[RESOLVED] listbox topindex change

[westconn1]

is it possible to detect when the topindex of a listbox changes, by mousewheel or any other method?

thnx

[RhinoBull]

Timer may come handy here:

Option Explicit

Private Sub Form_Load()
Dim i As Integer

    For i = 1 To 25
        List1.AddItem "Item " & i
    Next i
    
    Timer1.Interval = 1
    Timer1.Enabled = True

End Sub

Private Sub Timer1_Timer()
Static lastIndex As Integer

    If lastIndex <> List1.TopIndex Then
        Debug.Print List1.List(List1.TopIndex)
    End If
    
    lastIndex = List1.TopIndex

End Sub

NOTE: above sample is far from being complete so try enhancing it.

[LaVolpe]

I struggled with that when I creatd my own unicode listbox in order to raise an event. I eventually gave in and cached the top index and then compared its value to the value returned by SendMessage [LB_GETTOPINDEX] during these subclassed messages:

-- WM_MOUSEMOVE when button is down (i.e., dragging listbox item up/down to force scroll)
-- WM_VSCROLL/WM_HSCROLL
-- WM_COMMAND & lParam is lstbox hWnd & HiWord(wParam) is LBN_SELCHANGE
-- Though I didn't use MW_MOUSEWHEEL, I would think it could be used also?

If the listbox is ownerdrawn, you might want to get the top index during WM_DrawItem.

[westconn1]

@ rhino i did think about using the timer, just reduce its interval to a more responsive value, but was looking if there were any alternatives

@ lavolpe i found an example to use ownerdraw in vb.net to do this, but am not sure about modifying to vb6
http://social.msdn.microsoft.com/for...d-0a8ef2a62886

[RhinoBull]

i did think about using the timer, just reduce its interval to a more responsive value

1 = 1/1000 of a second so I think it's fast enough.

[westconn1]

1 = 1/1000 of a second so I think it's fast enough.

my existing timer was working at 10000, too slow for this

[RhinoBull]

You can use multiple timers without any problem.

[westconn1]

i had no problem using one, just put a counter for the other line that only needed to fire every few seconds