How To Disable the Close Option on Control Menu of a VB Form

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SUMMARY

To modify an item in the Visual Basic Control menu (also known as the System menu), you need to use the SetMenuItemInfo API function. This article describes how to enable/disable or check/uncheck the Close menu item in the Control menu.

MORE INFORMATION

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.

Example

  1. Start a new standard EXE project. Form1 is added by default.
  2. Add three CommandButtons to Form1.
  3. Add the following code to Form1:
          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
          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
              Command3.Caption = "Exit"
          End Sub
    
    						
  4. Press the F5 key to run the program.

Additional Notes

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

   '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&
				


Related APIs

SetMenuDefaultItem -- You must disable Close to use this in Visual Basic
HiliteMenuItem

REFERENCES

For the 16-bit equivalent, please see the following article in the Microsoft Knowledge Base:
82876 : How to Disable Close Command in VB Control Menu (System Menu)

Properties

Article ID: 184686 - Last Review: July 1, 2004 - Revision: 3.1
APPLIES TO
  • Microsoft Visual Basic 5.0 Learning Edition
  • Microsoft Visual Basic 6.0 Learning Edition
  • Microsoft Visual Basic 5.0 Professional Edition
  • Microsoft Visual Basic 6.0 Professional Edition
  • Microsoft Visual Basic 5.0 Enterprise Edition
  • Microsoft Visual Basic 6.0 Enterprise Edition
  • Microsoft Visual Basic 4.0 Standard Edition
  • Microsoft Visual Basic 4.0 Professional Edition
  • Microsoft Visual Basic 4.0 32-Bit Enterprise Edition
Keywords: 
kbhowto kbgrpdsvb KB184686

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