Keskustelu: Ohjelmointikysymykset: C: Nopea viiva SDL:ällä

void Line(Uint16 left,Uint16 top,Uint16 right,Uint16 bottom,Uint8 r, Uint8 g, Uint8 b)
{
Uint32 g_Color=SDL_MapRGB(screen->format,r,g,b);
char* g_pData;
SDL_LockSurface(screen);


Uint16 temp,dx,dy,x,y,x_sign,y_sign,flag;
dx=abs(right-left);dy=abs(bottom-top);

if (((dx>=dy) && (left>right)) || ((dy>dx) && (top>bottom)))
   {
   temp=left;
   left=right;
   right=temp;
   temp=top;
   top=bottom;
   bottom=temp;
   }
if ((bottom-top) < 0) y_sign=-1;else y_sign=1;
if ((right-left) < 0) x_sign=-1;else x_sign=1;
if (dx>=dy)
   {
   for (x=left,y=top,flag=0;x<=right;x++,flag+=dy)
       {
       if (flag>=dx)
	  {
	  flag -=dx;
	  y+=y_sign;
	  }
       //grab pixel pointer
			g_pData=(char*)screen->pixels;

			//vertical offset
			g_pData+=(y*screen->pitch);

			//horizontal offset
			g_pData+=(x*screen->format->BytesPerPixel);

			//copy from color to frame buffer
			memcpy(g_pData,&g_Color,screen->format->BytesPerPixel);

       }
   }
else
   {
   for (x=left,y=top,flag=0;y<=bottom;y++,flag+=dx)
       {
       if (flag>=dy)
	  {
	  flag -=dy;
	  x+=x_sign;
	  }
       //grab pixel pointer
			g_pData=(char*)screen->pixels;

			//vertical offset
			g_pData+=(y*screen->pitch);

			//horizontal offset
			g_pData+=(x*screen->format->BytesPerPixel);

			//copy from color to frame buffer
			memcpy(g_pData,&g_Color,screen->format->BytesPerPixel);

      }
   }
SDL_UnlockSurface(screen);
}