Positions in win32 wrong with multiple monitors and left-most not being main display

On origin/master, currently on 8d7bf3ad

Everything noted in this bug works fine if the left-most monitor is the Main Display.

On a win32 (msvc, but probably not compiler specific) with multiple monitors, and the leftmost monitor NOT being the main display (open windows Display Settings, select a non-left-most monitor on the "Select and rearrange displays" graphic, scroll down, check the "Make this my main display" checkbox) [in my case I have 3 monitors, and the center monitor is the main display]

Start gtk4-demo.exe, right click somewhere with text to bring up the copy/cut/paste etc. context menu. It will be in the wrong place (the far right side of the main display)

If you place the window on the left-most monitor, and open the context menu, it will appear on the main display in the same position it should be on the left-most monitor.

Additionally, tooltips seem to be affected by this as well, however if the left-most monitor is not the main display, they don't work at all, as the coordinates never match up properly. (my use case was with gtk_tree_view_set_tooltip_column which is currently missing from the demo applications, but it seems to have the same root cause as the popup menus)