Added way to specify in generic tree control

if the drop effect (a line) should be drawn
   above or below the item.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@31289 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/treectlg.cpp

@@ -758,6 +758,8 @@ void wxGenericTreeCtrl::Init()
 
     m_findTimer = NULL;
 
+    m_dropEffectAboveItem = false;
+
     m_lastOnSame = false;
 
 #ifdef __WXMAC_CARBON__
@@ -2499,7 +2501,7 @@ void wxGenericTreeCtrl::DrawDropEffect(wxGenericTreeItem *item)
         {
             // draw a line under the drop target because the item will be
             // dropped there
-            DrawLine(item, true /* below */);
+            DrawLine(item, !m_dropEffectAboveItem );
         }
 
         SetCursor(wxCURSOR_BULLSEYE);