参考http://blog.csdn.net/leixiaohua1020/article/details/38868499
SDL_Rect用于确定SDL_Texture显示的位置。一个SDL_Texture可以指定多个不同的SDL_Rect.
SDL_Rect sdlRect;
sdlRect.x=0;
sdlRect.y=0;
sdlRect.w=screen_w;
sdlRect.h=screen_h;
SDL_Rect sdlRect2;
sdlRect2.x = screen_w; //此处确定第二分屏显示位置
sdlRect2.y = 0;
sdlRect2.w = screen_w;
sdlRect2.h = screen_h;
SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, &sdlRect);
SDL_RenderCopy( sdlRenderer, sdlTexture, NULL, &sdlRect2 );