The solution doesn't really seem generic enough with only curve bevel/taper and modifiers taken into account. This skips for example Mesh.texcomesh and probably other pointers too? Should there be some kind of generic datablock function to loop over these pointers?

We could optimize things a bit bu adding flags like SKIP_MATERIALS to this looper. Pretty much straightforward to add if we agree on general layout.

Talked to Lukas in IRC, we don't allow having IDs in nodes other than in node->id. Simple to implement. Will do it.

@Brecht Van Lommel (brecht), what are exact changes you expect to be done? (apart from what i've mentioned above) ?

Oops, forgot the inline comments in another tab.

General comments on having an ID looper.

Even at thie basic level I think the patch could be extended a bit.

• have LibraryIDLinkCallback accept a single flag argument, so data about the ID can be passed (LibraryForeachIDEnum or so...)
  • NEVER_NULL
  • NEVER_SELF
  • ID_USER

realize this duplicates some info from RNA, but think this can't be helped.
to begin with just adding NEVER_NULL would be handy, then at least other flags can be added later.

Some way to avoid null check on every member before use could be nice too (can be done with macro but Im sure you wont like this :) )

Note: to avoid doubling up when checking for NULL and calling, it could do this...

if (mesh->texcomesh) {
    callback(user_data, &mesh->texcomesh->id);
}

with this...

id = &mesh->texcomesh->id;
if (id) {
    callback(user_data, id);
}

Link to edit to this diff which uses a NULL check macro to make BKE_library_foreach_ID_link more compact.

http://pastebin.com/cA7PdPee

Additional types to support...

• Scene? - objects, camera, world, set, marker-camera links, toolsettings (brush), sequencer data + all its strip id links (mask, movieclip, sound, camera override)
• Screen? scene
• Object Pose (display object, pose constraints)

... i could go on and keep checking more.

... is it worth making this more comprehensive?

Generally LGTM, some comments,.