Add a callback to `IDTypeInfo` to allow preservation of some data accross memfile undos

This is essentially adding that new callback, and using it only for already
existing Scene's 3DCursor.

Note that the place where this is called has been moved again, after all
have been lib-linked, such that those callbacks may also work on ID pointers.

Maniphest Tasks: T71759

Differential Revision: https://developer.blender.org/D9237

1 files changed, 13 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/scene.c b/source/blender/blenkernel/intern/scene.c
index 6a9fe4615f7..69f4584a359 100644
--- a/source/blender/blenkernel/intern/scene.c
+++ b/source/blender/blenkernel/intern/scene.c
@@ -104,6 +104,8 @@
 
 #include "SEQ_sequencer.h"
 
+#include "BLO_read_write.h"
+
 #include "engines/eevee/eevee_lightcache.h"
 
 #include "PIL_time.h"
@@ -620,6 +622,15 @@ static void scene_foreach_cache(ID *id,
                     user_data);
 }
 
+static void scene_undo_preserve(BlendLibReader *UNUSED(reader), ID *id_new, ID *id_old)
+{
+  Scene *scene_new = (Scene *)id_new;
+  Scene *scene_old = (Scene *)id_old;
+
+  SWAP(View3DCursor, scene_old->cursor, scene_new->cursor);
+  /* TODO: handle tool settings here too. */
+}
+
 IDTypeInfo IDType_ID_SCE = {
     .id_code = ID_SCE,
     .id_filter = FILTER_ID_SCE,
@@ -643,6 +654,8 @@ IDTypeInfo IDType_ID_SCE = {
     .blend_read_data = NULL,
     .blend_read_lib = NULL,
     .blend_read_expand = NULL,
+
+    .blend_read_undo_preserve = scene_undo_preserve,
 };
 
 const char *RE_engine_id_BLENDER_EEVEE = "BLENDER_EEVEE";