Code:

{

Die CreateRoundRectRgn lasst eine Form mit abgerundeten Ecken erscheinen.

The CreateRoundRectRgn function creates a rectangular

region with rounded corners

}

procedure TForm1.FormCreate(Sender: TObject);

var

  rgn: HRGN;

begin

  Form1.Borderstyle := bsNone;

  rgn := CreateRoundRectRgn(0,// x-coordinate of the region's upper-left corner

   0,            // y-coordinate of the region's upper-left corner

   ClientWidth,  // x-coordinate of the region's lower-right corner

   ClientHeight, // y-coordinate of the region's lower-right corner

   40,           // height of ellipse for rounded corners

   40);          // width of ellipse for rounded corners

SetWindowRgn(Handle, rgn, True);

end

{ The CreatePolygonRgn function creates a polygonal region. }

procedure TForm1.FormCreate(Sender: TObject);

const

  C = 20;

var

  Points: array [0..7] of TPoint;

  h, w: Integer;

begin

  h := Form1.Height;

  w := Form1.Width;

  Points[0].X := C;     Points[0].Y := 0;

  Points[1].X := 0;     Points[1].Y := C;

  Points[2].X := 0;     Points[2].Y := h - c;

  Points[3].X := C;     Points[3].Y := h;

  Points[4].X := w - c; Points[4].Y := h;

  Points[5].X := w;     Points[5].Y := h - c;

  Points[6].X := w;     Points[6].Y := C;

  Points[7].X := w - C; Points[7].Y := 0;

  SetWindowRgn(Form1.Handle, CreatePolygonRgn(Points, 8, WINDING), True);

end;