Savoir si un TMainMenu est ouvert

type
TForm1 = class(TForm)
// ...
private
IsMenuOpen: Boolean;
procedure WMMENUSELECT( var message: TWMMENUSELECT); message WM_MENUSELECT;

procedure TForm1.WMMENUSELECT( var message: TWMMENUSELECT);
begin
inherited;
IsMenuOpen := not ((message.MenuFlag and $FFFF > 0) and (message.Menu = 0));
end;