Previous code was doing N collection syncs when duplicating N objects.
New code avoids all the intermediate syncs by using
BKE_layer_collection_resync_forbid and
BKE_layer_collection_resync_allow, and then does one
BKE_main_collection_sync + BKE_main_collection_sync_remap for the
whole operation. There is some complexity involved where the Base
things of newly duplicated objects can't be found yet, without the
sync, so some work on them (marking them selected, active, ...) has
to be deferred until after the sync.
Timings: scene with 10k cubes, each with unique mesh (Windows, VS2022
Release build, AMD Ryzen 5950X):
- Shift+D duplicate: 13.6s -> 9.2s
- Alt+D duplicate: 4.76s -> 1.53s
Reviewed By: Bastien Montagne
Differential Revision: https://developer.blender.org/D14150
2d041fc468