When visible changed, do setup or unwatch and call visible_callback

def visible(self, visible):
        """When visible changed, do setup or unwatch and call visible_callback"""
        self._visible = visible

        if visible and len(self.panel.objects) == 0:
            self.setup()
            self.select.visible = True
            self.control_panel.extend(self.controls)
            self.panel.extend(self.children)
        elif not visible and len(self.panel.objects) > 0:
            self.unwatch()
            # do children
            self.select.visible = False
            self.control_panel.clear()
            self.search.visible = False
            self.add.visible = False
            self.panel.clear()
        if self.visible_callback:
            self.visible_callback(visible)