Example using draw:
http://msdn.microsoft.com/en-us/library/system.windows.forms.tooltip.draw.aspx[
^]
I think essentially that you need to measure the text to display without any truncating and allow wrap (if too long for the screen or tooltip popup).
Private Sub toolTip1_Popup(ByVal sender As System.Object, _
ByVal e As PopupEventArgs) Handles toolTip1.Popup
If e.AssociatedControl Is button2 Then
Dim f As New Font("Tahoma", 9)
Try
e.ToolTipSize = TextRenderer.MeasureText( _
toolTip1.GetToolTip(e.AssociatedControl), f)
Finally
f.Dispose()
End Try
End If
End Sub
I pulled that code from here:
http://msdn.microsoft.com/en-us/library/system.windows.forms.tooltip.ownerdraw.aspx[
^]