我的 C 程序是正确的，没有错误或警告，但没有显示 window。 为什么？

Question

This is my code, with no errors or warnings. I don't understand where i'm wrong.

It should show a window with a rectangle.

#include <stdio.h>
#include <SDL.h>

int main(int argc, const char * argv[]) {


    SDL_Window *window;     // Declare a window
    SDL_Renderer *renderer; // Declare a renderer

    SDL_Init(SDL_INIT_VIDEO); //Initialize SDL2

    //Create an application window with the fellowing settings:
    window = SDL_CreateWindow("Game Window",                                        // window title
                              SDL_WINDOWPOS_UNDEFINED,                             // initial x position
                              SDL_WINDOWPOS_UNDEFINED,                             // initial y position
                              640,                                                 // width, in pixels
                              480,                                                 // height, in pixels
                              0  );                                                // flag);

    renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);

    //

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

    //Clear the screen (to blue)
    SDL_RenderClear(renderer);

    // set the drawing color to white
    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);

    SDL_Rect rect = {220, 140, 200, 200};
    SDL_RenderFillRect(renderer, &rect);

    // We are done drawing, "present" or show to the screen what we have drawn
    SDL_RenderPresent(renderer);

    // Wait a few seconds before quitting
    SDL_Delay(2000);


    // Close and destroy the window
    SDL_DestroyWindow(window);
    SDL_DestroyRenderer(renderer);

    // Clean up
    SDL_Quit();
    return 0;

}

Answer 1

Draw&delay is unreliable method. It works on some OS/window managers for short delays, but not others. You need to handle events (or you might get eg "application hanged" prompt) and redraw when window manager asks you to - or just redrawing unconditionally.

#include <stdio.h>
#include <SDL.h>

int main(int argc, char * argv[]) {
    if(SDL_Init(SDL_INIT_VIDEO) != 0) {
        printf("SDL_Init error: %s\n", SDL_GetError());
        return 1;
    }

    SDL_Window *window = SDL_CreateWindow("Game Window",
            SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
            640, 480, 0);
    if(!window) {
        printf("SDL_CreateWindow error: %s\n", SDL_GetError());
        return 1;
    }

    SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
    if(!renderer) {
        printf("SDL_CreateRenderer error: %s\n", SDL_GetError());
        return 1;
    }

    // get timestamp when main loop have started
    Uint32 start_time = SDL_GetTicks();

    int quit = 0;
    while(!quit) {
        /* process events - essential part. Even if you don't want to react to events,
         * SDL_PollEvent (or SDL_PumpEvents) needs to be called frequently */
        SDL_Event ev;
        while(SDL_PollEvent(&ev)) {
            if(ev.type == SDL_QUIT) {
                // e.g. window closed
                quit = 1;
                break;
            }
        }

        // draw your frame
        SDL_SetRenderDrawColor(renderer, 0, 0, 255, 255);
        SDL_RenderClear(renderer);

        SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
        SDL_Rect rect = {220, 140, 200, 200};
        SDL_RenderFillRect(renderer, &rect);

        SDL_RenderPresent(renderer);

        if(SDL_GetTicks() - start_time > 2000) {
            // running longer than 2 seconds, break main loop
            quit = 1;
        }
    }

    SDL_DestroyWindow(window);
    SDL_DestroyRenderer(renderer);
    SDL_Quit();
    return 0;
}