Fix T88026: Repeated switch to rendered viewport crashes

Resolve ownership ambiguity with shared physics pointers.

Previously, LIB_ID_CREATE_NO_MAIN allowed pointer sharing with
the source ID so physics caches can be shared between original and
evaluated data: (Object.soft.shared & Object.rigidbody_object.shared).

This only worked properly for LIB_TAG_COPIED_ON_WRITE ID's,
as LIB_TAG_NO_MAIN can be used in situations where the original ID's
lifetime limited by it's original data.

This commit adds `LIB_ID_COPY_SET_COPIED_ON_WRITE` so ID's only share
memory with original data for ID's evaluated in the depsgraph.

For all other uses, a full copy of physics data is made.

Ref D11228#287094

1 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index ef553e60eb8..825f660fa3a 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -2292,7 +2292,7 @@ Object *BKE_object_add_for_data(
 void BKE_object_copy_softbody(Object *ob_dst, const Object *ob_src, const int flag)
 {
   SoftBody *sb = ob_src->soft;
-  bool tagged_no_main = ob_dst->id.tag & LIB_TAG_NO_MAIN;
+  const bool is_orig = (flag & LIB_ID_COPY_SET_COPIED_ON_WRITE) == 0;
 
   ob_dst->softflag = ob_src->softflag;
   if (sb == NULL) {
@@ -2333,7 +2333,7 @@ void BKE_object_copy_softbody(Object *ob_dst, const Object *ob_src, const int fl
 
   sbn->scratch = NULL;
 
-  if (!tagged_no_main) {
+  if (is_orig) {
     sbn->shared = MEM_dupallocN(sb->shared);
     sbn->shared->pointcache = BKE_ptcache_copy_list(
         &sbn->shared->ptcaches, &sb->shared->ptcaches, flag);