Add a new LOOPBACK flag to libquery's callbacks.

That one tags those ugly little 'from' ID pointers (shape keys and
proxies), which point back from used to user ID, and require a lot of
special care in data-block management...

2 files changed, 11 insertions, 15 deletions

diff --git a/source/blender/blenkernel/BKE_library_query.h b/source/blender/blenkernel/BKE_library_query.h
index 68bf9f43fe1..6cf18e28e17 100644
--- a/source/blender/blenkernel/BKE_library_query.h
+++ b/source/blender/blenkernel/BKE_library_query.h
@@ -51,6 +51,11 @@ enum {
 	 * This means callback shall not *do* anything, only use this as informative data if it needs it. */
 	IDWALK_CB_PRIVATE = (1 << 3),
 
+	/** That ID is not really used by its owner, it's just an internal hint/helper.
+	 * This addresses Their Highest Ugliness the 'from' pointers: Object->from_proxy and Key->from.
+	 * How to handle that kind of cases totally depends on what caller code is doing... */
+	IDWALK_CB_LOOPBACK = (1 << 4),
+
 	/**
 	 * Adjusts #ID.us reference-count.
 	 * \note keep in sync with 'newlibadr_us' use in readfile.c
diff --git a/source/blender/blenkernel/intern/library_query.c b/source/blender/blenkernel/intern/library_query.c
index 3d65fa9b6e1..931002e6bbc 100644
--- a/source/blender/blenkernel/intern/library_query.c
+++ b/source/blender/blenkernel/intern/library_query.c
@@ -540,7 +540,7 @@ void BKE_library_foreach_ID_link(Main *bmain, ID *id, LibraryIDLinkCallback call
 				if (object->proxy_from) {
 					data.cb_flag = ID_IS_LINKED_DATABLOCK(object->proxy_from) ? IDWALK_CB_INDIRECT_USAGE : 0;
 				}
-				CALLBACK_INVOKE(object->proxy_from, IDWALK_CB_NOP);
+				CALLBACK_INVOKE(object->proxy_from, IDWALK_CB_LOOPBACK);
 				data.cb_flag = data_cb_flag;
 
 				CALLBACK_INVOKE(object->poselib, IDWALK_CB_USER);
@@ -745,12 +745,8 @@ void BKE_library_foreach_ID_link(Main *bmain, ID *id, LibraryIDLinkCallback call
 
 			case ID_KE:
 			{
-				/* XXX Only ID pointer from shapekeys is the 'from' one, which is not actually ID usage.
-				 * Maybe we should even nuke it from here, not 100% sure yet...
-				 * (see also foreach_libblock_id_users_callback).
-				 */
 				Key *key = (Key *) id;
-				CALLBACK_INVOKE_ID(key->from, IDWALK_CB_NOP);
+				CALLBACK_INVOKE_ID(key->from, IDWALK_CB_LOOPBACK);
 				break;
 			}
 
@@ -1146,20 +1142,15 @@ typedef struct IDUsersIter {
 	int count_direct, count_indirect;  /* Set by callback. */
 } IDUsersIter;
 
-static int foreach_libblock_id_users_callback(void *user_data, ID *self_id, ID **id_p, int cb_flag)
+static int foreach_libblock_id_users_callback(void *user_data, ID *UNUSED(self_id), ID **id_p, int cb_flag)
 {
 	IDUsersIter *iter = user_data;
 
 	if (*id_p) {
-		/* XXX This is actually some kind of hack...
-		 * Issue is, shapekeys' 'from' ID pointer is not actually ID usage.
-		 * Maybe we should even nuke it from BKE_library_foreach_ID_link, not 100% sure yet...
+		/* 'Loopback' ID pointers (the ugly 'from' ones, Object->proxy_from and Key->from).
+		 * Those are not actually ID usage, we can ignore them here.
 		 */
-		if ((GS(self_id->name) == ID_KE) && (((Key *)self_id)->from == *id_p)) {
-			return IDWALK_RET_NOP;
-		}
-		/* XXX another hack, for similar reasons as above one. */
-		if ((GS(self_id->name) == ID_OB) && (((Object *)self_id)->proxy_from == (Object *)*id_p)) {
+		if (cb_flag & IDWALK_CB_LOOPBACK) {
 			return IDWALK_RET_NOP;
 		}