Blender Git Loki

libquery: add optional handling of 'UI' ID pointers.

Handling those through different ways /might/ be needed sometimes, but
in most case this is just a nest of issues, since you can easily forget
to take them into account.

Note that this should be a 'non-functional' change, as this new behavior
is not used anywhere yet.

Better handling of usages of usercount increment in readfile liblink.

Some places could/should still need proper ID refcounting in liblink:
* UI data (spaces) - although this should be strictly 'user one' only...
* Deprectaed data/pointers which are not handled by libquery code.

Not sure whether IPO pointers really need usercount actually...

Merge branch 'master' into readfile-rework-refcount-handling

Conflicts:
source/blender/blenloader/intern/readfile.c

readfile: Quick experiment with refcounting moved to libquery.

Having that extra ID users handling at readfile level, besides generic
one ensured by libquery, has been something bothering me for a long time
(had to fix my share of bugs due to mismatches between those two areas).

Further more, work on undo speedup will require even more complex ID
refcount management if we want to keep it in readfile.c area.

So idea is instead to generalize what we did for linked data already
when undoing: recompute properly usercount numbers after liblink step,
for all IDs.

Note that extra time required here is neglectable in a whole .blend file
reading (few extra milliseconds when loading a full production scene
e.g.).

Refactor readfile's liblink code.

Liblink specific ID type function was so far running a loop over all IDs
of relevant type, unlike almost any other 'ID-callback-like' functions
in Blender, which usually let the looping controll to calling code.

The latter approach is more convinient when one want to add generic
(i.e. type-agnostic) code, since it typically only has to change code in
one place (caller function) instead of tens of places (all the callback
functions).

This commit also changes/sanitizes a few things that had nothing to do
in main liblink code, like mesh conversion from tessfaces to polys
(which can be done in after-linking versionning code), or scenes' cycles
detection/check regarding background 'set' scenes.

Differential Revision: https://developer.blender.org/D6727