libquery: add new 'BKE_library_idtype_can_use_idtype()' helper.

This should allow us to avoid a lot of useless processing when iterating over the
whole main database (unlink/remap/usages checks/etc.).

Note that some ID types report they can use any type for now, due to
fuzzyness/indefined nature of some usages (like constraints/modifiers/game logic,
or ID pointer of nodes...). Maybe we could address this (like e.g. adding defines
in relevant headers to restrict ID types used by constraints, by modifiers, etc.).
But don’t think this is top priority for now.

2 files changed, 80 insertions, 2 deletions

diff --git a/source/blender/blenkernel/BKE_library_query.h b/source/blender/blenkernel/BKE_library_query.h
index 77a3b31f805..f7cdf1f50fc 100644
--- a/source/blender/blenkernel/BKE_library_query.h
+++ b/source/blender/blenkernel/BKE_library_query.h
@@ -76,6 +76,8 @@ void BKE_library_update_ID_link_user(struct ID *id_dst, struct ID *id_src, const
 
 int BKE_library_ID_use_ID(struct ID *id_user, struct ID *id_used);
 
+bool BKE_library_idtype_can_use_idtype(const short id_type_owner, const short id_type_used);
+
 bool BKE_library_ID_is_locally_used(struct Main *bmain, void *idv);
 bool BKE_library_ID_is_indirectly_used(struct Main *bmain, void *idv);
 void BKE_library_ID_test_usages(struct Main *bmain, void *idv, bool *is_used_local, bool *is_used_linked);
diff --git a/source/blender/blenkernel/intern/library_query.c b/source/blender/blenkernel/intern/library_query.c
index efaa5448fa3..afee80d5206 100644
--- a/source/blender/blenkernel/intern/library_query.c
+++ b/source/blender/blenkernel/intern/library_query.c
@@ -813,6 +813,82 @@ void BKE_library_update_ID_link_user(ID *id_dst, ID *id_src, const int cd_flag)
 	}
 }
 
+/**
+ * Say whether given \a id_type_owner can use (in any way) a datablock of \a id_type_used.
+ */
+/* This is a 'simplified' abstract version of BKE_library_foreach_ID_link() above, quite useful to reduce
+ * useless ietrations in some cases. */
+bool BKE_library_idtype_can_use_idtype(const short id_type_owner, const short id_type_used)
+{
+	if (id_type_used == ID_AC) {
+		return id_type_can_have_animdata(id_type_owner);
+	}
+
+	switch (id_type_owner) {
+		case ID_LI:
+			return ELEM(id_type_used, ID_LI);
+		case ID_SCE:
+			return (ELEM(id_type_used, ID_OB, ID_WO, ID_SCE, ID_MC, ID_MA, ID_GR, ID_TXT,
+			                           ID_LS, ID_MSK, ID_SO, ID_GD, ID_BR, ID_PAL, ID_IM, ID_NT) ||
+			        BKE_library_idtype_can_use_idtype(ID_NT, id_type_used));
+		case ID_OB:
+			/* Could be the following, but simpler to just always say 'yes' here. */
+#if 0
+			return ELEM(id_type_used, ID_ME, ID_CU, ID_MB, ID_LT, ID_SPK, ID_AR, ID_LA, ID_CA,  /* obdata */
+			                          ID_OB, ID_MA, ID_GD, ID_GR, ID_TE, ID_PA, ID_TXT, ID_SO, ID_MC, ID_IM, ID_AC
+			                          /* + constraints, modifiers and game logic ID types... */);
+#else
+			return true;
+#endif
+		case ID_ME:
+			return ELEM(id_type_used, ID_ME, ID_KE, ID_MA);
+		case ID_CU:
+			return ELEM(id_type_used, ID_OB, ID_KE, ID_MA, ID_VF);
+		case ID_MB:
+			return ELEM(id_type_used, ID_MA);
+		case ID_MA:
+			return (ELEM(id_type_used, ID_TE, ID_GR) || BKE_library_idtype_can_use_idtype(ID_NT, id_type_used));
+		case ID_TE:
+			return (ELEM(id_type_used, ID_IM, ID_OB) || BKE_library_idtype_can_use_idtype(ID_NT, id_type_used));
+		case ID_LT:
+			return ELEM(id_type_used, ID_KE);
+		case ID_LA:
+			return (ELEM(id_type_used, ID_TE) || BKE_library_idtype_can_use_idtype(ID_NT, id_type_used));
+		case ID_CA:
+			return ELEM(id_type_used, ID_OB);
+		case ID_KE:
+			return ELEM(id_type_used, ID_ME, ID_CU, ID_LT);  /* Warning! key->from, could be more types in future? */
+		case ID_SCR:
+			return ELEM(id_type_used, ID_SCE);
+		case ID_WO:
+			return (ELEM(id_type_used, ID_TE) || BKE_library_idtype_can_use_idtype(ID_NT, id_type_used));
+		case ID_SPK:
+			return ELEM(id_type_used, ID_SO);
+		case ID_GR:
+			return ELEM(id_type_used, ID_OB);
+		case ID_NT:
+			/* Could be the following, but node.id has no type restriction... */
+#if 0
+			return ELEM(id_type_used, ID_GD /* + node.id types... */);
+#else
+			return true;
+#endif
+		case ID_BR:
+			return ELEM(id_type_used, ID_BR, ID_IM, ID_PC, ID_TE);
+		case ID_PA:
+			return ELEM(id_type_used, ID_OB, ID_GR, ID_TE);
+		case ID_MC:
+			return ELEM(id_type_used, ID_GD, ID_IM);
+		case ID_MSK:
+			return ELEM(id_type_used, ID_MC);  /* WARNING! mask->parent.id, not typed. */
+		case ID_LS:
+			return (ELEM(id_type_used, ID_TE, ID_OB) || BKE_library_idtype_can_use_idtype(ID_NT, id_type_used));
+		default:
+			return false;
+	}
+}
+
+
 /* ***** ID users iterator. ***** */
 typedef struct IDUsersIter {
 	ID *id;
@@ -909,7 +985,7 @@ static bool library_ID_is_used(Main *bmain, void *idv, const bool check_linked)
 }
 
 /**
- * Check wether given ID is used locally (i.e. by another non-linked ID).
+ * Check whether given ID is used locally (i.e. by another non-linked ID).
  */
 bool BKE_library_ID_is_locally_used(Main *bmain, void *idv)
 {
@@ -917,7 +993,7 @@ bool BKE_library_ID_is_locally_used(Main *bmain, void *idv)
 }
 
 /**
- * Check wether given ID is used indirectly (i.e. by another linked ID).
+ * Check whether given ID is used indirectly (i.e. by another linked ID).
  */
 bool BKE_library_ID_is_indirectly_used(Main *bmain, void *idv)
 {