Fix (unreported) design flow in how workspace's relation data are read from .blend file.

Relying on pointer addresses across different data-blocks is extremely
not recommended (and should be strictly forbidden ideally), in
particular in direct_link step of blend file reading.
- It assumes a specific order in reading of data, which is not ensured
  in future, and is in any case a very bad, non explicit, hidden
  dependency on behaviors of other parts of the codebase.
- It is intrinsically unsafe (as in, it makes writing bad code and making
  mistakes easy, see e.g. fix in rB84b3f6e049b35f9).
- It makes advanced handling of data-blocks harder (thinking about
  partial undo code e.g., even though in this specific case it was not
  an issue as we do not re-read neither windowmanagers nor worspaces
  during undo).

New code uses windows' `winid` instead as 'anchor' to find again proper
workspace hook in windows at read time.

As a bonus, it will also cleanup the list of relations from any invalid
ones (afaict it was never done previously).

Differential Revision: https://developer.blender.org/D9073

1 files changed, 4 insertions, 0 deletions

diff --git a/source/blender/blenloader/intern/readfile.h b/source/blender/blenloader/intern/readfile.h
index 2ddf96a2d47..d3372a646a9 100644
--- a/source/blender/blenloader/intern/readfile.h
+++ b/source/blender/blenloader/intern/readfile.h
@@ -203,3 +203,7 @@ void do_versions_after_linking_270(struct Main *bmain);
 void do_versions_after_linking_280(struct Main *bmain, struct ReportList *reports);
 void do_versions_after_linking_290(struct Main *bmain, struct ReportList *reports);
 void do_versions_after_linking_cycles(struct Main *bmain);
+
+/* This is rather unfortunate to have to expose this here, but better use that nasty hack in
+ * do_version than readfile itself. */
+void *blo_read_get_new_globaldata_address(struct FileData *fd, const void *adr);