SDL曲面返回NULL？

我得到一个分段错误，并且我将它跟踪到了我的表面，它是NULL（但检查就位不会触发）。SDL曲面返回NULL？

我不确定是否正确创建表面。创建表面时是否需要添加某些东西，我错过了什么？

bool init() 
{ 
    //Initialize SDL 
    if(SDL_Init(SDL_INIT_VIDEO) < 0) 
    { 
     printf("SDL could not initialize! SDL Error: %s\n", SDL_GetError()); 
     return false; 
    } 
    else 
    { 
     //Set texture filtering to linear 
     if(!SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "1")) 
     { 
      printf("Warning: Linear texture filtering not enabled!"); 
      return false; 
     } 
     else 
     { 
      //Create window 
      gWindow = SDL_CreateWindow("kPaint", 575, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN); 
      GUI = SDL_CreateWindow("GUI", 0, SDL_WINDOWPOS_UNDEFINED, 573, 542, SDL_WINDOW_SHOWN); 

      if(gWindow == NULL || GUI == NULL) 
      { 
       printf("Window could not be created! SDL Error: %s\n", SDL_GetError()); 
       return false; 
      } 
      else 
      { 
       //Create renderer for window 
       gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_ACCELERATED); 

       if(gRenderer == NULL) 
       { 
        printf("Renderer could not be created! SDL Error: %s\n", SDL_GetError()); 
        return false; 
       } 
       surface = SDL_GetWindowSurface(gWindow); 
       GUIsurface = SDL_GetWindowSurface(GUI); 

       if(surface == NULL) 
       { 
        printf("surface could not be created!"); 
        return false; 
       } 
       SDL_FillRect(surface, NULL, SDL_MapRGB(surface->format, 255,255,255)); 

       //Initialize PNG loading 
       int imgFlags = IMG_INIT_PNG; 
       if(!(IMG_Init(imgFlags) && imgFlags)) 
       { 
        printf("SDL_image could not initialize! SDL_image Error: %s\n", IMG_GetError()); 
        return false; 
       } 

      } 
     } 
    } 
    return true; 
}

来源

2017-05-08 Kari Noriy

尝试在SDL_GetWindowSurface（）之前未创建渲染器。我可能是错的，但是一旦你为该窗口创建了渲染器，iirc SDL就不允许你获取窗口表面 – neoaggelos

如果它在创建之后不是空的，而是在以后为空，那么必须做一些事情来改变它插图中。 – molbdnilo

此外，您可以检查SDL_FillRect（）的返回值，以查看是否有错误 – neoaggelos

谢谢NeoAgglos。

我是在表面之前创建一个渲染器。

bool init() 
{ 
    //Initialize SDL 
    if(SDL_Init(SDL_INIT_VIDEO) < 0) 
    { 
     printf("SDL could not initialize! SDL Error: %s\n", SDL_GetError()); 
     return false; 
    } 
    else 
    { 
     //Set texture filtering to linear 
     if(!SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "1")) 
     { 
      printf("Warning: Linear texture filtering not enabled!"); 
      return false; 
     } 
     else 
     { 
      //Create window 
      gWindow = SDL_CreateWindow("kPaint", 575, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN); 
      GUI = SDL_CreateWindow("GUI", 0, SDL_WINDOWPOS_UNDEFINED, 573, 542, SDL_WINDOW_SHOWN); 

      if(gWindow == NULL || GUI == NULL) 
      { 
       printf("Window could not be created! SDL Error: %s\n", SDL_GetError()); 
       return false; 
      } 
      else 
      { 
       surface = SDL_GetWindowSurface(gWindow); 
       GUIsurface = SDL_GetWindowSurface(GUI); 

       if(surface == NULL) 
       { 
        printf("surface could not be created!"); 
        return false; 
       } 
       SDL_FillRect(surface, NULL, SDL_MapRGB(surface->format, 255,255,255)); 

       //Create renderer for window 
       gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_ACCELERATED); 
       if(gRenderer == NULL) 
       { 
        printf("Renderer could not be created! SDL Error: %s\n", SDL_GetError()); 
        return false; 
       } 

       //Initialize PNG loading 
       int imgFlags = IMG_INIT_PNG; 
       if(!(IMG_Init(imgFlags) && imgFlags)) 
       { 
        printf("SDL_image could not initialize! SDL_image Error: %s\n", IMG_GetError()); 
        return false; 
       } 
      } 
     } 
    } 
    return true; 
}

来源

2017-05-08 17:47:01

你不能那样做。您已经欺骗了SDL的内部错误检查，但它没有使其正确。 “SDL_GetWindowSurface”的SDL手册明确指出，您无法将其与渲染API混合使用。 – keltar

SDL曲面返回NULL？

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