Q184686: HOWTO: Disable the Close Option on Control Menu of a VB Form
Article: Q184686
Product(s): Microsoft Visual Basic for Windows
Version(s):
Operating System(s):
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 4.0
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0
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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:
Q82876 : How to Disable Close Command in VB Control Menu (System Menu)
Additional query words: kbVBp500 kbVBp400 kbSDKWin32 kbAPI kbMenu kbVBp kbDSupport kbDSD
kbVBp600
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Keywords : kbGrpDSVB
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbVB400Search kbVB400
Issue type : kbhowto
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