3 files changed, 42 insertions, 5 deletions
diff --git a/source/blender/editors/space_node/node_relationships.cc b/source/blender/editors/space_node/node_relationships.cc
index 76aad684b4c..55b547d3195 100644
--- a/source/blender/editors/space_node/node_relationships.cc
+++ b/source/blender/editors/space_node/node_relationships.cc
@@ -57,6 +57,7 @@
 
 #include "BLT_translation.h"
 
+#include "NOD_node_declaration.hh"
 #include "NOD_node_tree_ref.hh"
 
 #include "node_intern.h" /* own include */
@@ -2182,9 +2183,32 @@ static int get_main_socket_priority(const bNodeSocket *socket)
   return -1;
 }
 
-/** Get the "main" socket of a socket list using a heuristic based on socket types. */
-static bNodeSocket *get_main_socket(ListBase *sockets)
+/** Get the "main" socket based on the node declaration or an heuristic. */
+static bNodeSocket *get_main_socket(bNodeTree &ntree, bNode &node, eNodeSocketInOut in_out)
 {
+  using namespace blender;
+  using namespace blender::nodes;
+
+  ListBase *sockets = (in_out == SOCK_IN) ? &node.inputs : &node.outputs;
+
+  /* Try to get the main socket based on the socket declaration. */
+  nodeDeclarationEnsure(&ntree, &node);
+  const NodeDeclaration *node_decl = node.declaration;
+  if (node_decl != nullptr) {
+    Span<SocketDeclarationPtr> socket_decls = (in_out == SOCK_IN) ? node_decl->inputs() :
+                                                                    node_decl->outputs();
+    int index;
+    LISTBASE_FOREACH_INDEX (bNodeSocket *, socket, sockets, index) {
+      const SocketDeclaration &socket_decl = *socket_decls[index];
+      if (nodeSocketIsHidden(socket)) {
+        continue;
+      }
+      if (socket_decl.is_default_link_socket()) {
+        return socket;
+      }
+    }
+  }
+
   /* find priority range */
   int maxpriority = -1;
   LISTBASE_FOREACH (bNodeSocket *, sock, sockets) {
@@ -2561,8 +2585,8 @@ void ED_node_link_insert(Main *bmain, ScrArea *area)
   }
 
   if (link) {
-    bNodeSocket *best_input = get_main_socket(&select->inputs);
-    bNodeSocket *best_output = get_main_socket(&select->outputs);
+    bNodeSocket *best_input = get_main_socket(*snode->edittree, *select, SOCK_IN);
+    bNodeSocket *best_output = get_main_socket(*snode->edittree, *select, SOCK_OUT);
 
     if (best_input && best_output) {
       bNode *node = link->tonode;
diff --git a/source/blender/nodes/NOD_node_declaration.hh b/source/blender/nodes/NOD_node_declaration.hh
index 1481e69c00e..e9f2996bb30 100644
--- a/source/blender/nodes/NOD_node_declaration.hh
+++ b/source/blender/nodes/NOD_node_declaration.hh
@@ -89,6 +89,7 @@ class SocketDeclaration {
   bool is_multi_input_ = false;
   bool no_mute_links_ = false;
   bool is_attribute_name_ = false;
+  bool is_default_link_socket_ = false;
 
   InputSocketFieldType input_field_type_ = InputSocketFieldType::None;
   OutputFieldDependency output_field_dependency_;
@@ -107,6 +108,7 @@ class SocketDeclaration {
   StringRefNull description() const;
   StringRefNull identifier() const;
   bool is_attribute_name() const;
+  bool is_default_link_socket() const;
 
   InputSocketFieldType input_field_type() const;
   const OutputFieldDependency &output_field_dependency() const;
@@ -171,6 +173,12 @@ class SocketDeclarationBuilder : public BaseSocketDeclarationBuilder {
     return *(Self *)this;
   }
 
+  Self &is_default_link_socket(bool value = true)
+  {
+    decl_->is_default_link_socket_ = value;
+    return *(Self *)this;
+  }
+
   /** The input socket allows passing in a field. */
   Self &supports_field()
   {
@@ -363,6 +371,11 @@ inline bool SocketDeclaration::is_attribute_name() const
   return is_attribute_name_;
 }
 
+inline bool SocketDeclaration::is_default_link_socket() const
+{
+  return is_default_link_socket_;
+}
+
 inline InputSocketFieldType SocketDeclaration::input_field_type() const
 {
   return input_field_type_;
diff --git a/source/blender/nodes/shader/nodes/node_shader_curves.cc b/source/blender/nodes/shader/nodes/node_shader_curves.cc
index f8f0ee97eae..7ce5150bf85 100644
--- a/source/blender/nodes/shader/nodes/node_shader_curves.cc
+++ b/source/blender/nodes/shader/nodes/node_shader_curves.cc
@@ -357,7 +357,7 @@ static void sh_node_curve_float_declare(NodeDeclarationBuilder &b)
       .max(1.0f)
       .default_value(1.0f)
       .subtype(PROP_FACTOR);
-  b.add_input<decl::Float>(N_("Value")).default_value(1.0f);
+  b.add_input<decl::Float>(N_("Value")).default_value(1.0f).is_default_link_socket();
   b.add_output<decl::Float>(N_("Value"));
 };