Using ADDTOZONE from certain plugin handlers
This document is linked to from the standard POD documentation
Warning! Take care when adding to zones from the following plugin handlers:
Normally, adding to the same zone/id multiple times is fine - previous data is
ovewritten to ensure content only appears once in the output. However, because
these handlers are fired at the end of _renderZone() handling with
Foswiki::Meta::expandMacros() and
Foswiki::Meta::renderTML(),
it is possible that multiple renderings of a particular zone (normally, only
the first rendering should contain any content) will result in content
appearing more than once.
See
Tasks.Item9480 for background