[Bf-blender-cvs] [3a702ec0282] blender2.7: Fix (unreported) usercount of linked IDs becoming garbage after undo/redo.

[Bastien Montagne]

Commit: 3a702ec028231e7deb012edac3eee5ed7f2436d4
Author: Bastien Montagne
Date:   Wed May 22 21:10:36 2019 +0200
Branches: blender2.7
https://developer.blender.org/rB3a702ec028231e7deb012edac3eee5ed7f2436d4

Fix (unreported) usercount of linked IDs becoming garbage after undo/redo.

Not re-reading linked data-blocks in undo/redo case also means that we
do not touch to their usercounts. Even worse, lib_link process in
readfile will increase those (for cases where local data uses linked
one).

Whole data management code is now heavily relying on valid consistent
refcount of all IDs, so we cannot allow that anymore.

Simple solution here could have been to then not increase that one for
linked IDs in `newlibadr_us()`, but unfortunately that would not be
totally bullet-proof, as some local users of linked data may be added or
removed by an undo step...

So I cannot think of any other solution than the ugly brute force one,
i.e. going over the whole Main database and recompute linked IDs users
count... Should not be a big issue performance wise though, this is
fairly cheap process.

===================================================================

M	source/blender/blenloader/intern/readfile.c

===================================================================

diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index c5a8aaca11c..9b393d3881f 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -8790,6 +8790,15 @@ BlendFileData *blo_read_file_internal(FileData *fd, const char *filepath)
 
 	BKE_main_id_tag_all(bfd->main, LIB_TAG_NEW, false);
 
+	if (fd->memfile != NULL) {
+		/* In undo/redo case, we do a whole lot of magic tricks to avoid having to re-read linked datablocks from
+		 * libraries (since those are not supposed to change).
+		 * Unfortunately, that means that we do not reset their user count, however we do increase that one when
+		 * doing lib_link on local IDs using linked ones.
+		 * There is no real way to predict amount of changes here, so we have to fully redo refcounting . */
+		BLE_main_id_refcount_recompute(bfd->main, true);
+	}
+
 	lib_verify_nodetree(bfd->main, true);
 	fix_relpaths_library(fd->relabase, bfd->main); /* make all relative paths, relative to the open blend file */