[RESOLVED] Moving a Picturebox Horizontally with Limitations

I have a Picturebox on my Form that I'd like to be able to drag left and right but to only go so far (limitations). I have set the left limitation to 2400 and the right to 6000. It drags fine, but once it reaches the limitations, it doesn't stop. Here is my code:

Code:

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Private Sub Picture1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
Static lx As Single, ly As Single
If Button = vbLeftButton Then
    If (Picture1.Left > 2399) And (Picture1.Left < 6001) Then
        Picture1.Left = Picture1.Left + (X - lx)
    Else
        If Picture1.Left < 2400 Then Picture1.Left = 2400
        If Picture1.Left > 6000 Then Picture1.Left = 6000
    End If
Else
    lx = X: ly = Y
End If
End Sub

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It works, but when it gets to the left and right limitations, it does this:
Attachment 134087

It also randomly continues past the limitations. Anyway to correct this?

I've also run into trouble figuring out these kinds of movement issues in some of my programs, and what I've found helps is to resolve them is:

• Perform and store all calculation steps in variables and check the results using DEBUG.PRINT statements
• Add DEBUG.ASSERTS to pause execution at unexpected conditions - this gives you a chance to interrupt your assumptions and re-evaluate your approach early.
• Use constants for "magic numbers" like Min/Max values - sometimes you change your mind about a range, and miss changing the magic numbers everywhere in your code - this can lead to unexpected results and be a real time sink.

This code *should* work as required and also demonstrates some of the principles listed above. If it doesn't work as required, then the debugging information should help you diagnose the source of the problem. If not, then post your new code and I'll take a look :)

Code:

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Option Explicit

Private Const mc_MinLeft As Long = 2400
Private Const mc_MaxLeft As Long = 6000

Private Sub Form_Load()
  If mc_MinLeft > mc_MaxLeft Then
      ' Minimum left value must be less than maximum left value!
      Debug.Assert False  ' Stop here in debugger to warn developer of unexpected condition
     
      Err.Raise vbObjectError, , "Minimum left value must be less than maximum left value!"
  End If
 
  ' Make sure PB is within min/max bounds
  If Me.Picture1.Left < mc_MinLeft Then Me.Picture1.Left = mc_MinLeft
  If Me.Picture1.Left > mc_MaxLeft Then Me.Picture1.Left = mc_MaxLeft
End Sub

Private Sub Picture1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
  Static lx As Single, ly As Single

  Dim l_Left As Single
  Dim l_Delta As Single
  Dim l_NewPos As Single
 
  If Button = vbLeftButton Then
      ' Left mouse button is down, calculate the difference between the last position and the current position
      l_Delta = X - lx
     
      If l_Delta <> 0 Then
        ' Mouse has moved
        Debug.Print "Mouse has moved " & l_Delta & " from original position."
           
        ' Calculate new position
        l_NewPos = Picture1.Left + l_Delta
       
        Debug.Print "New position will be " & l_NewPos
       
        If (l_NewPos >= mc_MinLeft) And (l_NewPos < mc_MaxLeft) Then
            ' New position is within our min/max range, so reposition the PB
            Debug.Print "New position is within Min/Max bounds of " & mc_MinLeft & "/" & mc_MaxLeft & " - reposition PB."
           
            Me.Picture1.Left = l_NewPos
       
        Else
            ' New position is outside of our min/max range
            ' Test if we should move the PB to the min or max value
           
            Debug.Print "New position is NOT within Min/Max bounds of " & mc_MinLeft & "/" & mc_MaxLeft & ". Check if we should move PB to MIN/MAX boundary."
           
            If l_NewPos < mc_MinLeft Then
              ' The new position is less than our minimum position, so set the PB to the minimum position
              If Me.Picture1.Left > mc_MinLeft Then
                  ' The PB.Left is greater than our min position, so move it to our max position
                  Debug.Print "Current PB left position OUTSIDE min/max bounds - set it to minimum left boundary."
                 
                  Me.Picture1.Left = mc_MinLeft
              Else
                  Debug.Print "Current PB left position is within min/max bounds - leave everything alone."
             
              End If
            Else
              ' The new position is greater than our maximum position
              If Me.Picture1.Left < mc_MaxLeft Then
                  ' The PB.Left is less than our max position, so move it to our max position
                  Debug.Print "Current PB left position OUTSIDE min/max bounds - set it to maximum left boundary."
                 
                  Me.Picture1.Left = mc_MaxLeft
              Else
                  Debug.Print "Current PB left position is within min/max bounds - leave everything alone."
              End If
            End If
        End If
      End If
     
  ElseIf Button = 0 Then
      ' No button down, record current mouse position for calculating movement when button is down
      lx = X: ly = Y
  End If

End Sub

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That works perfectly. Now, to figure out why 1 / 3600 is giving me zero. :o