bug#32977: 26.1.50; Emacs (on gnome 3, wayland, debian buster) calculates incorrect horizontal positions

bug#32977: 26.1.50; Emacs (on gnome 3, wayland, debian buster) calculates incorrect horizontal positions

[Kai Tetzlaff]

The following happens within Gnome 3 (3.30, but also earlier versions),
Wayland on Debian Buster on a Laptop with HiDPI display with fractional
scaling factor set to 1.5.

Position frame at the left border of the display, evaluate:

    (frame-parameter (selected-frame) 'left)
    ;; -10

or

    (car (frame-position (selected-frame)))
    ;; '(+ -10)

The horizontal frame position should be 0, instead it gets reported as
-10 (indicating that part of the frame is invisible - which is not the
case). Even if the frame is positioned within the first 9 pixel
positions, the result is still negative.


In GNU Emacs 26.1.50 (build 6, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2018-09-15 built on moka
Repository revision: 20ecc5266e1ffb1cff3e31475631b5c76b99e997
Windowing system distributor 'The X.Org Foundation', version 11.0.12001000
System Description:	Debian GNU/Linux testing (buster)

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Auto-saving...
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Quit
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Auto-saving...done
Saving file /home/kail/.emacs.d/init/user/kai_tetzlaff.el...
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bug#32977: 26.1.50; Emacs (on gnome 3, wayland, debian buster) calculates incorrect horizontal positions

[Lars Ingebrigtsen]

Kai Tetzlaff <kai.tetzlaff@web.de> writes:

> The following happens within Gnome 3 (3.30, but also earlier versions),
> Wayland on Debian Buster on a Laptop with HiDPI display with fractional
> scaling factor set to 1.5.
>
> Position frame at the left border of the display, evaluate:
>
>     (frame-parameter (selected-frame) 'left)
>     ;; -10
>
> or
>
>     (car (frame-position (selected-frame)))
>     ;; '(+ -10)

(This bug report unfortunately got no response at the time.)

I can reproduce this bug in Emacs 28:

(set-frame-position (selected-frame) 0 0)
=> t
(frame-position (selected-frame))
=> (-10 . 66)

If I do this, I can clearly see that the frame isn't outside the screen
(i.e., I can see other windows between the Emacs frame and the border of
the screen):

(set-frame-position (selected-frame) 9 0)
=> t

But still:

(frame-position (selected-frame))
=> (-1 . 66)

This is a Debian bullseye system with Gnome Shell.

Anybody got an idea what's going on here?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#32977: 26.1.50; Emacs (on gnome 3, wayland, debian buster) calculates incorrect horizontal positions

[Robert Pluim]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> (This bug report unfortunately got no response at the time.)
>
> I can reproduce this bug in Emacs 28:
>
> (set-frame-position (selected-frame) 0 0)
> => t
> (frame-position (selected-frame))
> => (-10 . 66)
>
> If I do this, I can clearly see that the frame isn't outside the screen
> (i.e., I can see other windows between the Emacs frame and the border of
> the screen):
>
> (set-frame-position (selected-frame) 9 0)
> => t
>
> But still:
>
> (frame-position (selected-frame))
> => (-1 . 66)
>
> This is a Debian bullseye system with Gnome Shell.
>
> Anybody got an idea what's going on here?

This is under X, right? GTK/GDK's idea of window coordinates and
Emacs's idea sometimes disagree, especially when using Gnome Shell.

The answer is pure gtk, but in the pure gtk branch under Wayland,
frame-position will return (0 . 0) however the frame will not actually
move when you call set-frame-position.

pure gtk under X moves the frame, *and* returns (0 . 0), so I guess
this should be filed as a bug against the pure gtk branch.

Robert

bug#32977: 26.1.50; Emacs (on gnome 3, wayland, debian buster) calculates incorrect horizontal positions

[martin rudalics]

 > I can reproduce this bug in Emacs 28:
 >
 > (set-frame-position (selected-frame) 0 0)
 > => t
 > (frame-position (selected-frame))
 > => (-10 . 66)

-10 is the position of the WM border.  I tried to describe that in
Bug#40817.  The frame proper starts at 0.

 > If I do this, I can clearly see that the frame isn't outside the screen
 > (i.e., I can see other windows between the Emacs frame and the border of
 > the screen):
 >
 > (set-frame-position (selected-frame) 9 0)
 > => t
 >
 > But still:
 >
 > (frame-position (selected-frame))
 > => (-1 . 66)
 >
 > This is a Debian bullseye system with Gnome Shell.
 >
 > Anybody got an idea what's going on here?

Mutter doesn't like us.

martin

bug#32977: 26.1.50; Emacs (on gnome 3, wayland, debian buster) calculates incorrect horizontal positions

[Lars Ingebrigtsen]

martin rudalics <rudalics@gmx.at> writes:

> -10 is the position of the WM border.  I tried to describe that in
> Bug#40817.  The frame proper starts at 0.

I see.  Would it make sense to mention something about this in the
`frame-position' doc string.  I.e., that the value is (somewhat)
system-dependent?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#32977: 26.1.50; Emacs (on gnome 3, wayland, debian buster) calculates incorrect horizontal positions

[martin rudalics]

 >> -10 is the position of the WM border.  I tried to describe that in
 >> Bug#40817.  The frame proper starts at 0.
 >
 > I see.  Would it make sense to mention something about this in the
 > `frame-position' doc string.  I.e., that the value is (somewhat)
 > system-dependent?

So far, I haven't been able to find a suitable description of what these
WMs do or want to do.  Hence any recommendation (and that's what we
probably should provide in order to be of any assistance) would have to
be based on some sort of second guessing.  Maybe it's also an X issue
and using pgtk builds will improve things.

martin

bug#32977: 26.1.50; Emacs (on gnome 3, wayland, debian buster) calculates incorrect horizontal positions

[Lars Ingebrigtsen]

martin rudalics <rudalics@gmx.at> writes:

>> I see.  Would it make sense to mention something about this in the
>> `frame-position' doc string.  I.e., that the value is (somewhat)
>> system-dependent?
>
> So far, I haven't been able to find a suitable description of what these
> WMs do or want to do.  Hence any recommendation (and that's what we
> probably should provide in order to be of any assistance) would have to
> be based on some sort of second guessing.  Maybe it's also an X issue
> and using pgtk builds will improve things.

I think just mentioning that there's a quirk here in the doc string is
helpful, so I've now done that in the `frame-position' doc string.

With that, I'm closing this bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no