Nodes: Reuse input sockets when creating new node groups

**Problem**
Currently multiple input sockets are created when a new node group is
made from selected nodes. Some of these are linked from the same source.
It is not convenient to sort out and remove multiple input sockets that
represent the same input. These inputs usually have meaningless names
like 'value', 'x', etc.

**Solution**
Create common input sockets for each link starting from the same input.
Move links inside the new group's node tree and reroute it to connect
the common input socket to the original nodes. This is done by building
up a mapping between the incoming link sources to the input interfaces
created for them. The input interfaces are reused by the rest of the
links having the same source.

This patch also changes the way the input sockets get their names.
Output socket names of the group nodes usually are specific and are
given consciously. Use the output socket names from group nodes instead
of the inputs where the links point to.

Differential Revision: https://developer.blender.org/D15802

1 files changed, 12 insertions, 4 deletions

diff --git a/source/blender/blenkernel/intern/node.cc b/source/blender/blenkernel/intern/node.cc
index 8f8cd02e119..ad9d4e4fcca 100644
--- a/source/blender/blenkernel/intern/node.cc
+++ b/source/blender/blenkernel/intern/node.cc
@@ -3381,10 +3381,18 @@ struct bNodeSocket *ntreeAddSocketInterfaceFromSocket(bNodeTree *ntree,
                                                       bNode *from_node,
                                                       bNodeSocket *from_sock)
 {
-  bNodeSocket *iosock = ntreeAddSocketInterface(ntree,
-                                                static_cast<eNodeSocketInOut>(from_sock->in_out),
-                                                from_sock->idname,
-                                                DATA_(from_sock->name));
+  return ntreeAddSocketInterfaceFromSocketWithName(
+      ntree, from_node, from_sock, from_sock->idname, from_sock->name);
+}
+
+struct bNodeSocket *ntreeAddSocketInterfaceFromSocketWithName(bNodeTree *ntree,
+                                                              bNode *from_node,
+                                                              bNodeSocket *from_sock,
+                                                              const char *idname,
+                                                              const char *name)
+{
+  bNodeSocket *iosock = ntreeAddSocketInterface(
+      ntree, static_cast<eNodeSocketInOut>(from_sock->in_out), idname, DATA_(name));
   if (iosock) {
     if (iosock->typeinfo->interface_from_socket) {
       iosock->typeinfo->interface_from_socket(ntree, iosock, from_node, from_sock);