Test: Add Shift-Enter to switch between FS and desktop FS.

src/test/SDL_test_common.c

@@ -1433,7 +1433,19 @@ SDLTest_CommonEvent(SDLTest_CommonState * state, SDL_Event * event, int *done)
                         SDL_SetWindowFullscreen(window, SDL_WINDOW_FULLSCREEN_DESKTOP);
                     }
                 }
+            } else if (withShift) {
+                /* Shift-Enter toggle fullscreen desktop / fullscreen */
+                SDL_Window *window = SDL_GetWindowFromID(event->key.windowID);
+                if (window) {
+                    Uint32 flags = SDL_GetWindowFlags(window);
+                    if ((flags & SDL_WINDOW_FULLSCREEN_DESKTOP) == SDL_WINDOW_FULLSCREEN_DESKTOP) {
+                        SDL_SetWindowFullscreen(window, SDL_WINDOW_FULLSCREEN);
+                    } else {
+                        SDL_SetWindowFullscreen(window, SDL_WINDOW_FULLSCREEN_DESKTOP);
+                    }
+                }
             }
+
             break;
         case SDLK_b:
             if (withControl) {