sdl 3 software rendering skeleton.cpp

#ifdef __EMSCRIPTEN__
#include <emscripten/emscripten.h>
#endif
#include "SDL3/SDL.h"
#include "SDL3/SDL_main.h"

int* fb;
SDL_Window* window;
SDL_Renderer* renderer;
SDL_Texture* tex;
static int done;
const int WINDOW_WIDTH = 1920/2;
const int WINDOW_HEIGHT = 1080/2;

bool update()
{
	SDL_Event e;
	if (SDL_PollEvent(&e)) {
		if (e.type == SDL_EVENT_QUIT)
		{
			return false;
		}
		if (e.type == SDL_EVENT_KEY_UP && e.key.keysym.sym == SDLK_ESCAPE)
		{
			return false;
		}
	}

	char* pix;
	int pitch;
	SDL_LockTexture(tex, NULL, (void**)&pix, &pitch);
	for (int i = 0, sp = 0, dp = 0; i < WINDOW_HEIGHT; i++, dp += WINDOW_WIDTH, sp += pitch)
		memcpy(pix + sp, fb + dp, WINDOW_WIDTH * 4);
	SDL_UnlockTexture(tex);
	SDL_RenderTexture(renderer, tex, NULL, NULL);
	SDL_RenderPresent(renderer);
	return true;
}

void render(Uint64 ticks)
{
	for (int i = 0, c = 0; i < WINDOW_HEIGHT; i++)
		for (int j = 0; j < WINDOW_WIDTH; j++, c++)
			fb[c] = (int)(i * i + j * j + ticks);
}

void loop()
{
	if (!update())
	{
		done = 1;
#ifdef __EMSCRIPTEN__
		emscripten_cancel_main_loop();
#endif
	}
	else
	{
		render(SDL_GetTicks());
	}
}

int main(int argc, char** argv) 
{
	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS) < 0)
	{
		return -1;
	}

	fb = new int[WINDOW_WIDTH * WINDOW_HEIGHT];
	window = SDL_CreateWindow("SDL3 window", WINDOW_WIDTH, WINDOW_HEIGHT, SDL_WINDOW_OPENGL);
	renderer = SDL_CreateRenderer(window, NULL, SDL_RENDERER_ACCELERATED);
	tex = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ABGR8888, SDL_TEXTUREACCESS_STREAMING, WINDOW_WIDTH, WINDOW_HEIGHT);

	if (!fb || !window || !renderer || !tex)
		return -1;

	done = 0;
#ifdef __EMSCRIPTEN__
	emscripten_set_main_loop(loop, 0, 1);
#else
	while (!done) {
		loop();
	}
#endif

	SDL_DestroyTexture(tex);
	SDL_DestroyRenderer(renderer);
	SDL_DestroyWindow(window);
	SDL_Quit();

	return 0;
}