1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:
34:
35:
36:
37:
38:
39:
40:
41:
42:
43:
44:
45:

function CallWndHook(Code: Integer; WParam: wParam; Msg: PCWPStruct): Longint; stdcall;

procedure UpdateMDIMenuButtons;
var
I: Integer;
Parent: THandle;
ParentForm: TWinControl;
Form: TCustomForm;
begin
    Parent := GetParent(Msg.hwnd);
    if Parent = 0 then exit;
    ParentForm := FindControl(Parent);
    for I := 0 to MenuList.Count - 1 do
    begin
        Form := GetParentForm(MenuList.Menus[I]);
        if (Form = ParentForm) and
        (MenuList.Menus[I] is TCustomActionMainMenuBar) then
        begin
            if (Msg.Message = WM_MDIDESTROY) and (Form is TForm) and
            (TForm(Form).MDIChildCount = 1)  then
            with MenuList.Menus[I] as TCustomActionMainMenuBar do
            MDIChildRestored
            else
            with MenuList.Menus[I] as TCustomActionMainMenuBar do
            GetActiveMDIChild;
            break;
    end;
  end;
end;

begin
    if Code = HC_ACTION then
    case Msg.message of
    // Use of WM_SIZE is required for any Windows version except Themed XP
    WM_MDIGETACTIVE, WM_SIZE,
    WM_MDIDESTROY: UpdateMDIMenuButtons;
    WM_ACTIVATE:
    if ActiveMenu is TCustomActionPopupMenu then
    ActiveMenu.CloseMenu;
    WM_SETTINGCHANGE:
    if Assigned(UpdateActnMenusProc) then
    UpdateActnMenusProc;
end;
Result := CallNextHookEx(MenuCallWndHook, Code, WParam, Longint(Msg));
end;					

1:
2:
3:
4:
5:
6:
7:
8:
9:
10:

procedure TInternalMDIAction.ExecuteTarget(Target: TObject);
begin
    case MDIAction of
    maActivate: SendMessage(GetParent(Form.Handle), WM_MDIACTIVATE, Form.Handle, 0);
    maClose: Form.Close;
    maRestore: SendMessage(GetParent(Form.Handle), WM_MDIRESTORE, Form.Handle, 0);
    // Fixed to minimize the form not close it
    maMinimize: Form.WindowState := wsMinimized;
end;
end;					

1:

dcc32 ..\Source\Vcl\actnmenus.pas -N..\lib