SDL2渲染（闪烁）

Question

I'm having a problem with rendering a texture using SDL2. In my program, there are a bunch of pixels which move around the screen, however they visibly flicker. Here is my code:

Source.cpp

 frameStart = SDL_GetTicks();

    screen.update();

    // Makes the screen black
    for (int x = 0; x < Screen::SCREEN_WIDTH; x++)
    {
        for (int y = 0; y < Screen::SCREEN_HEIGHT; y++) {
            screen.setPixel(x, y, 0, 0, 0);
        }
    }

    // Draw + Update people (Code should be separated and moved)
    for (Person &p : people) {
        if (p.isAlive == true) {
            p.Update(p);
            cout << p.x << ", " << p.y << endl;
            screen.setPixel(p.x, p.y, 255, 0, 0);
        }
        else {
            screen.setPixel(p.x, p.y, 0, 0, 0);
        }
    }



    // Manage events
    if (screen.processEvents() == false) {
        break;
    }

    frameTime = SDL_GetTicks() - frameStart;

    if (frameDelay > frameTime) {
        SDL_Delay(frameDelay - frameTime);
    }
}

Screen.update points here:

 void Screen::update() {

    SDL_UpdateTexture(m_texture, NULL, m_buffer, SCREEN_WIDTH * sizeof(Uint32) );       
    SDL_RenderCopy(m_renderer, m_texture, NULL, NULL);
    SDL_RenderPresent(m_renderer);
    SDL_RenderClear(m_renderer);
}

And my renderer and texture setup are as follows:

 m_renderer = SDL_CreateRenderer(m_window, -1, SDL_RENDERER_PRESENTVSYNC);
    m_texture = SDL_CreateTexture(m_renderer, SDL_PIXELFORMAT_RGBA8888,
        SDL_TEXTUREACCESS_STATIC, SCREEN_WIDTH, SCREEN_HEIGHT);

I've messed around alot with the flags for both the renderer and texture but have not found a solution that stops the flickering. Any help would be really appreciated.

Answer 1

The sequence you should follow is:

• Clear
• Render
• Render present
• Wait
• Repeat.

What you are doing is basically, Render and clear right the way. If you make this way might work just fine

frameStart = SDL_GetTicks();

SDL_RenderClear(m_renderer);

/* Do you rendering */

/*Manage your events*/


SDL_RenderPresent(m_renderer);


frameTime = SDL_GetTicks() - frameStart;

if (frameDelay > frameTime) {
    SDL_Delay(frameDelay - frameTime);
}

Also about rendering pixels, when clearing the texture, you should use memset wich is faster. But your way still works

memset(pixels,0,h*pitch);