Dock widget visibility has changed.

def visibility_changed(self, enable):
        """
        Dock widget visibility has changed.
        """
        if self.dockwidget is None:
            return
        if enable:
            self.dockwidget.raise_()
            widget = self.get_focus_widget()
            if widget is not None and self.undocked_window is not None:
                widget.setFocus()
        visible = self.dockwidget.isVisible() or self.ismaximized
        if self.DISABLE_ACTIONS_WHEN_HIDDEN:
            toggle_actions(self.plugin_actions, visible)
        self.isvisible = enable and visible
        if self.isvisible:
            self.refresh_plugin()