c++ - 在 SDL 中渲染静止图像

Question

我目前正在学习 SDL，并且正在尝试创建一个 Pacman 游戏。我正在尝试逐步进行，以免陷入大量代码的困境。

到目前为止，我已经创建了一个空白窗口并在其上渲染了 Pacman 图像。我可以按箭头键并在窗口周围移动 Pacman。我设置了它，因此 Pacman 图像存储为 SDL_Texture，我使用 RenderCopy 将其 blit 到窗口。每次用户按下箭头时，我都会移动图像的坐标并重新渲染整个图像。这很好用。然而，现在我想在屏幕上放一些点让吃 bean 人吃。如果我加载一个点图像并将其存储为新纹理以与 Pacman 一起 blit 到屏幕，但是，每次我移动 Pacman 时，点都会闪烁，因为它正在被删除并与 Pacman 一起重新渲染。

我的问题是，如何避免这种“闪烁”？我能以某种方式只重新渲染吃 bean 人而不重新渲染屏幕的其余部分吗？还是有另一种方法可以做到这一点？我想当我稍后在后台创建迷宫时也会遇到同样的问题。如何制作静态背景，每次重新渲染时都不会闪烁？

到目前为止，下面是我的代码。如果那里有任何格式错误的代码，请原谅我。正如我所说，我才刚刚开始学习 SDL(对 C++ 也很陌生)，所以如果有任何明显的“你永远不应该那样做!”里面有一些东西，我很感激任何人指出它:)

#include <iostream>
#include <SDL2/SDL.h>
using namespace std;

const int WINDOW_HEIGHT = 480;
const int WINDOW_WIDTH = 640;
const int MOVE_WIDTH = 10;

int main(int argc, const char * argv[])
{
    SDL_Window* mainWindow = NULL; //To hold the main window
    SDL_Renderer* renderer = NULL; //To hold the renderer
    SDL_Rect targetRect; //Rectangle to which pacman image will be drawn
    SDL_Surface* bmpSurface = NULL; //To hold bmp image
    SDL_Texture* bmpTexture = NULL; //To hold bmp image

    //Initialize SDL and check for errors
    if ( SDL_Init(SDL_INIT_EVERYTHING) != 0 )
    {
        cout << "ERROR: could not initialize SDL." << endl;
    }

    //Create a window
    mainWindow = SDL_CreateWindow("BAM", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, WINDOW_WIDTH, WINDOW_HEIGHT, 0);

    if (mainWindow == NULL)
    {
        cout << "ERROR: could not initialize mainWindow." << endl;
    }

    //Initialize renderer
    renderer = SDL_CreateRenderer(mainWindow, -1, SDL_RENDERER_ACCELERATED);

    //Load image and store in an SDL_Surface
    bmpSurface = SDL_LoadBMP("/Users/billgrenard/Desktop/Programs/SDL/SDL_KeyPresses/SDL_KeyPresses/pacman_closed.bmp");
    if ( bmpSurface == NULL )
    {
        cout << "ERROR: could not load bmp file." << endl;
    }

    //Convert surface to texture for rendering
    bmpTexture = SDL_CreateTextureFromSurface(renderer, bmpSurface);
    if ( bmpTexture == NULL )
    {
        cout << "ERROR: could not convert bmp surface." << endl;
    }

    SDL_FreeSurface(bmpSurface);

    //Define rectangle where pacman image is to be blitted
    targetRect.w = 30;
    targetRect.h = 30;
    targetRect.x = (WINDOW_WIDTH/2) - (targetRect.w/2);
    targetRect.y = (WINDOW_HEIGHT/2) - (targetRect.h/2);


    //Main game loop
    while (1)
    {
        SDL_Event e;
        if (SDL_PollEvent(&e))
        {
            //Quit when user x's out the window
            if (e.type == SDL_QUIT)
            {
                break;
            }

            //If user presses a key enter switch statement
            else if( e.type == SDL_KEYDOWN )
            {
                switch ( e.key.keysym.sym ) {
                    //If user presses up arrow and the resulting move is inside the window, then move the Pacman's position
                    case SDLK_UP:
                        if ( targetRect.y - MOVE_WIDTH > 0 )
                        {
                            targetRect.y -= MOVE_WIDTH;
                        }

                        break;

                    //If user presses down arrow and the resulting move is inside the window, then move the Pacman's position
                    case SDLK_DOWN:
                        if ( targetRect.y + MOVE_WIDTH < (WINDOW_HEIGHT - targetRect.w) )
                        {
                            targetRect.y += MOVE_WIDTH;
                        }

                        break;

                    //If user presses right arrow and the resulting move is inside the window, then move the Pacman's position
                    case SDLK_RIGHT:
                        if ( targetRect.x + MOVE_WIDTH < (WINDOW_WIDTH - targetRect.w) )
                        {
                            targetRect.x += MOVE_WIDTH;
                        }

                        break;

                    //If user presses left arrow and the resulting move is inside the window, then move the Pacman's position
                    case SDLK_LEFT:
                        if ( targetRect.x - MOVE_WIDTH > 0 )
                        {
                            targetRect.x -= MOVE_WIDTH;
                        }

                        break;

                    default:
                        break;
                }
            }
        }

        SDL_RenderClear(renderer);
        SDL_RenderCopy(renderer, bmpTexture, NULL, &targetRect);
        SDL_RenderPresent(renderer);       
    }

    SDL_DestroyWindow(mainWindow);
    SDL_DestroyTexture(bmpTexture);
    SDL_DestroyRenderer(renderer);
    SDL_Quit();

    return 0;
}

编辑:为了回答 raser 的评论，这里是我找到 PollEvent 示例的链接:http://wiki.libsdl.org/SDL_CreateRenderer?highlight=%28%5CbCategoryAPI%5Cb%29%7C%28SDLFunctionTemplate%29

Answer 1

上述用于渲染 Pacman 的方法实际上可以很好地将点渲染到屏幕上。只需将点的图像存储在新纹理中，创建一个 SDL_Rect 来保存该纹理，然后使用 SDL_CreateRenderer 将点图像与吃 bean 人一起渲染到屏幕上。只要您没有使用 SDL_Delay 之类的东西来减慢帧速率，您就应该注意到渲染之间没有闪烁的点。