Override Delphi Form's Restore Operation

{ Private declarations }
procedure WMSysCommand (var Msg: TWMSysCommand) ; message WM_SYSCOMMAND;
procedure TForm1.WMSysCommand(var Msg: TWMSysCommand);
begin
if Msg.CmdType = SC_RESTORE then
begin
ShowMessage('SC_RESTORE');
if self.WindowState = wsMaximized then
begin
self.WindowState := wsMinimized;
Msg.Result := 0;
Exit;
end;
if self.WindowState = wsMinimized then
begin
self.WindowState := wsMaximized;
Msg.Result := 0;
Exit;
end;
end;
DefaultHandler(Msg) ;
end;