I have started seeing issues when set kdiff3 as my mergetool from git. Whenever my kdiff3 should display a conflict with 3 separate file sources and common output, as displayed usually from git mergetool.

I have found that happens with kdiff3-1.12.3-1.fc41.x86_64, only when --auto and -o target file is used. It displays somehow broken menus, which do not react. And transparent source panels, where no text is rendered. But the background is visible instead or some other artifacts in rendering.

This seems to happen only when I made kdiff3 maximized last time when running.

Strange is it prints warning, but it seems only when it is able to render it correctly:
The cached device pixel ratio value was stale on window update.  Please file a QTBUG which explains how to reproduce.

This happens when the text rendered is actually readable. When it is broken, no warning is printed.

Older kdiff3 version seemed to work much better.

Reproducible: Always

Steps to Reproduce:
1. cp /usr/share/licenses/glibc/LICENSES L
2. cp L L2
3. cp L L3
4. echo "# make diff" >> L3
5. /usr/bin/kdiff3 --auto -o L L2 L3 
Actual Results:
The window is not rendered correctly, source panels of both files are transparent. Menus are non-responsibe by mouse, but application can be terminated by clicking window cross button. Confirmation popup is rendered okay.

Expected Results:
The same like when I omit --auto or use --noauto at the end. It should just display the windows well and let me merge the conflict. Or like it does when I made the windows smaller.

Additional Information:
Maybe it requires scroll bars in the window. I have seen that on multiple spec files conflicts, but it did not appear when I tried just /etc/hosts as an L source.

This seems to happen only, when in previous run the kdiff3 window were maximized on my main monitor. When I make the window smaller and quit without saving, then reexecute, it will render window okay. But it will maximize the window next time. When I close without saving and reexecute, it would be broken again.

3 have 3 screens, 1 full HD and 2 with higher resolution. It does not seems to matter on which I start it.

My screen configuration in case it matters:

Screen 0: minimum 16 x 16, current 12368 x 2880, maximum 32767 x 32767
eDP-1 connected 3408x2130+8960+750 (normal left inverted right x axis y axis) 340mm x 220mm
   3408x2130     59.99*+
   2048x1536     59.95  
   1920x1440     59.97  
   1600x1200     59.87  
   1440x1080     59.99  
   1400x1050     59.98  
   1280x1024     59.89  
   1280x960      59.94  
   1152x864      59.96  
   1024x768      59.92  
   800x600       59.86  
   640x480       59.38  
   320x240       59.52  
   2560x1600     59.99  
   1920x1200     59.88  
   1680x1050     59.95  
   1440x900      59.89  
   1280x800      59.81  
   1152x720      59.97  
   960x600       59.63  
   928x580       59.88  
   800x500       59.50  
   768x480       59.90  
   720x480       59.71  
   640x400       59.95  
   320x200       58.96  
   3200x1800     59.96  
   2880x1620     59.96  
   2560x1440     59.96  
   2048x1152     59.90  
   1920x1080     59.96  
   1600x900      59.95  
   1368x768      59.88  
   1280x720      59.86  
   1024x576      59.90  
   864x486       59.92  
   720x400       59.55  
   640x350       59.77  
DP-7 connected 3840x2160+0+0 (normal left inverted right x axis y axis) 510mm x 290mm
   3840x2160     59.98*+
   2048x1536     59.95  
   1920x1440     59.97  
   1600x1200     59.87  
   1440x1080     59.99  
   1400x1050     59.98  
   1280x1024     59.89  
   1280x960      59.94  
   1152x864      59.96  
   1024x768      59.92  
   800x600       59.86  
   640x480       59.38  
   320x240       59.52  
   2560x1600     59.99  
   1920x1200     59.88  
   1680x1050     59.95  
   1440x900      59.89  
   1280x800      59.81  
   1152x720      59.97  
   960x600       59.63  
   928x580       59.88  
   800x500       59.50  
   768x480       59.90  
   720x480       59.71  
   640x400       59.95  
   320x200       58.96  
   3200x1800     59.96  
   2880x1620     59.96  
   2560x1440     59.96  
   2048x1152     59.90  
   1920x1080     59.96  
   1600x900      59.95  
   1368x768      59.88  
   1280x720      59.86  
   1024x576      59.90  
   864x486       59.92  
   720x400       59.55  
   640x350       59.77  
DP-8 connected primary 5120x2880+3840+0 (normal left inverted right x axis y axis) 600mm x 340mm
   5120x2880     59.93*+
   2048x1536     59.90  
   1920x1440     59.90  
   1600x1200     59.87  
   1440x1080     59.87  
   1400x1050     59.86  
   1280x1024     59.76  
   1280x960      59.94  
   1152x864      59.78  
   1024x768      59.68  
   800x600       59.86  
   640x480       59.38  
   320x240       59.52  
   2560x1600     59.90  
   1920x1200     59.88  
   1680x1050     59.85  
   1440x900      59.89  
   1280x800      59.81  
   1152x720      59.75  
   960x600       59.63  
   928x580       59.88  
   800x500       59.50  
   768x480       59.38  
   720x480       59.71  
   640x400       59.20  
   320x200       58.96  
   4096x2304     59.93  
   3840x2160     59.94  
   3200x1800     59.93  
   2880x1620     59.92  
   2560x1440     59.91  
   2048x1152     59.90  
   1920x1080     59.88  
   1600x900      59.82  
   1368x768      59.88  
   1280x720      59.86  
   1024x576      59.90  
   864x486       59.45  
   720x400       59.55  
   640x350       59.77