#include "metawndow.h"


/*---------------------------------------------------------------------\
  ASPECT.C 
  Shows what to do when you are using a monitor that doesn't have
  square pixels and you need points at a certain angle.
\---------------------------------------------------------------------*/
/*---------------------------------------------------------------------\
 MapAspectPt takes oval, the angle, and gives you a matching newPoint.
 Note that I cheat and assume that you're in virtual coordinates.  If
 you aren't, take SetLocal() and SetVirtual () out.
\---------------------------------------------------------------------*/
void MapAspectPt (rect *oval, int angle, point *newPoint)
{
   rect Square = { -2048, -2048, 2048, 2048 };
   /*
      I use 2048 because the CPU can divide by 2048 by simply shifting down
      the bits 11 times.
   */
   point temp;
   point Center;
   int radiusX;
   int radiusY;
   
   radiusX = (oval->Xmax - oval->Xmin) / 2 ;
   radiusY = (oval->Ymax - oval->Ymin) / 2 ;

   Center.X = oval->Xmin + radiusX;
   Center.Y = oval->Ymin + radiusY;

   SetLocal();
   /*
      OvalPt give us X and Y values which we use to determine the ratio
      of X to Y, which is constant for any triangle of the same angle.
   */

   OvalPt (&Square, angle, &temp);
   /*
      Several things happen here.  The multiplication and division
      (right shift) give us the Delta X and Y.  By adding them to the
      center X and Y we get the actual location.
   */
   newPoint->X = Center.X + (int) (((long)radiusX * (long)temp.X) >> 11);
   newPoint->Y = Center.Y + (int) (((long)radiusY * (long)temp.Y) >> 11);
   SetVirtual ();
}

extern unsigned _stklen = 14336U;

void main ()
{
   rect vRect;
   rect oval;
   int x;
   point thePoint;

   InitGraphics(CGA640x200);
   SetDisplay (GrafPg0);
   ScreenRect (&vRect);
   EraseRect (&vRect);

   SetRect (&vRect, 0, 0, 640, 480);
   /* 640 x 480 gives you square pixels given the aspect ratio of
      the computer monitor.  This way you can draw an oval with X = Y
      and you'll get something that more or less looks like a circle.
      */
   VirtualRect (&vRect);

   SetRect (&oval, 0, 0, 400, 400);
   FrameOval (&oval);
   for (x= 0; x < 3600; x += 300) {
      MoveTo (200, 200);
      MapAspectPt (&oval, x, &thePoint);
      LineTo (thePoint.X, thePoint.Y);
      };
   getch();
   SetDisplay(TextPg0);
   StopGraphics();
}