Fix T89771: Cloth disk cache is not read on library overrides when original linked data is already set to use 'Disk Cache'

Yet another try at that hairy issue... See comment in commit for
details, essentially this extend the workaround introduced in Objects'
`lib_override_apply_post` callback to try to also properly 're-use'
`OUTDATED` and `BAKED` flags from old source liboverride into new
destination one.

1 files changed, 53 insertions, 8 deletions

diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index 2f3b229a180..0d5fd6aadec 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -1131,18 +1131,63 @@ static void object_blend_read_expand(BlendExpander *expander, ID *id)
   }
 }
 
-static void object_lib_override_apply_post(ID *id_dst, ID *UNUSED(id_src))
+static void object_lib_override_apply_post(ID *id_dst, ID *id_src)
 {
-  Object *object = (Object *)id_dst;
+  /* id_dst is the new local override copy of the linked reference data. id_src is the old override
+   * data stored on disk, used as source data for override operations. */
+  Object *object_dst = (Object *)id_dst;
+  Object *object_src = (Object *)id_src;
 
-  ListBase pidlist;
-  BKE_ptcache_ids_from_object(&pidlist, object, NULL, 0);
-  LISTBASE_FOREACH (PTCacheID *, pid, &pidlist) {
-    LISTBASE_FOREACH (PointCache *, point_cache, pid->ptcaches) {
-      point_cache->flag |= PTCACHE_FLAG_INFO_DIRTY;
+  ListBase pidlist_dst, pidlist_src;
+  BKE_ptcache_ids_from_object(&pidlist_dst, object_dst, NULL, 0);
+  BKE_ptcache_ids_from_object(&pidlist_src, object_src, NULL, 0);
+
+  /* Problem with point caches is that several status flags (like OUTDATED or BAKED) are read-only
+   * at RNA level, and therefore not overridable per-se.
+   *
+   * This code is a workaround this to check all pointcaches from both source and destination
+   * objects in parallel, and transfer those flags when it makes sense.
+   *
+   * This allows to keep baked caches across liboverrides applies.
+   *
+   * NOTE: This is fairly hackish and weak, but so is the pointcache system as its whole. A more
+   * robust solution would be e.g. to have a specific RNA entry point to deal with such cases
+   * (maybe a new flag to allow override code to set values of some read-only properties?).
+   */
+  PTCacheID *pid_src, *pid_dst;
+  for (pid_dst = pidlist_dst.first, pid_src = pidlist_src.first; pid_dst != NULL;
+       pid_dst = pid_dst->next, pid_src = (pid_src != NULL) ? pid_src->next : NULL) {
+    /* If pid's do not match, just tag info of caches in dst as dirty and continue. */
+    if (pid_src == NULL || pid_dst->type != pid_src->type ||
+        pid_dst->file_type != pid_src->file_type ||
+        pid_dst->default_step != pid_src->default_step || pid_dst->max_step != pid_src->max_step ||
+        pid_dst->data_types != pid_src->data_types || pid_dst->info_types != pid_src->info_types) {
+      LISTBASE_FOREACH (PointCache *, point_cache_src, pid_src->ptcaches) {
+        point_cache_src->flag |= PTCACHE_FLAG_INFO_DIRTY;
+      }
+      continue;
+    }
+
+    PointCache *point_cache_dst, *point_cache_src;
+    for (point_cache_dst = pid_dst->ptcaches->first, point_cache_src = pid_src->ptcaches->first;
+         point_cache_dst != NULL;
+         point_cache_dst = point_cache_dst->next,
+        point_cache_src = (point_cache_src != NULL) ? point_cache_src->next : NULL) {
+      /* Always force updating info about caches of applied liboverrides. */
+      point_cache_dst->flag |= PTCACHE_FLAG_INFO_DIRTY;
+      if (point_cache_src == NULL || !STREQ(point_cache_dst->name, point_cache_src->name)) {
+        continue;
+      }
+      if ((point_cache_src->flag & PTCACHE_BAKED) != 0) {
+        point_cache_dst->flag |= PTCACHE_BAKED;
+      }
+      if ((point_cache_src->flag & PTCACHE_OUTDATED) == 0) {
+        point_cache_dst->flag &= ~PTCACHE_OUTDATED;
+      }
     }
   }
-  BLI_freelistN(&pidlist);
+  BLI_freelistN(&pidlist_dst);
+  BLI_freelistN(&pidlist_src);
 }
 
 IDTypeInfo IDType_ID_OB = {