Rework library_query foreach looper - add optional recursivity.

This commit:
* Fixes bad handling of 'stop iteration' (by adding a status flag, so that we can actually
  stop in helper functions too, and jumping to a finalize label instead of raw return, to
  allow propper clean up).
* Adds optional recursion into 'ID tree' - callback can also decide to exclude current id_pp
  from recursion. Note that this implies 'readonly', modifying IDs while recursing is not
  something we want to support!
* Changes callback signature/expected behavior: return behavior is now handled through flags,
  and 'parent' ID of id_pp is also passed (since it may not always be root id anymore).

Reviewers: sergey, campbellbarton

Differential Revision: https://developer.blender.org/D1869

source/blender/blenkernel/BKE_library_query.h

@@ -50,15 +50,23 @@ enum {
 	IDWALK_USER_ONE = (1 << 9),
 };
 
-/* Call a callback for each ID link which the given ID uses.
+enum {
+	IDWALK_RET_NOP            = 0,
+	IDWALK_RET_STOP_ITER      = 1 << 0,  /* Completly top iteration. */
+	IDWALK_RET_STOP_RECURSION = 1 << 1,  /* Stop recursion, that is, do not loop over ID used by current one. */
+};
+
+/**
+ * Call a callback for each ID link which the given ID uses.
  *
- * Return 'false' if you want to stop iteration.
+ * \return a set of flags to controll further iteration (0 to keep going).
  */
-typedef bool (*LibraryIDLinkCallback) (void *user_data, struct ID **id_pointer, int cd_flag);
+typedef int (*LibraryIDLinkCallback) (void *user_data, struct ID *id_self, struct ID **id_pointer, int cd_flag);
 
 /* Flags for the foreach function itself. */
 enum {
 	IDWALK_READONLY = (1 << 0),
+	IDWALK_RECURSE  = (1 << 1),  /* Also implies IDWALK_READONLY. */
 };
 
 /* Loop over all of the ID's this datablock links to. */

source/blender/blenkernel/intern/library.c

@@ -1086,7 +1086,7 @@ void *BKE_libblock_copy(ID *id)
 	return BKE_libblock_copy_ex(G.main, id);
 }
 
-static bool id_relink_looper(void *UNUSED(user_data), ID **id_pointer, const int cd_flag)
+static int id_relink_looper(void *UNUSED(user_data), ID *UNUSED(self_id), ID **id_pointer, const int cd_flag)
 {
 	ID *id = *id_pointer;
 	if (id) {
@@ -1100,7 +1100,7 @@ static bool id_relink_looper(void *UNUSED(user_data), ID **id_pointer, const int
 			BKE_libblock_relink(id);
 		}
 	}
-	return true;
+	return IDWALK_RET_NOP;
 }
 
 void BKE_libblock_relink(ID *id)

source/blender/editors/object/object_relations.c

@@ -2123,12 +2123,14 @@ enum {
 	MAKE_LOCAL_ALL                    = 4,
 };
 
-static bool tag_localizable_looper(void *UNUSED(user_data), ID **id_pointer, const int UNUSED(cd_flag))
+static int tag_localizable_looper(
+        void *UNUSED(user_data), ID *UNUSED(self_id), ID **id_pointer, const int UNUSED(cd_flag))
 {
 	if (*id_pointer) {
 		(*id_pointer)->tag &= ~LIB_TAG_DOIT;
 	}
-	return true;
+
+	return IDWALK_RET_NOP;
 }
 
 static void tag_localizable_objects(bContext *C, const int mode)

source/blender/python/intern/bpy_rna_id_collection.c

@@ -80,7 +80,8 @@ static bool id_check_type(const ID *id, const BLI_bitmap *types_bitmap)
 	return BLI_BITMAP_TEST_BOOL(types_bitmap, id_code_as_index(GS(id->name)));
 }
 
-static bool foreach_libblock_id_user_map_callback(void *user_data, ID **id_p, int UNUSED(cb_flag))
+static int foreach_libblock_id_user_map_callback(
+        void *user_data, ID *UNUSED(self_id), ID **id_p, int UNUSED(cb_flag))
 {
 	IDUserMapData *data = user_data;
 
@@ -88,7 +89,7 @@ static bool foreach_libblock_id_user_map_callback(void *user_data, ID **id_p, in
 
 		if (data->types_bitmap) {
 			if (!id_check_type(*id_p, data->types_bitmap)) {
-				return true;
+				return IDWALK_RET_NOP;
 			}
 		}
 
@@ -104,7 +105,7 @@ static bool foreach_libblock_id_user_map_callback(void *user_data, ID **id_p, in
 
 			/* limit to key's added already */
 			if (data->is_subset) {
-				return true;
+				return IDWALK_RET_NOP;
 			}
 
 			/* Cannot use our placeholder key here! */
@@ -122,7 +123,7 @@ static bool foreach_libblock_id_user_map_callback(void *user_data, ID **id_p, in
 		PySet_Add(set, data->py_id_curr);
 	}
 
-	return true;
+	return IDWALK_RET_NOP;
 }
 
 PyDoc_STRVAR(bpy_user_map_doc,

source/blender/windowmanager/intern/wm_operators.c

@@ -4913,7 +4913,7 @@ static void previews_id_ensure(bContext *C, Scene *scene, ID *id)
 	}
 }
 
-static bool previews_id_ensure_callback(void *todo_v, ID **idptr, int UNUSED(cd_flag))
+static int previews_id_ensure_callback(void *todo_v, ID *UNUSED(idself), ID **idptr, int UNUSED(cd_flag))
 {
 	PreviewsIDEnsureStack *todo = todo_v;
 	ID *id = *idptr;
@@ -4926,7 +4926,7 @@ static bool previews_id_ensure_callback(void *todo_v, ID **idptr, int UNUSED(cd_
 		BLI_LINKSTACK_PUSH(todo->id_stack, id);
 	}
 
-	return true;
+	return IDWALK_RET_NOP;
 }
 
 static int previews_ensure_exec(bContext *C, wmOperator *UNUSED(op))