Inserts group into this.
Children of this that implement [[email protected]] can then be associated with actions in
group by setting their “action-name” to prefix.`action-name`.
Note that inheritance is defined for individual actions. I.e. even if you insert a group with prefix prefix, actions with
the same prefix will still be inherited from the parent, unless the group contains an action with the same name.
If group is null, a previously inserted group for name is removed from
this.
| this |
a `GtkWidget` |
| name |
the prefix for actions in |
| group |
a `GActionGroup`, or null to remove the previously inserted group for |