User-provided callback function to create a popup for a gtk.menu_button.MenuButton on demand.
This function is called when the popup of menu_button is shown, but none has been provided via gtk.menu_button.MenuButton.setPopover or gtk.menu_button.MenuButton.setMenuModel.
User-provided callback function to create a popup for a gtk.menu_button.MenuButton on demand.
This function is called when the popup of menu_button is shown, but none has been provided via gtk.menu_button.MenuButton.setPopover or gtk.menu_button.MenuButton.setMenuModel.