What are the different settings I should test for a custom WPF UI component?

I have developed a fancy WPF control based on WPF popup that can positioned on the screen using absolute screen coordinates. To test it, I made sure I test it with high DPI and various resolutions.

Only recently though have I noticed its positioning is broken on tablet PCs due to Windows handedness settings. I have fixed that as well but now I need to make sure I have not missed any other setting or configuration.