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, 5 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_multi_value_map.hh b/source/blender/blenlib/BLI_multi_value_map.hh
index 4b6300c09aa..1fc5a797574 100644
--- a/source/blender/blenlib/BLI_multi_value_map.hh
+++ b/source/blender/blenlib/BLI_multi_value_map.hh
@@ -137,6 +137,11 @@ template<typename Key, typename Value> class MultiValueMap {
   {
     return map_.values();
   }
+
+  void clear()
+  {
+    map_.clear();
+  }
 };
 
 }  // namespace blender