/* compile with -lSDL2 */
#include <SDL2/SDL.h>
#include <errno.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

enum {
    WIDTH = 320,
    HEIGHT = 240,
    PFORMAT = SDL_PIXELFORMAT_ARGB8888,
};

static inline Uint32 rgb(Uint8 r, Uint8 g, Uint8 b)
{
    static SDL_PixelFormat *pf = NULL;
    Uint32 ret;
    if (pf == NULL) {
        pf = SDL_AllocFormat(PFORMAT);
        if (pf == NULL) {
            fprintf(stderr, "Could not allocte pixel format: %s\n",
                SDL_GetError());
            exit(EXIT_FAILURE);
        }
    }
    ret = SDL_MapRGB(pf, r, g, b);
    SDL_FreeFormat(pf);
    return ret;
}

int main(void)
{
    SDL_Window *sw;
    SDL_Renderer *sr;
    SDL_Texture *st;
    Uint32 *buffer;

    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        fprintf(stderr, "Could not initialise SDL: %s\n", SDL_GetError());
        return EXIT_FAILURE;
    }

    sw = SDL_CreateWindow("Test", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
                  WIDTH, HEIGHT, 0);
    if (sw == NULL) {
        fprintf(stderr, "Could not create window: %s\n", SDL_GetError());
        return EXIT_FAILURE;
    }

    sr = SDL_CreateRenderer(sw, -1, SDL_RENDERER_PRESENTVSYNC);
    if (sr == NULL) {
        fprintf(stderr, "Could not create renderer: %s\n", SDL_GetError());
        return EXIT_FAILURE;
    }

    st = SDL_CreateTexture(sr, PFORMAT, SDL_TEXTUREACCESS_STREAMING, WIDTH, HEIGHT);
    if (st == NULL) {
        fprintf(stderr, "Could not create texture: %s\n", SDL_GetError());
        return EXIT_FAILURE;
    }

    buffer = malloc(WIDTH * HEIGHT * sizeof *buffer);
    if (buffer == NULL) {
        fprintf(stderr, "Could not allocate memory: %s\n", strerror(errno));
        return EXIT_FAILURE;
    }

    for (int x = 0; x < WIDTH; x++)
        for (int y = 0; y < HEIGHT; y++)
            buffer[x + WIDTH * y] = rgb(rand(), rand(), rand());

    SDL_UpdateTexture(st, NULL, buffer, WIDTH * sizeof *buffer);
    SDL_RenderCopy(sr, st, NULL, NULL);
    SDL_RenderPresent(sr);

    int shouldquit = 0;
    SDL_Event se;
    while (!shouldquit) {
        if(0 == SDL_WaitEvent(&se)) continue;
        if (se.type == SDL_QUIT)
            shouldquit = 1;
    }

    SDL_DestroyTexture(st);
    SDL_DestroyRenderer(sr);
    SDL_DestroyWindow(sw);

    free(buffer);
    SDL_Quit();
}