Bug 424254 - On X11, mirroring internal laptop 4k screen to external 1080p screen shows clipped output on external screen
Summary: On X11, mirroring internal laptop 4k screen to external 1080p screen shows cl...
Status: REPORTED
Alias: None
Product: kwin
Classification: Plasma
Component: platform-x11-standalone (show other bugs)
Version: git master
Platform: Other Linux
: NOR grave
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords: multiscreen
Depends on:
Blocks:
 
Reported: 2020-07-15 19:48 UTC by Nate Graham
Modified: 2024-03-07 15:41 UTC (History)
0 users

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

Attachments
Clipped output rather than scaled output (2.20 MB, image/jpeg)
2020-07-15 19:48 UTC, Nate Graham 		Details
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Description Nate Graham 2020-07-15 19:48:22 UTC 
Created attachment 130148 [details]
Clipped output rather than scaled output

All KDE software built from source today on top of openSUSE Tumbleweed.

STEPS TO REPRODUCE
1. Have a laptop with a 4k screen
2. Set appropriate >100% scale factor in KScreen KCM (I'm using 250%)
2. Plug in an external 1080p screen via HDMI


OBSERVED RESULT
External screen shows only the top-left quarter of the internal screen. See attached screenshot.


EXPECTED RESULT
external screen shows an exact mirror of the internal screen, but scaled to fit rather than clipped.


ADDITIONAL INFORMATION
Reproduces both with and without PLASMA_USE_QT_SCALING=1 set in the environment, so it doesn't seem to be related to that.
Comment 1 Nate Graham 2020-07-15 20:22:53 UTC 
Happens on X11, but not Wayland.

Still, seems important to fix on X11 so that the use case of giving a presentation with a high resolution laptop works properly.
Comment 2 Nate Graham 2022-10-11 15:23:45 UTC 
Now happens on Wayland too; I've filed Bug 460246.