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

1 files changed, 11 insertions, 3 deletions

diff --git a/source/blender/blenkernel/BKE_library_query.h b/source/blender/blenkernel/BKE_library_query.h
index f07644dc833..86628ea8b6f 100644
--- a/source/blender/blenkernel/BKE_library_query.h
+++ b/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. */