Bug 473319 - On X11, when a screen is mirrored to another one with a different resolution it's not scaled correctly
Summary: On X11, when a screen is mirrored to another one with a different resolution ...
Status: CONFIRMED
Alias: None
Product: KScreen
Classification: Plasma
Component: common (show other bugs)
Version: 5.27.7
Platform: Arch Linux Linux
: NOR normal
Target Milestone: ---
Assignee: kscreen-bugs-null@kde.org
URL:
Keywords: X11-only
Depends on:
Blocks:
 
Reported: 2023-08-12 18:33 UTC by QuetschKuh
Modified: 2025-02-24 17:59 UTC (History)
2 users (show)

See Also:
Latest Commit:
Version Fixed In:
Sentry Crash Report:


Attachments
Shows the problem in four images. Top ones are the settings, and bottom ones are the physical screen being replicated on (1.80 MB, image/png)
2023-08-12 18:33 UTC, QuetschKuh
Details

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Description QuetschKuh 2023-08-12 18:33:48 UTC
Created attachment 160926 [details]
Shows the problem in four images. Top ones are the settings, and bottom ones are the physical screen being replicated on

SUMMARY
When replicating screen 1 onto screen 2, with screen 1 having a larger resolution than screen 2, screen 2 will only show parts of screen 1.

STEPS TO REPRODUCE
1. Have two screens with different resolutions
2. Go into Display Configuration
3. Select the smaller screen
4. Set "Replica of:" to the larger screen

OBSERVED RESULT
The replicated screen only shows the top left part of the original image

EXPECTED RESULT
The screen should be scaled down to match the target resolution

SOFTWARE/OS VERSIONS
Linux: Archlinux
Kernel: 6.4.7-arch1-3
KDE Plasma Version: 5.27.7
KDE Frameworks Version: 5.108.0
Qt Version: 5.15.10

ADDITIONAL INFORMATION
None
Comment 1 Nate Graham 2023-08-13 20:18:09 UTC
Are you using the Wayland session or the X11 session?
Comment 2 QuetschKuh 2023-08-14 07:48:33 UTC
I'm using X11
Comment 3 Nate Graham 2023-08-14 19:24:02 UTC
I had a feeling.

This use case is not well-supported on X11. In particular, the mixed-DPI multi-screen use case is explicitly unsupported. For that, we recommend using the Wayland session.

However in this case maybe there's some way we can improve the situation simply by setting both screens to the same resolution--if there's any intersection between the resolutions that each screen supports. If there isn't, then there's not much we can do with the existing X11 backend.

Regardless, I recommend using the Wayland session if a better multi-screen experience is important.
Comment 4 TraceyC 2025-02-24 17:59:15 UTC
Adding the x11-only keyword