Squashed 'external/sdl/SDL/' content from commit b8d91252c

git-subtree-dir: external/sdl/SDL
git-subtree-split: b8d91252c6488cf9c645aba447b56bb9dbd9609a

cmake/test/main_gui.c

@@ -0,0 +1,24 @@
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+
+int main(int argc, char *argv[])
+{
+    SDL_Window *window = NULL;
+    SDL_Surface *screenSurface = NULL;
+    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
+        SDL_Log("Could not initialize SDL: %s\n", SDL_GetError());
+        return 1;
+    }
+    window = SDL_CreateWindow("Hello SDL", 640, 480, 0);
+    if (window == NULL) {
+        SDL_Log("could not create window: %s\n", SDL_GetError());
+        return 1;
+    }
+    screenSurface = SDL_GetWindowSurface(window);
+    SDL_FillSurfaceRect(screenSurface, NULL, SDL_MapRGB(screenSurface->format, 0xff, 0xff, 0xff));
+    SDL_UpdateWindowSurface(window);
+    SDL_Delay(100);
+    SDL_DestroyWindow(window);
+    SDL_Quit();
+    return 0;
+}