How To Suppress a TextBox Control's Popup Menu (224302)

MORE INFORMATION

When a user right clicks a textbox, the textbox window receives a WM_CONTEXTMENU message. When the WM_CONTEXTMENU message is received, the textbox window shows the popup menu. A window procedure can capture all WM_CONTEXTMENU messages sent to a textbox window, thus suppressing the default popup window.

WARNING: This sample replaces the WindowProc of the text box window using a technique called a hook. Failure to unhook a window before its imminent destruction results in application errors, invalid page faults, and data loss. This is due to the fact that the new WindowProc function being pointed to no longer exists, but the window has not been notified of the change. Always unhook the sub-classed window upon unloading the sub-classed form or exiting the application. This is especially important while debugging an application that uses this technique within the Microsoft Visual Basic Development Environment. Pressing the END button on the toolbar or selecting End from the Run menu without unhooking will cause an invalid page fault and close Microsoft Visual Basic.

NOTE: This functionality is not available in any release of Microsoft Visual Basic for Applications (VBA) prior to Microsoft Office 2000.

Step-by-Step Example

1. Start a new Visual Basic Standard EXE project. Form1 is created by default.
2. Add two text boxes to Form1.
3. Add a standard module to the project.
4. Add the following code to the General Declarations section of Module1:

   Option Explicit
   
   Public Declare Function SetWindowLong Lib "user32" Alias _
      "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, _
      ByVal dwNewLong As Long) As Long
    
   Public Declare Function CallWindowProc Lib "user32" _
      Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, _
      ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, _
      ByVal lParam As Long) As Long
   
   Public Const GWL_WNDPROC = (-4)
   
   Public Const WM_CONTEXTMENU = &H7B
   
   Global lpPrevWndProc As Long
   Global gHW As Long
   
   Public Sub Hook()
      lpPrevWndProc = SetWindowLong(gHW, GWL_WNDPROC, _
      AddressOf gWindowProc)
   End Sub
   
   Public Sub Unhook()
      Dim temp As Long
      temp = SetWindowLong(gHW, GWL_WNDPROC, lpPrevWndProc)
   End Sub
   
   Public Function gWindowProc(ByVal hWnd As Long, ByVal Msg As Long, _
                    ByVal wParam As Long, ByVal lParam As Long) As Long
      If Msg = WM_CONTEXTMENU Then
         Debug.Print "Intercepted WM_CONTEXTMENU at " & Now
         gWindowProc = True
      Else ' Send all other messages to the default message handler
         gWindowProc = CallWindowProc(lpPrevWndProc, hWnd, Msg, wParam, _
            lParam)
      End If
   End Function
   					

5. Add the following code to the General Declarations section of Form1:

   Private Sub Form_Load()
      gHW = Text1.hwnd
      Hook
   End Sub
   
   Private Sub Form_Unload(Cancel As Integer)
      Unhook
   End Sub
   					

6. Run the project. Right-click Text1. No popup menu appears. Right-click Text2 and the standard popup menu appears.