Passing NULL to SDL_SetDisplayMode() will set the desktop mode.

include/SDL_video.h

@@ -458,7 +458,7 @@ extern DECLSPEC SDL_DisplayMode *SDLCALL SDL_GetClosestDisplayMode(const
  *
  * \brief Set up the closest available mode on the current display.
  *
- * \param mode The desired display mode
+ * \param mode The desired display mode, or NULL to set the desktop mode.
  *
  * \return 0 on success, or -1 if setting the display mode failed.
  */

src/video/SDL_video.c

@@ -534,10 +534,8 @@ SDL_SetDisplayMode(const SDL_DisplayMode * mode)
         return -1;
     }
 
-    /* Make sure there's an actual display mode to set */
     if (!mode) {
-        SDL_SetError("No mode passed to SDL_SetDisplayMode");
-        return -1;
+        mode = SDL_GetDesktopDisplayMode();
     }
     display = &SDL_CurrentDisplay;
     display_mode = *mode;

test/testsprite2.c

@@ -155,22 +155,10 @@ main(int argc, char *argv[])
         }
     }
 
-    /* Initialize the video mode, if necessary */
-    current_mode = SDL_GetCurrentDisplayMode();
-    if (!current_mode->w || !current_mode->h) {
-        SDL_DisplayMode mode;
-
-        /* Let the driver pick something it likes, we don't care */
-        mode.format = 0;
-        mode.w = 0;
-        mode.h = 0;
-        mode.refresh_rate = 0;
-
-        if (SDL_SetDisplayMode(&mode) < 0) {
-            fprintf(stderr, "Couldn't set display mode: %s\n",
-                    SDL_GetError());
-            quit(2);
-        }
+    /* Set the desktop mode, we don't care what it is */
+    if (SDL_SetDisplayMode(NULL) < 0) {
+        fprintf(stderr, "Couldn't set display mode: %s\n", SDL_GetError());
+        quit(2);
     }
 
     /* Create the windows, initialize the renderers, and load the textures */