Re: [dev] [dwm] dwm breaks on synchronized screens

From: v4hn <>
Date: Fri, 12 Nov 2021 11:53:30 +0100

Hey everyone,

I can verify issues with multi-monitor setups when screens are overlapping/mirrored.
I usually avoid this by working with independent screens as well.

With XINERAMA support in dwm you can dynamically configure monitors via xrandr.
If you configure them to coincide, e.g.,
`xrandr --output <display2> --auto --same-as <display1>`,
it seems that at least for some configurations dwm creates separate `Monitor` structs
unconditionally and you can cycle through the monitors via shortcuts.
But because they overlap you will not even see the bar for one of the monitors
and window management is screwed up as well.
Notice that there is actually logic in the code that should prevent this
for the case where virtual screen positions coincide. (`isuniquegeom`)

Along the same lines of code I recently noticed that dynamically adding an
independent/unique screen via xrandr can change the Monitor->physical screen association
and thus move all existing windows to a different physical screen.
Maybe it's a different bug altogether though, I did not have time to investigate.


On Fri, Nov 12, 2021 at 09:18:22AM +0100, Laslo Hunhold wrote:
> On Thu, 11 Nov 2021 19:34:08 +0100
> Thomas Oltmann <> wrote:
> Dear Thomas,
> > What do I do about this?
> > Is it even a bug or just me using dwm for stuff it's not intended to
> > do? One way or another, how can I do my presentations without
> > fighting the WM all the time?
> do you have a way so we can reproduce this?
> With best regards
> Laslo

Michael 'v4hn' Görner, M.Sc. Cognitive Science, PhD Student
Universität Hamburg
Faculty of Mathematics, Informatics and Natural Sciences
Department of Informatics
Group Technical Aspects of Multimodal Systems
Vogt-Kölln-Straße 30
D-22527 Hamburg
Room: F-315
Phone: +49 40 42883-2432

Received on Fri Nov 12 2021 - 11:53:30 CET

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