Fix T97002: Preserve multi socket link order

Preserve multi socket link order when copying nodes or adding a new
group input sockets by linking directly to multi inputs from the group
input node's extension socket.

This is done by also copying the `multi_input_socket_index` when
the new links are created by copying existing or temporary links.

Reviewed By: Hans Goudey

Differential Revision: http://developer.blender.org/D14535

1 files changed, 4 insertions, 1 deletions

diff --git a/source/blender/nodes/intern/node_common.cc b/source/blender/nodes/intern/node_common.cc
index c4befd5828c..abbfe4b823d 100644
--- a/source/blender/nodes/intern/node_common.cc
+++ b/source/blender/nodes/intern/node_common.cc
@@ -476,7 +476,10 @@ void node_group_input_update(bNodeTree *ntree, bNode *node)
 
     /* redirect links from the extension socket */
     for (link = (bNodeLink *)tmplinks.first; link; link = link->next) {
-      nodeAddLink(ntree, node, newsock, link->tonode, link->tosock);
+      bNodeLink *newlink = nodeAddLink(ntree, node, newsock, link->tonode, link->tosock);
+      if (newlink->tosock->flag & SOCK_MULTI_INPUT) {
+        newlink->multi_input_socket_index = link->multi_input_socket_index;
+      }
     }
   }