Bug 492310

Summary: On X11, wallpaper on secondary monitor is cropped when primary monitor is configured to be vertically higher than secondary
Product: [Plasma] plasmashell Reporter: Majenko <matt+kde>
Component: Image & Slideshow wallpaper pluginsAssignee: Plasma Bugs List <plasma-bugs-null>
Status: RESOLVED UNMAINTAINED    
Severity: normal CC: kdedev, nate, notmart, qydwhotmail, xaver.hugl
Priority: NOR Keywords: multiscreen, X11-only
Version First Reported In: 6.1.4   
Target Milestone: 1.0   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Desktop crop with wallpaper settings

Description Majenko 2024-08-28 11:16:18 UTC
SUMMARY

When you have two monitors side by side, and one is offset vertically, if the "primary" monitor is the higher of the two the secondary monitor has its wallpaper cut off.

STEPS TO REPRODUCE
1. Set up two monitors in Plasma X11. Left at 0,0, right vertically offset by, say, 30% upwards. Configure suitable wallpapers on the monitors.
2. Reboot with auto-login enabled.

OBSERVED RESULT

The left-hand, lower, monitor will sometimes (though not always....) have the lower third of the wallpaper cut off. Changing the wallpaper does not fix it. However switching the left-hand monitor to be primary does fix it, then switching back to the right hand as primary the wallpaper remains intact.

EXPECTED RESULT

All the wallpaper....

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.1.4
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2
Kernel Version: 6.10.6-arch1-1 (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i3-10105 CPU @ 3.70GHz
Memory: 15.4 GiB of RAM
Graphics Processor: NVIDIA GeForce GTX 1050 Ti/PCIe/SSE2


ADDITIONAL INFORMATION
Comment 1 Nate Graham 2024-08-28 18:25:44 UTC
Cannot reproduce on Wayland with current git master.
Comment 2 Majenko 2024-08-28 18:27:24 UTC
(In reply to Nate Graham from comment #1)
> Cannot reproduce on Wayland with current git master.

This is most likely an X11-only bug.
Comment 3 TraceyC 2024-08-28 19:39:11 UTC
I'm unable to reproduce this on X11 with 6.1.4 or git-master with the same settings
Do you mind sharing a screenshot of the settings screen for the wallpaper on the secondary monitor (where the wallpaper is sometimes cut off)?
I had the wallpaper set to an image that was scaled.
Comment 4 Majenko 2024-08-28 19:46:23 UTC
Created attachment 173057 [details]
Desktop crop with wallpaper settings
Comment 5 Majenko 2024-08-28 19:47:43 UTC
(In reply to TraceyC from comment #3)
> I'm unable to reproduce this on X11 with 6.1.4 or git-master with the same
> settings
> Do you mind sharing a screenshot of the settings screen for the wallpaper on
> the secondary monitor (where the wallpaper is sometimes cut off)?
> I had the wallpaper set to an image that was scaled.

Better than that, I can show it with the wallpaper copping happening :)

TLDOA:

Layout: Folder View,
Wallpaper type: Image
Positioning: Scaled and Cropped

Changing the positioning has no effect on the cropping.
Comment 6 TraceyC 2024-08-29 20:03:36 UTC
Thank you for the screenshot and additional detail. I'm still not able to reproduce this, after quite a few reboots. 
Something I did notice is that when the wallpaper first loads, the image on the lower, smaller screen is cut off as in your screenshot. After a moment, the displays are redrawn and the wallpapers look normal. I'm guessing your system isn't doing that redraw, or it's not redrawing properly.

I'll leave this open in case someone else is able to reproduce or dig further.
Comment 7 TraceyC 2024-08-29 20:18:34 UTC
Out of curiosity, I tried reproducing with the specific wallpaper you're using, and I am seeing similar behavior. I set both displays to use that. I had tried a few other stock and custom-added wallpapers before, when I couldn't reproduce

It is not necessary to enable auto-login
I can reproduce on git-master, almost every login
On my system, it's the larger / higher monitor where the wallpaper is cut off
Comment 8 Majenko 2024-08-29 20:22:43 UTC
It's a puzzler, for sure. I've done a bit more experimentation and, on my system:

* It only does it if the right-hand monitor is higher than the left - the other way around and it's fine.
* The higher one has to be primary.
* I have tried different themes, including Breeze, and it's the same.

Here's my monitor setup in case it helps:

Screen 0: minimum 8 x 8, current 3840 x 1622, maximum 32767 x 32767
DVI-D-0 disconnected (normal left inverted right x axis y axis)
HDMI-0 connected 1920x1200+0+422 (normal left inverted right x axis y axis) 519mm x 324mm
   1920x1200     59.95*+
   1920x1080     59.94    60.05    60.00  
   1680x1050     59.95  
   1600x1200     60.00  
   1440x900      74.98    59.89  
   1440x480      60.05  
   1280x1024     76.00    75.02    72.00    60.02  
   1280x720      60.00    59.94  
   1152x864      75.00  
   1024x768      75.03    70.07    60.00  
   800x600       75.00    72.19    60.32  
   720x480       59.94  
   640x480       75.00    72.81    59.94    59.93  
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 connected primary 1920x1200+1920+0 (normal left inverted right x axis y axis) 519mm x 324mm
   1920x1200     59.95*+
   1920x1080     59.94    60.05    60.00  
   1680x1050     59.95  
   1600x1200     60.00  
   1440x900      74.98    59.89  
   1440x480      60.05  
   1280x1024     76.00    75.02    72.00    60.02  
   1280x720      60.00    59.94  
   1152x864      75.00  
   1024x768      75.03    70.07    60.00  
   800x600       75.00    72.19    60.32  
   720x480       59.94  
   640x480       75.00    72.81    59.94    59.93  
HDMI-2-1 disconnected (normal left inverted right x axis y axis)
DP-2-1 disconnected (normal left inverted right x axis y axis)
HDMI-2-2 disconnected (normal left inverted right x axis y axis)
Comment 9 Majenko 2024-08-29 20:29:59 UTC
I tried moving the high right monitor to be on the left of the lower one instead of the right. The main problem vanished - so the high monitor has to be on the right. However in doing so lots of other strange things happened while editing the display settings - blank black wallpaper on one monitor at one point, one monitor with the wallpaper split in half and repeated, with my lower panel plonked in the middle of the screen, all very strange stuff.
Comment 10 TraceyC 2025-02-24 17:58:37 UTC
Adding the x11-only keyword
Comment 11 Nate Graham 2025-08-19 22:22:15 UTC
I'm afraid complex multi-screen configurations are known to be poorly supported on X11, and fixing this ranges between "very difficult" and "impossible" due to X11 limitations. The Wayland session offers a better multi-screen experience that also gets better because it's actively developed and maintained. If you need support for complex multi-screen arrangements, I'd recommend using use the Wayland session.