Bug 459595

Summary: KScreen allows to overlap screens
Product: [Applications] systemsettings Reporter: postix <postix>
Component: kcm_kscreenAssignee: kscreen-bugs-null <kscreen-bugs-null>
Status: RESOLVED INTENTIONAL    
Severity: wishlist CC: lemmyg, nate, plasma-bugs-null, postix
Priority: NOR    
Version First Reported In: 5.25.90   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Screenshot for illustration, showing a partial overlap

Description postix 2022-09-24 10:23:49 UTC
SUMMARY

In the kscreens kcm one can arrange the positions of the screens.

While it makes sense to put screens next to each other at some edge, putting them above another seems less useful, covers the screen below in the kcm and also causes visual glitches.

Therefore this should be prevented. For instance, in Gnome (42) placing a screen above another screen is not possible in the first place.

SOFTWARE/OS VERSIONS 
Linux/KDE Plasma: openSUSE TW
KDE Plasma Version: Plasma 5.25.5+
KDE Frameworks Version:  5.98
Qt Version: 5.15.5
Comment 1 Nate Graham 2022-09-26 17:04:49 UTC
When you say "stack", do you mean:
1. 100% cover one screen with another
2. any overlap between screens?
Comment 2 postix 2022-09-26 17:07:46 UTC
(In reply to Nate Graham from comment #1)
> When you say "stack", do you mean:
> 1. 100% cover one screen with another
> 2. any overlap between screens?

Yes, this describes it perfectly.
Comment 3 postix 2022-09-26 17:09:43 UTC
Created attachment 152440 [details]
Screenshot for illustration, showing a partial overlap
Comment 4 Nate Graham 2022-09-27 14:24:54 UTC
So you're saying that you think even partial overlaps don't make sense?

When if your physical screen arrangement involves some overlap? This would probably never happen with desktop monitors, but if you have a laptop connected to a desktop monitor, it's not inconceivable that the laptop screen would overlap part of the corner of the desktop screen. Indeed, I find myself in this situation rather frequently.
Comment 5 postix 2022-09-27 15:33:45 UTC
(In reply to Nate Graham from comment #4)
> So you're saying that you think even partial overlaps don't make sense?

Fortunately I was always able to avoid it, also since it's not implemented in Gnome (42), on Windows 10 or MacOS.

However, I just gave it a try on Plasma 5.25.5 Wayland and plugged in a FullHD 24" screen into my 14" laptop with 2560x1440@150% and positioned both so that a smaller corner of the external display was covered by the laptop's screen.

Obviously I ran into scaling issues, as I'd need a factor of 1 1/3 to make both scale equally and the UX is not the best, since by design screen space is shared.

Nonetheless, I can see your point now.  ;-)
So, maybe we should close this report and I only open one to improve the case, where one cannot see directly that one screen fully covers a second one in the KCM?
Comment 6 Nate Graham 2022-09-28 15:59:08 UTC
Yes, I agree that letting screens fully overlap makes no sense.

Even letting them overlap 50% doesn't really make sense either. That's not a sensible physical layout. Really I can only think of a use case for like a 25% overlap at most, to cover the case of a laptop sitting on a desk that partially covers the corner of an external screen. Any more overlap than that, and any sane person would move the external screen a few centimeters away!

So I think requesting that could make sense too.