+#if wxUSE_MOUSEWHEEL
+
+void wxVScrolledWindow::OnMouseWheel(wxMouseEvent& event)
+{
+ m_sumWheelRotation += event.GetWheelRotation();
+ int delta = event.GetWheelDelta();
+
+ // how much to scroll this time
+ int units_to_scroll = -(m_sumWheelRotation/delta);
+ if ( !units_to_scroll )
+ return;
+
+ m_sumWheelRotation += units_to_scroll*delta;
+
+ if ( !event.IsPageScroll() )
+ ScrollLines( units_to_scroll*event.GetLinesPerAction() );
+ else
+ // scroll pages instead of lines
+ ScrollPages( units_to_scroll );
+}
+
+#endif