Implemented IsVisible and GetFirst/NextVisibleItem for generic tree control

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@8126 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

contrib/samples/gizmos/splittree/tree.h

@@ -77,6 +77,8 @@ public:
     TestTree(wxWindow* parent, wxWindowID id, const wxPoint& pt = wxDefaultPosition,
         const wxSize& sz = wxDefaultSize, long style = wxTR_HAS_BUTTONS);
 	~TestTree();
+
+	void OnPaint(wxPaintEvent& event);
     DECLARE_EVENT_TABLE()
 protected:
 	wxImageList*	m_imageList;