Using Gamemaker:Studio, I spent several hours this week working on my full screen shader affect for my latest game. When I developed it, I had a problem with the way it displayed when I tested my game outside of windowed mode. Once in full screen, the effect contained the entire screen , but shrunk in the corner with an overlay of the existing screen. This definitely was not the desirable effect.
After reading up about drawing surfaces, I realized the problem was that my room has a smaller area (1280X704) than the actual display dimensions (1600*900). So the fix is to stretch the screen size to the display size.
Original Call –
if full_screen_effect draw_surface(application_surface,0,0);
if full_screen_effect draw_surface_stretched(application_surface,0,0,var_resolution_x,var_resolution_y);