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.

3 files changed, 6 insertions, 5 deletions

diff --git a/source/blender/windowmanager/WM_api.h b/source/blender/windowmanager/WM_api.h
index 388837af67a..9bb2462a4e9 100644
--- a/source/blender/windowmanager/WM_api.h
+++ b/source/blender/windowmanager/WM_api.h
@@ -191,7 +191,7 @@ void		WM_ndof_deadzone_set(float deadzone);
 void		WM_event_add_notifier(const struct bContext *C, unsigned int type, void *reference);
 void		WM_main_add_notifier(unsigned int type, void *reference);
 void		WM_main_remove_notifier_reference(const void *reference);
-void		WM_main_remove_editor_id_reference(const struct ID *id);
+void		WM_main_remap_editor_id_reference(struct ID *old_id, struct ID *new_id);
 
 			/* reports */
 void        WM_report_banner_show(void);
diff --git a/source/blender/windowmanager/intern/wm_event_system.c b/source/blender/windowmanager/intern/wm_event_system.c
index f632dd9aff4..4515ae92f66 100644
--- a/source/blender/windowmanager/intern/wm_event_system.c
+++ b/source/blender/windowmanager/intern/wm_event_system.c
@@ -241,7 +241,7 @@ void WM_main_remove_notifier_reference(const void *reference)
 	}
 }
 
-void WM_main_remove_editor_id_reference(const ID *id)
+void WM_main_remap_editor_id_reference(ID *old_id, ID *new_id)
 {
 	Main *bmain = G.main;
 	bScreen *sc;
@@ -253,7 +253,7 @@ void WM_main_remove_editor_id_reference(const ID *id)
 			SpaceLink *sl;
 
 			for (sl = sa->spacedata.first; sl; sl = sl->next) {
-				ED_spacedata_id_unref(sl, id);
+				ED_spacedata_id_remap(sa, sl, old_id, new_id);
 			}
 		}
 	}
diff --git a/source/blender/windowmanager/intern/wm_init_exit.c b/source/blender/windowmanager/intern/wm_init_exit.c
index 917e2bf5913..a1ca89c6a8c 100644
--- a/source/blender/windowmanager/intern/wm_init_exit.c
+++ b/source/blender/windowmanager/intern/wm_init_exit.c
@@ -61,6 +61,7 @@
 #include "BKE_global.h"
 #include "BKE_icons.h"
 #include "BKE_library.h"
+#include "BKE_library_remap.h"
 #include "BKE_main.h"
 #include "BKE_mball_tessellate.h"
 #include "BKE_node.h"
@@ -160,9 +161,9 @@ void WM_init(bContext *C, int argc, const char **argv)
 
 	BKE_library_callback_free_window_manager_set(wm_close_and_free);   /* library.c */
 	BKE_library_callback_free_notifier_reference_set(WM_main_remove_notifier_reference);   /* library.c */
-	BKE_library_callback_free_editor_id_reference_set(WM_main_remove_editor_id_reference);   /* library.c */
+	BKE_library_callback_remap_editor_id_reference_set(WM_main_remap_editor_id_reference);   /* library.c */
 	BKE_blender_callback_test_break_set(wm_window_testbreak); /* blender.c */
-	BKE_spacedata_callback_id_unref_set(ED_spacedata_id_unref); /* screen.c */
+	BKE_spacedata_callback_id_remap_set(ED_spacedata_id_remap); /* screen.c */
 	DAG_editors_update_cb(ED_render_id_flush_update,
 	                      ED_render_scene_update,
 	                      ED_render_scene_update_pre); /* depsgraph.c */