Sets the GtkWidget to use to line the menu with when popped up. Note that the align_widget must contain the GtkMenuButton itself. Setting it to NULL means that the popup menu will be aligned with the button itself.
a GtkWidget. [allow-none] Since 3.6
See Implementation
Sets the GtkWidget to use to line the menu with when popped up. Note that the align_widget must contain the GtkMenuButton itself. Setting it to NULL means that the popup menu will be aligned with the button itself.