DELPHI - FAQ

type
  TTransparentPanel = class(TCustomPanel)
  private
    procedure WMEraseBkgnd(var Message: TWmEraseBkgnd);
                          message WM_ERASEBKGND;
  public
    procedure Paint; override;
    procedure CreateParams(var Params: TCreateParams); override;
  end;

procedure TTransparentPanel.CreateParams(var Params: TCreateParams);
begin
  inherited CreateParams(Params);
  Params.ExStyle:=Params.ExStyle or WS_EX_TRANSPARENT;
  ControlStyle := ControlStyle - [csOpaque];
end;

procedure TTransparentPanel.Paint;
begin
end;

procedure TTransparentPanel.WMEraseBkgnd(var Message: TWmEraseBkgnd);
begin
  Message.Result:=1;
end;