Modify a SDL3 texture using a framebuffer?

Question

I'm trying to modify a texture pixel by pixel using a framebuffer, In my code I'm trying to fill the texture with white pixels, nothing seems to work.

#include <iostream> 
#include <SDL3/SDL.h>

int main() {
    SDL_Window* window = SDL_CreateWindow("test", 500, 500, 0);
    SDL_Renderer* renderer = SDL_CreateRenderer(window, "test");
    SDL_Texture* screen_texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_STREAMING, 500, 500);
    uint32_t framebuffer[500 * 500]; 
    SDL_FRect dest_rect = {0, 0, 500, 500};
    for (int i = 0; i < 500*500; i++) {
        framebuffer[i] = 0xFFFFFFFF; 
    }
    bool running = true;
    SDL_Event e;    
    while (running) {
        while (SDL_PollEvent(&e)) {
            if (e.type == SDL_EVENT_QUIT) {
                running = false; 
            }
        }
        SDL_RenderClear(renderer);
        SDL_UpdateTexture(screen_texture, NULL, framebuffer, 500 * 4);
        SDL_RenderTexture(renderer, screen_texture, nullptr, &dest_rect);
        SDL_RenderPresent(renderer);
        SDL_Delay(16);
    }
}

Answer 1

Take a look at:

SDL_Renderer * SDL_CreateRenderer(SDL_Window *window, const char *name);

Function Parameters

Type	Name	Description
SDL_Window *	window	the window where rendering is displayed.
const char *	name	the name of the rendering driver to initialize, or NULL to let SDL choose one.

When you give it the name parameter "test", you request a driver named test, which most probably don't exist.

Let SDL3 choose one for you - and check the return values for errors:

SDL_Renderer* renderer = SDL_CreateRenderer(window, nullptr);
//                           let SDL3 choose driver ^^^^^^^

if (!renderer) {
    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "SDL_CreateRenderer: %s",
                 SDL_GetError());
    return 1;
}

You should also call SDL_Init(SDL_INIT_VIDEO) at startup.