From 06ac5992618a75c453e495e06af7c5faf30499a7 Mon Sep 17 00:00:00 2001
From: Jacques Lucke <jacques@blender.org>
Date: Wed, 9 Feb 2022 11:19:11 +0100
Subject: Fix T91840: do not create invalid links when inserting a node

Differential Revision: https://developer.blender.org/D14050
---
 .../editors/space_node/node_relationships.cc       | 79 ++++++++++++++--------
 1 file changed, 49 insertions(+), 30 deletions(-)

(limited to 'source/blender/editors')

diff --git a/source/blender/editors/space_node/node_relationships.cc b/source/blender/editors/space_node/node_relationships.cc
index bc79925b51d..2a197e93f42 100644
--- a/source/blender/editors/space_node/node_relationships.cc
+++ b/source/blender/editors/space_node/node_relationships.cc
@@ -2428,54 +2428,73 @@ void ED_node_link_insert(Main *bmain, ScrArea *area)
 {
   using namespace blender::ed::space_node;
 
-  bNode *select;
+  bNode *node_to_insert;
   SpaceNode *snode;
-  if (!ed_node_link_conditions(area, true, &snode, &select)) {
+  if (!ed_node_link_conditions(area, true, &snode, &node_to_insert)) {
     return;
   }
 
-  /* get the link */
-  bNodeLink *link;
-  for (link = (bNodeLink *)snode->edittree->links.first; link; link = link->next) {
+  /* Find link to insert on. */
+  bNodeTree &ntree = *snode->edittree;
+  bNodeLink *old_link = nullptr;
+  LISTBASE_FOREACH (bNodeLink *, link, &ntree.links) {
     if (link->flag & NODE_LINKFLAG_HILITE) {
+      old_link = link;
       break;
     }
   }
+  if (old_link == nullptr) {
+    return;
+  }
 
-  if (link) {
-    bNodeSocket *best_input = get_main_socket(*snode->edittree, *select, SOCK_IN);
-    bNodeSocket *best_output = get_main_socket(*snode->edittree, *select, SOCK_OUT);
+  old_link->flag &= ~NODE_LINKFLAG_HILITE;
 
-    if (best_input && best_output) {
-      bNode *node = link->tonode;
-      bNodeSocket *sockto = link->tosock;
+  bNodeSocket *best_input = get_main_socket(ntree, *node_to_insert, SOCK_IN);
+  bNodeSocket *best_output = get_main_socket(ntree, *node_to_insert, SOCK_OUT);
 
-      link->tonode = select;
-      link->tosock = best_input;
-      node_remove_extra_links(*snode, *link);
-      link->flag &= ~NODE_LINKFLAG_HILITE;
+  /* Ignore main sockets when the types don't match. */
+  if (best_input != nullptr &&
+      !ntree.typeinfo->validate_link(static_cast<eNodeSocketDatatype>(old_link->fromsock->type),
+                                     static_cast<eNodeSocketDatatype>(best_input->type))) {
+    best_input = nullptr;
+  }
+  if (best_output != nullptr &&
+      !ntree.typeinfo->validate_link(static_cast<eNodeSocketDatatype>(best_output->type),
+                                     static_cast<eNodeSocketDatatype>(old_link->tosock->type))) {
+    best_output = nullptr;
+  }
 
-      bNodeLink *new_link = nodeAddLink(snode->edittree, select, best_output, node, sockto);
+  bNode *from_node = old_link->fromnode;
+  bNodeSocket *from_socket = old_link->fromsock;
+  bNode *to_node = old_link->tonode;
 
-      /* Copy the socket index for the new link, and reset it for the old link. This way the
-       * relative order of links is preserved, and the links get drawn in the right place. */
-      new_link->multi_input_socket_index = link->multi_input_socket_index;
-      link->multi_input_socket_index = 0;
+  if (best_output != nullptr) {
+    /* Relink the "start" of the existing link to the newly inserted node. */
+    old_link->fromnode = node_to_insert;
+    old_link->fromsock = best_output;
+    BKE_ntree_update_tag_link_changed(&ntree);
+  }
+  else {
+    nodeRemLink(&ntree, old_link);
+  }
 
-      /* set up insert offset data, it needs stuff from here */
-      if ((snode->flag & SNODE_SKIP_INSOFFSET) == 0) {
-        NodeInsertOfsData *iofsd = MEM_cnew<NodeInsertOfsData>(__func__);
+  if (best_input != nullptr) {
+    /* Add a new link that connects the node on the left to the newly inserted node. */
+    nodeAddLink(&ntree, from_node, from_socket, node_to_insert, best_input);
+  }
 
-        iofsd->insert = select;
-        iofsd->prev = link->fromnode;
-        iofsd->next = node;
+  /* Set up insert offset data, it needs stuff from here. */
+  if ((snode->flag & SNODE_SKIP_INSOFFSET) == 0) {
+    NodeInsertOfsData *iofsd = MEM_cnew<NodeInsertOfsData>(__func__);
 
-        snode->runtime->iofsd = iofsd;
-      }
+    iofsd->insert = node_to_insert;
+    iofsd->prev = from_node;
+    iofsd->next = to_node;
 
-      ED_node_tree_propagate_change(nullptr, bmain, snode->edittree);
-    }
+    snode->runtime->iofsd = iofsd;
   }
+
+  ED_node_tree_propagate_change(nullptr, bmain, snode->edittree);
 }
 
 /** \} */
-- 
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