 Sep 2023 14:47:34 +0100
> 
> On 09.09.2023, at 13:59, Eli Zaretskii <eliz@gnu.org> wrote:
> > 
> >> Date: Sat, 09 Sep 2023 12:32:42 -0000
> >> From: tanzer--- via "Bug reports for GNU Emacs,
> >> the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> >> 
> >> In GNU Emacs 29.1, desktop-load moves frames to the right and down.
> > 
> > This is probably specific to macOS, or maybe even to your window
> > manager, because it doesn't happen to me, and I'm a heavy user of
> > desktop.el.
> 
> I am using plain macOS without any additional window manager.
> 
> > When you say "In GNU Emacs 29.1", do you mean this issue is specific
> > to Emacs 29.1, and does not happen with Emacs 28 and older?
> 
> It doesn’t happen on 28.2 or older. 

So it could be due to massive changes in the macOS display code we did
in Emacs 29.

> 
> >> The three attachements show the shifts in frame positions:
> >> 
> >> - .emacs.desktop.1 contains the correct frame positions after using
> >>  `desktop-save` and copying .emacs.desktop to .emacs.desktop.1
> >> 
> >> - Loading .emacs.desktop.1 into Emacs 29 results in the frames being
> >>  shifted. On exiting Emacs 29, the shifted positions are stored in
> >>  .emacs.desktop and copied to .emacs.desktop.2.
> >> 
> >> - Loading .emacs.desktop.2 into Emacs 29 results in the frames being
> >>  shifted again. On exiting Emacs 29, the shifted positions are stored
> >>  in .emacs.desktop and copied to .emacs.desktop.3.
> >> 
> >> - Loading any of these .emacs.desktop files into Emacs 28.2 results in
> >>  the expected frame positions (in case of .2 and .3 the positions
> >>  incorrectly shifted to by Emacs 29).
> > 
> > You are aware, I hope, that on X and similar GUI systems, the
> > coordinates of the frames we request from the window-manager are
> > advisory: the WM doesn't have to adhere to what we request.  I'm not
> > sure what you see is not a manifestation of that.
> 
> I am aware of that but there is a clear regression here. 
> 
> Loading the same .emacs.desktop in 28.2 works as expected while in 29.1 all 
> frames are shifted (one of my test frames first to behind the dock and then 
> partly outside the visible screen). In 29.1, each load/save cycle of the 
> .emacs.desktop will shift all the frames a bit farther right and down. 
> 
> If the WM was the real culprit I would expect the version of Emacs to be 
> irrelevant!
> 
> For me, the desktop machinery started getting flaky with Emacs 28.1 which 
> crashes when reading larger desktop files written by Emacs 27. Emacs 29.1 
> still shows that behavior. Unfortunately I have not been able to find a small 
> reproducible test case for these crashes.
> 
> Both 28.2 and 29.1 work with a smaller desktop file that I created with 29.1 
> but then I noticed the frames being shifted by each restart of 29.1, which 
> 28.2 doesn’t do.
> 
> I don’t want to be stuck with Emacs 27 and I am getting nervous about the 
> desktop problems of 28 and 29.

Hopefully, the advice posted by Po Lu could lead us to understanding
the problem.