Description:
Selecting and applying a preinstalled theme, instead of the default look, from Tools>Options>Personalization, leads to the color of the theme filling only the right part of the window, if the window is wide enough, on a high resolution display.
The problem seem to be common to Write, Calc, Draw, Presentation, maybe other parts as well.

Steps to Reproduce:
1. Open any LibreOffice app, on a systems with a high resolution display
2. Select and apply a preinstalled theme from Tools>Options>Personalization
3. Widen the window until you notice the problem.
4. Voila!

Actual Results:
The color of the preinstalled theme is filling only a part of the window, starting from the right side [of the user].

Expected Results:
The color of the preinstalled theme should fill the entire window.


Reproducible: Always


User Profile Reset: No


OpenGL enabled: Yes

Additional Info:
System: Windows 10 Pro, version 20H2, build 19042.572, display resolution of (3840 by 2400) pixel, when this was noticed.
Allowing or disabling OpenCL does not seem to matter.

PS. In your bug reporting form, there is a section entitled "Is OpenGL enabled?". If you meant OpenCL, you might want to rephrase the title to "Is OpenCL enabled?".