Yes, this is the intended out-of-the-box behavior when using Xtend. You may be getting black bars with your setup, but that's still game area you can draw in (rather than empty space as would be the case without it). By default, Xtend always matches GUI resolution to window resolution. If you want different behavior, you can disable GUI scaling in xtend_config and set GUI resolution and position manually using built-in functions (display_set_gui_size and display_set_gui_maximize, to be exact). See here for more details: https://docs.xgasoft.com/xtend/reference-guide/config