Merge branch 'blender2.7'
authorBastien Montagne <montagne29@wanadoo.fr>
Thu, 23 May 2019 08:23:11 +0000 (10:23 +0200)
committerBastien Montagne <montagne29@wanadoo.fr>
Thu, 23 May 2019 08:23:11 +0000 (10:23 +0200)
Conflicts:
source/blender/blenkernel/intern/library_remap.c

1  2 
source/blender/blenkernel/intern/library_remap.c

index e0e473978f8bd08b00eb97fd879cdb7bd1b8a687,7e3af8528cbaae2fa9b0b42e5e90b1c787d81e24..802f13ea69fa3dd3403692b258d11aeb3abca0e5
@@@ -14,8 -14,8 +14,8 @@@
   * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
   */
  
 -/** \file blender/blenkernel/intern/library_remap.c
 - *  \ingroup bke
 +/** \file
 + * \ingroup bke
   *
   * Contains management of ID's and libraries remap, unlink and free logic.
   */
@@@ -27,8 -27,6 +27,8 @@@
  #include <stddef.h>
  #include <assert.h>
  
 +#include "CLG_log.h"
 +
  #include "MEM_guardedalloc.h"
  
  /* all types are needed here, in order to do memory operations */
  #include "DNA_brush_types.h"
  #include "DNA_camera_types.h"
  #include "DNA_cachefile_types.h"
 -#include "DNA_group_types.h"
 +#include "DNA_collection_types.h"
  #include "DNA_gpencil_types.h"
  #include "DNA_ipo_types.h"
  #include "DNA_key_types.h"
 -#include "DNA_lamp_types.h"
 +#include "DNA_light_types.h"
  #include "DNA_lattice_types.h"
  #include "DNA_linestyle_types.h"
  #include "DNA_material_types.h"
@@@ -51,7 -49,6 +51,7 @@@
  #include "DNA_mask_types.h"
  #include "DNA_node_types.h"
  #include "DNA_object_types.h"
 +#include "DNA_lightprobe_types.h"
  #include "DNA_scene_types.h"
  #include "DNA_screen_types.h"
  #include "DNA_speaker_types.h"
@@@ -59,7 -56,6 +59,7 @@@
  #include "DNA_text_types.h"
  #include "DNA_vfont_types.h"
  #include "DNA_windowmanager_types.h"
 +#include "DNA_workspace_types.h"
  #include "DNA_world_types.h"
  
  #include "BLI_blenlib.h"
  #include "BKE_brush.h"
  #include "BKE_camera.h"
  #include "BKE_cachefile.h"
 +#include "BKE_collection.h"
  #include "BKE_curve.h"
 -#include "BKE_depsgraph.h"
  #include "BKE_fcurve.h"
  #include "BKE_font.h"
 -#include "BKE_group.h"
  #include "BKE_gpencil.h"
  #include "BKE_idprop.h"
  #include "BKE_image.h"
  #include "BKE_ipo.h"
  #include "BKE_key.h"
 -#include "BKE_lamp.h"
 +#include "BKE_light.h"
  #include "BKE_lattice.h"
 +#include "BKE_layer.h"
  #include "BKE_library.h"
 +#include "BKE_library_override.h"
  #include "BKE_library_query.h"
  #include "BKE_library_remap.h"
  #include "BKE_linestyle.h"
  #include "BKE_object.h"
  #include "BKE_paint.h"
  #include "BKE_particle.h"
 -#include "BKE_sca.h"
 +#include "BKE_lightprobe.h"
  #include "BKE_speaker.h"
  #include "BKE_sound.h"
  #include "BKE_screen.h"
  #include "BKE_scene.h"
  #include "BKE_text.h"
  #include "BKE_texture.h"
 +#include "BKE_workspace.h"
  #include "BKE_world.h"
  
 +#include "DEG_depsgraph.h"
 +#include "DEG_depsgraph_build.h"
 +
  #ifdef WITH_PYTHON
 -#include "BPY_extern.h"
 +#  include "BPY_extern.h"
  #endif
  
 +static CLG_LogRef LOG = {"bke.library_remap"};
 +
  static BKE_library_free_window_manager_cb free_windowmanager_cb = NULL;
  
  void BKE_library_callback_free_window_manager_set(BKE_library_free_window_manager_cb func)
  {
 -      free_windowmanager_cb = func;
 +  free_windowmanager_cb = func;
  }
  
  static BKE_library_free_notifier_reference_cb free_notifier_reference_cb = NULL;
  
  void BKE_library_callback_free_notifier_reference_set(BKE_library_free_notifier_reference_cb func)
  {
 -      free_notifier_reference_cb = func;
 +  free_notifier_reference_cb = func;
  }
  
  static BKE_library_remap_editor_id_reference_cb remap_editor_id_reference_cb = NULL;
  
 -void BKE_library_callback_remap_editor_id_reference_set(BKE_library_remap_editor_id_reference_cb func)
 +void BKE_library_callback_remap_editor_id_reference_set(
 +    BKE_library_remap_editor_id_reference_cb func)
  {
 -      remap_editor_id_reference_cb = func;
 +  remap_editor_id_reference_cb = func;
  }
  
  typedef struct IDRemap {
 -      Main *bmain;  /* Only used to trigger depsgraph updates in the right bmain. */
 -      ID *old_id;
 -      ID *new_id;
 -      ID *id;  /* The ID in which we are replacing old_id by new_id usages. */
 -      short flag;
 -
 -      /* 'Output' data. */
 -      short status;
 -      int skipped_direct;  /* Number of direct usecases that could not be remapped (e.g.: obdata when in edit mode). */
 -      int skipped_indirect;  /* Number of indirect usecases that could not be remapped. */
 -      int skipped_refcounted;  /* Number of skipped usecases that refcount the datablock. */
 +  Main *bmain; /* Only used to trigger depsgraph updates in the right bmain. */
 +  ID *old_id;
 +  ID *new_id;
 +  /** The ID in which we are replacing old_id by new_id usages. */
 +  ID *id;
 +  short flag;
 +
 +  /* 'Output' data. */
 +  short status;
 +  /** Number of direct usecases that could not be remapped (e.g.: obdata when in edit mode). */
 +  int skipped_direct;
 +  /** Number of indirect usecases that could not be remapped. */
 +  int skipped_indirect;
 +  /** Number of skipped usecases that refcount the datablock. */
 +  int skipped_refcounted;
  } IDRemap;
  
  /* IDRemap->flag enums defined in BKE_library.h */
  
  /* IDRemap->status */
  enum {
 -      /* *** Set by callback. *** */
 -      ID_REMAP_IS_LINKED_DIRECT       = 1 << 0,  /* new_id is directly linked in current .blend. */
 -      ID_REMAP_IS_USER_ONE_SKIPPED    = 1 << 1,  /* There was some skipped 'user_one' usages of old_id. */
 +  /* *** Set by callback. *** */
 +  ID_REMAP_IS_LINKED_DIRECT = 1 << 0,    /* new_id is directly linked in current .blend. */
 +  ID_REMAP_IS_USER_ONE_SKIPPED = 1 << 1, /* There was some skipped 'user_one' usages of old_id. */
  };
  
  static int foreach_libblock_remap_callback(void *user_data, ID *id_self, ID **id_p, int cb_flag)
  {
 -      if (cb_flag & IDWALK_CB_PRIVATE) {
 -              return IDWALK_RET_NOP;
 -      }
 -
 -      IDRemap *id_remap_data = user_data;
 -      ID *old_id = id_remap_data->old_id;
 -      ID *new_id = id_remap_data->new_id;
 -      ID *id = id_remap_data->id;
 -
 -      if (!old_id) {  /* Used to cleanup all IDs used by a specific one. */
 -              BLI_assert(!new_id);
 -              old_id = *id_p;
 -      }
 -
 -      if (*id_p && (*id_p == old_id)) {
 -              const bool is_indirect = (cb_flag & IDWALK_CB_INDIRECT_USAGE) != 0;
 -              const bool skip_indirect = (id_remap_data->flag & ID_REMAP_SKIP_INDIRECT_USAGE) != 0;
 -              /* Note: proxy usage implies LIB_TAG_EXTERN, so on this aspect it is direct,
 -               *       on the other hand since they get reset to lib data on file open/reload it is indirect too...
 -               *       Edit Mode is also a 'skip direct' case. */
 -              const bool is_obj = (GS(id->name) == ID_OB);
 -              const bool is_obj_proxy = (is_obj && (((Object *)id)->proxy || ((Object *)id)->proxy_group));
 -              const bool is_obj_editmode = (is_obj && BKE_object_is_in_editmode((Object *)id));
 -              const bool is_never_null = ((cb_flag & IDWALK_CB_NEVER_NULL) && (new_id == NULL) &&
 -                                          (id_remap_data->flag & ID_REMAP_FORCE_NEVER_NULL_USAGE) == 0);
 -              const bool skip_never_null = (id_remap_data->flag & ID_REMAP_SKIP_NEVER_NULL_USAGE) != 0;
 +  if (cb_flag & IDWALK_CB_PRIVATE) {
 +    return IDWALK_RET_NOP;
 +  }
 +
 +  IDRemap *id_remap_data = user_data;
 +  ID *old_id = id_remap_data->old_id;
 +  ID *new_id = id_remap_data->new_id;
 +  ID *id = id_remap_data->id;
 +
 +  if (!old_id) { /* Used to cleanup all IDs used by a specific one. */
 +    BLI_assert(!new_id);
 +    old_id = *id_p;
 +  }
 +
 +  if (*id_p && (*id_p == old_id)) {
 +    /* Better remap to NULL than not remapping at all,
 +     * then we can handle it as a regular remap-to-NULL case. */
 +    if ((cb_flag & IDWALK_CB_NEVER_SELF) && (new_id == id_self)) {
 +      new_id = NULL;
 +    }
 +
 +    const bool is_reference = (cb_flag & IDWALK_CB_STATIC_OVERRIDE_REFERENCE) != 0;
 +    const bool is_indirect = (cb_flag & IDWALK_CB_INDIRECT_USAGE) != 0;
 +    const bool skip_indirect = (id_remap_data->flag & ID_REMAP_SKIP_INDIRECT_USAGE) != 0;
 +    /* Note: proxy usage implies LIB_TAG_EXTERN, so on this aspect it is direct,
 +     * on the other hand since they get reset to lib data on file open/reload it is indirect too.
 +     * Edit Mode is also a 'skip direct' case. */
 +    const bool is_obj = (GS(id->name) == ID_OB);
 +    const bool is_obj_proxy = (is_obj && (((Object *)id)->proxy || ((Object *)id)->proxy_group));
 +    const bool is_obj_editmode = (is_obj && BKE_object_is_in_editmode((Object *)id));
 +    const bool is_never_null = ((cb_flag & IDWALK_CB_NEVER_NULL) && (new_id == NULL) &&
 +                                (id_remap_data->flag & ID_REMAP_FORCE_NEVER_NULL_USAGE) == 0);
 +    const bool skip_reference = (id_remap_data->flag & ID_REMAP_SKIP_STATIC_OVERRIDE) != 0;
 +    const bool skip_never_null = (id_remap_data->flag & ID_REMAP_SKIP_NEVER_NULL_USAGE) != 0;
  
  #ifdef DEBUG_PRINT
 -              printf("In %s: Remapping %s (%p) to %s (%p) (is_indirect: %d, skip_indirect: %d)\n",
 -                     id->name, old_id->name, old_id, new_id ? new_id->name : "<NONE>", new_id, is_indirect, skip_indirect);
 +    printf(
 +        "In %s (lib %p): Remapping %s (%p) to %s (%p) "
 +        "(is_indirect: %d, skip_indirect: %d, is_reference: %d, skip_reference: %d)\n",
 +        id->name,
 +        id->lib,
 +        old_id->name,
 +        old_id,
 +        new_id ? new_id->name : "<NONE>",
 +        new_id,
 +        is_indirect,
 +        skip_indirect,
 +        is_reference,
 +        skip_reference);
  #endif
  
 -              if ((id_remap_data->flag & ID_REMAP_FLAG_NEVER_NULL_USAGE) && (cb_flag & IDWALK_CB_NEVER_NULL)) {
 -                      id->tag |= LIB_TAG_DOIT;
 -              }
 -
 -              /* Special hack in case it's Object->data and we are in edit mode, and new_id is not NULL
 -               * (otherwise, we follow common NEVER_NULL flags).
 -               * (skipped_indirect too). */
 -              if ((is_never_null && skip_never_null) ||
 -                  (is_obj_editmode && (((Object *)id)->data == *id_p) && new_id != NULL) ||
 -                  (skip_indirect && is_indirect))
 -              {
 -                      if (is_indirect) {
 -                              id_remap_data->skipped_indirect++;
 -                              if (is_obj) {
 -                                      Object *ob = (Object *)id;
 -                                      if (ob->data == *id_p && ob->proxy != NULL) {
 -                                              /* And another 'Proudly brought to you by Proxy Hell' hack!
 -                                               * This will allow us to avoid clearing 'LIB_EXTERN' flag of obdata of proxies... */
 -                                              id_remap_data->skipped_direct++;
 -                                      }
 -                              }
 -                      }
 -                      else if (is_never_null || is_obj_editmode) {
 -                              id_remap_data->skipped_direct++;
 -                      }
 -                      else {
 -                              BLI_assert(0);
 -                      }
 -                      if (cb_flag & IDWALK_CB_USER) {
 -                              id_remap_data->skipped_refcounted++;
 -                      }
 -                      else if (cb_flag & IDWALK_CB_USER_ONE) {
 -                              /* No need to count number of times this happens, just a flag is enough. */
 -                              id_remap_data->status |= ID_REMAP_IS_USER_ONE_SKIPPED;
 -                      }
 -              }
 -              else {
 -                      if (!is_never_null) {
 -                              *id_p = new_id;
 -                              DAG_id_tag_update_ex(id_remap_data->bmain, id_self, OB_RECALC_OB | OB_RECALC_DATA | OB_RECALC_TIME);
 -                      }
 -                      if (cb_flag & IDWALK_CB_USER) {
 -                              id_us_min(old_id);
 -                              /* We do not want to handle LIB_TAG_INDIRECT/LIB_TAG_EXTERN here. */
 -                              if (new_id)
 -                                      new_id->us++;
 -                      }
 -                      else if (cb_flag & IDWALK_CB_USER_ONE) {
 -                              id_us_ensure_real(new_id);
 -                              /* We cannot affect old_id->us directly, LIB_TAG_EXTRAUSER(_SET) are assumed to be set as needed,
 -                               * that extra user is processed in final handling... */
 -                      }
 -                      if (!is_indirect || is_obj_proxy) {
 -                              id_remap_data->status |= ID_REMAP_IS_LINKED_DIRECT;
 -                      }
 -                      /* We need to remap proxy_from pointer of remapped proxy... sigh. */
 -                      if (is_obj_proxy && new_id != NULL) {
 -                              Object *ob = (Object *)id;
 -                              if (ob->proxy == (Object *)new_id) {
 -                                      ob->proxy->proxy_from = ob;
 -                              }
 -                      }
 -              }
 -      }
 -
 -      return IDWALK_RET_NOP;
 -}
 -
 -/* Some remapping unfortunately require extra and/or specific handling, tackle those here. */
 -static void libblock_remap_data_preprocess_scene_base_unlink(
 -        IDRemap *r_id_remap_data, Scene *sce, Base *base, const bool skip_indirect, const bool is_indirect)
 -{
 -      if (skip_indirect && is_indirect) {
 -              r_id_remap_data->skipped_indirect++;
 -              r_id_remap_data->skipped_refcounted++;
 -      }
 -      else {
 -              id_us_min((ID *)base->object);
 -              BKE_scene_base_unlink(sce, base);
 -              MEM_freeN(base);
 -              if (!is_indirect) {
 -                      r_id_remap_data->status |= ID_REMAP_IS_LINKED_DIRECT;
 -              }
 -      }
 +    if ((id_remap_data->flag & ID_REMAP_FLAG_NEVER_NULL_USAGE) &&
 +        (cb_flag & IDWALK_CB_NEVER_NULL)) {
 +      id->tag |= LIB_TAG_DOIT;
 +    }
 +
 +    /* Special hack in case it's Object->data and we are in edit mode, and new_id is not NULL
 +     * (otherwise, we follow common NEVER_NULL flags).
 +     * (skipped_indirect too). */
 +    if ((is_never_null && skip_never_null) ||
 +        (is_obj_editmode && (((Object *)id)->data == *id_p) && new_id != NULL) ||
 +        (skip_indirect && is_indirect) || (is_reference && skip_reference)) {
 +      if (is_indirect) {
 +        id_remap_data->skipped_indirect++;
 +        if (is_obj) {
 +          Object *ob = (Object *)id;
 +          if (ob->data == *id_p && ob->proxy != NULL) {
 +            /* And another 'Proudly brought to you by Proxy Hell' hack!
 +             * This will allow us to avoid clearing 'LIB_EXTERN' flag of obdata of proxies... */
 +            id_remap_data->skipped_direct++;
 +          }
 +        }
 +      }
 +      else if (is_never_null || is_obj_editmode || is_reference) {
 +        id_remap_data->skipped_direct++;
 +      }
 +      else {
 +        BLI_assert(0);
 +      }
 +      if (cb_flag & IDWALK_CB_USER) {
 +        id_remap_data->skipped_refcounted++;
 +      }
 +      else if (cb_flag & IDWALK_CB_USER_ONE) {
 +        /* No need to count number of times this happens, just a flag is enough. */
 +        id_remap_data->status |= ID_REMAP_IS_USER_ONE_SKIPPED;
 +      }
 +    }
 +    else {
 +      if (!is_never_null) {
 +        *id_p = new_id;
 +        DEG_id_tag_update_ex(id_remap_data->bmain,
 +                             id_self,
 +                             ID_RECALC_COPY_ON_WRITE | ID_RECALC_TRANSFORM | ID_RECALC_GEOMETRY);
 +      }
 +      if (cb_flag & IDWALK_CB_USER) {
 +        /* NOTE: We don't user-count IDs which are not in the main database.
 +         * This is because in certain conditions we can have datablocks in
 +         * the main which are referencing datablocks outside of it.
 +         * For example, BKE_mesh_new_from_object() called on an evaluated
 +         * object will cause such situation.
 +         */
 +        if ((old_id->tag & LIB_TAG_NO_MAIN) == 0) {
 +          id_us_min(old_id);
 +        }
 +        if (new_id != NULL && (new_id->tag & LIB_TAG_NO_MAIN) == 0) {
 +          /* We do not want to handle LIB_TAG_INDIRECT/LIB_TAG_EXTERN here. */
 +          new_id->us++;
 +        }
 +      }
 +      else if (cb_flag & IDWALK_CB_USER_ONE) {
 +        id_us_ensure_real(new_id);
 +        /* We cannot affect old_id->us directly, LIB_TAG_EXTRAUSER(_SET)
 +         * are assumed to be set as needed, that extra user is processed in final handling. */
 +      }
 +      if (!is_indirect || is_obj_proxy) {
 +        id_remap_data->status |= ID_REMAP_IS_LINKED_DIRECT;
 +      }
++      /* We need to remap proxy_from pointer of remapped proxy... sigh. */
++      if (is_obj_proxy && new_id != NULL) {
++        Object *ob = (Object *)id;
++        if (ob->proxy == (Object *)new_id) {
++          ob->proxy->proxy_from = ob;
++        }
++      }
 +    }
 +  }
 +
 +  return IDWALK_RET_NOP;
  }
  
  static void libblock_remap_data_preprocess(IDRemap *r_id_remap_data)
  {
 -      switch (GS(r_id_remap_data->id->name)) {
 -              case ID_SCE:
 -              {
 -                      Scene *sce = (Scene *)r_id_remap_data->id;
 -
 -                      if (!r_id_remap_data->new_id) {
 -                              const bool is_indirect = (sce->id.lib != NULL);
 -                              const bool skip_indirect = (r_id_remap_data->flag & ID_REMAP_SKIP_INDIRECT_USAGE) != 0;
 -
 -                              /* In case we are unlinking... */
 -                              if (!r_id_remap_data->old_id) {
 -                                      /* ... everything from scene. */
 -                                      Base *base, *base_next;
 -                                      for (base = sce->base.first; base; base = base_next) {
 -                                              base_next = base->next;
 -                                              libblock_remap_data_preprocess_scene_base_unlink(
 -                                                          r_id_remap_data, sce, base, skip_indirect, is_indirect);
 -                                      }
 -                              }
 -                              else if (GS(r_id_remap_data->old_id->name) == ID_OB) {
 -                                      /* ... a specific object from scene. */
 -                                      Object *old_ob = (Object *)r_id_remap_data->old_id;
 -                                      Base *base = BKE_scene_base_find(sce, old_ob);
 -
 -                                      if (base) {
 -                                              libblock_remap_data_preprocess_scene_base_unlink(
 -                                                          r_id_remap_data, sce, base, skip_indirect, is_indirect);
 -                                      }
 -                              }
 -                      }
 -                      break;
 -              }
 -              case ID_OB:
 -              {
 -                      ID *old_id = r_id_remap_data->old_id;
 -                      if (!old_id || GS(old_id->name) == ID_AR) {
 -                              Object *ob = (Object *)r_id_remap_data->id;
 -                              /* Object's pose holds reference to armature bones... sic */
 -                              /* Note that in theory, we should have to bother about linked/non-linked/never-null/etc. flags/states.
 -                               * Fortunately, this is just a tag, so we can accept to 'over-tag' a bit for pose recalc, and avoid
 -                               * another complex and risky condition nightmare like the one we have in
 -                               * foreach_libblock_remap_callback()... */
 -                              if (ob->pose && (!old_id || ob->data == old_id)) {
 -                                      BLI_assert(ob->type == OB_ARMATURE);
 -                                      ob->pose->flag |= POSE_RECALC;
 -                                      /* We need to clear pose bone pointers immediately, things like undo writefile may be called
 -                                       * before pose is actually recomputed, can lead to segfault... */
 -                                      BKE_pose_clear_pointers(ob->pose);
 -                              }
 -                      }
 -                      break;
 -              }
 -              default:
 -                      break;
 -      }
 +  switch (GS(r_id_remap_data->id->name)) {
 +    case ID_OB: {
 +      ID *old_id = r_id_remap_data->old_id;
 +      if (!old_id || GS(old_id->name) == ID_AR) {
 +        Object *ob = (Object *)r_id_remap_data->id;
 +        /* Object's pose holds reference to armature bones... sic */
 +        /* Note that in theory, we should have to bother about
 +         * linked/non-linked/never-null/etc. flags/states.
 +         * Fortunately, this is just a tag, so we can accept to 'over-tag' a bit for pose recalc,
 +         * and avoid another complex and risky condition nightmare like the one we have in
 +         * foreach_libblock_remap_callback()... */
 +        if (ob->pose && (!old_id || ob->data == old_id)) {
 +          BLI_assert(ob->type == OB_ARMATURE);
 +          ob->pose->flag |= POSE_RECALC;
 +          /* We need to clear pose bone pointers immediately, things like undo writefile may be
 +           * called before pose is actually recomputed, can lead to segfault... */
 +          BKE_pose_clear_pointers(ob->pose);
 +        }
 +      }
 +      break;
 +    }
 +    default:
 +      break;
 +  }
  }
  
 -static void libblock_remap_data_postprocess_object_update(Main *bmain, Object *old_ob, Object *new_ob)
 +/**
 + * Can be called with both old_ob and new_ob being NULL,
 + * this means we have to check whole Main database then.
 + */
 +static void libblock_remap_data_postprocess_object_update(Main *bmain,
 +                                                          Object *old_ob,
 +                                                          Object *new_ob)
  {
 -      if (old_ob->flag & OB_FROMGROUP) {
 -              /* Note that for Scene's BaseObject->flag, either we:
 -               *     - unlinked old_ob (i.e. new_ob is NULL), in which case scenes' bases have been removed already.
 -               *     - remapped old_ob by new_ob, in which case scenes' bases are still valid as is.
 -               * So in any case, no need to update them here. */
 -              if (BKE_group_object_find(bmain, NULL, old_ob) == NULL) {
 -                      old_ob->flag &= ~OB_FROMGROUP;
 -              }
 -              if (new_ob == NULL) {  /* We need to remove NULL-ified groupobjects... */
 -                      for (Group *group = bmain->group.first; group; group = group->id.next) {
 -                              BKE_group_object_unlink(bmain, group, NULL, NULL, NULL);
 -                      }
 -              }
 -              else {
 -                      new_ob->flag |= OB_FROMGROUP;
 -              }
 -      }
 -      if (old_ob->type == OB_MBALL) {
 -              for (Object *ob = bmain->object.first; ob; ob = ob->id.next) {
 -                      if (ob->type == OB_MBALL && BKE_mball_is_basis_for(ob, old_ob)) {
 -                              DAG_id_tag_update(&ob->id, OB_RECALC_DATA);
 -                      }
 -              }
 -      }
 +  if (new_ob == NULL) {
 +    /* In case we unlinked old_ob (new_ob is NULL), the object has already
 +     * been removed from the scenes and their collections. We still have
 +     * to remove the NULL children from collections not used in any scene. */
 +    BKE_collections_object_remove_nulls(bmain);
 +  }
 +
 +  BKE_main_collection_sync_remap(bmain);
 +
 +  if (old_ob == NULL) {
 +    for (Object *ob = bmain->objects.first; ob != NULL; ob = ob->id.next) {
 +      if (ob->type == OB_MBALL && BKE_mball_is_basis(ob)) {
 +        DEG_id_tag_update(&ob->id, ID_RECALC_GEOMETRY);
 +      }
 +    }
 +  }
 +  else {
 +    for (Object *ob = bmain->objects.first; ob != NULL; ob = ob->id.next) {
 +      if (ob->type == OB_MBALL && BKE_mball_is_basis_for(ob, old_ob)) {
 +        DEG_id_tag_update(&ob->id, ID_RECALC_GEOMETRY);
 +        break; /* There is only one basis... */
 +      }
 +    }
 +  }
  }
  
 -static void libblock_remap_data_postprocess_group_scene_unlink(Main *bmain, Scene *sce, ID *old_id)
 +/* Can be called with both old_collection and new_collection being NULL,
 + * this means we have to check whole Main database then. */
 +static void libblock_remap_data_postprocess_collection_update(Main *bmain,
 +                                                              Collection *UNUSED(old_collection),
 +                                                              Collection *new_collection)
  {
 -      /* Note that here we assume no object has no base (i.e. all objects are assumed instanced
 -       * in one scene...). */
 -      for (Base *base = sce->base.first; base; base = base->next) {
 -              if (base->flag & OB_FROMGROUP) {
 -                      Object *ob = base->object;
 -
 -                      if (ob->flag & OB_FROMGROUP) {
 -                              Group *grp = BKE_group_object_find(bmain, NULL, ob);
 -
 -                              /* Unlinked group (old_id) is still in bmain... */
 -                              if (grp && (&grp->id == old_id || grp->id.us == 0)) {
 -                                      grp = BKE_group_object_find(bmain, grp, ob);
 -                              }
 -                              if (!grp) {
 -                                      ob->flag &= ~OB_FROMGROUP;
 -                              }
 -                      }
 -                      if (!(ob->flag & OB_FROMGROUP)) {
 -                              base->flag &= ~OB_FROMGROUP;
 -                      }
 -              }
 -      }
 +  if (new_collection == NULL) {
 +    /* XXX Complex cases can lead to NULL pointers in other collections than old_collection,
 +     * and BKE_main_collection_sync_remap() does not tolerate any of those, so for now always check
 +     * whole existing collections for NULL pointers.
 +     * I'd consider optimizing that whole collection remapping process a TODO for later. */
 +    BKE_collections_child_remove_nulls(bmain, NULL /*old_collection*/);
 +  }
 +  else {
 +    /* Temp safe fix, but a "tad" brute force... We should probably be able to use parents from
 +     * old_collection instead? */
 +    BKE_main_collections_parent_relations_rebuild(bmain);
 +  }
 +
 +  BKE_main_collection_sync_remap(bmain);
  }
  
  static void libblock_remap_data_postprocess_obdata_relink(Main *bmain, Object *ob, ID *new_id)
  {
 -      if (ob->data == new_id) {
 -              switch (GS(new_id->name)) {
 -                      case ID_ME:
 -                              multires_force_update(ob);
 -                              break;
 -                      case ID_CU:
 -                              BKE_curve_type_test(ob);
 -                              break;
 -                      default:
 -                              break;
 -              }
 -              test_object_modifiers(ob);
 -              test_object_materials(bmain, ob, new_id);
 -      }
 +  if (ob->data == new_id) {
 +    switch (GS(new_id->name)) {
 +      case ID_ME:
 +        multires_force_update(ob);
 +        break;
 +      case ID_CU:
 +        BKE_curve_type_test(ob);
 +        break;
 +      default:
 +        break;
 +    }
 +    test_object_modifiers(ob);
 +    test_object_materials(bmain, ob, new_id);
 +  }
  }
  
  static void libblock_remap_data_postprocess_nodetree_update(Main *bmain, ID *new_id)
  {
 -      /* Verify all nodetree user nodes. */
 -      ntreeVerifyNodes(bmain, new_id);
 -
 -      /* Update node trees as necessary. */
 -      FOREACH_NODETREE_BEGIN(bmain, ntree, id) {
 -              /* make an update call for the tree */
 -              ntreeUpdateTree(bmain, ntree);
 -      } FOREACH_NODETREE_END;
 +  /* Update all group nodes using a node group. */
 +  ntreeUpdateAllUsers(bmain, new_id);
  }
  
  /**
   *
   * Behavior differs depending on whether given \a id is NULL or not:
   * - \a id NULL: \a old_id must be non-NULL, \a new_id may be NULL (unlinking \a old_id) or not
 - *   (remapping \a old_id to \a new_id). The whole \a bmain database is checked, and all pointers to \a old_id
 + *   (remapping \a old_id to \a new_id).
 + *   The whole \a bmain database is checked, and all pointers to \a old_id
   *   are remapped to \a new_id.
   * - \a id is non-NULL:
 - *   + If \a old_id is NULL, \a new_id must also be NULL, and all ID pointers from \a id are cleared (i.e. \a id
 - *     does not references any other datablock anymore).
 + *   + If \a old_id is NULL, \a new_id must also be NULL,
 + *     and all ID pointers from \a id are cleared
 + *     (i.e. \a id does not references any other datablock anymore).
   *   + If \a old_id is non-NULL, behavior is as with a NULL \a id, but only within given \a id.
   *
   * \param bmain: the Main data storage to operate on (must never be NULL).
 - * \param id: the datablock to operate on (can be NULL, in which case we operate over all IDs from given bmain).
 + * \param id: the datablock to operate on
 + * (can be NULL, in which case we operate over all IDs from given bmain).
   * \param old_id: the datablock to dereference (may be NULL if \a id is non-NULL).
   * \param new_id: the new datablock to replace \a old_id references with (may be NULL).
 - * \param r_id_remap_data: if non-NULL, the IDRemap struct to use (uselful to retrieve info about remapping process).
 + * \param r_id_remap_data: if non-NULL, the IDRemap struct to use
 + * (uselful to retrieve info about remapping process).
   */
 -ATTR_NONNULL(1) static void libblock_remap_data(
 -        Main *bmain, ID *id, ID *old_id, ID *new_id, const short remap_flags, IDRemap *r_id_remap_data)
 +ATTR_NONNULL(1)
 +static void libblock_remap_data(
 +    Main *bmain, ID *id, ID *old_id, ID *new_id, const short remap_flags, IDRemap *r_id_remap_data)
  {
 -      IDRemap id_remap_data;
 -      ListBase *lb_array[MAX_LIBARRAY];
 -      int i;
 -      const int foreach_id_flags = (remap_flags & ID_REMAP_NO_INDIRECT_PROXY_DATA_USAGE) != 0 ? IDWALK_NO_INDIRECT_PROXY_DATA_USAGE : IDWALK_NOP;
 -
 -      if (r_id_remap_data == NULL) {
 -              r_id_remap_data = &id_remap_data;
 -      }
 -      r_id_remap_data->bmain = bmain;
 -      r_id_remap_data->old_id = old_id;
 -      r_id_remap_data->new_id = new_id;
 -      r_id_remap_data->id = NULL;
 -      r_id_remap_data->flag = remap_flags;
 -      r_id_remap_data->status = 0;
 -      r_id_remap_data->skipped_direct = 0;
 -      r_id_remap_data->skipped_indirect = 0;
 -      r_id_remap_data->skipped_refcounted = 0;
 -
 -      if (id) {
 +  IDRemap id_remap_data;
 +  const int foreach_id_flags = (remap_flags & ID_REMAP_NO_INDIRECT_PROXY_DATA_USAGE) != 0 ?
 +                                   IDWALK_NO_INDIRECT_PROXY_DATA_USAGE :
 +                                   IDWALK_NOP;
 +
 +  if (r_id_remap_data == NULL) {
 +    r_id_remap_data = &id_remap_data;
 +  }
 +  r_id_remap_data->bmain = bmain;
 +  r_id_remap_data->old_id = old_id;
 +  r_id_remap_data->new_id = new_id;
 +  r_id_remap_data->id = NULL;
 +  r_id_remap_data->flag = remap_flags;
 +  r_id_remap_data->status = 0;
 +  r_id_remap_data->skipped_direct = 0;
 +  r_id_remap_data->skipped_indirect = 0;
 +  r_id_remap_data->skipped_refcounted = 0;
 +
 +  if (id) {
  #ifdef DEBUG_PRINT
 -              printf("\tchecking id %s (%p, %p)\n", id->name, id, id->lib);
 +    printf("\tchecking id %s (%p, %p)\n", id->name, id, id->lib);
  #endif
 -              r_id_remap_data->id = id;
 -              libblock_remap_data_preprocess(r_id_remap_data);
 -              BKE_library_foreach_ID_link(NULL, id, foreach_libblock_remap_callback, (void *)r_id_remap_data, foreach_id_flags);
 -      }
 -      else {
 -              i = set_listbasepointers(bmain, lb_array);
 -
 -              /* Note that this is a very 'bruteforce' approach, maybe we could use some depsgraph to only process
 -               * objects actually using given old_id... sounds rather unlikely currently, though, so this will do for now. */
 -
 -              while (i--) {
 -                      for (ID *id_curr = lb_array[i]->first; id_curr; id_curr = id_curr->next) {
 -                              if (BKE_library_id_can_use_idtype(id_curr, GS(old_id->name))) {
 -                                      /* Note that we cannot skip indirect usages of old_id here (if requested), we still need to check it for
 -                                       * the user count handling...
 -                                       * XXX No more true (except for debug usage of those skipping counters). */
 -                                      r_id_remap_data->id = id_curr;
 -                                      libblock_remap_data_preprocess(r_id_remap_data);
 -                                      BKE_library_foreach_ID_link(
 -                                                  NULL, id_curr, foreach_libblock_remap_callback, (void *)r_id_remap_data, foreach_id_flags);
 -                              }
 -                      }
 -              }
 -      }
 -
 -      if (old_id && GS(old_id->name) == ID_OB) {
 -              BKE_sca_logic_links_remap(bmain, (Object *)old_id, (Object *)new_id);
 -      }
 -
 -      /* XXX We may not want to always 'transfer' fakeuser from old to new id... Think for now it's desired behavior
 -       *     though, we can always add an option (flag) to control this later if needed. */
 -      if (old_id && (old_id->flag & LIB_FAKEUSER)) {
 -              id_fake_user_clear(old_id);
 -              id_fake_user_set(new_id);
 -      }
 -
 -      id_us_clear_real(old_id);
 -
 -      if (new_id && (new_id->tag & LIB_TAG_INDIRECT) && (r_id_remap_data->status & ID_REMAP_IS_LINKED_DIRECT)) {
 -              new_id->tag &= ~LIB_TAG_INDIRECT;
 -              new_id->tag |= LIB_TAG_EXTERN;
 -      }
 +    r_id_remap_data->id = id;
 +    libblock_remap_data_preprocess(r_id_remap_data);
 +    BKE_library_foreach_ID_link(
 +        NULL, id, foreach_libblock_remap_callback, (void *)r_id_remap_data, foreach_id_flags);
 +  }
 +  else {
 +    /* Note that this is a very 'brute force' approach,
 +     * maybe we could use some depsgraph to only process objects actually using given old_id...
 +     * sounds rather unlikely currently, though, so this will do for now. */
 +    ID *id_curr;
 +
 +    FOREACH_MAIN_ID_BEGIN (bmain, id_curr) {
 +      if (BKE_library_id_can_use_idtype(id_curr, GS(old_id->name))) {
 +        /* Note that we cannot skip indirect usages of old_id here (if requested),
 +         * we still need to check it for the user count handling...
 +         * XXX No more true (except for debug usage of those skipping counters). */
 +        r_id_remap_data->id = id_curr;
 +        libblock_remap_data_preprocess(r_id_remap_data);
 +        BKE_library_foreach_ID_link(NULL,
 +                                    id_curr,
 +                                    foreach_libblock_remap_callback,
 +                                    (void *)r_id_remap_data,
 +                                    foreach_id_flags);
 +      }
 +    }
 +    FOREACH_MAIN_ID_END;
 +  }
 +
 +  /* XXX We may not want to always 'transfer' fakeuser from old to new id...
 +   *     Think for now it's desired behavior though,
 +   *     we can always add an option (flag) to control this later if needed. */
 +  if (old_id && (old_id->flag & LIB_FAKEUSER)) {
 +    id_fake_user_clear(old_id);
 +    id_fake_user_set(new_id);
 +  }
 +
 +  id_us_clear_real(old_id);
 +
 +  if (new_id && (new_id->tag & LIB_TAG_INDIRECT) &&
 +      (r_id_remap_data->status & ID_REMAP_IS_LINKED_DIRECT)) {
 +    new_id->tag &= ~LIB_TAG_INDIRECT;
 +    new_id->tag |= LIB_TAG_EXTERN;
 +  }
  
  #ifdef DEBUG_PRINT
 -      printf("%s: %d occurrences skipped (%d direct and %d indirect ones)\n", __func__,
 -             r_id_remap_data->skipped_direct + r_id_remap_data->skipped_indirect,
 -             r_id_remap_data->skipped_direct, r_id_remap_data->skipped_indirect);
 +  printf("%s: %d occurrences skipped (%d direct and %d indirect ones)\n",
 +         __func__,
 +         r_id_remap_data->skipped_direct + r_id_remap_data->skipped_indirect,
 +         r_id_remap_data->skipped_direct,
 +         r_id_remap_data->skipped_indirect);
  #endif
  }
  
   * Replace all references in given Main to \a old_id by \a new_id
   * (if \a new_id is NULL, it unlinks \a old_id).
   */
 -void BKE_libblock_remap_locked(
 -        Main *bmain, void *old_idv, void *new_idv,
 -        const short remap_flags)
 +void BKE_libblock_remap_locked(Main *bmain, void *old_idv, void *new_idv, const short remap_flags)
  {
 -      IDRemap id_remap_data;
 -      ID *old_id = old_idv;
 -      ID *new_id = new_idv;
 -      int skipped_direct, skipped_refcounted;
 -
 -      BLI_assert(old_id != NULL);
 -      BLI_assert((new_id == NULL) || GS(old_id->name) == GS(new_id->name));
 -      BLI_assert(old_id != new_id);
 -
 -      libblock_remap_data(bmain, NULL, old_id, new_id, remap_flags, &id_remap_data);
 -
 -      if (free_notifier_reference_cb) {
 -              free_notifier_reference_cb(old_id);
 -      }
 -
 -      /* We assume editors do not hold references to their IDs... This is false in some cases
 -       * (Image is especially tricky here), editors' code is to handle refcount (id->us) itself then. */
 -      if (remap_editor_id_reference_cb) {
 -              remap_editor_id_reference_cb(old_id, new_id);
 -      }
 -
 -      skipped_direct = id_remap_data.skipped_direct;
 -      skipped_refcounted = id_remap_data.skipped_refcounted;
 -
 -      /* If old_id was used by some ugly 'user_one' stuff (like Image or Clip editors...), and user count has actually
 -       * been incremented for that, we have to decrease once more its user count... unless we had to skip
 -       * some 'user_one' cases. */
 -      if ((old_id->tag & LIB_TAG_EXTRAUSER_SET) && !(id_remap_data.status & ID_REMAP_IS_USER_ONE_SKIPPED)) {
 -              id_us_clear_real(old_id);
 -      }
 -
 -      if (old_id->us - skipped_refcounted < 0) {
 -              printf("Error in remapping process from '%s' (%p) to '%s' (%p): "
 -                     "wrong user count in old ID after process (summing up to %d)\n",
 -                     old_id->name, old_id, new_id ? new_id->name : "<NULL>", new_id, old_id->us - skipped_refcounted);
 -              BLI_assert(0);
 -      }
 -
 -      if (skipped_direct == 0) {
 -              /* old_id is assumed to not be used directly anymore... */
 -              if (old_id->lib && (old_id->tag & LIB_TAG_EXTERN)) {
 -                      old_id->tag &= ~LIB_TAG_EXTERN;
 -                      old_id->tag |= LIB_TAG_INDIRECT;
 -              }
 -      }
 -
 -      /* Some after-process updates.
 -       * This is a bit ugly, but cannot see a way to avoid it. Maybe we should do a per-ID callback for this instead?
 -       */
 -      switch (GS(old_id->name)) {
 -              case ID_OB:
 -                      libblock_remap_data_postprocess_object_update(bmain, (Object *)old_id, (Object *)new_id);
 -                      break;
 -              case ID_GR:
 -                      if (!new_id) {  /* Only affects us in case group was unlinked. */
 -                              for (Scene *sce = bmain->scene.first; sce; sce = sce->id.next) {
 -                                      libblock_remap_data_postprocess_group_scene_unlink(bmain, sce, old_id);
 -                              }
 -                      }
 -                      break;
 -              case ID_ME:
 -              case ID_CU:
 -              case ID_MB:
 -                      if (new_id) {  /* Only affects us in case obdata was relinked (changed). */
 -                              for (Object *ob = bmain->object.first; ob; ob = ob->id.next) {
 -                                      libblock_remap_data_postprocess_obdata_relink(bmain, ob, new_id);
 -                              }
 -                      }
 -                      break;
 -              default:
 -                      break;
 -      }
 -
 -      /* Node trees may virtually use any kind of data-block... */
 -      /* XXX Yuck!!!! nodetree update can do pretty much any thing when talking about py nodes,
 -       *     including creating new data-blocks (see T50385), so we need to unlock main here. :(
 -       *     Why can't we have re-entrent locks? */
 -      BKE_main_unlock(bmain);
 -      libblock_remap_data_postprocess_nodetree_update(bmain, new_id);
 -      BKE_main_lock(bmain);
 -
 -      /* Full rebuild of DAG! */
 -      DAG_relations_tag_update(bmain);
 +  IDRemap id_remap_data;
 +  ID *old_id = old_idv;
 +  ID *new_id = new_idv;
 +  int skipped_direct, skipped_refcounted;
 +
 +  BLI_assert(old_id != NULL);
 +  BLI_assert((new_id == NULL) || GS(old_id->name) == GS(new_id->name));
 +  BLI_assert(old_id != new_id);
 +
 +  libblock_remap_data(bmain, NULL, old_id, new_id, remap_flags, &id_remap_data);
 +
 +  if (free_notifier_reference_cb) {
 +    free_notifier_reference_cb(old_id);
 +  }
 +
 +  /* We assume editors do not hold references to their IDs... This is false in some cases
 +   * (Image is especially tricky here),
 +   * editors' code is to handle refcount (id->us) itself then. */
 +  if (remap_editor_id_reference_cb) {
 +    remap_editor_id_reference_cb(old_id, new_id);
 +  }
 +
 +  skipped_direct = id_remap_data.skipped_direct;
 +  skipped_refcounted = id_remap_data.skipped_refcounted;
 +
 +  /* If old_id was used by some ugly 'user_one' stuff (like Image or Clip editors...), and user
 +   * count has actually been incremented for that, we have to decrease once more its user count...
 +   * unless we had to skip some 'user_one' cases. */
 +  if ((old_id->tag & LIB_TAG_EXTRAUSER_SET) &&
 +      !(id_remap_data.status & ID_REMAP_IS_USER_ONE_SKIPPED)) {
 +    id_us_clear_real(old_id);
 +  }
 +
 +  if (old_id->us - skipped_refcounted < 0) {
 +    CLOG_ERROR(&LOG,
 +               "Error in remapping process from '%s' (%p) to '%s' (%p): "
 +               "wrong user count in old ID after process (summing up to %d)",
 +               old_id->name,
 +               old_id,
 +               new_id ? new_id->name : "<NULL>",
 +               new_id,
 +               old_id->us - skipped_refcounted);
 +    BLI_assert(0);
 +  }
 +
 +  if (skipped_direct == 0) {
 +    /* old_id is assumed to not be used directly anymore... */
 +    if (old_id->lib && (old_id->tag & LIB_TAG_EXTERN)) {
 +      old_id->tag &= ~LIB_TAG_EXTERN;
 +      old_id->tag |= LIB_TAG_INDIRECT;
 +    }
 +  }
 +
 +  /* Some after-process updates.
 +   * This is a bit ugly, but cannot see a way to avoid it.
 +   * Maybe we should do a per-ID callback for this instead? */
 +  switch (GS(old_id->name)) {
 +    case ID_OB:
 +      libblock_remap_data_postprocess_object_update(bmain, (Object *)old_id, (Object *)new_id);
 +      break;
 +    case ID_GR:
 +      libblock_remap_data_postprocess_collection_update(
 +          bmain, (Collection *)old_id, (Collection *)new_id);
 +      break;
 +    case ID_ME:
 +    case ID_CU:
 +    case ID_MB:
 +      if (new_id) { /* Only affects us in case obdata was relinked (changed). */
 +        for (Object *ob = bmain->objects.first; ob; ob = ob->id.next) {
 +          libblock_remap_data_postprocess_obdata_relink(bmain, ob, new_id);
 +        }
 +      }
 +      break;
 +    default:
 +      break;
 +  }
 +
 +  /* Node trees may virtually use any kind of data-block... */
 +  /* XXX Yuck!!!! nodetree update can do pretty much any thing when talking about py nodes,
 +   *     including creating new data-blocks (see T50385), so we need to unlock main here. :(
 +   *     Why can't we have re-entrent locks? */
 +  BKE_main_unlock(bmain);
 +  libblock_remap_data_postprocess_nodetree_update(bmain, new_id);
 +  BKE_main_lock(bmain);
 +
 +  /* Full rebuild of DEG! */
 +  DEG_relations_tag_update(bmain);
  }
  
  void BKE_libblock_remap(Main *bmain, void *old_idv, void *new_idv, const short remap_flags)
  {
 -      BKE_main_lock(bmain);
 +  BKE_main_lock(bmain);
  
 -      BKE_libblock_remap_locked(bmain, old_idv, new_idv, remap_flags);
 +  BKE_libblock_remap_locked(bmain, old_idv, new_idv, remap_flags);
  
 -      BKE_main_unlock(bmain);
 +  BKE_main_unlock(bmain);
  }
  
  /**
 - * Unlink given \a id from given \a bmain (does not touch to indirect, i.e. library, usages of the ID).
 + * Unlink given \a id from given \a bmain
 + * (does not touch to indirect, i.e. library, usages of the ID).
   *
 - * \param do_flag_never_null: If true, all IDs using \a idv in a 'non-NULL' way are flagged by \a LIB_TAG_DOIT flag
 - * (quite obviously, 'non-NULL' usages can never be unlinked by this function...).
 + * \param do_flag_never_null: If true, all IDs using \a idv in a 'non-NULL' way are flagged by
 + * #LIB_TAG_DOIT flag (quite obviously, 'non-NULL' usages can never be unlinked by this function).
   */
 -void BKE_libblock_unlink(Main *bmain, void *idv, const bool do_flag_never_null, const bool do_skip_indirect)
 +void BKE_libblock_unlink(Main *bmain,
 +                         void *idv,
 +                         const bool do_flag_never_null,
 +                         const bool do_skip_indirect)
  {
 -      const short remap_flags = (do_skip_indirect ? ID_REMAP_SKIP_INDIRECT_USAGE : 0) |
 -                                (do_flag_never_null ? ID_REMAP_FLAG_NEVER_NULL_USAGE : 0);
 +  const short remap_flags = (do_skip_indirect ? ID_REMAP_SKIP_INDIRECT_USAGE : 0) |
 +                            (do_flag_never_null ? ID_REMAP_FLAG_NEVER_NULL_USAGE : 0);
  
 -      BKE_main_lock(bmain);
 +  BKE_main_lock(bmain);
  
 -      BKE_libblock_remap_locked(bmain, idv, NULL, remap_flags);
 +  BKE_libblock_remap_locked(bmain, idv, NULL, remap_flags);
  
 -      BKE_main_unlock(bmain);
 +  BKE_main_unlock(bmain);
  }
  
  /** Similar to libblock_remap, but only affects IDs used by given \a idv ID.
   *     ... sigh
   */
  void BKE_libblock_relink_ex(
 -        Main *bmain, void *idv, void *old_idv, void *new_idv, const bool us_min_never_null)
 +    Main *bmain, void *idv, void *old_idv, void *new_idv, const bool us_min_never_null)
  {
 -      ID *id = idv;
 -      ID *old_id = old_idv;
 -      ID *new_id = new_idv;
 -      int remap_flags = us_min_never_null ? 0 : ID_REMAP_SKIP_NEVER_NULL_USAGE;
 -
 -      /* No need to lock here, we are only affecting given ID, not bmain database. */
 -
 -      BLI_assert(id);
 -      if (old_id) {
 -              BLI_assert((new_id == NULL) || GS(old_id->name) == GS(new_id->name));
 -              BLI_assert(old_id != new_id);
 -      }
 -      else {
 -              BLI_assert(new_id == NULL);
 -      }
 -
 -      libblock_remap_data(bmain, id, old_id, new_id, remap_flags, NULL);
 -
 -      /* Some after-process updates.
 -       * This is a bit ugly, but cannot see a way to avoid it. Maybe we should do a per-ID callback for this instead?
 -       */
 -      switch (GS(id->name)) {
 -              case ID_SCE:
 -              {
 -                      Scene *sce = (Scene *)id;
 -
 -                      if (old_id) {
 -                              switch (GS(old_id->name)) {
 -                                      case ID_OB:
 -                                      {
 -                                              libblock_remap_data_postprocess_object_update(bmain, (Object *)old_id, (Object *)new_id);
 -                                              break;
 -                                      }
 -                                      case ID_GR:
 -                                              if (!new_id) {  /* Only affects us in case group was unlinked. */
 -                                                      libblock_remap_data_postprocess_group_scene_unlink(bmain, sce, old_id);
 -                                              }
 -                                              break;
 -                                      default:
 -                                              break;
 -                              }
 -                      }
 -                      else {
 -                              /* No choice but to check whole objects/groups. */
 -                              for (Object *ob = bmain->object.first; ob; ob = ob->id.next) {
 -                                      libblock_remap_data_postprocess_object_update(bmain, ob, NULL);
 -                              }
 -                              for (Group *grp = bmain->group.first; grp; grp = grp->id.next) {
 -                                      libblock_remap_data_postprocess_group_scene_unlink(bmain, sce, NULL);
 -                              }
 -                      }
 -                      break;
 -              }
 -              case ID_OB:
 -                      if (new_id) {  /* Only affects us in case obdata was relinked (changed). */
 -                              libblock_remap_data_postprocess_obdata_relink(bmain, (Object *)id, new_id);
 -                      }
 -                      break;
 -              default:
 -                      break;
 -      }
 +  ID *id = idv;
 +  ID *old_id = old_idv;
 +  ID *new_id = new_idv;
 +  int remap_flags = us_min_never_null ? 0 : ID_REMAP_SKIP_NEVER_NULL_USAGE;
 +
 +  /* No need to lock here, we are only affecting given ID, not bmain database. */
 +
 +  BLI_assert(id);
 +  if (old_id) {
 +    BLI_assert((new_id == NULL) || GS(old_id->name) == GS(new_id->name));
 +    BLI_assert(old_id != new_id);
 +  }
 +  else {
 +    BLI_assert(new_id == NULL);
 +  }
 +
 +  libblock_remap_data(bmain, id, old_id, new_id, remap_flags, NULL);
 +
 +  /* Some after-process updates.
 +   * This is a bit ugly, but cannot see a way to avoid it.
 +   * Maybe we should do a per-ID callback for this instead?
 +   */
 +  switch (GS(id->name)) {
 +    case ID_SCE: {
 +      if (old_id) {
 +        switch (GS(old_id->name)) {
 +          case ID_OB:
 +            libblock_remap_data_postprocess_object_update(
 +                bmain, (Object *)old_id, (Object *)new_id);
 +            break;
 +          case ID_GR:
 +            libblock_remap_data_postprocess_collection_update(
 +                bmain, (Collection *)old_id, (Collection *)new_id);
 +            break;
 +          default:
 +            break;
 +        }
 +      }
 +      else {
 +        /* No choice but to check whole objects/collections. */
 +        libblock_remap_data_postprocess_collection_update(bmain, NULL, NULL);
 +        libblock_remap_data_postprocess_object_update(bmain, NULL, NULL);
 +      }
 +      break;
 +    }
 +    case ID_OB:
 +      if (new_id) { /* Only affects us in case obdata was relinked (changed). */
 +        libblock_remap_data_postprocess_obdata_relink(bmain, (Object *)id, new_id);
 +      }
 +      break;
 +    default:
 +      break;
 +  }
  }
  
 -static int id_relink_to_newid_looper(void *UNUSED(user_data), ID *UNUSED(self_id), ID **id_pointer, const int cb_flag)
 +static int id_relink_to_newid_looper(void *UNUSED(user_data),
 +                                     ID *UNUSED(self_id),
 +                                     ID **id_pointer,
 +                                     const int cb_flag)
  {
 -      if (cb_flag & IDWALK_CB_PRIVATE) {
 -              return IDWALK_RET_NOP;
 -      }
 -
 -      ID *id = *id_pointer;
 -      if (id) {
 -              /* See: NEW_ID macro */
 -              if (id->newid) {
 -                      BKE_library_update_ID_link_user(id->newid, id, cb_flag);
 -                      *id_pointer = id->newid;
 -              }
 -              else if (id->tag & LIB_TAG_NEW) {
 -                      id->tag &= ~LIB_TAG_NEW;
 -                      BKE_libblock_relink_to_newid(id);
 -              }
 -      }
 -      return IDWALK_RET_NOP;
 +  if (cb_flag & IDWALK_CB_PRIVATE) {
 +    return IDWALK_RET_NOP;
 +  }
 +
 +  ID *id = *id_pointer;
 +  if (id) {
 +    /* See: NEW_ID macro */
 +    if (id->newid) {
 +      BKE_library_update_ID_link_user(id->newid, id, cb_flag);
 +      *id_pointer = id->newid;
 +    }
 +    else if (id->tag & LIB_TAG_NEW) {
 +      id->tag &= ~LIB_TAG_NEW;
 +      BKE_libblock_relink_to_newid(id);
 +    }
 +  }
 +  return IDWALK_RET_NOP;
  }
  
 -/** Similar to libblock_relink_ex, but is remapping IDs to their newid value if non-NULL, in given \a id.
 +/**
 + * Similar to #libblock_relink_ex,
 + * but is remapping IDs to their newid value if non-NULL, in given \a id.
   *
 - * Very specific usage, not sure we'll keep it on the long run, currently only used in Object duplication code...
 + * Very specific usage, not sure we'll keep it on the long run,
 + * currently only used in Object/Collection duplication code...
   */
  void BKE_libblock_relink_to_newid(ID *id)
  {
 -      if (ID_IS_LINKED(id))
 -              return;
 +  if (ID_IS_LINKED(id)) {
 +    return;
 +  }
  
 -      BKE_library_foreach_ID_link(NULL, id, id_relink_to_newid_looper, NULL, 0);
 +  BKE_library_foreach_ID_link(NULL, id, id_relink_to_newid_looper, NULL, 0);
  }
  
  void BKE_libblock_free_data(ID *id, const bool do_id_user)
  {
 -      if (id->properties) {
 -              IDP_FreeProperty_ex(id->properties, do_id_user);
 -              MEM_freeN(id->properties);
 -      }
 +  if (id->properties) {
 +    IDP_FreePropertyContent_ex(id->properties, do_id_user);
 +    MEM_freeN(id->properties);
 +  }
  
 -      /* XXX TODO remove animdata handling from each type's freeing func, and do it here, like for copy! */
 +  if (id->override_static) {
 +    BKE_override_static_free(&id->override_static);
 +  }
 +
 +  /* XXX TODO remove animdata handling from each type's freeing func,
 +   * and do it here, like for copy! */
  }
  
  void BKE_libblock_free_datablock(ID *id, const int UNUSED(flag))
  {
 -      const short type = GS(id->name);
 -      switch (type) {
 -              case ID_SCE:
 -                      BKE_scene_free((Scene *)id);
 -                      break;
 -              case ID_LI:
 -                      BKE_library_free((Library *)id);
 -                      break;
 -              case ID_OB:
 -                      BKE_object_free((Object *)id);
 -                      break;
 -              case ID_ME:
 -                      BKE_mesh_free((Mesh *)id);
 -                      break;
 -              case ID_CU:
 -                      BKE_curve_free((Curve *)id);
 -                      break;
 -              case ID_MB:
 -                      BKE_mball_free((MetaBall *)id);
 -                      break;
 -              case ID_MA:
 -                      BKE_material_free((Material *)id);
 -                      break;
 -              case ID_TE:
 -                      BKE_texture_free((Tex *)id);
 -                      break;
 -              case ID_IM:
 -                      BKE_image_free((Image *)id);
 -                      break;
 -              case ID_LT:
 -                      BKE_lattice_free((Lattice *)id);
 -                      break;
 -              case ID_LA:
 -                      BKE_lamp_free((Lamp *)id);
 -                      break;
 -              case ID_CA:
 -                      BKE_camera_free((Camera *) id);
 -                      break;
 -              case ID_IP:  /* Deprecated. */
 -                      BKE_ipo_free((Ipo *)id);
 -                      break;
 -              case ID_KE:
 -                      BKE_key_free((Key *)id);
 -                      break;
 -              case ID_WO:
 -                      BKE_world_free((World *)id);
 -                      break;
 -              case ID_SCR:
 -                      BKE_screen_free((bScreen *)id);
 -                      break;
 -              case ID_VF:
 -                      BKE_vfont_free((VFont *)id);
 -                      break;
 -              case ID_TXT:
 -                      BKE_text_free((Text *)id);
 -                      break;
 -              case ID_SPK:
 -                      BKE_speaker_free((Speaker *)id);
 -                      break;
 -              case ID_SO:
 -                      BKE_sound_free((bSound *)id);
 -                      break;
 -              case ID_GR:
 -                      BKE_group_free((Group *)id);
 -                      break;
 -              case ID_AR:
 -                      BKE_armature_free((bArmature *)id);
 -                      break;
 -              case ID_AC:
 -                      BKE_action_free((bAction *)id);
 -                      break;
 -              case ID_NT:
 -                      ntreeFreeTree((bNodeTree *)id);
 -                      break;
 -              case ID_BR:
 -                      BKE_brush_free((Brush *)id);
 -                      break;
 -              case ID_PA:
 -                      BKE_particlesettings_free((ParticleSettings *)id);
 -                      break;
 -              case ID_WM:
 -                      if (free_windowmanager_cb)
 -                              free_windowmanager_cb(NULL, (wmWindowManager *)id);
 -                      break;
 -              case ID_GD:
 -                      BKE_gpencil_free((bGPdata *)id, true);
 -                      break;
 -              case ID_MC:
 -                      BKE_movieclip_free((MovieClip *)id);
 -                      break;
 -              case ID_MSK:
 -                      BKE_mask_free((Mask *)id);
 -                      break;
 -              case ID_LS:
 -                      BKE_linestyle_free((FreestyleLineStyle *)id);
 -                      break;
 -              case ID_PAL:
 -                      BKE_palette_free((Palette *)id);
 -                      break;
 -              case ID_PC:
 -                      BKE_paint_curve_free((PaintCurve *)id);
 -                      break;
 -              case ID_CF:
 -                      BKE_cachefile_free((CacheFile *)id);
 -                      break;
 -      }
 +  const short type = GS(id->name);
 +  switch (type) {
 +    case ID_SCE:
 +      BKE_scene_free_ex((Scene *)id, false);
 +      break;
 +    case ID_LI:
 +      BKE_library_free((Library *)id);
 +      break;
 +    case ID_OB:
 +      BKE_object_free((Object *)id);
 +      break;
 +    case ID_ME:
 +      BKE_mesh_free((Mesh *)id);
 +      break;
 +    case ID_CU:
 +      BKE_curve_free((Curve *)id);
 +      break;
 +    case ID_MB:
 +      BKE_mball_free((MetaBall *)id);
 +      break;
 +    case ID_MA:
 +      BKE_material_free((Material *)id);
 +      break;
 +    case ID_TE:
 +      BKE_texture_free((Tex *)id);
 +      break;
 +    case ID_IM:
 +      BKE_image_free((Image *)id);
 +      break;
 +    case ID_LT:
 +      BKE_lattice_free((Lattice *)id);
 +      break;
 +    case ID_LA:
 +      BKE_light_free((Light *)id);
 +      break;
 +    case ID_CA:
 +      BKE_camera_free((Camera *)id);
 +      break;
 +    case ID_IP: /* Deprecated. */
 +      BKE_ipo_free((Ipo *)id);
 +      break;
 +    case ID_KE:
 +      BKE_key_free((Key *)id);
 +      break;
 +    case ID_WO:
 +      BKE_world_free((World *)id);
 +      break;
 +    case ID_SCR:
 +      BKE_screen_free((bScreen *)id);
 +      break;
 +    case ID_VF:
 +      BKE_vfont_free((VFont *)id);
 +      break;
 +    case ID_TXT:
 +      BKE_text_free((Text *)id);
 +      break;
 +    case ID_SPK:
 +      BKE_speaker_free((Speaker *)id);
 +      break;
 +    case ID_LP:
 +      BKE_lightprobe_free((LightProbe *)id);
 +      break;
 +    case ID_SO:
 +      BKE_sound_free((bSound *)id);
 +      break;
 +    case ID_GR:
 +      BKE_collection_free((Collection *)id);
 +      break;
 +    case ID_AR:
 +      BKE_armature_free((bArmature *)id);
 +      break;
 +    case ID_AC:
 +      BKE_action_free((bAction *)id);
 +      break;
 +    case ID_NT:
 +      ntreeFreeTree((bNodeTree *)id);
 +      break;
 +    case ID_BR:
 +      BKE_brush_free((Brush *)id);
 +      break;
 +    case ID_PA:
 +      BKE_particlesettings_free((ParticleSettings *)id);
 +      break;
 +    case ID_WM:
 +      if (free_windowmanager_cb) {
 +        free_windowmanager_cb(NULL, (wmWindowManager *)id);
 +      }
 +      break;
 +    case ID_GD:
 +      BKE_gpencil_free((bGPdata *)id, true);
 +      break;
 +    case ID_MC:
 +      BKE_movieclip_free((MovieClip *)id);
 +      break;
 +    case ID_MSK:
 +      BKE_mask_free((Mask *)id);
 +      break;
 +    case ID_LS:
 +      BKE_linestyle_free((FreestyleLineStyle *)id);
 +      break;
 +    case ID_PAL:
 +      BKE_palette_free((Palette *)id);
 +      break;
 +    case ID_PC:
 +      BKE_paint_curve_free((PaintCurve *)id);
 +      break;
 +    case ID_CF:
 +      BKE_cachefile_free((CacheFile *)id);
 +      break;
 +    case ID_WS:
 +      BKE_workspace_free((WorkSpace *)id);
 +      break;
 +  }
  }
  
 -
 +/**
 + * Complete ID freeing, extended version for corner cases.
 + * Can override default (and safe!) freeing process, to gain some speed up.
 + *
 + * At that point, given id is assumed to not be used by any other data-block already
 + * (might not be actually true, in case e.g. several inter-related IDs get freed together...).
 + * However, they might still be using (referencing) other IDs, this code takes care of it if
 + * #LIB_TAG_NO_USER_REFCOUNT is not defined.
 + *
 + * \param bmain: #Main database containing the freed #ID,
 + * can be NULL in case it's a temp ID outside of any #Main.
 + * \param idv: Pointer to ID to be freed.
 + * \param flag: Set of \a LIB_ID_FREE_... flags controlling/overriding usual freeing process,
 + * 0 to get default safe behavior.
 + * \param use_flag_from_idtag: Still use freeing info flags from given #ID datablock,
 + * even if some overriding ones are passed in \a flag parameter.
 + */
  void BKE_id_free_ex(Main *bmain, void *idv, int flag, const bool use_flag_from_idtag)
  {
 -      ID *id = idv;
 -
 -      if (use_flag_from_idtag) {
 -              if ((id->tag & LIB_TAG_NO_MAIN) != 0) {
 -                      flag |= LIB_ID_FREE_NO_MAIN;
 -              }
 -              else {
 -                      flag &= ~LIB_ID_FREE_NO_MAIN;
 -              }
 -
 -              if ((id->tag & LIB_TAG_NO_USER_REFCOUNT) != 0) {
 -                      flag |= LIB_ID_FREE_NO_USER_REFCOUNT;
 -              }
 -              else {
 -                      flag &= ~LIB_ID_FREE_NO_USER_REFCOUNT;
 -              }
 -
 -              if ((id->tag & LIB_TAG_NOT_ALLOCATED) != 0) {
 -                      flag |= LIB_ID_FREE_NOT_ALLOCATED;
 -              }
 -              else {
 -                      flag &= ~LIB_ID_FREE_NOT_ALLOCATED;
 -              }
 -      }
 -
 -      BLI_assert((flag & LIB_ID_FREE_NO_MAIN) != 0 || bmain != NULL);
 -      BLI_assert((flag & LIB_ID_FREE_NO_MAIN) != 0 || (flag & LIB_ID_FREE_NOT_ALLOCATED) == 0);
 -      BLI_assert((flag & LIB_ID_FREE_NO_MAIN) != 0 || (flag & LIB_ID_FREE_NO_USER_REFCOUNT) == 0);
 -
 -      const short type = GS(id->name);
 -
 -      if (bmain && (flag & LIB_ID_FREE_NO_DEG_TAG) == 0) {
 -              DAG_id_type_tag(bmain, type);
 -      }
 +  ID *id = idv;
 +
 +  if (use_flag_from_idtag) {
 +    if ((id->tag & LIB_TAG_NO_MAIN) != 0) {
 +      flag |= LIB_ID_FREE_NO_MAIN | LIB_ID_FREE_NO_UI_USER | LIB_ID_FREE_NO_DEG_TAG;
 +    }
 +    else {
 +      flag &= ~LIB_ID_FREE_NO_MAIN;
 +    }
 +
 +    if ((id->tag & LIB_TAG_NO_USER_REFCOUNT) != 0) {
 +      flag |= LIB_ID_FREE_NO_USER_REFCOUNT;
 +    }
 +    else {
 +      flag &= ~LIB_ID_FREE_NO_USER_REFCOUNT;
 +    }
 +
 +    if ((id->tag & LIB_TAG_NOT_ALLOCATED) != 0) {
 +      flag |= LIB_ID_FREE_NOT_ALLOCATED;
 +    }
 +    else {
 +      flag &= ~LIB_ID_FREE_NOT_ALLOCATED;
 +    }
 +  }
 +
 +  BLI_assert((flag & LIB_ID_FREE_NO_MAIN) != 0 || bmain != NULL);
 +  BLI_assert((flag & LIB_ID_FREE_NO_MAIN) != 0 || (flag & LIB_ID_FREE_NOT_ALLOCATED) == 0);
 +  BLI_assert((flag & LIB_ID_FREE_NO_MAIN) != 0 || (flag & LIB_ID_FREE_NO_USER_REFCOUNT) == 0);
 +
 +  const short type = GS(id->name);
 +
 +  if (bmain && (flag & LIB_ID_FREE_NO_DEG_TAG) == 0) {
 +    DEG_id_type_tag(bmain, type);
 +  }
  
  #ifdef WITH_PYTHON
 -      BPY_id_release(id);
 +#  ifdef WITH_PYTHON_SAFETY
 +  BPY_id_release(id);
 +#  endif
 +  if (id->py_instance) {
 +    BPY_DECREF_RNA_INVALIDATE(id->py_instance);
 +  }
  #endif
  
 -      if ((flag & LIB_ID_FREE_NO_USER_REFCOUNT) == 0) {
 -              BKE_libblock_relink_ex(bmain, id, NULL, NULL, true);
 -      }
 +  if ((flag & LIB_ID_FREE_NO_USER_REFCOUNT) == 0) {
 +    BKE_libblock_relink_ex(bmain, id, NULL, NULL, true);
 +  }
  
 -      BKE_libblock_free_datablock(id, flag);
 +  BKE_libblock_free_datablock(id, flag);
  
 -      /* avoid notifying on removed data */
 -      if (bmain) {
 -              BKE_main_lock(bmain);
 -      }
 +  /* avoid notifying on removed data */
 +  if ((flag & LIB_ID_FREE_NO_MAIN) == 0) {
 +    BKE_main_lock(bmain);
 +  }
  
 -      if ((flag & LIB_ID_FREE_NO_UI_USER) == 0) {
 -              if (free_notifier_reference_cb) {
 -                      free_notifier_reference_cb(id);
 -              }
 +  if ((flag & LIB_ID_FREE_NO_UI_USER) == 0) {
 +    if (free_notifier_reference_cb) {
 +      free_notifier_reference_cb(id);
 +    }
  
 -              if (remap_editor_id_reference_cb) {
 -                      remap_editor_id_reference_cb(id, NULL);
 -              }
 -      }
 +    if (remap_editor_id_reference_cb) {
 +      remap_editor_id_reference_cb(id, NULL);
 +    }
 +  }
  
 -      if ((flag & LIB_ID_FREE_NO_MAIN) == 0) {
 -              ListBase *lb = which_libbase(bmain, type);
 -              BLI_remlink(lb, id);
 -      }
 +  if ((flag & LIB_ID_FREE_NO_MAIN) == 0) {
 +    ListBase *lb = which_libbase(bmain, type);
 +    BLI_remlink(lb, id);
 +  }
  
 -      BKE_libblock_free_data(id, (flag & LIB_ID_FREE_NO_USER_REFCOUNT) == 0);
 +  BKE_libblock_free_data(id, (flag & LIB_ID_FREE_NO_USER_REFCOUNT) == 0);
  
 -      if (bmain) {
 -              BKE_main_unlock(bmain);
 -      }
 +  if ((flag & LIB_ID_FREE_NO_MAIN) == 0) {
 +    BKE_main_unlock(bmain);
 +  }
  
 -      if ((flag & LIB_ID_FREE_NOT_ALLOCATED) == 0) {
 -              MEM_freeN(id);
 -      }
 +  if ((flag & LIB_ID_FREE_NOT_ALLOCATED) == 0) {
 +    MEM_freeN(id);
 +  }
  }
  
 +/**
 + * Complete ID freeing, should be usable in most cases (even for out-of-Main IDs).
 + *
 + * See #BKE_id_free_ex description for full details.
 + *
 + * \param bmain: Main database containing the freed ID,
 + * can be NULL in case it's a temp ID outside of any Main.
 + * \param idv: Pointer to ID to be freed.
 + */
  void BKE_id_free(Main *bmain, void *idv)
  {
 -      BKE_id_free_ex(bmain, idv, 0, true);
 +  BKE_id_free_ex(bmain, idv, 0, true);
  }
  
  /**
 - * used in headerbuttons.c image.c mesh.c screen.c sound.c and library.c
 - *
 - * \param do_id_user: if \a true, try to release other ID's 'references' hold by \a idv.
 - *                    (only applies to main database)
 - * \param do_ui_user: similar to do_id_user but makes sure UI does not hold references to
 - *                    \a id.
 + * Not really a freeing function by itself,
 + * it decrements usercount of given id, and only frees it if it reaches 0.
   */
 -void BKE_libblock_free_ex(Main *bmain, void *idv, const bool do_id_user, const bool do_ui_user)
 +void BKE_id_free_us(Main *bmain, void *idv) /* test users */
  {
 -      ID *id = idv;
 -      short type = GS(id->name);
 -      ListBase *lb = which_libbase(bmain, type);
 -
 -      DAG_id_type_tag(bmain, type);
 -
 -#ifdef WITH_PYTHON
 -#ifdef WITH_PYTHON_SAFETY
 -      BPY_id_release(id);
 -#endif
 -      if (id->py_instance) {
 -              BPY_DECREF_RNA_INVALIDATE(id->py_instance);
 -      }
 -#endif
 -
 -      if (do_id_user) {
 -              BKE_libblock_relink_ex(bmain, id, NULL, NULL, true);
 -      }
 -
 -      BKE_libblock_free_datablock(id, 0);
 -
 -      /* avoid notifying on removed data */
 -      BKE_main_lock(bmain);
 -
 -      if (do_ui_user) {
 -              if (free_notifier_reference_cb) {
 -                      free_notifier_reference_cb(id);
 -              }
 -
 -              if (remap_editor_id_reference_cb) {
 -                      remap_editor_id_reference_cb(id, NULL);
 -              }
 -      }
 -
 -      BLI_remlink(lb, id);
 -
 -      BKE_libblock_free_data(id, do_id_user);
 -      BKE_main_unlock(bmain);
 -
 -      MEM_freeN(id);
 +  ID *id = idv;
 +
 +  id_us_min(id);
 +
 +  /* XXX This is a temp (2.77) hack so that we keep same behavior as in 2.76 regarding collections
 +   *     when deleting an object. Since only 'user_one' usage of objects is collections,
 +   *     and only 'real user' usage of objects is scenes, removing that 'user_one' tag when there
 +   *     is no more real (scene) users of an object ensures it gets fully unlinked.
 +   *     But only for local objects, not linked ones!
 +   *     Otherwise, there is no real way to get rid of an object anymore -
 +   *     better handling of this is TODO.
 +   */
 +  if ((GS(id->name) == ID_OB) && (id->us == 1) && (id->lib == NULL)) {
 +    id_us_clear_real(id);
 +  }
 +
 +  if (id->us == 0) {
 +    BKE_libblock_unlink(bmain, id, false, false);
 +
 +    BKE_id_free(bmain, id);
 +  }
  }
  
 -void BKE_libblock_free(Main *bmain, void *idv)
 +static void id_delete(Main *bmain, const bool do_tagged_deletion)
  {
 -      BKE_libblock_free_ex(bmain, idv, true, true);
 +  const int tag = LIB_TAG_DOIT;
 +  ListBase *lbarray[MAX_LIBARRAY];
 +  Link dummy_link = {0};
 +  int base_count, i;
 +
 +  /* Used by batch tagged deletion, when we call BKE_id_free then, id is no more in Main database,
 +   * and has already properly unlinked its other IDs usages.
 +   * UI users are always cleared in BKE_libblock_remap_locked() call, so we can always skip it. */
 +  const int free_flag = LIB_ID_FREE_NO_UI_USER |
 +                        (do_tagged_deletion ? LIB_ID_FREE_NO_MAIN | LIB_ID_FREE_NO_USER_REFCOUNT :
 +                                              0);
 +  ListBase tagged_deleted_ids = {NULL};
 +
 +  base_count = set_listbasepointers(bmain, lbarray);
 +
 +  BKE_main_lock(bmain);
 +  if (do_tagged_deletion) {
 +    /* Main idea of batch deletion is to remove all IDs to be deleted from Main database.
 +     * This means that we won't have to loop over all deleted IDs to remove usages
 +     * of other deleted IDs.
 +     * This gives tremendous speed-up when deleting a large amount of IDs from a Main
 +     * containing thousands of those.
 +     * This also means that we have to be very careful here, as we by-pass many 'common'
 +     * processing, hence risking to 'corrupt' at least user counts, if not IDs themselves. */
 +    bool keep_looping = true;
 +    while (keep_looping) {
 +      ID *id, *id_next;
 +      ID *last_remapped_id = tagged_deleted_ids.last;
 +      keep_looping = false;
 +
 +      /* First tag and remove from Main all datablocks directly from target lib.
 +       * Note that we go forward here, since we want to check dependencies before users
 +       * (e.g. meshes before objects). Avoids to have to loop twice. */
 +      for (i = 0; i < base_count; i++) {
 +        ListBase *lb = lbarray[i];
 +
 +        for (id = lb->first; id; id = id_next) {
 +          id_next = id->next;
 +          /* Note: in case we delete a library, we also delete all its datablocks! */
 +          if ((id->tag & tag) || (id->lib != NULL && (id->lib->id.tag & tag))) {
 +            BLI_remlink(lb, id);
 +            BLI_addtail(&tagged_deleted_ids, id);
 +            /* Do not tag as no_main now, we want to unlink it first (lower-level ID management
 +             * code has some specific handling of 'nom main'
 +             * IDs that would be a problem in that case). */
 +            id->tag |= tag;
 +            keep_looping = true;
 +          }
 +        }
 +      }
 +      if (last_remapped_id == NULL) {
 +        dummy_link.next = tagged_deleted_ids.first;
 +        last_remapped_id = (ID *)(&dummy_link);
 +      }
 +      for (id = last_remapped_id->next; id; id = id->next) {
 +        /* Will tag 'never NULL' users of this ID too.
 +         * Note that we cannot use BKE_libblock_unlink() here,
 +         * since it would ignore indirect (and proxy!)
 +         * links, this can lead to nasty crashing here in second, actual deleting loop.
 +         * Also, this will also flag users of deleted data that cannot be unlinked
 +         * (object using deleted obdata, etc.), so that they also get deleted. */
 +        BKE_libblock_remap_locked(
 +            bmain, id, NULL, ID_REMAP_FLAG_NEVER_NULL_USAGE | ID_REMAP_FORCE_NEVER_NULL_USAGE);
 +        /* Since we removed ID from Main,
 +         * we also need to unlink its own other IDs usages ourself. */
 +        BKE_libblock_relink_ex(bmain, id, NULL, NULL, true);
 +        /* Now we can safely mark that ID as not being in Main database anymore. */
 +        id->tag |= LIB_TAG_NO_MAIN;
 +        /* This is needed because we may not have remapped usages
 +         * of that ID by other deleted ones. */
 +        // id->us = 0;  /* Is it actually? */
 +      }
 +    }
 +  }
 +  else {
 +    /* First tag all datablocks directly from target lib.
 +     * Note that we go forward here, since we want to check dependencies before users
 +     * (e.g. meshes before objects).
 +     * Avoids to have to loop twice. */
 +    for (i = 0; i < base_count; i++) {
 +      ListBase *lb = lbarray[i];
 +      ID *id, *id_next;
 +
 +      for (id = lb->first; id; id = id_next) {
 +        id_next = id->next;
 +        /* Note: in case we delete a library, we also delete all its datablocks! */
 +        if ((id->tag & tag) || (id->lib != NULL && (id->lib->id.tag & tag))) {
 +          id->tag |= tag;
 +
 +          /* Will tag 'never NULL' users of this ID too.
 +           * Note that we cannot use BKE_libblock_unlink() here, since it would ignore indirect
 +           * (and proxy!) links, this can lead to nasty crashing here in second,
 +           * actual deleting loop.
 +           * Also, this will also flag users of deleted data that cannot be unlinked
 +           * (object using deleted obdata, etc.), so that they also get deleted. */
 +          BKE_libblock_remap_locked(
 +              bmain, id, NULL, ID_REMAP_FLAG_NEVER_NULL_USAGE | ID_REMAP_FORCE_NEVER_NULL_USAGE);
 +        }
 +      }
 +    }
 +  }
 +  BKE_main_unlock(bmain);
 +
 +  /* In usual reversed order, such that all usage of a given ID, even 'never NULL' ones,
 +   * have been already cleared when we reach it
 +   * (e.g. Objects being processed before meshes, they'll have already released their 'reference'
 +   * over meshes when we come to freeing obdata). */
 +  for (i = do_tagged_deletion ? 1 : base_count; i--;) {
 +    ListBase *lb = lbarray[i];
 +    ID *id, *id_next;
 +
 +    for (id = do_tagged_deletion ? tagged_deleted_ids.first : lb->first; id; id = id_next) {
 +      id_next = id->next;
 +      if (id->tag & tag) {
 +        if (id->us != 0) {
 +#ifdef DEBUG_PRINT
 +          printf("%s: deleting %s (%d)\n", __func__, id->name, id->us);
 +#endif
 +          BLI_assert(id->us == 0);
 +        }
 +        BKE_id_free_ex(bmain, id, free_flag, !do_tagged_deletion);
 +      }
 +    }
 +  }
 +
 +  bmain->is_memfile_undo_written = false;
  }
  
 -void BKE_libblock_free_us(Main *bmain, void *idv)      /* test users */
 +/**
 + * Properly delete a single ID from given \a bmain database.
 + */
 +void BKE_id_delete(Main *bmain, void *idv)
  {
 -      ID *id = idv;
 -
 -      id_us_min(id);
 -
 -      /* XXX This is a temp (2.77) hack so that we keep same behavior as in 2.76 regarding groups when deleting an object.
 -       *     Since only 'user_one' usage of objects is groups, and only 'real user' usage of objects is scenes,
 -       *     removing that 'user_one' tag when there is no more real (scene) users of an object ensures it gets
 -       *     fully unlinked.
 -       *     But only for local objects, not linked ones!
 -       *     Otherwise, there is no real way to get rid of an object anymore - better handling of this is TODO.
 -       */
 -      if ((GS(id->name) == ID_OB) && (id->us == 1) && (id->lib == NULL)) {
 -              id_us_clear_real(id);
 -      }
 -
 -      if (id->us == 0) {
 -              BKE_libblock_unlink(bmain, id, false, false);
 -
 -              BKE_libblock_free(bmain, id);
 -      }
 +  BKE_main_id_tag_all(bmain, LIB_TAG_DOIT, false);
 +  ((ID *)idv)->tag |= LIB_TAG_DOIT;
 +
 +  id_delete(bmain, false);
  }
  
 -void BKE_libblock_delete(Main *bmain, void *idv)
 +/**
 + * Properly delete all IDs tagged with \a LIB_TAG_DOIT, in given \a bmain database.
 + *
 + * This is more efficient than calling #BKE_id_delete repetitively on a large set of IDs
 + * (several times faster when deleting most of the IDs at once)...
 + *
 + * \warning Considered experimental for now, seems to be working OK but this is
 + *          risky code in a complicated area.
 + */
 +void BKE_id_multi_tagged_delete(Main *bmain)
  {
 -      ListBase *lbarray[MAX_LIBARRAY];
 -      int base_count, i;
 -
 -      base_count = set_listbasepointers(bmain, lbarray);
 -      BKE_main_id_tag_all(bmain, LIB_TAG_DOIT, false);
 -
 -      /* First tag all datablocks directly from target lib.
 -       * Note that we go forward here, since we want to check dependencies before users (e.g. meshes before objects).
 -       * Avoids to have to loop twice. */
 -      for (i = 0; i < base_count; i++) {
 -              ListBase *lb = lbarray[i];
 -              ID *id;
 -
 -              for (id = lb->first; id; id = id->next) {
 -                      /* Note: in case we delete a library, we also delete all its datablocks! */
 -                      if ((id == (ID *)idv) || (id->lib == (Library *)idv) || (id->tag & LIB_TAG_DOIT)) {
 -                              id->tag |= LIB_TAG_DOIT;
 -                              /* Will tag 'never NULL' users of this ID too.
 -                               * Note that we cannot use BKE_libblock_unlink() here, since it would ignore indirect (and proxy!)
 -                               * links, this can lead to nasty crashing here in second, actual deleting loop.
 -                               * Also, this will also flag users of deleted data that cannot be unlinked
 -                               * (object using deleted obdata, etc.), so that they also get deleted. */
 -                              BKE_libblock_remap(bmain, id, NULL, ID_REMAP_FLAG_NEVER_NULL_USAGE | ID_REMAP_FORCE_NEVER_NULL_USAGE);
 -                      }
 -              }
 -      }
 -
 -      /* In usual reversed order, such that all usage of a given ID, even 'never NULL' ones, have been already cleared
 -       * when we reach it (e.g. Objects being processed before meshes, they'll have already released their 'reference'
 -       * over meshes when we come to freeing obdata). */
 -      for (i = base_count; i--; ) {
 -              ListBase *lb = lbarray[i];
 -              ID *id, *id_next;
 -
 -              for (id = lb->first; id; id = id_next) {
 -                      id_next = id->next;
 -                      if (id->tag & LIB_TAG_DOIT) {
 -                              if (id->us != 0) {
 -#ifdef DEBUG_PRINT
 -                                      printf("%s: deleting %s (%d)\n", __func__, id->name, id->us);
 -#endif
 -                                      BLI_assert(id->us == 0);
 -                              }
 -                              BKE_libblock_free(bmain, id);
 -                      }
 -              }
 -      }
 +  id_delete(bmain, true);
  }