BUG: MouseMove Button Is Incorrect with ListView MultiSelect

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 32-bit only, for Windows, version 4.0

SYMPTOMS

The Button argument of the ListView's MouseMove event may not always correctly reflect the most current mouse button status. This can occur if the MultiSelect property of the ListView control is set to True. The Button argument of the MouseMove event is updated only when the MouseDown event is fired, not every time the MouseMove event is fired.

WORKAROUND

To work around this problem, one could use an OCX or tool that allows the trapping of Windows messages. The code would need to be written, but one possible scheme could involve a flag variable that would be set whenever the ListView control received a WM_LBUTTONDOWN or WM_RBUTTONDOWN message and only reset when a corresponding WM_LBUTTONUP or WM_RBUTTONUP message was received. This flag variable could be used as the equivalent of the button argument in the MouseMove event, because it will return different values when the mouse button has been clicked or when the mouse button has been clicked but not released. The Message Blaster OCX, produced by WareWithAll, is a good tool to use to trap Windows messages.

STATUS

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

MORE INFORMATION

Steps to Reproduce

1. Start Visual Basic 4.0. Form1 is created by default.

2. Add a single ListView control to the form. Also add one label control.

3. Set the following property of the ListView control:

      MultiSelect:      True
   
   

4. Add this code to the form:

      Private Sub Form_Load()
          ListView1.ListItems.Add , , "item 1"
      End Sub
   
      Private Sub ListView1_MouseMove(Button As Integer, Shift As Integer, x
      As Single, y As Single)
          Label1.Caption = Button
      End Sub
   
   

5. Press F5 or select Start from the Run menu to run the application. Click once on the white space of the control and see that the label changes to show a 1--the constant for the left mouse button. Now move the mouse button around and see that the label still shows 1 even though the left mouse button is not pressed.