SDL2不渲染多个视口

#include <SDL2/SDL.h>

int main(int argc, char* argv[]) {
    SDL_Window* window = NULL;
    SDL_Renderer* renderer = NULL;

    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        SDL_Log("Unable to initialize SDL: %s", SDL_GetError());
        return 1;
    }

    window = SDL_CreateWindow("SDL2 Multiple Viewports", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 800, 600, SDL_WINDOW_SHOWN);
    if (!window) {
        SDL_Log("Window could not be created: %s", SDL_GetError());
        return 1;
    }

    renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
    if (!renderer) {
        SDL_Log("Renderer could not be created: %s", SDL_GetError());
        return 1;
    }

    SDL_Rect viewport1 = {0, 0, 400, 300};
    SDL_Rect viewport2 = {400, 0, 400, 300};

    while (1) {
        SDL_Event event;
        if (SDL_PollEvent(&event)) {
            if (event.type == SDL_QUIT) {
                break;
            }
        }

        SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
        SDL_RenderClear(renderer);

        // Render to the first viewport
        SDL_RenderSetViewport(renderer, &viewport1);
        SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);
        SDL_RenderFillRect(renderer, NULL);

        // Render to the second viewport
        SDL_RenderSetViewport(renderer, &viewport2);
        SDL_SetRenderDrawColor(renderer, 0, 255, 0, 255);
        SDL_RenderFillRect(renderer, NULL);

        SDL_RenderPresent(renderer);
    }

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

    return 0;
}