Binaryworld - How to disable form's Close button (X)? ... [ VB -> Menu ]

To modify an item in the Visual Basic Control menu (also known as the System menu), you need to use the SetMenuItemInfo API function. You can use ModifyMenuItem or EnablemenuItem api, both functions work. However it appears that Visual Basic re-enables the menu item whose ID is SC_CLOSE. This is why it may appear as if the ModifyMenu or EnableMenuItem function failed. . This article describes how to enable/disable or check/uncheck the Close menu item in the Control menu.

If you do not want the user to close a window via the Control menu or the Close box on your Form's title bar, you can disable the Close menu item on the Control menu. This method also disables double-clicking the Control box and disables the Close button on the Form's title bar.

The following code sample enables/disables and checks/unchecks the Close command in the Visual Basic Control menu.

Step-By-Step Example

- Start a new standard EXE project. Form1 is added by default.
- Add three CommandButtons to Form1.
- Add the following code to Form1:

Click here to copy the following block

Option Explicit

'Menu item constants.
Private Const SC_CLOSE    As Long = &HF060&

'SetMenuItemInfo fMask constants.
Private Const MIIM_STATE   As Long = &H1&
Private Const MIIM_ID    As Long = &H2&

'SetMenuItemInfo fState constants.
Private Const MFS_GRAYED   As Long = &H3&
Private Const MFS_CHECKED  As Long = &H8&

'SendMessage constants.
Private Const WM_NCACTIVATE As Long = &H86

'User-defined Types.
Private Type MENUITEMINFO
  cbSize    As Long
  fMask     As Long
  fType     As Long
  fState    As Long
  wID      As Long
  hSubMenu   As Long
  hbmpChecked As Long
  hbmpUnchecked As Long
  dwItemData  As Long
  dwTypeData  As String
  cch      As Long
End Type

'Declarations.
Private Declare Function GetSystemMenu Lib "user32" ( _
    ByVal hwnd As Long, ByVal bRevert As Long) As Long

Private Declare Function GetMenuItemInfo Lib "user32" Alias _
    "GetMenuItemInfoA" (ByVal hMenu As Long, ByVal un As Long, _
    ByVal b As Boolean, lpMenuItemInfo As MENUITEMINFO) As Long

Private Declare Function SetMenuItemInfo Lib "user32" Alias _
    "SetMenuItemInfoA" (ByVal hMenu As Long, ByVal un As Long, _
    ByVal bool As Boolean, lpcMenuItemInfo As MENUITEMINFO) As Long

Private Declare Function SendMessage Lib "user32" Alias _
    "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, _
    ByVal wParam As Long, lParam As Any) As Long

'Application-specific constants and variables.
Private Const xSC_CLOSE As Long = -10
Private Const SwapID   As Long = 1
Private Const ResetID  As Long = 2

Private hMenu As Long
Private MII  As MENUITEMINFO

Private Sub Command1_Click()
  Dim Ret As Long

  Ret = SetId(SwapID)
  If Ret <> 0 Then
    If MII.fState = (MII.fState Or MFS_GRAYED) Then
      MII.fState = MII.fState - MFS_GRAYED
    Else
      MII.fState = (MII.fState Or MFS_GRAYED)
    End If

    MII.fMask = MIIM_STATE
    Ret = SetMenuItemInfo(hMenu, MII.wID, False, MII)
    If Ret = 0 Then
      Ret = SetId(ResetID)
    End If

    Ret = SendMessage(Me.hwnd, WM_NCACTIVATE, True, 0)
    SetButtons
  End If
End Sub

Private Sub Command2_Click()
  Dim Ret As Long

  If MII.fState = (MII.fState Or MFS_CHECKED) Then
    MII.fState = MII.fState - MFS_CHECKED
  Else
    MII.fState = (MII.fState Or MFS_CHECKED)
  End If

  MII.fMask = MIIM_STATE
  Ret = SetMenuItemInfo(hMenu, MII.wID, False, MII)
  SetButtons
End Sub

Private Sub Command3_Click()
  Unload Me
End Sub

Private Function SetId(Action As Long) As Long
  Dim MenuID As Long
  Dim Ret As Long

  MenuID = MII.wID
  If MII.fState = (MII.fState Or MFS_GRAYED) Then
    If Action = SwapID Then
      MII.wID = SC_CLOSE
    Else
      MII.wID = xSC_CLOSE
    End If
  Else
    If Action = SwapID Then
      MII.wID = xSC_CLOSE
    Else
      MII.wID = SC_CLOSE
    End If
  End If

  MII.fMask = MIIM_ID
  Ret = SetMenuItemInfo(hMenu, MenuID, False, MII)
  If Ret = 0 Then
    MII.wID = MenuID
  End If
  SetId = Ret
End Function

Private Sub SetButtons()
  If MII.fState = (MII.fState Or MFS_GRAYED) Then
    Command1.Caption = "Enable"
  Else
    Command1.Caption = "Disable"
  End If
  If MII.fState = (MII.fState Or MFS_CHECKED) Then
    Command2.Caption = "Uncheck"
  Else
    Command2.Caption = "Check"
  End If

  Command3.Caption = "Exit"
End Sub

Private Sub Form_Load()
  Dim Ret As Long

  hMenu = GetSystemMenu(Me.hwnd, 0)
  MII.cbSize = Len(MII)
  MII.dwTypeData = String(80, 0)
  MII.cch = Len(MII.dwTypeData)
  MII.fMask = MIIM_STATE
  MII.wID = SC_CLOSE
  Ret = GetMenuItemInfo(hMenu, MII.wID, False, MII)
  SetButtons

End Sub

- Now press F5 to run the project

Visual Basic handles enabling and disabling the standard Control menu items, including Restore, Size, Move, Minimize, and Maximize (the Close menu is always enabled). Generally, Visual Basic enables/disables the menu items depending on the window's state (minimized, maximized, or normal) by referencing these menu items by their menu item IDs.

As a result, if we merely add or remove MFS_GRAYED from a menu's fState, Visual Basic immediately resets it. The workaround is to change the menu item's ID (which also renders the item inoperable).

Using this workaround, we can effectively disable a menu item that Visual Basic intends to be enabled, but we cannot enable a menu item Visual Basic intends to be disabled (the menu item must have its regular ID to be operable).

Enabling a menu item that Visual Basic intends to be disabled requires removing the item and replacing it with a menu item of our own (this is not covered in this article).

When the Close menu item is enabled or disabled, the Close box on the title bar should also be normal or grayed, respectively. Sending the message WM_NCACTIVATE (nonclient activate) notifies the window to refresh its title bar so the Close box is updated to appear normal or grayed.

Additional Constants

Click here to copy the following block

'Menu item constants
    Const SC_SIZE     As Long = &HF000&
    Const SC_SEPARATOR  As Long = &HF00F&
    Const SC_MOVE     As Long = &HF010&
    Const SC_MINIMIZE   As Long = &HF020&
    Const SC_MAXIMIZE   As Long = &HF030&
    Const SC_CLOSE    As Long = &HF060&
    Const SC_RESTORE   As Long = &HF120&

'SetMenuItemInfo fMask Constants
    Const MIIM_STATE   As Long = &H1&
    Const MIIM_ID     As Long = &H2&
    Const MIIM_SUBMENU  As Long = &H4&
    Const MIIM_CHECKMARKS As Long = &H8&
    Const MIIM_TYPE    As Long = &H10&
    Const MIIM_DATA    As Long = &H20&