問題渲染，單緩衝式效應

Question

情況：我目前正試圖在C++中使用SDL_image和SDL來渲染一些東西（圖像和一些文本）。然而，我遇到了一些看起來像緩衝問題的問題，但是我試圖解決這個問題，但我一直堅持幾個小時而無濟於事。

問題：渲染時，屏幕顯示單緩衝效果，其中前一個位置的圖像仍然顯示在屏幕上，就像它在上一個緩衝區中一樣。我懷疑問題在於我繪製函數中的某處（主循環功能）

problem http://oi41.tinypic.com/28v6gc0.jpg

這裏是我的main.cpp：

#include "SDL.h" 
#include "SDL_image.h" 
#include "Player.h" 
#include "Values.h" 
#include <string> 
#include <sstream> 
#include "SDL_ttf.h" 
#include "Timer.h" 


//The surfaces that will be used 
SDL_Surface *message = NULL; 
SDL_Surface *background = NULL; 
SDL_Surface *text = NULL; 
SDL_Surface *screen = NULL; 
SDL_Surface *startStop = NULL; 
SDL_Surface *pauseMessage = NULL; 
SDL_Surface *seconds = NULL; 
//The font thats going to be used 
TTF_Font *font = NULL; 
//The colour of the font 
SDL_Color textColor = {255,255,255}; 

Player ** player; 

Timer myTimer; 

bool quit = false; 
Uint32 start = 0; 
bool running = true; 

int fame = 0; 
bool cap = true; 
//Timer fps; 

SDL_Event event; 

void clean_up() 
{ 
    //Free the surfaces 
    //SDL_FreeSurface(message); 
    player[0]->clean(); 
    SDL_FreeSurface(background); 
    SDL_FreeSurface(seconds); 
    SDL_FreeSurface(startStop); 
    SDL_FreeSurface(pauseMessage); 
    TTF_CloseFont(font); 
    TTF_Quit(); 
    //Quit SDL 
    SDL_Quit(); 
} 

SDL_Surface *load_image(std::string filename) 
{ 
    //Temporary storage for the image that's loaded 
    SDL_Surface* loadedImage = NULL; 

    //The optimized image that will be used 
    SDL_Surface* optimizedImage = NULL; 

    //Load the image 
    loadedImage = SDL_LoadBMP(filename.c_str()); 

    //If nothing went wrong in loading the image 
    if(loadedImage != NULL) 
    { 
     //Create an optimized image 
     optimizedImage = SDL_DisplayFormat(loadedImage); 

     //Free the old image 
     SDL_FreeSurface(loadedImage); 
    } 

    //Return the optimized image 
    return optimizedImage; 
} 

void apply_surface(int x, int y, SDL_Surface* source, SDL_Surface* destination) 
{ 
    //Make a temporary rectangle to hold the offsets 
    SDL_Rect offset; 

    //Give the offsets to the rectangle 
    offset.x = x; 
    offset.y = y; 

    //Blit the surface 
    SDL_BlitSurface(source, NULL, destination, &offset); 
} 

bool loadFiles() 
{ 
    player[0]->load_files(); 
    background = load_image("Floor1.bmp"); 

    //Open the font 
    font = TTF_OpenFont("lazy.ttf",28); 

    //If there was a problem in loadin the font 
    if(font == NULL) 
    { 
     return false; 
    } 
    return true; 
} 

bool init() 
{ 
    //Initialize all SDL subsystems 
    SDL_Init(SDL_INIT_EVERYTHING); 

    //Set up the screen 
    //screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE); 
    screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, 0, 
     SDL_HWSURFACE | SDL_DOUBLEBUF); 
    //Initialize SDL_tff 
    if(TTF_Init() == -1) 
    { 
     return false; 
    } 

    //Set the window caption 
    SDL_WM_SetCaption("10 seconds", NULL);  

    player = new Player*[1]; 
    player[0] = new Player(screen); 
    loadFiles(); 



    return true; 
}; 

void mainloop() 
{ 
    startStop = TTF_RenderText_Solid(font, "Press S to start or stop the timer", textColor); 
    pauseMessage = TTF_RenderText_Solid(font, "Press P to pause or unpause the timer", textColor); 

    myTimer.start(); 
    while (quit == false) 
    { 
     //While there's events to handle 
     while(SDL_PollEvent(&event)) 
     { 
      //Handle events for the dot 
      player[0]->handleInput(event); 

      if (event.type == SDL_KEYDOWN) 
      { 
       //if s was pressed 
       if(event.key.keysym.sym == SDLK_s) 
       { 
        //if the timer is running 
        if(myTimer.isStarted() == true) 
        { 
         //Stop the timer 
         myTimer.stop();      
        } 
        else 
        { 
         //Start the timer 
         myTimer.start(); 
        } 
       } 
       if (event.key.keysym.sym == SDLK_p) 
       { 
        //If the timer is paused 
        if (myTimer.isPaused() == true) 
        { 
         //Unpause the timer 
         myTimer.unpause(); 
        } 
        else 
        { 
         //Pause the timer 
         myTimer.pause(); 
        } 
       } 
      } 
       //If the user has Xed out the window 
      else if(event.type == SDL_QUIT) 
      { 
       //Quit the program 
       quit = true; 
      } 

     } 

     //Apply all images to screen 
     apply_surface(0, 0, background, screen); 
     apply_surface((SCREEN_WIDTH - startStop->w)/2, 200, startStop, screen); 
      apply_surface((SCREEN_WIDTH - pauseMessage->w)/2, 250, pauseMessage, screen); 
     //The timers time as a string 
      std::stringstream time; 
      //convert the timers time to a string 
      time << "Timer: " << myTimer.getTicks()/1000.f; 
      seconds = TTF_RenderText_Solid(font, time.str().c_str(), textColor); 
      //Render the time surface 
      apply_surface((SCREEN_WIDTH - seconds->w)/2, 0, seconds, screen); 
      /Free the time surface 

     //PlayerHandling 
     player[0]->move(); 
     player[0]->setCamera(); 
     player[0]->draw(); 
      SDL_FreeSurface(seconds); 

     SDL_Flip(screen); 
    } 
} 



int main(int argc, char* args[]) 
{ 

    init(); 
    mainloop(); 
    clean_up(); 

    return 0; 
} 

Answer 1

看來，在圖形效果和事實判斷你的背景全是黑色，你的代碼加載背景失敗。你可以用顏色填充background來測試它。

background = SDL_CreateRGBSurface(0, SCREEN_WIDTH, SCREEN_HEIGHT, 32, 0x000000ff, 0x0000ff00, 0x00ff0000, 0xff000000); 
SDL_FillRect(background, NULL, SDL_MapRGBA(background->format, 125, 125, 0, 255)); 

由於SDL不破或警告你，如果你嘗試使用SDL_Surface*指向NULL，我還建議增加一條錯誤消息，您的load_image：

SDL_Surface *load_image(std::string filename) 
{ 
    //Temporary storage for the image that's loaded 
    SDL_Surface* loadedImage = NULL; 

    //The optimized image that will be used 
    SDL_Surface* optimizedImage = NULL; 

    //Load the image 
    loadedImage = SDL_LoadBMP(filename.c_str()); 

    //If nothing went wrong in loading the image 
    if(loadedImage != NULL) 
    { 
     //Create an optimized image 
     optimizedImage = SDL_DisplayFormat(loadedImage); 

     //Free the old image 
     SDL_FreeSurface(loadedImage); 
    } else 
    { 
     std::cout << "ERROR : Failed to load image : " << filename << std::endl; 
    } 

    //Return the optimized image 
    return optimizedImage; 
}