BUG: TreeView: NodeCheck Event Does Not Occur (221557)

RESOLUTION

Step by Step Example

1. Open a new Visual Basic Standard Exe project. Form1 is created by default.
2. On the Project menu, click Components. Select Microsoft Common Controls 6.0 and click OK.
3. Add a TreeView control to Form1.
4. Add the following code to the General Declarations section of Form1:

   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   ' <---
   
   ' treeview messages
   Private Const TV_FIRST = &H1100
   ' wParam = 0, lParam = lptvhti, rtns hItem
   Private Const TVM_HITTEST = (TV_FIRST + 17)
   
   Private Type POINTAPI   ' pt
      x As Long
      y As Long
   End Type
   
   ' structure passed with the TVM_HITTEST message
   Private Type TVHITTESTINFO
      pt As POINTAPI
      flags As Long
      hItem As Long
   End Type
   
   ' TVHITTESTINFO.flags value. An item's checkbox
   ' is in fact held in the item's state icon image.
   Private Const TVHT_ONITEMSTATEICON = &H40
   
   Private m_nodChecked As Node
   
   Private Sub Form_Load()
      Dim Node1 As Node
      Dim Node2 As Node
      Dim Node3 As Node
      Dim i As Integer
      Dim j As Integer
      Dim k As Integer
      ' For some convenience...
      With TreeView1
         .HideSelection = False
         .Indentation = 19 * Screen.TwipsPerPixelX
         .LabelEdit = tvwManual
         .LineStyle = tvwRootLines
         .Checkboxes = True
      End With
   
   ' Fill up the treeview...
      For i = 1 To 2
         Set Node1 = TreeView1.Nodes.Add(, , , "Root" & i)
         For j = 1 To 3
            Set Node2 = TreeView1.Nodes.Add(Node1.Index, tvwChild, , _
            "Root" & i & "Child" & j)
            For k = 1 To 3
               Set Node3 = TreeView1.Nodes.Add(Node2.Index, tvwChild, , _
                     "GrandChild" & (16 * (i - 1)) + (4 * (j - 1)) + k)
            Next k
         Next j
         Node1.Expanded = True
      Next i
   End Sub
   
   Private Sub TreeView1_MouseDown(Button As Integer, Shift As Integer, _
                                   x As Single, y As Single)
      Dim tvhti As TVHITTESTINFO
   
       Debug.Print "MouseDown: " & Button & " " & Shift & "  " & _
                  x & " " & y
   
      If (Button = vbLeftButton) Then
         ' determine if the mouse pointer is being depressed over the Node's
         ' checkbox (assumes that the Form's ScaleMode is set to vbTwips).
         tvhti.pt.x = x / Screen.TwipsPerPixelX
         tvhti.pt.y = y / Screen.TwipsPerPixelY
         If (SendMessage(TreeView1.hWnd, TVM_HITTEST, 0, tvhti)) Then
   
            If (tvhti.flags And TVHT_ONITEMSTATEICON) Then
               ' the value of the Node's Checked property will be toggled
               ' *after* this procedure finishes execution.
               Set m_nodChecked = TreeView1.HitTest(x, y)
            End If
   
         End If   ' TVM_HITTEST
      End If   ' (Button = vbLeftButton)
   End Sub
   
   Private Sub TreeView1_NodeCheck(ByVal Node As MSComctlLib.Node)
   
      If (Node Is m_nodChecked) Then
   
         ' Either the left-mouse button is being released over the Node
         ' whose checkbox has been toggled, or this event procedure
         ' is being called from TreeView1_MouseUp. This *is* where we
         ' want to process code...
         Debug.Print "NodeCheck: " & m_nodChecked & _
         ".Checked = " & m_nodChecked.Checked & _
         vbCrLf & vbTab & " (do process code here)"
      
         ' De-reference the module level Node variable so you don't
         ' call this event again in TreeView1_MouseUp.
         Set m_nodChecked = Nothing
   
      Else
         ' This event is being raised by the TreeView because the mouse
         ' pointer is being released over a node whose checkbox state
         ' has *not* been toggled. you do *not* want to process code here...
         Debug.Print "NodeCheck: " & Node & _
         ".Checked = " & Node.Checked & _
         vbCrLf & vbTab & " (do *not* process code here)"
   
      End If
   End Sub
   
   Private Sub TreeView1_MouseUp(Button As Integer, Shift As Integer, _
               x As Single, y As Single)
   
      If (m_nodChecked Is Nothing) = False Then
   
         ' You didn't get a NodeCheck event (the variable is still set),
         ' the mouse pointer is *not* over the Node whose checkbox
         ' state has been toggled. Explicitly call the event procedure.
         Call TreeView1_NodeCheck(m_nodChecked)
   
      End If
   
         Debug.Print "MouseUp: " & Button & " " & Shift & " " & _
                  x & " " & y
      End Sub
   						

5. Run the program and position the mouse cursor over a checkbox. Press and hold down the left-mouse button, drag the mouse cursor away from the checkbox, and then release the mouse button. Note that a message verifying that the NodeCheck event occurred is printed in the Immediate pane.