Squashed 'external/SDL/' content from commit 4d17b99d0a

git-subtree-dir: external/SDL
git-subtree-split: 4d17b99d0a1c33c5257063b098f883c669ade40b

cmake/test/main_gui.c

@@ -0,0 +1,37 @@
+#define SDL_MAIN_USE_CALLBACKS
+#include <SDL3/SDL_main.h>
+#include <SDL3/SDL.h>
+
+static SDL_Window *window;
+
+SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
+{
+    return SDL_APP_CONTINUE;
+}
+
+SDL_AppResult SDL_AppIterate(void *appstate)
+{
+    SDL_Surface *screenSurface = NULL;
+    screenSurface = SDL_GetWindowSurface(window);
+    SDL_FillSurfaceRect(screenSurface, NULL, SDL_MapSurfaceRGB(screenSurface, 0xff, 0xff, 0xff));
+    SDL_UpdateWindowSurface(window);
+    return SDL_APP_CONTINUE;
+}
+
+SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
+{
+    if (!SDL_Init(SDL_INIT_VIDEO)) {
+        SDL_Log("Could not initialize SDL: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+    window = SDL_CreateWindow("Hello SDL", 640, 480, 0);
+    if (!window) {
+        SDL_Log("could not create window: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+    return SDL_APP_CONTINUE;
+}
+
+void SDL_AppQuit(void *appstate, SDL_AppResult result) {
+    SDL_DestroyWindow(window);
+}