Refactor ID copying (and to some extent, ID freeing).

This will allow much finer controll over how we copy data-blocks, from
full copy in Main database, to "lighter" ones (out of Main, inside an
already allocated datablock, etc.).

This commit also transfers a llot of what was previously handled by
per-ID-type custom code to generic ID handling code in BKE_library.
Hopefully will avoid in future inconsistencies and missing bits we had
all over the codebase in the past.

It also adds missing copying handling for a few types, most notably
Scene (which where using a fully customized handling previously).

Note that the type of allocation used during copying (regular in Main,
allocated but outside of Main, or not allocated by ID handling code at
all) is stored in ID's, which allows to handle them correctly when
freeing. This needs to be taken care of with caution when doing 'weird'
unusual things with ID copying and/or allocation!

As a final note, while rather noisy, this commit will hopefully not
break too much existing branches, old 'API' has been kept for the main
part, as a wrapper around new code. Cleaning it up will happen later.

Design task : T51804
Phab Diff: D2714

2 files changed, 4 insertions, 1 deletions

diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index f224f0b5633..31964373716 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -638,7 +638,7 @@ static Main *blo_find_main(FileData *fd, const char *filepath, const char *relab
 	
 	/* Add library datablock itself to 'main' Main, since libraries are **never** linked data.
 	 * Fixes bug where you could end with all ID_LI datablocks having the same name... */
-	lib = BKE_libblock_alloc(mainlist->first, ID_LI, "Lib");
+	lib = BKE_libblock_alloc(mainlist->first, ID_LI, "Lib", 0);
 	lib->id.us = ID_FAKE_USERS(lib);  /* Important, consistency with main ID reading code from read_libblock(). */
 	BLI_strncpy(lib->name, filepath, sizeof(lib->name));
 	BLI_strncpy(lib->filepath, name1, sizeof(lib->filepath));
diff --git a/source/blender/blenloader/intern/writefile.c b/source/blender/blenloader/intern/writefile.c
index ee9665dc834..6c5bfb01829 100644
--- a/source/blender/blenloader/intern/writefile.c
+++ b/source/blender/blenloader/intern/writefile.c
@@ -3841,6 +3841,9 @@ static bool write_file_handle(
 		}
 
 		for (; id; id = id->next) {
+			/* We should never attempt to write non-regular IDs (i.e. all kind of temp/runtime ones). */
+			BLI_assert((id->tag & (LIB_TAG_NO_MAIN | LIB_TAG_NO_USER_REFCOUNT | LIB_TAG_NOT_ALLOCATED)) == 0);
+
 			switch ((ID_Type)GS(id->name)) {
 				case ID_WM:
 					write_windowmanager(wd, (wmWindowManager *)id);