Dominik Huber wrote:
2. A subtype of IObjectModifiedEvent is cluttering because of
redundant modification events. The modification is caused by the
containment.
Regularly the dispatching related to the containment hierarchy tries
to emulate an information flow from *parent -> child*, because
children should be informed if the location information has been
changed. But the other way around you need *never* a notification,
because the container is aware of changes related to the container
framework! Here an more adequat solution would be an internal
container framework event that derives from IObjectEvent but not from
IObjectModifiedEvent, because otherwise we would notify the same
modification using two redundant modification events.
For your interest, the W3C DOM event model uses a two-way event
propagation: from parent to child and from child to parent.
- the parent -> child model (event capturing) corresponds to the
original Netscape 4 implementation. It is similar to the one currently
implemented in Zope3 for containers (dispatchToSublocations).
- the child -> parent model (event bubbling) is implemented in IE5
the W3C model mixes both approaches.
I would suggest reading the Document Object Model Events recommendation
[1] and for some background information some great introduction to
events models in browsers [2]. The notion of event cancellation might be
useful to consider.
[1] http://www.w3.org/TR/2000/REC-DOM-Level-2-Events-20001113/events.html
[2] http://www.quirksmode.org/js/events_order.html
/JM
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