From 8fc2b634684dca6348c91becbae8ccb95a2fe701 Mon Sep 17 00:00:00 2001
From: Bastien Montagne <bastien@blender.org>
Date: Thu, 23 Nov 2023 15:06:21 +0100
Subject: [PATCH] Fix (unreported) Scene Collection runtime data not cleared on
 write.

---
 source/blender/blenkernel/BKE_collection.h     |  4 ++++
 source/blender/blenkernel/intern/collection.cc | 11 ++++++++---
 source/blender/blenkernel/intern/scene.cc      |  3 +++
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/source/blender/blenkernel/BKE_collection.h b/source/blender/blenkernel/BKE_collection.h
index 3f3e5296550..a79b57caa71 100644
--- a/source/blender/blenkernel/BKE_collection.h
+++ b/source/blender/blenkernel/BKE_collection.h
@@ -312,6 +312,10 @@ bool BKE_collection_validate(struct Collection *collection);
 
 /* .blend file I/O */
 
+/** Perform some pre-writing cleanup on the COllection data itself (_not_ in any sub-data
+ * referenced by pointers). To be called before writing the Collection struct itself. */
+void BKE_collection_blend_write_prepare_nolib(struct BlendWriter *writer,
+                                              struct Collection *collection);
 void BKE_collection_blend_write_nolib(struct BlendWriter *writer, struct Collection *collection);
 void BKE_collection_blend_read_data(struct BlendDataReader *reader,
                                     struct Collection *collection,
diff --git a/source/blender/blenkernel/intern/collection.cc b/source/blender/blenkernel/intern/collection.cc
index cd3b6144b7a..07e79e2e456 100644
--- a/source/blender/blenkernel/intern/collection.cc
+++ b/source/blender/blenkernel/intern/collection.cc
@@ -232,6 +232,13 @@ static ID **collection_owner_pointer_get(ID *id)
   return &master_collection->owner_id;
 }
 
+void BKE_collection_blend_write_prepare_nolib(BlendWriter * /*writer*/, Collection *collection)
+{
+  memset(&collection->runtime, 0, sizeof(collection->runtime));
+  /* Clean up, important in undo case to reduce false detection of changed data-blocks. */
+  collection->flag &= ~COLLECTION_FLAG_ALL_RUNTIME;
+}
+
 void BKE_collection_blend_write_nolib(BlendWriter *writer, Collection *collection)
 {
   BKE_id_blend_write(writer, &collection->id);
@@ -252,9 +259,7 @@ static void collection_blend_write(BlendWriter *writer, ID *id, const void *id_a
 {
   Collection *collection = (Collection *)id;
 
-  memset(&collection->runtime, 0, sizeof(collection->runtime));
-  /* Clean up, important in undo case to reduce false detection of changed data-blocks. */
-  collection->flag &= ~COLLECTION_FLAG_ALL_RUNTIME;
+  BKE_collection_blend_write_prepare_nolib(writer, collection);
 
   /* write LibData */
   BLO_write_id_struct(writer, Collection, id_address, &collection->id);
diff --git a/source/blender/blenkernel/intern/scene.cc b/source/blender/blenkernel/intern/scene.cc
index fa06ff28e16..20aacd42a52 100644
--- a/source/blender/blenkernel/intern/scene.cc
+++ b/source/blender/blenkernel/intern/scene.cc
@@ -1186,6 +1186,9 @@ static void scene_blend_write(BlendWriter *writer, ID *id, const void *id_addres
   if (sce->master_collection) {
     BLO_write_init_id_buffer_from_id(
         temp_embedded_id_buffer, &sce->master_collection->id, BLO_write_is_undo(writer));
+    BKE_collection_blend_write_prepare_nolib(
+        writer,
+        reinterpret_cast<Collection *>(BLO_write_get_id_buffer_temp_id(temp_embedded_id_buffer)));
     BLO_write_struct_at_address(writer,
                                 Collection,
                                 sce->master_collection,