I have a triple display setup on Debian, and am using
gtk_window_fullscreen_on_monitor() to display on two of the monitors.
A bizarre thing occurs where my default installed desktop environment (i.e. the one selected on tasksel during system installation) does not properly fullscreen one monitor and instead, one row of GTK Buttons overlaps into the second monitor and leaves open space under the app.
If I install a new desktop environment with APT and switch to that one, the full screen works properly. I have tried this with both 1) GNOME tasksel, manually install
cinnamon and use that to fix the issue, and Cinnamon tasksel, manually install
gnome-session and use that gnome to fix the issue.
Before I delve deeper, has this ever happened to anybody else? There must be some system setting that renders content differently from the default-installed desktop environment versus the manually-installed one. Or perhaps GTK reacts differently to the latter option.