ID-Remap - Step one: core work (cleanup and rework of generic ID datablock handling).

This commit changes a lot of how IDs are handled internally, especially the unlinking/freeing
processes. So far, this was very fuzy, to summarize cleanly deleting or replacing a datablock
was pretty much impossible, except for a few special cases.

Also, unlinking was handled by each datatype, in a rather messy and prone-to-errors way (quite
a few ID usages were missed or wrongly handled that way).

One of the main goal of id-remap branch was to cleanup this, and fatorize ID links handling
by using library_query utils to allow generic handling of those, which is now the case
(now, generic ID links handling is only "knwon" from readfile.c and library_query.c).

This commit also adds backends to allow live replacement and deletion of datablocks in Blender
(so-called 'remapping' process, where we replace all usages of a given ID pointer by a new one,
or NULL one in case of unlinking).

This will allow nice new features, like ability to easily reload or relocate libraries, real immediate
deletion of datablocks in blender, replacement of one datablock by another, etc.
Some of those are for next commits.

A word of warning: this commit is highly risky, because it affects potentially a lot in Blender core.
Though it was tested rather deeply, being totally impossible to check all possible ID usage cases,
it's likely there are some remaining issues and bugs in new code... Please report them! ;)

Review task: D2027 (https://developer.blender.org/D2027).
Reviewed by campbellbarton, thanks a bunch.

1 files changed, 76 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_library_remap.h b/source/blender/blenkernel/BKE_library_remap.h
new file mode 100644
index 00000000000..e85a3e60751
--- /dev/null
+++ b/source/blender/blenkernel/BKE_library_remap.h
@@ -0,0 +1,76 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+#ifndef __BKE_LIBRARY_REMAP_H__
+#define __BKE_LIBRARY_REMAP_H__
+
+/** \file BKE_library_remap.h
+ *  \ingroup bke
+ */
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "BLI_compiler_attrs.h"
+
+/* BKE_libblock_free, delete are declared in BKE_library.h for convenience. */
+
+/* Also IDRemap->flag. */
+enum {
+	/* Do not remap indirect usages of IDs (that is, when user is some linked data). */
+	ID_REMAP_SKIP_INDIRECT_USAGE    = 1 << 0,
+	/* This flag should always be set, *except for 'unlink' scenarios* (only relevant when new_id == NULL).
+	 * Basically, when unset, NEVER_NULL ID usages will keep pointing to old_id, but (if needed) old_id user count
+	 * will still be decremented. This is mandatory for 'delete ID' case, but in all other situation this would lead
+	 * to invalid user counts! */
+	ID_REMAP_SKIP_NEVER_NULL_USAGE  = 1 << 1,
+	/* This tells the callback func to flag with LIB_DOIT all IDs using target one with a 'never NULL' pointer
+	 * (like e.g. Object->data). */
+	ID_REMAP_FLAG_NEVER_NULL_USAGE  = 1 << 2,
+	/* This tells the callback func to force setting IDs using target one with a 'never NULL' pointer to NULL.
+	 * WARNING! Use with extreme care, this will leave database in broken state! */
+	ID_REMAP_FORCE_NEVER_NULL_USAGE = 1 << 3,
+};
+
+/* Note: Requiring new_id to be non-null, this *may* not be the case ultimately, but makes things simpler for now. */
+void BKE_libblock_remap_locked(
+        struct Main *bmain, void *old_idv, void *new_idv,
+        const short remap_flags) ATTR_NONNULL(1, 2);
+void BKE_libblock_remap(
+        struct Main *bmain, void *old_idv, void *new_idv,
+        const short remap_flags) ATTR_NONNULL(1, 2);
+
+void BKE_libblock_unlink(struct Main *bmain, void *idv, const bool do_flag_never_null) ATTR_NONNULL();
+
+void BKE_libblock_relink_ex(void *idv, void *old_idv, void *new_idv, const bool us_min_never_null) ATTR_NONNULL(1);
+
+
+typedef void (*BKE_library_free_window_manager_cb)(struct bContext *, struct wmWindowManager *);
+typedef void (*BKE_library_free_notifier_reference_cb)(const void *);
+typedef void (*BKE_library_remap_editor_id_reference_cb)(struct ID *, struct ID *);
+
+void BKE_library_callback_free_window_manager_set(BKE_library_free_window_manager_cb func);
+void BKE_library_callback_free_notifier_reference_set(BKE_library_free_notifier_reference_cb func);
+void BKE_library_callback_remap_editor_id_reference_set(BKE_library_remap_editor_id_reference_cb func);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  /* __BKE_LIBRARY_REMAP_H__ */
\ No newline at end of file