If ( ALLEGRO_OPENGL | ALLEGRO_WINDOWED ) has been passed to al_set_new_display_flags(), switching from windowed to fullscreen via al_toggle_display( ALLEGRO_FULLSCREEN_WINDOW, 1 ) works, but switching back from fullscreen to windowed via al_toggle_display( ALLEGRO_FULLSCREEN_WINDOW, 0 ) does not work properly. The game is shown in the bottom left corner of a black screen, reduced in size. Screenshot attached.
sorry, typo, I meant al_toggle_display_flag