Assets: Support automatic collection previews

Adds supports for collection previews that are rendered automatically when
collections are marked as assets. (Or when preview rendering is triggered
differently, e.g. through the //Refresh Data-Block Previews// operator).

Idea in this patch is to create a collection instance empty outside of main for
the collection, and then reuse the object rendering code to render the preview.
This keeps things very simple and works just fine.

Differential Revision: https://developer.blender.org/D14460

Reviewed by: Bastien Montagne

2 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/blenkernel/intern/icons.cc b/source/blender/blenkernel/intern/icons.cc
index 8883613786b..2ba6510ee71 100644
--- a/source/blender/blenkernel/intern/icons.cc
+++ b/source/blender/blenkernel/intern/icons.cc
@@ -416,7 +416,7 @@ void BKE_previewimg_id_custom_set(ID *id, const char *path)
 
 bool BKE_previewimg_id_supports_jobs(const ID *id)
 {
-  return ELEM(GS(id->name), ID_OB, ID_MA, ID_TE, ID_LA, ID_WO, ID_IM, ID_BR);
+  return ELEM(GS(id->name), ID_OB, ID_MA, ID_TE, ID_LA, ID_WO, ID_IM, ID_BR, ID_GR);
 }
 
 void BKE_previewimg_deferred_release(PreviewImage *prv)
diff --git a/source/blender/blenkernel/intern/object.cc b/source/blender/blenkernel/intern/object.cc
index 6006ce88896..84d9002f4d2 100644
--- a/source/blender/blenkernel/intern/object.cc
+++ b/source/blender/blenkernel/intern/object.cc
@@ -2217,7 +2217,7 @@ Object *BKE_object_add_only_object(Main *bmain, int type, const char *name)
   }
 
   /* We cannot use #BKE_id_new here as we need some custom initialization code. */
-  Object *ob = (Object *)BKE_libblock_alloc(bmain, ID_OB, name, 0);
+  Object *ob = (Object *)BKE_libblock_alloc(bmain, ID_OB, name, bmain ? 0 : LIB_ID_CREATE_NO_MAIN);
 
   /* We increase object user count when linking to Collections. */
   id_us_min(&ob->id);