It's easier to keep track of state in these algorithms if it's stored in
a central place like a set. Plus, using flags requires clearing them
beforehand. For the selected linked operators, using the topology
cache means we don't have to iterate over all links.
The purpose of `NodeTreeRef` was to speed up various queries on a read-only
`bNodeTree`. Not that we have runtime data in nodes and sockets, we can also
store the result of some queries there. This has some benefits:
* No need for a read-only separate node tree data structure which increased
complexity.
* Makes it easier to reuse cached queries in more parts of Blender that can
benefit from it.
A downside is that we loose some type safety that we got by having different
types for input and output sockets, as well as internal and non-internal links.
This patch also refactors `DerivedNodeTree` so that it does not use
`NodeTreeRef` anymore, but uses `bNodeTree` directly instead.
To provide a convenient API (that is also close to what `NodeTreeRef` has), a
new approach is implemented: `bNodeTree`, `bNode`, `bNodeSocket` and `bNodeLink`
now have C++ methods declared in `DNA_node_types.h` which are implemented in
`BKE_node_runtime.hh`. To make this work, `makesdna` now skips c++ sections when
parsing dna header files.
No user visible changes are expected.
Differential Revision: https://developer.blender.org/D15491
This is a follow up to rBbb0fc675822f313c5546a2498a162472c2571ecb.
Now the same kind of run-time data is added to nodes and sockets.
Differential Revision: https://developer.blender.org/D15060
`bNodeTree` has a lot of run-time embedded in it currently. Having a separately
allocated run-time struct has some benefits:
* Run-time data is not stored in files.
* Makes it easy to use c++ types as run-time data.
* More clear distinction between what data only exists at run-time and which doesn't.
This commit doesn't move all run-time data to the new struct yet, only the data where
I know for sure how it is used. The remaining data can be moved separately.
Differential Revision: https://developer.blender.org/D15033
