def add_tab(self, widget):
        """Add tab."""
        self.clients.append(widget)
        index = self.tabwidget.addTab(widget, widget.get_short_name())
        self.tabwidget.setCurrentIndex(index)
        self.tabwidget.setTabToolTip(index, widget.get_filename())
        if self.dockwidget and not self.ismaximized:
            self.dockwidget.setVisible(True)
            self.dockwidget.raise_()
        self.activateWindow()
        widget.notebookwidget.setFocus()