PRB: UserControl Resize Event Fails with MoveWindow API (187740)


The information in this article applies to:

  • Microsoft Visual Basic Learning Edition for Windows 5.0
  • Microsoft Visual Basic Learning Edition for Windows 6.0
  • Microsoft Visual Basic Professional Edition for Windows 5.0
  • Microsoft Visual Basic Professional Edition for Windows 6.0
  • Microsoft Visual Basic Enterprise Edition for Windows 5.0
  • Microsoft Visual Basic Enterprise Edition for Windows 6.0
This article was previously published under Q187740

SYMPTOMS

The Resize Event of a UserControl will not fire if you use the MoveWindow API function to resize the window of the UserControl.

NOTE: Other API calls that manipulate the UserControl window, such as SetWindowPos, may also show this behavior.

CAUSE

When you manipulate the UserControl window through API calls, you bypass the UserControl Object. So any of the events that would normally get raised from a COM call to the UserControl may fail when you bypass the UserControl object and manipulate the UserControl's window directly.

RESOLUTION

Use the Visual Basic Move method.

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

When using the MoveWindow API function to move or resize a UserControl, the UserControl's Resize event will not fire. You will see the same behavior if the UserControl is in a standard EXE or a compiled OCX.

Steps to Reproduce Behavior

  1. Create a standard Exe Project. Form1 is created by default.
  2. Click Add UserControl from the Project menu to add a UserControl to the project.
  3. Change the BackColor of the UserControl to Red so you will be able to see the control.
  4. Add the following code to the UserControl: 
          Public Property Get hWnd() As Long
        hWnd = UserControl.hWnd
      End Property

      Private Sub UserControl_Resize()
        Debug.Print "Resize!"
      End Sub
  5. Add the UserControl to Form1.
  6. Add the following code to Form1: 
          Private Declare Function MoveWindow Lib "user32" (ByVal hWnd As _
       Long, ByVal X As Long, ByVal Y As Long, ByVal nWidth As Long, _
       ByVal nHeight As Long, ByVal bRepaint As Long) As Long

      Private Sub Form_Load()
        Me.ScaleMode = vbPixels
      End Sub

      Private Sub Form_MouseDown(Button As Integer, Shift As Integer, _
       X As Single, Y As Single)
        Static Chop As Boolean

        Chop = Not Chop
        With UserControl1
          If Chop Then
           Call MoveWindow(.hWnd, X, Y, .Width \ 2, .Height \ 2, True)
           '.Move X, Y, .Width \ 2, .Height \ 2 'VB Move Method
          Else
           Call MoveWindow(.hWnd, X, Y, .Width * 2, .Height * 2, True)
           '.Move X, Y, .Width * 2, .Height * 2 'VB Move Method
          End If
        End With
      End Sub
  7. Save and run the project. Try clicking on the form and note that you will not see the Resize code in the UserControl run. If you comment out the call to the MoveWindow API function and use the Visual Basic Move method in place of the API call, you will see the Resize code for the UserControl run.
Modification Type:MajorLast Reviewed:5/13/2003
Keywords:kbprb KB187740
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