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

3 files changed, 487 insertions, 1 deletions

diff --git a/source/blender/nodes/intern/node_declaration.cc b/source/blender/nodes/intern/node_declaration.cc
new file mode 100644
index 00000000000..dff92d5884f
--- /dev/null
+++ b/source/blender/nodes/intern/node_declaration.cc
@@ -0,0 +1,65 @@
+/*
+ * 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.
+ */
+
+#include "NOD_node_declaration.hh"
+
+namespace blender::nodes {
+
+void NodeDeclaration::build(bNodeTree &ntree, bNode &node) const
+{
+  for (const SocketDeclarationPtr &decl : inputs_) {
+    decl->build(ntree, node, SOCK_IN);
+  }
+  for (const SocketDeclarationPtr &decl : outputs_) {
+    decl->build(ntree, node, SOCK_OUT);
+  }
+}
+
+bool NodeDeclaration::matches(const bNode &node) const
+{
+  auto check_sockets = [&](ListBase sockets, Span<SocketDeclarationPtr> socket_decls) {
+    const int tot_sockets = BLI_listbase_count(&sockets);
+    if (tot_sockets != socket_decls.size()) {
+      return false;
+    }
+    int i;
+    LISTBASE_FOREACH_INDEX (const bNodeSocket *, socket, &sockets, i) {
+      const SocketDeclaration &socket_decl = *socket_decls[i];
+      if (!socket_decl.matches(*socket)) {
+        return false;
+      }
+    }
+    return true;
+  };
+
+  if (!check_sockets(node.inputs, inputs_)) {
+    return false;
+  }
+  if (!check_sockets(node.outputs, outputs_)) {
+    return false;
+  }
+  return true;
+}
+
+bNodeSocket &SocketDeclaration::update_or_build(bNodeTree &ntree,
+                                                bNode &node,
+                                                bNodeSocket &socket) const
+{
+  /* By default just rebuild. */
+  return this->build(ntree, node, (eNodeSocketInOut)socket.in_out);
+}
+
+}  // namespace blender::nodes
diff --git a/source/blender/nodes/intern/node_socket.cc b/source/blender/nodes/intern/node_socket.cc
index 528616eb23a..d386781e3ce 100644
--- a/source/blender/nodes/intern/node_socket.cc
+++ b/source/blender/nodes/intern/node_socket.cc
@@ -44,10 +44,14 @@
 
 #include "MEM_guardedalloc.h"
 
+#include "NOD_node_declaration.hh"
 #include "NOD_socket.h"
 
 #include "FN_cpp_type_make.hh"
 
+using namespace blender;
+using blender::nodes::SocketDeclarationPtr;
+
 struct bNodeSocket *node_add_socket_from_template(struct bNodeTree *ntree,
                                                   struct bNode *node,
                                                   struct bNodeSocketTemplate *stemp,
@@ -182,9 +186,96 @@ static void verify_socket_template_list(bNodeTree *ntree,
   }
 }
 
-void node_verify_socket_templates(bNodeTree *ntree, bNode *node)
+static void refresh_socket_list(bNodeTree &ntree,
+                                bNode &node,
+                                ListBase &sockets,
+                                Span<SocketDeclarationPtr> socket_decls,
+                                const eNodeSocketInOut in_out,
+                                const bool do_id_user)
+{
+  Vector<bNodeSocket *> old_sockets = sockets;
+  VectorSet<bNodeSocket *> new_sockets;
+  for (const SocketDeclarationPtr &socket_decl : socket_decls) {
+    /* Try to find a socket that corresponds to the declaration. */
+    bNodeSocket *old_socket_with_same_identifier = nullptr;
+    for (const int i : old_sockets.index_range()) {
+      bNodeSocket &old_socket = *old_sockets[i];
+      if (old_socket.identifier == socket_decl->identifier()) {
+        old_sockets.remove_and_reorder(i);
+        old_socket_with_same_identifier = &old_socket;
+        break;
+      }
+    }
+    bNodeSocket *new_socket = nullptr;
+    if (old_socket_with_same_identifier == nullptr) {
+      /* Create a completely new socket. */
+      new_socket = &socket_decl->build(ntree, node, in_out);
+    }
+    else {
+      STRNCPY(old_socket_with_same_identifier->name, socket_decl->name().c_str());
+      if (socket_decl->matches(*old_socket_with_same_identifier)) {
+        /* The existing socket matches exactly, just use it. */
+        new_socket = old_socket_with_same_identifier;
+      }
+      else {
+        /* Clear out identifier to avoid name collisions when a new socket is created. */
+        old_socket_with_same_identifier->identifier[0] = '\0';
+        new_socket = &socket_decl->update_or_build(ntree, node, *old_socket_with_same_identifier);
+
+        if (new_socket == old_socket_with_same_identifier) {
+          /* The existing socket has been updated, set the correct identifier again. */
+          STRNCPY(new_socket->identifier, socket_decl->identifier().c_str());
+        }
+        else {
+          /* Move links to new socket with same identifier. */
+          LISTBASE_FOREACH (bNodeLink *, link, &ntree.links) {
+            if (link->fromsock == old_socket_with_same_identifier) {
+              link->fromsock = new_socket;
+            }
+            else if (link->tosock == old_socket_with_same_identifier) {
+              link->tosock = new_socket;
+            }
+          }
+        }
+      }
+    }
+    new_sockets.add_new(new_socket);
+  }
+  LISTBASE_FOREACH_MUTABLE (bNodeSocket *, old_socket, &sockets) {
+    if (!new_sockets.contains(old_socket)) {
+      nodeRemoveSocketEx(&ntree, &node, old_socket, do_id_user);
+    }
+  }
+  BLI_listbase_clear(&sockets);
+  for (bNodeSocket *socket : new_sockets) {
+    BLI_addtail(&sockets, socket);
+  }
+}
+
+static void refresh_node(bNodeTree &ntree,
+                         bNode &node,
+                         blender::nodes::NodeDeclaration &node_decl,
+                         bool do_id_user)
+{
+  refresh_socket_list(ntree, node, node.inputs, node_decl.inputs(), SOCK_IN, do_id_user);
+  refresh_socket_list(ntree, node, node.outputs, node_decl.outputs(), SOCK_OUT, do_id_user);
+}
+
+void node_verify_sockets(bNodeTree *ntree, bNode *node, bool do_id_user)
 {
   bNodeType *ntype = node->typeinfo;
+  if (ntype == nullptr) {
+    return;
+  }
+  if (ntype->declare != nullptr) {
+    blender::nodes::NodeDeclaration node_decl;
+    blender::nodes::NodeDeclarationBuilder builder{node_decl};
+    ntype->declare(builder);
+    if (!node_decl.matches(*node)) {
+      refresh_node(*ntree, *node, node_decl, do_id_user);
+    }
+    return;
+  }
   /* Don't try to match socket lists when there are no templates.
    * This prevents dynamically generated sockets to be removed, like for
    * group, image or render layer nodes. We have an explicit check for the
diff --git a/source/blender/nodes/intern/node_socket_declarations.cc b/source/blender/nodes/intern/node_socket_declarations.cc
new file mode 100644
index 00000000000..418fed146fb
--- /dev/null
+++ b/source/blender/nodes/intern/node_socket_declarations.cc
@@ -0,0 +1,330 @@
+/*
+ * 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.
+ */
+
+#include "NOD_socket_declarations.hh"
+
+#include "BKE_node.h"
+
+#include "BLI_math_vector.h"
+
+namespace blender::nodes::decl {
+
+static void modify_subtype_except_for_storage(bNodeSocket &socket, int new_subtype)
+{
+  const char *idname = nodeStaticSocketType(socket.type, new_subtype);
+  BLI_strncpy(socket.idname, idname, sizeof(socket.idname));
+  bNodeSocketType *socktype = nodeSocketTypeFind(idname);
+  socket.typeinfo = socktype;
+}
+
+/* --------------------------------------------------------------------
+ * Float.
+ */
+
+bNodeSocket &Float::build(bNodeTree &ntree, bNode &node, eNodeSocketInOut in_out) const
+{
+  bNodeSocket &socket = *nodeAddStaticSocket(
+      &ntree, &node, in_out, SOCK_FLOAT, subtype_, identifier_.c_str(), name_.c_str());
+  bNodeSocketValueFloat &value = *(bNodeSocketValueFloat *)socket.default_value;
+  value.min = soft_min_value_;
+  value.max = soft_max_value_;
+  value.value = default_value_;
+  return socket;
+}
+
+bool Float::matches(const bNodeSocket &socket) const
+{
+  if (socket.type != SOCK_FLOAT) {
+    return false;
+  }
+  if (socket.typeinfo->subtype != subtype_) {
+    return false;
+  }
+  if (socket.name != name_) {
+    return false;
+  }
+  if (socket.identifier != identifier_) {
+    return false;
+  }
+  bNodeSocketValueFloat &value = *(bNodeSocketValueFloat *)socket.default_value;
+  if (value.min != soft_min_value_) {
+    return false;
+  }
+  if (value.max != soft_max_value_) {
+    return false;
+  }
+  return true;
+}
+
+bNodeSocket &Float::update_or_build(bNodeTree &ntree, bNode &node, bNodeSocket &socket) const
+{
+  if (socket.type != SOCK_FLOAT) {
+    return this->build(ntree, node, (eNodeSocketInOut)socket.in_out);
+  }
+  if (socket.typeinfo->subtype != subtype_) {
+    modify_subtype_except_for_storage(socket, subtype_);
+  }
+  bNodeSocketValueFloat &value = *(bNodeSocketValueFloat *)socket.default_value;
+  value.min = soft_min_value_;
+  value.max = soft_max_value_;
+  value.subtype = subtype_;
+  return socket;
+}
+
+/* --------------------------------------------------------------------
+ * Int.
+ */
+
+bNodeSocket &Int::build(bNodeTree &ntree, bNode &node, eNodeSocketInOut in_out) const
+{
+  bNodeSocket &socket = *nodeAddStaticSocket(
+      &ntree, &node, in_out, SOCK_INT, subtype_, identifier_.c_str(), name_.c_str());
+  bNodeSocketValueInt &value = *(bNodeSocketValueInt *)socket.default_value;
+  value.min = soft_min_value_;
+  value.max = soft_max_value_;
+  value.value = default_value_;
+  return socket;
+}
+
+bool Int::matches(const bNodeSocket &socket) const
+{
+  if (socket.type != SOCK_INT) {
+    return false;
+  }
+  if (socket.typeinfo->subtype != subtype_) {
+    return false;
+  }
+  if (socket.name != name_) {
+    return false;
+  }
+  if (socket.identifier != identifier_) {
+    return false;
+  }
+  bNodeSocketValueInt &value = *(bNodeSocketValueInt *)socket.default_value;
+  if (value.min != soft_min_value_) {
+    return false;
+  }
+  if (value.max != soft_max_value_) {
+    return false;
+  }
+  return true;
+}
+
+bNodeSocket &Int::update_or_build(bNodeTree &ntree, bNode &node, bNodeSocket &socket) const
+{
+  if (socket.type != SOCK_INT) {
+    return this->build(ntree, node, (eNodeSocketInOut)socket.in_out);
+  }
+  if (socket.typeinfo->subtype != subtype_) {
+    modify_subtype_except_for_storage(socket, subtype_);
+  }
+  bNodeSocketValueInt &value = *(bNodeSocketValueInt *)socket.default_value;
+  value.min = soft_min_value_;
+  value.max = soft_max_value_;
+  value.subtype = subtype_;
+  return socket;
+}
+
+/* --------------------------------------------------------------------
+ * Vector.
+ */
+
+bNodeSocket &Vector::build(bNodeTree &ntree, bNode &node, eNodeSocketInOut in_out) const
+{
+  bNodeSocket &socket = *nodeAddStaticSocket(
+      &ntree, &node, in_out, SOCK_VECTOR, subtype_, identifier_.c_str(), name_.c_str());
+  bNodeSocketValueVector &value = *(bNodeSocketValueVector *)socket.default_value;
+  copy_v3_v3(value.value, default_value_);
+  return socket;
+}
+
+bool Vector::matches(const bNodeSocket &socket) const
+{
+  if (socket.type != SOCK_VECTOR) {
+    return false;
+  }
+  if (socket.typeinfo->subtype != subtype_) {
+    return false;
+  }
+  if (socket.name != name_) {
+    return false;
+  }
+  if (socket.identifier != identifier_) {
+    return false;
+  }
+  return true;
+}
+
+bNodeSocket &Vector::update_or_build(bNodeTree &ntree, bNode &node, bNodeSocket &socket) const
+{
+  if (socket.type != SOCK_VECTOR) {
+    return this->build(ntree, node, (eNodeSocketInOut)socket.in_out);
+  }
+  if (socket.typeinfo->subtype != subtype_) {
+    modify_subtype_except_for_storage(socket, subtype_);
+  }
+  bNodeSocketValueVector &value = *(bNodeSocketValueVector *)socket.default_value;
+  value.subtype = subtype_;
+  STRNCPY(socket.name, name_.c_str());
+  return socket;
+}
+
+/* --------------------------------------------------------------------
+ * Bool.
+ */
+
+bNodeSocket &Bool::build(bNodeTree &ntree, bNode &node, eNodeSocketInOut in_out) const
+{
+  bNodeSocket &socket = *nodeAddStaticSocket(
+      &ntree, &node, in_out, SOCK_BOOLEAN, PROP_NONE, identifier_.c_str(), name_.c_str());
+  bNodeSocketValueBoolean &value = *(bNodeSocketValueBoolean *)socket.default_value;
+  value.value = default_value_;
+  return socket;
+}
+
+bool Bool::matches(const bNodeSocket &socket) const
+{
+  if (socket.type != SOCK_BOOLEAN) {
+    return false;
+  }
+  if (socket.name != name_) {
+    return false;
+  }
+  if (socket.identifier != identifier_) {
+    return false;
+  }
+  return true;
+}
+
+/* --------------------------------------------------------------------
+ * Color.
+ */
+
+bNodeSocket &Color::build(bNodeTree &ntree, bNode &node, eNodeSocketInOut in_out) const
+{
+  bNodeSocket &socket = *nodeAddStaticSocket(
+      &ntree, &node, in_out, SOCK_RGBA, PROP_NONE, identifier_.c_str(), name_.c_str());
+  bNodeSocketValueRGBA &value = *(bNodeSocketValueRGBA *)socket.default_value;
+  copy_v4_v4(value.value, default_value_);
+  return socket;
+}
+
+bool Color::matches(const bNodeSocket &socket) const
+{
+  if (socket.type != SOCK_RGBA) {
+    return false;
+  }
+  if (socket.name != name_) {
+    return false;
+  }
+  if (socket.identifier != identifier_) {
+    return false;
+  }
+  return true;
+}
+
+/* --------------------------------------------------------------------
+ * String.
+ */
+
+bNodeSocket &String::build(bNodeTree &ntree, bNode &node, eNodeSocketInOut in_out) const
+{
+  bNodeSocket &socket = *nodeAddStaticSocket(
+      &ntree, &node, in_out, SOCK_STRING, PROP_NONE, identifier_.c_str(), name_.c_str());
+  return socket;
+}
+
+bool String::matches(const bNodeSocket &socket) const
+{
+  if (socket.type != SOCK_STRING) {
+    return false;
+  }
+  if (socket.name != name_) {
+    return false;
+  }
+  if (socket.identifier != identifier_) {
+    return false;
+  }
+  return true;
+}
+
+/* --------------------------------------------------------------------
+ * IDSocketDeclaration.
+ */
+
+namespace detail {
+bNodeSocket &build_id_socket(bNodeTree &ntree,
+                             bNode &node,
+                             eNodeSocketInOut in_out,
+                             const CommonIDSocketData &data,
+                             StringRefNull name,
+                             StringRefNull identifier)
+{
+  bNodeSocket &socket = *nodeAddSocket(
+      &ntree, &node, in_out, data.idname, name.c_str(), identifier.c_str());
+  if (data.hide_label) {
+    socket.flag |= SOCK_HIDE_LABEL;
+  }
+  return socket;
+}
+
+bool matches_id_socket(const bNodeSocket &socket,
+                       const CommonIDSocketData &data,
+                       StringRefNull name,
+                       StringRefNull identifier)
+{
+  if (!STREQ(socket.idname, data.idname)) {
+    return false;
+  }
+  if (data.hide_label != ((socket.flag & SOCK_HIDE_LABEL) != 0)) {
+    return false;
+  }
+  if (socket.name != name) {
+    return false;
+  }
+  if (socket.identifier != identifier) {
+    return false;
+  }
+  return true;
+}
+}  // namespace detail
+
+/* --------------------------------------------------------------------
+ * Geometry.
+ */
+
+bNodeSocket &Geometry::build(bNodeTree &ntree, bNode &node, eNodeSocketInOut in_out) const
+{
+  bNodeSocket &socket = *nodeAddSocket(
+      &ntree, &node, in_out, "NodeSocketGeometry", identifier_.c_str(), name_.c_str());
+  return socket;
+}
+
+bool Geometry::matches(const bNodeSocket &socket) const
+{
+  if (socket.type != SOCK_GEOMETRY) {
+    return false;
+  }
+  if (socket.name != name_) {
+    return false;
+  }
+  if (socket.identifier != identifier_) {
+    return false;
+  }
+  return true;
+}
+
+}  // namespace blender::nodes::decl