Making a transparent form
Add a Button (Button1) to a Delphi form (Form1) procedure TForm1.FormCreate(Sender: TObject) ; var FullRgn, ClientRgn, ButtonRgn: THandle; Margin, X, Y: Integer; begin Margin := (Width - ClientWidth) div 2; FullRgn := CreateRectRgn(0, 0, Width, Height) ; X := Margin; Y := Height - ClientHeight - Margin; ClientRgn := CreateRectRgn (X, Y, X + ClientWidth, Y + ClientHeight) ; CombineRgn(FullRgn, FullRgn, ClientRgn, RGN_DIFF) ; X := X + Button1.Left; Y := Y + Button1.Top; ButtonRgn := CreateRectRgn (X, Y, X + Button1.Width, Y + Button1.Height) ; CombineRgn(FullRgn, FullRgn, ButtonRgn, RGN_OR) ; SetWindowRgn(Handle, FullRgn, True) ; end; from: about.com