From c6f85d7a8dce7b39cb7cb895a7dd918fe3bcb05a Mon Sep 17 00:00:00 2001
From: Jacques Lucke <jacques@blender.org>
Date: Wed, 10 Nov 2021 11:47:36 +0100
Subject: improve handling of incompatible enums

---
 source/blender/blenkernel/intern/node.cc        | 30 ++++++++++++++++++++++---
 source/blender/editors/space_node/drawnode.cc   |  6 +++++
 source/blender/makesdna/DNA_node_types.h        |  3 ++-
 source/blender/nodes/NOD_socket_declarations.hh |  2 ++
 4 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/source/blender/blenkernel/intern/node.cc b/source/blender/blenkernel/intern/node.cc
index 0e23992432f..4522dca9519 100644
--- a/source/blender/blenkernel/intern/node.cc
+++ b/source/blender/blenkernel/intern/node.cc
@@ -5138,8 +5138,23 @@ static EnumInputInferencingInfo get_input_enum_socket_inferencing_info(
 struct EnumState {
   std::shared_ptr<EnumItems> items;
   int group_output_index = -1;
+  bool targets_are_invalid = false;
 };
 
+static bool enum_states_are_compatible(const EnumState &a, const EnumState &b)
+{
+  if (a.items && b.items) {
+    return a.items->items() == b.items->items();
+  }
+  if (a.group_output_index == -1 || b.group_output_index == -1) {
+    return true;
+  }
+  if (a.group_output_index == b.group_output_index) {
+    return true;
+  }
+  return false;
+}
+
 static bool update_enum_inferencing(const NodeTreeRef &tree)
 {
   using namespace blender::nodes;
@@ -5169,12 +5184,19 @@ static bool update_enum_inferencing(const NodeTreeRef &tree)
       if (socket->typeinfo()->type != SOCK_ENUM) {
         continue;
       }
-      /* TODO: Handle case when connected to incompatible enums. */
       EnumState enum_state;
       for (const InputSocketRef *target_socket : socket->directly_linked_sockets()) {
         if (target_socket->is_available()) {
-          enum_state = state_by_socket.lookup_default(target_socket, {});
-          break;
+          EnumState new_state = state_by_socket.lookup_default(target_socket, {});
+          if (enum_states_are_compatible(enum_state, new_state)) {
+            enum_state = new_state;
+            enum_state.targets_are_invalid = false;
+          }
+          else {
+            enum_state = {};
+            enum_state.targets_are_invalid = true;
+            break;
+          }
         }
       }
       state_by_socket.add_new(socket, enum_state);
@@ -5202,6 +5224,7 @@ static bool update_enum_inferencing(const NodeTreeRef &tree)
         BLI_assert(inference_index >= 0);
         const OutputSocketRef &output_socket = node->output(inference_index);
         input_state = state_by_socket.lookup(&output_socket);
+        input_state.targets_are_invalid = false;
       }
       state_by_socket.add_new(socket, input_state);
     }
@@ -5217,6 +5240,7 @@ static bool update_enum_inferencing(const NodeTreeRef &tree)
     else {
       socket_value->items = nullptr;
     }
+    socket_value->targets_are_invalid = state.targets_are_invalid;
   }
 
   EnumInferencingInterface *new_inferencing_interface = new EnumInferencingInterface();
diff --git a/source/blender/editors/space_node/drawnode.cc b/source/blender/editors/space_node/drawnode.cc
index 6554dc699ac..104f48cda0a 100644
--- a/source/blender/editors/space_node/drawnode.cc
+++ b/source/blender/editors/space_node/drawnode.cc
@@ -4450,6 +4450,12 @@ void node_draw_link(const bContext *C, View2D *v2d, SpaceNode *snode, bNodeLink
       th_col1 = th_col2 = th_col3 = TH_REDALERT;
     }
   }
+  if (link->fromsock && link->fromsock->type == SOCK_ENUM) {
+    bNodeSocketValueEnum *socket_value = (bNodeSocketValueEnum *)link->fromsock->default_value;
+    if (socket_value->targets_are_invalid) {
+      th_col1 = th_col2 = th_col3 = TH_REDALERT;
+    }
+  }
 
   node_draw_link_bezier(C, v2d, snode, link, th_col1, th_col2, th_col3);
 }
diff --git a/source/blender/makesdna/DNA_node_types.h b/source/blender/makesdna/DNA_node_types.h
index e2d55f006f4..bf4a54f904a 100644
--- a/source/blender/makesdna/DNA_node_types.h
+++ b/source/blender/makesdna/DNA_node_types.h
@@ -687,7 +687,8 @@ typedef struct bNodeSocketValueMaterial {
 /* TODO: Add something to help with versioning for built-in enums. */
 typedef struct bNodeSocketValueEnum {
   int value;
-  char _pad[4];
+  char targets_are_invalid;
+  char _pad[3];
   /**
    * Possible items for the enum. This is only runtime data and is not owned by the socket.
    */
diff --git a/source/blender/nodes/NOD_socket_declarations.hh b/source/blender/nodes/NOD_socket_declarations.hh
index f6a4af397ba..ac9fc0c1adb 100644
--- a/source/blender/nodes/NOD_socket_declarations.hh
+++ b/source/blender/nodes/NOD_socket_declarations.hh
@@ -16,6 +16,8 @@
 
 #pragma once
 
+#include <functional>
+
 #include "NOD_node_declaration.hh"
 
 #include "RNA_types.h"
-- 
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