#include "SDL.h"


// this timer class I've taken from Enginuity by Superpig
class CGlobalTimer
{
public:

	float dT;
	unsigned long lastFrameIndex;
	unsigned long thisFrameIndex;

	bool Start();
	void Update();

};

bool CGlobalTimer::Start()
{
	thisFrameIndex=SDL_GetTicks();
	lastFrameIndex=thisFrameIndex;
	dT=0;
	return true;
}

void CGlobalTimer::Update()
{
	lastFrameIndex=thisFrameIndex;
	thisFrameIndex=SDL_GetTicks();
	dT=((float)(thisFrameIndex-lastFrameIndex))/1000.0f;
}

#define abs(x) ((x>0) ? (x) : (-x))

CGlobalTimer timer;

int main(int argc, char ** argv)
 {
 
  // initialization...
  SDL_Init(SDL_INIT_VIDEO);  
  SDL_Surface * screen = SDL_SetVideoMode (640 , 480, 0, SDL_SWSURFACE  ) ;
  SDL_Event event ;
  
  float x = 450;
  int vx = -1;
  
  SDL_Rect rect = { int(x), 150, 60, 60 };
  
  SDL_ShowCursor(0);

  timer.Start();

  // endless loop
  for ( ; ; )
  {
    if ( SDL_PollEvent ( &event ) )
    {
      if ( event.type == SDL_KEYDOWN )
       {
        // if space was pressed, change the direction of movement
        if (event.key.keysym.sym == SDLK_SPACE) vx = -vx;
         else break;
       } 
      if ( event.type == SDL_QUIT ) break ;
    } 
    
   // now the update phase 
   timer.Update(); 
  
   // for clearing ugly border
   if (vx > 0) rect.x-=abs(vx);        
    else rect.x+=abs(vx);
                  
   SDL_FillRect ( screen , &rect , SDL_MapRGB ( screen->format , 0, 0 , 0) ) ;
   
   if (vx > 0) rect.x+=abs(vx);        
    else rect.x-=abs(vx);
   
   if (x+rect.w > 638) vx = -vx;
   if (x < 0) vx = -vx;
   
   x += vx * (timer.dT);  // !!! without the multiplication
   rect.x = x;            // rectangle is moving normally 
   
   // now draw the rectangle
   SDL_FillRect ( screen , &rect , SDL_MapRGB ( screen->format , 0, 0 , 255 ) ) ;
      
   SDL_Flip(screen);
     
  }
 
  SDL_Quit();
  return 0;
 };