Nodes: move NodeTreeRef functionality into node runtime data

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

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/nodes/function/nodes/node_fn_compare.cc b/source/blender/nodes/function/nodes/node_fn_compare.cc
index e3f13dc7d6b..122d1a3c93e 100644
--- a/source/blender/nodes/function/nodes/node_fn_compare.cc
+++ b/source/blender/nodes/function/nodes/node_fn_compare.cc
@@ -167,7 +167,7 @@ static float component_average(float3 a)
   return (a.x + a.y + a.z) / 3.0f;
 }
 
-static const fn::MultiFunction *get_multi_function(bNode &node)
+static const fn::MultiFunction *get_multi_function(const bNode &node)
 {
   const NodeFunctionCompare *data = (NodeFunctionCompare *)node.storage;