Fix issue of events for setting cursor of treeview. - comp_dock_base.refresh() would set cursor, it cause an event. But, we don't want it. - The reason of the issue is that MBScene.show() is not monitored. So, we monitor it by move its body to do_show().

<LEFT>		Turn to left.
<RIGHT>		Turn to right.
<UP>		Turn to up.
<DOWN>		Turn to down.
<SPACE>		To Fire.