_track_canvas->signal_enter_notify_event().connect (sigc::mem_fun(*this, &Editor::entered_track_canvas), false);
_track_canvas->set_flags (CAN_FOCUS);
+ _track_canvas->PreRender.connect (sigc::mem_fun(*this, &Editor::pre_render));
+
/* set up drag-n-drop */
vector<TargetEntry> target_table;