Fix T73129: sculpt mode slow on mesh with fake user

We can't use the fast path when the mesh is used by mulitple objects and so
slower sculpting is expected then. But fake users should not affect this. This
also fixes the same type of error in a few other areas.

source/blender/blenkernel/BKE_library.h

@@ -184,6 +184,7 @@ void id_us_plus(struct ID *id);
 void id_us_min(struct ID *id);
 void id_fake_user_set(struct ID *id);
 void id_fake_user_clear(struct ID *id);
+int BKE_id_num_real_users(const struct ID *id);
 void BKE_id_clear_newpoin(struct ID *id);
 
 void BKE_id_make_local_generic(struct Main *bmain,

source/blender/blenkernel/intern/library.c

@@ -294,6 +294,11 @@ void id_fake_user_clear(ID *id)
   }
 }
 
+int BKE_id_num_real_users(const ID *id)
+{
+  return (id->flag & LIB_FAKEUSER) ? id->us - 1 : id->us;
+}
+
 void BKE_id_clear_newpoin(ID *id)
 {
   if (id->newid) {

source/blender/collada/MeshImporter.cpp

@@ -1014,12 +1014,12 @@ void MeshImporter::optimize_material_assignements()
        ++it) {
     Object *ob = (*it);
     Mesh *me = (Mesh *)ob->data;
-    if (me->id.us == 1) {
+    if (BKE_id_num_real_users(&me->id) == 1) {
       bc_copy_materials_to_data(ob, me);
       bc_remove_materials_from_object(ob, me);
       bc_remove_mark(ob);
     }
-    else if (me->id.us > 1) {
+    else if (BKE_id_num_real_users(&me->id) > 1) {
       bool can_move = true;
       std::vector<Object *> mesh_users = get_all_users_of(me);
       if (mesh_users.size() > 1) {

source/blender/draw/engines/overlay/overlay_extra.c

@@ -29,6 +29,7 @@
 #include "BKE_constraint.h"
 #include "BKE_curve.h"
 #include "BKE_global.h"
+#include "BKE_library.h"
 #include "BKE_mball.h"
 #include "BKE_mesh.h"
 #include "BKE_movieclip.h"
@@ -1500,7 +1501,7 @@ static void OVERLAY_object_center(OVERLAY_ExtraCallBuffers *cb,
                                   OVERLAY_PrivateData *pd,
                                   ViewLayer *view_layer)
 {
-  const bool is_library = ob->id.us > 1 || ID_IS_LINKED(ob);
+  const bool is_library = BKE_id_num_real_users(&ob->id) > 1 || ID_IS_LINKED(ob);
 
   if (ob == OBACT(view_layer)) {
     DRW_buffer_add_entry(cb->center_active, ob->obmat[3]);

source/blender/editors/object/object_add.c

@@ -2344,7 +2344,7 @@ static int convert_exec(bContext *C, wmOperator *op)
 
       if (!keep_original) {
         /* other users */
-        if (cu->id.us > 1) {
+        if (BKE_id_num_real_users(&cu->id) > 1) {
           for (ob1 = bmain->objects.first; ob1; ob1 = ob1->id.next) {
             if (ob1->data == ob->data) {
               ob1->type = OB_CURVE;

source/blender/editors/sculpt_paint/sculpt.c

@@ -7562,7 +7562,8 @@ static void sculpt_flush_update_done(const bContext *C, Object *ob, SculptUpdate
   RegionView3D *rv3d = CTX_wm_region_view3d(C);
   SculptSession *ss = ob->sculpt;
   Mesh *mesh = ob->data;
-  bool need_tag = (mesh->id.us > 1); /* Always needed for linked duplicates. */
+  bool need_tag = (BKE_id_num_real_users(&mesh->id) >
+                   1); /* Always needed for linked duplicates. */
 
   if (rv3d) {
     rv3d->rflag &= ~RV3D_PAINTING;

source/blender/editors/sculpt_paint/sculpt_undo.c

@@ -46,6 +46,7 @@
 #include "BKE_multires.h"
 #include "BKE_paint.h"
 #include "BKE_key.h"
+#include "BKE_library.h"
 #include "BKE_mesh.h"
 #include "BKE_scene.h"
 #include "BKE_subsurf.h"
@@ -632,7 +633,7 @@ static void sculpt_undo_restore_list(bContext *C, Depsgraph *depsgraph, ListBase
       }
     }
 
-    tag_update |= ((Mesh *)ob->data)->id.us > 1 || !BKE_sculptsession_use_pbvh_draw(ob, v3d);
+    tag_update |= BKE_id_num_real_users(ob->data) > 1 || !BKE_sculptsession_use_pbvh_draw(ob, v3d);
 
     if (ss->shapekey_active || ss->deform_modifiers_active) {
       Mesh *mesh = ob->data;