DDS11 — (R#181) Clarify listener and mask behavior with respect to built-in entitie

This issue subsumes two related issues.

· Presumably, listener callbacks pertaining to built-in entities should fall back to the DomainParticipantListener of their containing DomainParticipant in the usual way in the event that those built-in entities have not requested to receive the callbacks themselves. However, this behavior may prove inconvenient in practice: users-even those completely uninterested in built-in entities-must recognize the callbacks pertaining to those entities and deal with them in some way whenever they install a participant listener. Implementers are also constrained, as they will find it difficult to ensure the correct listener behavior while preserving the freedom to create built-in entities on demand.

· The specification does not state the behavior of installing a nil listener or what mask values are acceptable in that case.
Proposed Resolution:

Installing a nil listener should be equivalent to installing a listener that does nothing. It is acceptable to provide a mask with a nil listener; in that case, no callback will be delivered to the entity or to its containing entities.

A DomainParticipant's built-in Subscriber and all of its built-in Topics should by default have nil listeners with all mask bits set. Therefore their callbacks will no propagate back to the DomainParticipantListener unless the user explicitly calls set_listener on them.

Proposed Revised Text:

Insert a new paragraph after the existing first paragraph of section 2.1.2.1.1.3 set_listener:

It is permitted to set a nil listener with any listener mask; it is behaviorally equivalent to installing a listener that does nothing.

Append a new sentence to the final bullet in the list in section 2.1.4.3.1:

Any statuses appearing in the mask associated with a nil listener will neither be dispatched to the entity itself nor propagated to its containing entities.

Insert the following paragraph immediately following the table of built-in entity QoS on page 2-129:

Built-in entities have default listener settings as well. A DomainParticipant's built-in Subscriber and all of its built-in Topics have nil listeners with all statuses appearing in their listener masks. The built-in DataReaders have nil listeners with no statuses in their masks.

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