BUG: Moving Controls on a Form Triggers Form_MouseMove Event

• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 6.0

SYMPTOMS

When you move controls on a form and the cursor is over the form, the form's MouseMove event gets triggered even if the cursor is not moving.

RESOLUTION

In this scenario, if you need to place code in the form's MouseMove event and want to be sure it runs only when the mouse is actually moving, you will need to set a flag before moving any control on the form. Check the flag in the MouseMove event before executing any code.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

Steps to Reproduce Behavior

1. Start a new Standard EXE project. Form1 is created by default.



2. Add a PictureBox control (Picture1) to Form1.



3. Add a TextBox control (Text1) to Form1. Make it high enough to display multiple lines and set the Multiline property to True.



4. Place three CommandButtons on the form. Name them as below and set the captions accordingly:

   
   cmdMove       &Move
   cmdStart      &Start Log
   cmdStop       &End Log 




5. Add the following code to the module of Form1:

   
   Option Explicit
   Dim iLog As Long
   
   Private Sub cmdMove_Click()
       Dim l As Integer, t As Integer
       l = Picture1.Left + Picture1.Width / 2
       t = Picture1.Top
       Picture1.Move l, t
   End Sub
   
   Private Sub cmdStart_Click()
       Text1.Text = ""
       iLog = 1
   End Sub
   
   Private Sub cmdStop_Click()
       iLog = 0
   End Sub
   
   Private Sub Form_Load()
       iLog = 0
   End Sub
   
   Private Sub Form_MouseMove(Button As Integer, Shift As Integer, _
      x As Single, y As Single)
       If iLog = 1 Then Text1.Text = Text1.Text & "Form " & x & _
          " " & y & " " & Date & vbCrLf
   End Sub 




6. Save the project.



7. Press F5 to run the project.



8. Place the mouse over the form.



9. You can move Picture1 by using Alt+M.



10. You can start logging MouseMove events by using Alt+S.



11. Start logging and move Picture1. Every time you move the picture, a MouseMove event gets logged in the TextBox. Note that this only happens if the mouse is over the form.

Additional query words:

Keywords : kbActivexEvents kbVBp kbVBp600bug kbGrpVB kbDSupport
Version : WINDOWS:6.0
Platform : WINDOWS
Issue type : kbbug