什么是C++中的双缓冲技术？

#include <SDL2/SDL.h>
#include <iostream>

const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;

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

    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        std::cout << "SDL could not initialize! SDL_Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    window = SDL_CreateWindow("Double Buffering Example", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
    if (window == nullptr) {
        std::cout << "Window could not be created! SDL_Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
    if (renderer == nullptr) {
        std::cout << "Renderer could not be created! SDL_Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    bool quit = false;
    SDL_Event e;

    while (!quit) {
        while (SDL_PollEvent(&e) != 0) {
            if (e.type == SDL_QUIT) {
                quit = true;
            }
        }

        // Clear the back buffer
        SDL_SetRenderDrawColor(renderer, 0xFF, 0xFF, 0xFF, 0xFF);
        SDL_RenderClear(renderer);

        // Draw on the back buffer
        SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 0xFF);
        SDL_Rect fillRect = { SCREEN_WIDTH / 4, SCREEN_HEIGHT / 4, SCREEN_WIDTH / 2, SCREEN_HEIGHT / 2 };
        SDL_RenderFillRect(renderer, &fillRect);

        // Update the screen with the back buffer
        SDL_RenderPresent(renderer);
    }

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

    return 0;
}