def _tree_stat(self, mode, infostr, stat):
        """ update stat regarding to tree generating process,
            e.g. show_tree()
        """
        action_str = mode.upper()
        info_str = infostr
        if stat == 'OK':
            self.action_st_panel.SetBackgroundColour('#00FF00')
        else:  # ERR
            self.action_st_panel.SetBackgroundColour('#FF0000')
        self.action_st.SetLabel(action_str)
        if info_str is None:
            pass
        if stat == 'OK':
            child_cnt_0 = self.mainview_tree.GetChildrenCount(
                self.mainview_tree.GetRootItem(),
                recursively=False)
            child_cnt_1 = self.mainview_tree.GetChildrenCount(
                self.mainview_tree.GetRootItem(),
                recursively=True)
            self.info_st.SetLabel("{0} ({1} elements.)".format(info_str, child_cnt_0))
            self.log.append({'stat': stat,
                             'logstr':
                                 "[{ts}] {acts:<10s} : {infs} ({cnt1}|{cnt2})".format(
                                     ts=time.strftime("%Y/%m/%d-%H:%M:%S",
                                                      time.localtime()),
                                     acts=action_str,
                                     infs=info_str,
                                     cnt1=child_cnt_0,
                                     cnt2=child_cnt_1), })
        else:
            self.info_st.SetLabel("{0} (0 elements.)".format(info_str))
            self.log.append({'stat': stat,
                             'logstr':
                                 "[{ts}] {acts:<10s} : {infs} ({cnt1}|{cnt2})".format(
                                     ts=time.strftime("%Y/%m/%d-%H:%M:%S",
                                                      time.localtime()),
                                     acts=action_str,
                                     infs=info_str,
                                     cnt1=0,
                                     cnt2=0), })

        if self.info_st.IsEllipsized():
            self.info_st.SetToolTip(wx.ToolTip(info_str))