how to search/query for objects

[ichthyo]

define a top-level entry point for retrieving specific objects from the session. Later this may/will be unified with the ConfigQuery and the DefaultsManager

[ichthyo]

Starting to collect thoughts and informations regarding this topic....

• first off -- yes indeed, thats something needing clarification, it isn't settled yet
• currently we've gotten three different kinds of queries: config, default, discovery.
• the intention is to unify them eventually, but this isn't going to happen soon
• this problem here relates mostly to discovery queries
• but later, the general config queries will too allow to pose such discovery requests
• discovery queries happen on the QueryFocus and alternatively on the dedicated query functions ("Track::getClips()") of the session API
• here, we're indeed lacking a variant of the query() function allowing to pick specific objects found during the discovery.

See the following pages in the TiddlyWiki:

• http://lumiera.org/wiki/renderengine.html#Query
• http://lumiera.org/wiki/renderengine.html#SessionStructureQuery

[ichthyo]

So, more specifically, the question is:

• shall we implement a kind of additional filtering on the query()-function, beyond just the filtering by type (which is already in place)?
• is such a filtering easy to use in practice? (read: how to code up the required closure/functor when issuing an actual query?)
• doesn't this interfere with the more generic "config queries" (which are only planned by now)?
• how could an equivalent "config query" implemented in practice? (read: how to implement the respective predicates by Proc functionality?)

[ichthyo]

Coded up and basically done now (with the exception of the question regarding the general "config query".... thats future work).

Implemented a filtering mechanism with client-provided predicate (functor) and defined a session interface to invoke it. Usage passes compiler, but can't test it yet because of the missing QueryFocus implementation (see #310 )

[ichthyo]

Meanwhile QueryFocus is fully implemented and working...

Defined a SessionElementQuery_test just to be sure this fetch-element-from-session works as expected