Theoretically, we could check the presence of NET_WM_STATE_FULLSCREEN in data->current_state.net_wm_state before calling xinerama_get_fullscreen_monitors(). However, we filter out NET_WM_STATE_FULLSCREEN with Gamescope on Proton due to other issues. To avoid differences between Proton and Wine, xinerama_get_fullscreen_monitors() is modified to check if the input rect is fullscreen.