The goal is to be able to define a node in as few files as possible. Currently,
RNA definitions for nodes are put in `rna_nodetree.cc`. However, it seems
surprisingly simple to move them from there to the node files. Of course this
means that `makesrna.cc` won't generate these properties and their accessor
functions anymore. Fortunately, C++ lambdas and the preprocessor make it
fairly straight forward to generate those without the `makesrna` preprocessor.
Using the preprocessor here is not great of course, but I'd argue that it feels
less magical than it was before, so it's an improvement.
This patch changes a few files to test the feasibility of this approach. Eventually,
this approach should be used by all nodes. It can't be used for shader nodes for
now, because cycles still relies on the C++ API generated by RNA.
Right now, only properties are defined the node files. The `StructRNA` is still
generated by `makesrna`. It seems feasible to generate it at runtime as well
though with potentially minor RNA API changes. This is related to #75724.
Pull Request: https://projects.blender.org/blender/blender/pulls/110840
f7c0ef1f73