macintosh_cookbook/units/Graf2D.pas

program ExampleRotate;

 uses
  FixMath;

 const
  PI = 3.141592654;
  RADDEG = 0.017453292; { PI/180 }
  DEGRAD = 57.29577951; { 180/PI }

 type
  Point2D = record
    x: Fixed;
    y: Fixed;
   end;

 var
  origin, target: Point2D;

 procedure SetPoint2D (var point: Point2D; x, y: Fixed);
 begin
  point.x := Long2Fix(x);
  point.y := Long2Fix(y);
 end;

 function Distance2D (a, b: Point2D): Fixed;
  var
   val: Fixed;
 begin
  val := FracMul((b.x - a.x), (b.x - a.x)) + FracMul((b.y - a.y), (b.y - a.y));
  Distance2D := Frac2Fix(FracSqrt(val));
 end;

 procedure RotatePoint2D (var target, origin: Point2D; angle: Fixed);
  var
   radians, cos, sin, x, y, r: Fixed;
 begin
  radians := FixRatio(angle, 314);
  r := Distance2D(target, origin);
  target.x := origin.x + FixMul(r, FracCos(radians));
  target.y := origin.y + FixMul(r, FracSin(radians));
 end;

 procedure DrawPoint2D (point: Point2D);
  var
   dotRect: Rect;
   radius: Integer;
 begin
  SetRect(dotRect, Fix2Long(point.x), Fix2Long(point.y), Fix2Long(point.x) + 5, Fix2Long(point.y) + 5);
  PaintOval(dotRect);
 end;

begin

 ShowDrawing;

{ origin }
 SetPoint2D(origin, 100, 100);
 DrawPoint2D(origin);

{ origin }
 SetPoint2D(target, 150, 100);
 RotatePoint2D(target, origin, 0);
 DrawPoint2D(target);
 SetPoint2D(target, 150, 100);
 RotatePoint2D(target, origin, 90);
 DrawPoint2D(target);
 SetPoint2D(target, 150, 100);
 RotatePoint2D(target, origin, 180);
 DrawPoint2D(target);
 SetPoint2D(target, 150, 100);
 RotatePoint2D(target, origin, 270);
 DrawPoint2D(target);

end.

{ note: This project requires the FixMath library. }