I'm finally moving along on another project of mine and dropped Xtend in. It's working great for scaling my game to full screen on Windows. I have one question - I switched xtend_view.halign to be set to va_center. I noticed that this worked to make my game have bars on the left and right in fullscreen instead of just the right side. However my UI buttons, the only objects that employ the Draw GUI event in my project, seem to have not moved in the same way. I have a vague idea of why this is the case, but don't know how to fix it yet, if you have any tips.
Viewing post in Xtend - Display Scaler comments
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