Nodes: add more flexible method to declare sockets of a node

Previously, built-in nodes had to implement "socket templates"
(`bNodeSocketTemplate`) to tell Blender which sockets they have.
It was nice that this was declarative, but this approach was way
too rigid and was cumbersome to use in many cases.

This commit starts to move us away from this rigid structure
by letting nodes implement a function that declares the sockets
the node has. Right now this is used as a direct replacement
of the "socket template" approach to keep the refactor smaller.
It's just a bit easier to read and write.

In the future we want to support more complex features like
dynamic numbers of sockets and type inferencing. Those features
will be easier to build on this new approach.

This new approach can live side by side with `bNodeSocketTemplate`
for a while. That makes it easier to update nodes one by one.

Note: In `bNodeSocketTemplate` socket identifiers were made
unique automatically. In this new approach, one has to specify
unique identifiers manually (unless the name is unique already).

Differential Revision: https://developer.blender.org/D12335

1 files changed, 135 insertions, 0 deletions

diff --git a/source/blender/nodes/NOD_node_declaration.hh b/source/blender/nodes/NOD_node_declaration.hh
new file mode 100644
index 00000000000..9c461885859
--- /dev/null
+++ b/source/blender/nodes/NOD_node_declaration.hh
@@ -0,0 +1,135 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+#include <type_traits>
+
+#include "BLI_string_ref.hh"
+#include "BLI_vector.hh"
+
+#include "DNA_node_types.h"
+
+namespace blender::nodes {
+
+class NodeDeclarationBuilder;
+
+class SocketDeclaration {
+ protected:
+  std::string name_;
+  std::string identifier_;
+
+  friend NodeDeclarationBuilder;
+
+ public:
+  virtual bNodeSocket &build(bNodeTree &ntree, bNode &node, eNodeSocketInOut in_out) const = 0;
+  virtual bool matches(const bNodeSocket &socket) const = 0;
+  virtual bNodeSocket &update_or_build(bNodeTree &ntree, bNode &node, bNodeSocket &socket) const;
+
+  StringRefNull name() const;
+  StringRefNull identifier() const;
+};
+
+using SocketDeclarationPtr = std::unique_ptr<SocketDeclaration>;
+
+class NodeDeclaration {
+ private:
+  Vector<SocketDeclarationPtr> inputs_;
+  Vector<SocketDeclarationPtr> outputs_;
+
+  friend NodeDeclarationBuilder;
+
+ public:
+  void build(bNodeTree &ntree, bNode &node) const;
+  bool matches(const bNode &node) const;
+
+  Span<SocketDeclarationPtr> inputs() const;
+  Span<SocketDeclarationPtr> outputs() const;
+};
+
+class NodeDeclarationBuilder {
+ private:
+  NodeDeclaration &declaration_;
+
+ public:
+  NodeDeclarationBuilder(NodeDeclaration &declaration);
+
+  template<typename DeclType> DeclType &add_input(StringRef name, StringRef identifier = "");
+  template<typename DeclType> DeclType &add_output(StringRef name, StringRef identifier = "");
+};
+
+/* --------------------------------------------------------------------
+ * SocketDeclaration inline methods.
+ */
+
+inline StringRefNull SocketDeclaration::name() const
+{
+  return name_;
+}
+
+inline StringRefNull SocketDeclaration::identifier() const
+{
+  return identifier_;
+}
+
+/* --------------------------------------------------------------------
+ * NodeDeclarationBuilder inline methods.
+ */
+
+inline NodeDeclarationBuilder::NodeDeclarationBuilder(NodeDeclaration &declaration)
+    : declaration_(declaration)
+{
+}
+
+template<typename DeclType>
+inline DeclType &NodeDeclarationBuilder::add_input(StringRef name, StringRef identifier)
+{
+  static_assert(std::is_base_of_v<SocketDeclaration, DeclType>);
+  std::unique_ptr<DeclType> socket_decl = std::make_unique<DeclType>();
+  DeclType &ref = *socket_decl;
+  ref.name_ = name;
+  ref.identifier_ = identifier.is_empty() ? name : identifier;
+  declaration_.inputs_.append(std::move(socket_decl));
+  return ref;
+}
+
+template<typename DeclType>
+inline DeclType &NodeDeclarationBuilder::add_output(StringRef name, StringRef identifier)
+{
+  static_assert(std::is_base_of_v<SocketDeclaration, DeclType>);
+  std::unique_ptr<DeclType> socket_decl = std::make_unique<DeclType>();
+  DeclType &ref = *socket_decl;
+  ref.name_ = name;
+  ref.identifier_ = identifier.is_empty() ? name : identifier;
+  declaration_.outputs_.append(std::move(socket_decl));
+  return ref;
+}
+
+/* --------------------------------------------------------------------
+ * NodeDeclaration inline methods.
+ */
+
+inline Span<SocketDeclarationPtr> NodeDeclaration::inputs() const
+{
+  return inputs_;
+}
+
+inline Span<SocketDeclarationPtr> NodeDeclaration::outputs() const
+{
+  return outputs_;
+}
+
+}  // namespace blender::nodes