Refactor: move Mesh .blend I/O to IDTypeInfo callbacks

I'm also adding `BKE_id_blend_write`, so that it can be accessed
outside of `readfile.c`.

5 files changed, 242 insertions, 228 deletions

diff --git a/source/blender/blenkernel/BKE_lib_id.h b/source/blender/blenkernel/BKE_lib_id.h
index a2cbe537349..7768e903ac3 100644
--- a/source/blender/blenkernel/BKE_lib_id.h
+++ b/source/blender/blenkernel/BKE_lib_id.h
@@ -59,6 +59,8 @@ struct Main;
 struct PointerRNA;
 struct PropertyRNA;
 struct bContext;
+struct BlendWriter;
+struct BlendDataReader;
 
 size_t BKE_libblock_get_alloc_info(short type, const char **name);
 void *BKE_libblock_alloc_notest(short type) ATTR_WARN_UNUSED_RESULT;
@@ -285,6 +287,8 @@ bool BKE_id_is_in_global_main(struct ID *id);
 void BKE_id_ordered_list(struct ListBase *ordered_lb, const struct ListBase *lb);
 void BKE_id_reorder(const struct ListBase *lb, struct ID *id, struct ID *relative, bool after);
 
+void BKE_id_blend_write(struct BlendWriter *writer, struct ID *id);
+
 #define IS_TAGGED(_id) ((_id) && (((ID *)_id)->tag & LIB_TAG_DOIT))
 
 #ifdef __cplusplus
diff --git a/source/blender/blenkernel/intern/lib_id.c b/source/blender/blenkernel/intern/lib_id.c
index 7fb19458eec..678f717efe4 100644
--- a/source/blender/blenkernel/intern/lib_id.c
+++ b/source/blender/blenkernel/intern/lib_id.c
@@ -75,6 +75,8 @@
 
 #include "RNA_access.h"
 
+#include "BLO_read_write.h"
+
 #include "atomic_ops.h"
 
 //#define DEBUG_TIME
@@ -2326,3 +2328,30 @@ void BKE_id_reorder(const ListBase *lb, ID *id, ID *relative, bool after)
     *id_order = relative_order - 1;
   }
 }
+
+void BKE_id_blend_write(BlendWriter *writer, ID *id)
+{
+  /* ID_WM's id->properties are considered runtime only, and never written in .blend file. */
+  if (id->properties && !ELEM(GS(id->name), ID_WM)) {
+    IDP_BlendWrite(writer, id->properties);
+  }
+
+  if (id->override_library) {
+    BLO_write_struct(writer, IDOverrideLibrary, id->override_library);
+
+    BLO_write_struct_list(writer, IDOverrideLibraryProperty, &id->override_library->properties);
+    LISTBASE_FOREACH (IDOverrideLibraryProperty *, op, &id->override_library->properties) {
+      BLO_write_string(writer, op->rna_path);
+
+      BLO_write_struct_list(writer, IDOverrideLibraryPropertyOperation, &op->operations);
+      LISTBASE_FOREACH (IDOverrideLibraryPropertyOperation *, opop, &op->operations) {
+        if (opop->subitem_reference_name) {
+          BLO_write_string(writer, opop->subitem_reference_name);
+        }
+        if (opop->subitem_local_name) {
+          BLO_write_string(writer, opop->subitem_local_name);
+        }
+      }
+    }
+  }
+}
diff --git a/source/blender/blenkernel/intern/mesh.c b/source/blender/blenkernel/intern/mesh.c
index b6e77c100f0..3e606a5a512 100644
--- a/source/blender/blenkernel/intern/mesh.c
+++ b/source/blender/blenkernel/intern/mesh.c
@@ -23,6 +23,9 @@
 
 #include "MEM_guardedalloc.h"
 
+/* allow using deprecated functionality for .blend file I/O */
+#define DNA_DEPRECATED_ALLOW
+
 #include "DNA_defaults.h"
 #include "DNA_key_types.h"
 #include "DNA_material_types.h"
@@ -32,6 +35,7 @@
 
 #include "BLI_bitmap.h"
 #include "BLI_edgehash.h"
+#include "BLI_endian_switch.h"
 #include "BLI_ghash.h"
 #include "BLI_hash.h"
 #include "BLI_linklist.h"
@@ -43,6 +47,7 @@
 #include "BLT_translation.h"
 
 #include "BKE_anim_data.h"
+#include "BKE_deform.h"
 #include "BKE_editmesh.h"
 #include "BKE_global.h"
 #include "BKE_idtype.h"
@@ -63,6 +68,8 @@
 #include "DEG_depsgraph.h"
 #include "DEG_depsgraph_query.h"
 
+#include "BLO_read_write.h"
+
 static void mesh_clear_geometry(Mesh *mesh);
 static void mesh_tessface_clear_intern(Mesh *mesh, int free_customdata);
 
@@ -163,6 +170,158 @@ static void mesh_foreach_id(ID *id, LibraryForeachIDData *data)
   }
 }
 
+static void mesh_blend_write(BlendWriter *writer, ID *id, const void *id_address)
+{
+  Mesh *mesh = (Mesh *)id;
+  if (mesh->id.us > 0 || BLO_write_is_undo(writer)) {
+    /* cache only - don't write */
+    mesh->mface = NULL;
+    mesh->totface = 0;
+    memset(&mesh->fdata, 0, sizeof(mesh->fdata));
+    memset(&mesh->runtime, 0, sizeof(mesh->runtime));
+
+    BLO_write_id_struct(writer, Mesh, id_address, &mesh->id);
+    BKE_id_blend_write(writer, &mesh->id);
+
+    /* direct data */
+    if (mesh->adt) {
+      BKE_animdata_blend_write(writer, mesh->adt);
+    }
+
+    BLO_write_pointer_array(writer, mesh->totcol, mesh->mat);
+    BLO_write_raw(writer, sizeof(MSelect) * mesh->totselect, mesh->mselect);
+
+    CustomData_blend_write(writer, &mesh->vdata, mesh->totvert, CD_MASK_MESH.vmask, &mesh->id);
+    CustomData_blend_write(writer, &mesh->edata, mesh->totedge, CD_MASK_MESH.emask, &mesh->id);
+    /* fdata is really a dummy - written so slots align */
+    CustomData_blend_write(writer, &mesh->fdata, mesh->totface, CD_MASK_MESH.fmask, &mesh->id);
+    CustomData_blend_write(writer, &mesh->ldata, mesh->totloop, CD_MASK_MESH.lmask, &mesh->id);
+    CustomData_blend_write(writer, &mesh->pdata, mesh->totpoly, CD_MASK_MESH.pmask, &mesh->id);
+  }
+}
+
+static void mesh_blend_read_data(BlendDataReader *reader, ID *id)
+{
+  Mesh *mesh = (Mesh *)id;
+  BLO_read_pointer_array(reader, (void **)&mesh->mat);
+
+  BLO_read_data_address(reader, &mesh->mvert);
+  BLO_read_data_address(reader, &mesh->medge);
+  BLO_read_data_address(reader, &mesh->mface);
+  BLO_read_data_address(reader, &mesh->mloop);
+  BLO_read_data_address(reader, &mesh->mpoly);
+  BLO_read_data_address(reader, &mesh->tface);
+  BLO_read_data_address(reader, &mesh->mtface);
+  BLO_read_data_address(reader, &mesh->mcol);
+  BLO_read_data_address(reader, &mesh->dvert);
+  BLO_read_data_address(reader, &mesh->mloopcol);
+  BLO_read_data_address(reader, &mesh->mloopuv);
+  BLO_read_data_address(reader, &mesh->mselect);
+
+  /* animdata */
+  BLO_read_data_address(reader, &mesh->adt);
+  BKE_animdata_blend_read_data(reader, mesh->adt);
+
+  /* Normally BKE_defvert_blend_read should be called in CustomData_blend_read,
+   * but for backwards compatibility in do_versions to work we do it here. */
+  BKE_defvert_blend_read(reader, mesh->totvert, mesh->dvert);
+
+  CustomData_blend_read(reader, &mesh->vdata, mesh->totvert);
+  CustomData_blend_read(reader, &mesh->edata, mesh->totedge);
+  CustomData_blend_read(reader, &mesh->fdata, mesh->totface);
+  CustomData_blend_read(reader, &mesh->ldata, mesh->totloop);
+  CustomData_blend_read(reader, &mesh->pdata, mesh->totpoly);
+
+  mesh->texflag &= ~ME_AUTOSPACE_EVALUATED;
+  mesh->edit_mesh = NULL;
+  BKE_mesh_runtime_reset(mesh);
+
+  /* happens with old files */
+  if (mesh->mselect == NULL) {
+    mesh->totselect = 0;
+  }
+
+  /* Multires data */
+  BLO_read_data_address(reader, &mesh->mr);
+  if (mesh->mr) {
+    BLO_read_list(reader, &mesh->mr->levels);
+    MultiresLevel *lvl = mesh->mr->levels.first;
+
+    CustomData_blend_read(reader, &mesh->mr->vdata, lvl->totvert);
+    BKE_defvert_blend_read(
+        reader, lvl->totvert, CustomData_get(&mesh->mr->vdata, 0, CD_MDEFORMVERT));
+    CustomData_blend_read(reader, &mesh->mr->fdata, lvl->totface);
+
+    BLO_read_data_address(reader, &mesh->mr->edge_flags);
+    BLO_read_data_address(reader, &mesh->mr->edge_creases);
+
+    BLO_read_data_address(reader, &mesh->mr->verts);
+
+    /* If mesh has the same number of vertices as the
+     * highest multires level, load the current mesh verts
+     * into multires and discard the old data. Needed
+     * because some saved files either do not have a verts
+     * array, or the verts array contains out-of-date
+     * data. */
+    if (mesh->totvert == ((MultiresLevel *)mesh->mr->levels.last)->totvert) {
+      if (mesh->mr->verts) {
+        MEM_freeN(mesh->mr->verts);
+      }
+      mesh->mr->verts = MEM_dupallocN(mesh->mvert);
+    }
+
+    for (; lvl; lvl = lvl->next) {
+      BLO_read_data_address(reader, &lvl->verts);
+      BLO_read_data_address(reader, &lvl->faces);
+      BLO_read_data_address(reader, &lvl->edges);
+      BLO_read_data_address(reader, &lvl->colfaces);
+    }
+  }
+
+  /* if multires is present but has no valid vertex data,
+   * there's no way to recover it; silently remove multires */
+  if (mesh->mr && !mesh->mr->verts) {
+    multires_free(mesh->mr);
+    mesh->mr = NULL;
+  }
+
+  if ((BLO_read_requires_endian_switch(reader)) && mesh->tface) {
+    TFace *tf = mesh->tface;
+    for (int i = 0; i < mesh->totface; i++, tf++) {
+      BLI_endian_switch_uint32_array(tf->col, 4);
+    }
+  }
+}
+
+static void mesh_blend_read_lib(BlendLibReader *reader, ID *id)
+{
+  Mesh *me = (Mesh *)id;
+  /* this check added for python created meshes */
+  if (me->mat) {
+    for (int i = 0; i < me->totcol; i++) {
+      BLO_read_id_address(reader, me->id.lib, &me->mat[i]);
+    }
+  }
+  else {
+    me->totcol = 0;
+  }
+
+  BLO_read_id_address(reader, me->id.lib, &me->ipo);  // XXX: deprecated: old anim sys
+  BLO_read_id_address(reader, me->id.lib, &me->key);
+  BLO_read_id_address(reader, me->id.lib, &me->texcomesh);
+}
+
+static void mesh_read_expand(BlendExpander *expander, ID *id)
+{
+  Mesh *me = (Mesh *)id;
+  for (int a = 0; a < me->totcol; a++) {
+    BLO_expand(expander, me->mat[a]);
+  }
+
+  BLO_expand(expander, me->key);
+  BLO_expand(expander, me->texcomesh);
+}
+
 IDTypeInfo IDType_ID_ME = {
     .id_code = ID_ME,
     .id_filter = FILTER_ID_ME,
@@ -180,10 +339,10 @@ IDTypeInfo IDType_ID_ME = {
     .foreach_id = mesh_foreach_id,
     .foreach_cache = NULL,
 
-    .blend_write = NULL,
-    .blend_read_data = NULL,
-    .blend_read_lib = NULL,
-    .blend_read_expand = NULL,
+    .blend_write = mesh_blend_write,
+    .blend_read_data = mesh_blend_read_data,
+    .blend_read_lib = mesh_blend_read_lib,
+    .blend_read_expand = mesh_read_expand,
 };
 
 enum {
diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 0e134d172c2..dd7ea003cc5 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -4109,115 +4109,6 @@ static void direct_link_particlesystems(BlendDataReader *reader, ListBase *parti
 /** \name Read ID: Mesh
  * \{ */
 
-static void lib_link_mesh(BlendLibReader *reader, Mesh *me)
-{
-  /* this check added for python created meshes */
-  if (me->mat) {
-    for (int i = 0; i < me->totcol; i++) {
-      BLO_read_id_address(reader, me->id.lib, &me->mat[i]);
-    }
-  }
-  else {
-    me->totcol = 0;
-  }
-
-  BLO_read_id_address(reader, me->id.lib, &me->ipo);  // XXX: deprecated: old anim sys
-  BLO_read_id_address(reader, me->id.lib, &me->key);
-  BLO_read_id_address(reader, me->id.lib, &me->texcomesh);
-}
-
-static void direct_link_mesh(BlendDataReader *reader, Mesh *mesh)
-{
-  BLO_read_pointer_array(reader, (void **)&mesh->mat);
-
-  BLO_read_data_address(reader, &mesh->mvert);
-  BLO_read_data_address(reader, &mesh->medge);
-  BLO_read_data_address(reader, &mesh->mface);
-  BLO_read_data_address(reader, &mesh->mloop);
-  BLO_read_data_address(reader, &mesh->mpoly);
-  BLO_read_data_address(reader, &mesh->tface);
-  BLO_read_data_address(reader, &mesh->mtface);
-  BLO_read_data_address(reader, &mesh->mcol);
-  BLO_read_data_address(reader, &mesh->dvert);
-  BLO_read_data_address(reader, &mesh->mloopcol);
-  BLO_read_data_address(reader, &mesh->mloopuv);
-  BLO_read_data_address(reader, &mesh->mselect);
-
-  /* animdata */
-  BLO_read_data_address(reader, &mesh->adt);
-  BKE_animdata_blend_read_data(reader, mesh->adt);
-
-  /* Normally BKE_defvert_blend_read should be called in CustomData_blend_read,
-   * but for backwards compatibility in do_versions to work we do it here. */
-  BKE_defvert_blend_read(reader, mesh->totvert, mesh->dvert);
-
-  CustomData_blend_read(reader, &mesh->vdata, mesh->totvert);
-  CustomData_blend_read(reader, &mesh->edata, mesh->totedge);
-  CustomData_blend_read(reader, &mesh->fdata, mesh->totface);
-  CustomData_blend_read(reader, &mesh->ldata, mesh->totloop);
-  CustomData_blend_read(reader, &mesh->pdata, mesh->totpoly);
-
-  mesh->texflag &= ~ME_AUTOSPACE_EVALUATED;
-  mesh->edit_mesh = NULL;
-  BKE_mesh_runtime_reset(mesh);
-
-  /* happens with old files */
-  if (mesh->mselect == NULL) {
-    mesh->totselect = 0;
-  }
-
-  /* Multires data */
-  BLO_read_data_address(reader, &mesh->mr);
-  if (mesh->mr) {
-    BLO_read_list(reader, &mesh->mr->levels);
-    MultiresLevel *lvl = mesh->mr->levels.first;
-
-    CustomData_blend_read(reader, &mesh->mr->vdata, lvl->totvert);
-    BKE_defvert_blend_read(
-        reader, lvl->totvert, CustomData_get(&mesh->mr->vdata, 0, CD_MDEFORMVERT));
-    CustomData_blend_read(reader, &mesh->mr->fdata, lvl->totface);
-
-    BLO_read_data_address(reader, &mesh->mr->edge_flags);
-    BLO_read_data_address(reader, &mesh->mr->edge_creases);
-
-    BLO_read_data_address(reader, &mesh->mr->verts);
-
-    /* If mesh has the same number of vertices as the
-     * highest multires level, load the current mesh verts
-     * into multires and discard the old data. Needed
-     * because some saved files either do not have a verts
-     * array, or the verts array contains out-of-date
-     * data. */
-    if (mesh->totvert == ((MultiresLevel *)mesh->mr->levels.last)->totvert) {
-      if (mesh->mr->verts) {
-        MEM_freeN(mesh->mr->verts);
-      }
-      mesh->mr->verts = MEM_dupallocN(mesh->mvert);
-    }
-
-    for (; lvl; lvl = lvl->next) {
-      BLO_read_data_address(reader, &lvl->verts);
-      BLO_read_data_address(reader, &lvl->faces);
-      BLO_read_data_address(reader, &lvl->edges);
-      BLO_read_data_address(reader, &lvl->colfaces);
-    }
-  }
-
-  /* if multires is present but has no valid vertex data,
-   * there's no way to recover it; silently remove multires */
-  if (mesh->mr && !mesh->mr->verts) {
-    multires_free(mesh->mr);
-    mesh->mr = NULL;
-  }
-
-  if ((BLO_read_requires_endian_switch(reader)) && mesh->tface) {
-    TFace *tf = mesh->tface;
-    for (int i = 0; i < mesh->totface; i++, tf++) {
-      BLI_endian_switch_uint32_array(tf->col, 4);
-    }
-  }
-}
-
 /** \} */
 
 /* -------------------------------------------------------------------- */
@@ -8158,9 +8049,6 @@ static bool direct_link_id(FileData *fd, Main *main, const int tag, ID *id, ID *
     case ID_OB:
       direct_link_object(&reader, (Object *)id);
       break;
-    case ID_ME:
-      direct_link_mesh(&reader, (Mesh *)id);
-      break;
     case ID_CU:
       direct_link_curve(&reader, (Curve *)id);
       break;
@@ -8266,6 +8154,9 @@ static bool direct_link_id(FileData *fd, Main *main, const int tag, ID *id, ID *
     case ID_SIM:
       direct_link_simulation(&reader, (Simulation *)id);
       break;
+    case ID_ME:
+      /* Do nothing. Handled by IDTypeInfo callback. */
+      break;
   }
 
   /* try to restore (when undoing) or clear ID's cache pointers. */
@@ -8938,9 +8829,6 @@ static void lib_link_all(FileData *fd, Main *bmain)
       case ID_CU:
         lib_link_curve(&reader, (Curve *)id);
         break;
-      case ID_ME:
-        lib_link_mesh(&reader, (Mesh *)id);
-        break;
       case ID_CF:
         lib_link_cachefiles(&reader, (CacheFile *)id);
         break;
@@ -8994,6 +8882,9 @@ static void lib_link_all(FileData *fd, Main *bmain)
       case ID_LI:
         lib_link_library(&reader, (Library *)id); /* Only init users. */
         break;
+      case ID_ME:
+        /* Do nothing. Handled by IDTypeInfo callback. */
+        break;
     }
 
     id->tag &= ~LIB_TAG_NEED_LINK;
@@ -9843,16 +9734,6 @@ static void expand_curve(BlendExpander *expander, Curve *cu)
   BLO_expand(expander, cu->textoncurve);
 }
 
-static void expand_mesh(BlendExpander *expander, Mesh *me)
-{
-  for (int a = 0; a < me->totcol; a++) {
-    BLO_expand(expander, me->mat[a]);
-  }
-
-  BLO_expand(expander, me->key);
-  BLO_expand(expander, me->texcomesh);
-}
-
 /* callback function used to expand constraint ID-links */
 static void expand_constraint_cb(bConstraint *UNUSED(con),
                                  ID **idpoin,
@@ -10286,9 +10167,6 @@ void BLO_expand_main(void *fdhandle, Main *mainvar)
             case ID_OB:
               expand_object(&expander, (Object *)id);
               break;
-            case ID_ME:
-              expand_mesh(&expander, (Mesh *)id);
-              break;
             case ID_CU:
               expand_curve(&expander, (Curve *)id);
               break;
diff --git a/source/blender/blenloader/intern/writefile.c b/source/blender/blenloader/intern/writefile.c
index c764f2d9e05..0c703f97f4d 100644
--- a/source/blender/blenloader/intern/writefile.c
+++ b/source/blender/blenloader/intern/writefile.c
@@ -659,33 +659,6 @@ static void writelist_id(WriteData *wd, int filecode, const char *structname, co
  * These functions are used by blender's .blend system for file saving/loading.
  * \{ */
 
-static void write_iddata(BlendWriter *writer, ID *id)
-{
-  /* ID_WM's id->properties are considered runtime only, and never written in .blend file. */
-  if (id->properties && !ELEM(GS(id->name), ID_WM)) {
-    IDP_BlendWrite(writer, id->properties);
-  }
-
-  if (id->override_library) {
-    BLO_write_struct(writer, IDOverrideLibrary, id->override_library);
-
-    BLO_write_struct_list(writer, IDOverrideLibraryProperty, &id->override_library->properties);
-    LISTBASE_FOREACH (IDOverrideLibraryProperty *, op, &id->override_library->properties) {
-      BLO_write_string(writer, op->rna_path);
-
-      BLO_write_struct_list(writer, IDOverrideLibraryPropertyOperation, &op->operations);
-      LISTBASE_FOREACH (IDOverrideLibraryPropertyOperation *, opop, &op->operations) {
-        if (opop->subitem_reference_name) {
-          BLO_write_string(writer, opop->subitem_reference_name);
-        }
-        if (opop->subitem_local_name) {
-          BLO_write_string(writer, opop->subitem_local_name);
-        }
-      }
-    }
-  }
-}
-
 static void write_previews(BlendWriter *writer, const PreviewImage *prv_orig)
 {
   /* Note we write previews also for undo steps. It takes up some memory,
@@ -714,7 +687,7 @@ static void write_action(BlendWriter *writer, bAction *act, const void *id_addre
 {
   if (act->id.us > 0 || BLO_write_is_undo(writer)) {
     BLO_write_id_struct(writer, bAction, id_address, &act->id);
-    write_iddata(writer, &act->id);
+    BKE_id_blend_write(writer, &act->id);
 
     BKE_fcurve_blend_write(writer, &act->curves);
 
@@ -1172,7 +1145,7 @@ static void write_particlesettings(BlendWriter *writer,
   if (part->id.us > 0 || BLO_write_is_undo(writer)) {
     /* write LibData */
     BLO_write_id_struct(writer, ParticleSettings, id_address, &part->id);
-    write_iddata(writer, &part->id);
+    BKE_id_blend_write(writer, &part->id);
 
     if (part->adt) {
       BKE_animdata_blend_write(writer, part->adt);
@@ -1594,7 +1567,7 @@ static void write_object(BlendWriter *writer, Object *ob, const void *id_address
 
     /* write LibData */
     BLO_write_id_struct(writer, Object, id_address, &ob->id);
-    write_iddata(writer, &ob->id);
+    BKE_id_blend_write(writer, &ob->id);
 
     if (ob->adt) {
       BKE_animdata_blend_write(writer, ob->adt);
@@ -1662,7 +1635,7 @@ static void write_vfont(BlendWriter *writer, VFont *vf, const void *id_address)
 
     /* write LibData */
     BLO_write_id_struct(writer, VFont, id_address, &vf->id);
-    write_iddata(writer, &vf->id);
+    BKE_id_blend_write(writer, &vf->id);
 
     /* direct data */
     if (vf->packedfile) {
@@ -1678,7 +1651,7 @@ static void write_key(BlendWriter *writer, Key *key, const void *id_address)
   if (key->id.us > 0 || BLO_write_is_undo(writer)) {
     /* write LibData */
     BLO_write_id_struct(writer, Key, id_address, &key->id);
-    write_iddata(writer, &key->id);
+    BKE_id_blend_write(writer, &key->id);
 
     if (key->adt) {
       BKE_animdata_blend_write(writer, key->adt);
@@ -1699,7 +1672,7 @@ static void write_camera(BlendWriter *writer, Camera *cam, const void *id_addres
   if (cam->id.us > 0 || BLO_write_is_undo(writer)) {
     /* write LibData */
     BLO_write_id_struct(writer, Camera, id_address, &cam->id);
-    write_iddata(writer, &cam->id);
+    BKE_id_blend_write(writer, &cam->id);
 
     if (cam->adt) {
       BKE_animdata_blend_write(writer, cam->adt);
@@ -1724,7 +1697,7 @@ static void write_mball(BlendWriter *writer, MetaBall *mb, const void *id_addres
 
     /* write LibData */
     BLO_write_id_struct(writer, MetaBall, id_address, &mb->id);
-    write_iddata(writer, &mb->id);
+    BKE_id_blend_write(writer, &mb->id);
 
     /* direct data */
     BLO_write_pointer_array(writer, mb->totcol, mb->mat);
@@ -1748,7 +1721,7 @@ static void write_curve(BlendWriter *writer, Curve *cu, const void *id_address)
 
     /* write LibData */
     BLO_write_id_struct(writer, Curve, id_address, &cu->id);
-    write_iddata(writer, &cu->id);
+    BKE_id_blend_write(writer, &cu->id);
 
     /* direct data */
     BLO_write_pointer_array(writer, cu->totcol, cu->mat);
@@ -1785,35 +1758,6 @@ static void write_curve(BlendWriter *writer, Curve *cu, const void *id_address)
   }
 }
 
-static void write_mesh(BlendWriter *writer, Mesh *mesh, const void *id_address)
-{
-  if (mesh->id.us > 0 || BLO_write_is_undo(writer)) {
-    /* cache only - don't write */
-    mesh->mface = NULL;
-    mesh->totface = 0;
-    memset(&mesh->fdata, 0, sizeof(mesh->fdata));
-    memset(&mesh->runtime, 0, sizeof(mesh->runtime));
-
-    BLO_write_id_struct(writer, Mesh, id_address, &mesh->id);
-    write_iddata(writer, &mesh->id);
-
-    /* direct data */
-    if (mesh->adt) {
-      BKE_animdata_blend_write(writer, mesh->adt);
-    }
-
-    BLO_write_pointer_array(writer, mesh->totcol, mesh->mat);
-    BLO_write_raw(writer, sizeof(MSelect) * mesh->totselect, mesh->mselect);
-
-    CustomData_blend_write(writer, &mesh->vdata, mesh->totvert, CD_MASK_MESH.vmask, &mesh->id);
-    CustomData_blend_write(writer, &mesh->edata, mesh->totedge, CD_MASK_MESH.emask, &mesh->id);
-    /* fdata is really a dummy - written so slots align */
-    CustomData_blend_write(writer, &mesh->fdata, mesh->totface, CD_MASK_MESH.fmask, &mesh->id);
-    CustomData_blend_write(writer, &mesh->ldata, mesh->totloop, CD_MASK_MESH.lmask, &mesh->id);
-    CustomData_blend_write(writer, &mesh->pdata, mesh->totpoly, CD_MASK_MESH.pmask, &mesh->id);
-  }
-}
-
 static void write_lattice(BlendWriter *writer, Lattice *lt, const void *id_address)
 {
   if (lt->id.us > 0 || BLO_write_is_undo(writer)) {
@@ -1823,7 +1767,7 @@ static void write_lattice(BlendWriter *writer, Lattice *lt, const void *id_addre
 
     /* write LibData */
     BLO_write_id_struct(writer, Lattice, id_address, &lt->id);
-    write_iddata(writer, &lt->id);
+    BKE_id_blend_write(writer, &lt->id);
 
     /* write animdata */
     if (lt->adt) {
@@ -1851,7 +1795,7 @@ static void write_image(BlendWriter *writer, Image *ima, const void *id_address)
 
     /* write LibData */
     BLO_write_id_struct(writer, Image, id_address, &ima->id);
-    write_iddata(writer, &ima->id);
+    BKE_id_blend_write(writer, &ima->id);
 
     for (imapf = ima->packedfiles.first; imapf; imapf = imapf->next) {
       BLO_write_struct(writer, ImagePackedFile, imapf);
@@ -1882,7 +1826,7 @@ static void write_texture(BlendWriter *writer, Tex *tex, const void *id_address)
   if (tex->id.us > 0 || BLO_write_is_undo(writer)) {
     /* write LibData */
     BLO_write_id_struct(writer, Tex, id_address, &tex->id);
-    write_iddata(writer, &tex->id);
+    BKE_id_blend_write(writer, &tex->id);
 
     if (tex->adt) {
       BKE_animdata_blend_write(writer, tex->adt);
@@ -1912,7 +1856,7 @@ static void write_material(BlendWriter *writer, Material *ma, const void *id_add
 
     /* write LibData */
     BLO_write_id_struct(writer, Material, id_address, &ma->id);
-    write_iddata(writer, &ma->id);
+    BKE_id_blend_write(writer, &ma->id);
 
     if (ma->adt) {
       BKE_animdata_blend_write(writer, ma->adt);
@@ -1941,7 +1885,7 @@ static void write_world(BlendWriter *writer, World *wrld, const void *id_address
 
     /* write LibData */
     BLO_write_id_struct(writer, World, id_address, &wrld->id);
-    write_iddata(writer, &wrld->id);
+    BKE_id_blend_write(writer, &wrld->id);
 
     if (wrld->adt) {
       BKE_animdata_blend_write(writer, wrld->adt);
@@ -1962,7 +1906,7 @@ static void write_light(BlendWriter *writer, Light *la, const void *id_address)
   if (la->id.us > 0 || BLO_write_is_undo(writer)) {
     /* write LibData */
     BLO_write_id_struct(writer, Light, id_address, &la->id);
-    write_iddata(writer, &la->id);
+    BKE_id_blend_write(writer, &la->id);
 
     if (la->adt) {
       BKE_animdata_blend_write(writer, la->adt);
@@ -2007,7 +1951,7 @@ static void write_collection(BlendWriter *writer, Collection *collection, const
 
     /* write LibData */
     BLO_write_id_struct(writer, Collection, id_address, &collection->id);
-    write_iddata(writer, &collection->id);
+    BKE_id_blend_write(writer, &collection->id);
 
     write_collection_nolib(writer, collection);
   }
@@ -2133,7 +2077,7 @@ static void write_scene(BlendWriter *writer, Scene *sce, const void *id_address)
 
   /* write LibData */
   BLO_write_id_struct(writer, Scene, id_address, &sce->id);
-  write_iddata(writer, &sce->id);
+  BKE_id_blend_write(writer, &sce->id);
 
   if (sce->adt) {
     BKE_animdata_blend_write(writer, sce->adt);
@@ -2367,7 +2311,7 @@ static void write_gpencil(BlendWriter *writer, bGPdata *gpd, const void *id_addr
 
     /* write gpd data block to file */
     BLO_write_id_struct(writer, bGPdata, id_address, &gpd->id);
-    write_iddata(writer, &gpd->id);
+    BKE_id_blend_write(writer, &gpd->id);
 
     if (gpd->adt) {
       BKE_animdata_blend_write(writer, gpd->adt);
@@ -2641,7 +2585,7 @@ static void write_area_map(BlendWriter *writer, ScrAreaMap *area_map)
 static void write_windowmanager(BlendWriter *writer, wmWindowManager *wm, const void *id_address)
 {
   BLO_write_id_struct(writer, wmWindowManager, id_address, &wm->id);
-  write_iddata(writer, &wm->id);
+  BKE_id_blend_write(writer, &wm->id);
   write_wm_xr_data(writer, &wm->xr);
 
   LISTBASE_FOREACH (wmWindow *, win, &wm->windows) {
@@ -2676,7 +2620,7 @@ static void write_screen(BlendWriter *writer, bScreen *screen, const void *id_ad
     /* write LibData */
     /* in 2.50+ files, the file identifier for screens is patched, forward compatibility */
     writestruct_at_address(writer->wd, ID_SCRN, bScreen, 1, id_address, screen);
-    write_iddata(writer, &screen->id);
+    BKE_id_blend_write(writer, &screen->id);
 
     write_previews(writer, screen->preview);
 
@@ -2716,7 +2660,7 @@ static void write_armature(BlendWriter *writer, bArmature *arm, const void *id_a
     arm->act_edbone = NULL;
 
     BLO_write_id_struct(writer, bArmature, id_address, &arm->id);
-    write_iddata(writer, &arm->id);
+    BKE_id_blend_write(writer, &arm->id);
 
     if (arm->adt) {
       BKE_animdata_blend_write(writer, arm->adt);
@@ -2741,7 +2685,7 @@ static void write_text(BlendWriter *writer, Text *text, const void *id_address)
 
   /* write LibData */
   BLO_write_id_struct(writer, Text, id_address, &text->id);
-  write_iddata(writer, &text->id);
+  BKE_id_blend_write(writer, &text->id);
 
   if (text->filepath) {
     BLO_write_string(writer, text->filepath);
@@ -2764,7 +2708,7 @@ static void write_speaker(BlendWriter *writer, Speaker *spk, const void *id_addr
   if (spk->id.us > 0 || BLO_write_is_undo(writer)) {
     /* write LibData */
     BLO_write_id_struct(writer, Speaker, id_address, &spk->id);
-    write_iddata(writer, &spk->id);
+    BKE_id_blend_write(writer, &spk->id);
 
     if (spk->adt) {
       BKE_animdata_blend_write(writer, spk->adt);
@@ -2783,7 +2727,7 @@ static void write_sound(BlendWriter *writer, bSound *sound, const void *id_addre
 
     /* write LibData */
     BLO_write_id_struct(writer, bSound, id_address, &sound->id);
-    write_iddata(writer, &sound->id);
+    BKE_id_blend_write(writer, &sound->id);
 
     if (sound->packedfile) {
       PackedFile *pf = sound->packedfile;
@@ -2798,7 +2742,7 @@ static void write_probe(BlendWriter *writer, LightProbe *prb, const void *id_add
   if (prb->id.us > 0 || BLO_write_is_undo(writer)) {
     /* write LibData */
     BLO_write_id_struct(writer, LightProbe, id_address, &prb->id);
-    write_iddata(writer, &prb->id);
+    BKE_id_blend_write(writer, &prb->id);
 
     if (prb->adt) {
       BKE_animdata_blend_write(writer, prb->adt);
@@ -2820,7 +2764,7 @@ static void write_nodetree(BlendWriter *writer, bNodeTree *ntree, const void *id
     BLO_write_id_struct(writer, bNodeTree, id_address, &ntree->id);
     /* Note that trees directly used by other IDs (materials etc.) are not 'real' ID, they cannot
      * be linked, etc., so we write actual id data here only, for 'real' ID trees. */
-    write_iddata(writer, &ntree->id);
+    BKE_id_blend_write(writer, &ntree->id);
 
     write_nodetree_nolib(writer, ntree);
   }
@@ -2830,7 +2774,7 @@ static void write_brush(BlendWriter *writer, Brush *brush, const void *id_addres
 {
   if (brush->id.us > 0 || BLO_write_is_undo(writer)) {
     BLO_write_id_struct(writer, Brush, id_address, &brush->id);
-    write_iddata(writer, &brush->id);
+    BKE_id_blend_write(writer, &brush->id);
 
     if (brush->curve) {
       BKE_curvemapping_blend_write(writer, brush->curve);
@@ -2878,7 +2822,7 @@ static void write_palette(BlendWriter *writer, Palette *palette, const void *id_
   if (palette->id.us > 0 || BLO_write_is_undo(writer)) {
     PaletteColor *color;
     BLO_write_id_struct(writer, Palette, id_address, &palette->id);
-    write_iddata(writer, &palette->id);
+    BKE_id_blend_write(writer, &palette->id);
 
     for (color = palette->colors.first; color; color = color->next) {
       BLO_write_struct(writer, PaletteColor, color);
@@ -2890,7 +2834,7 @@ static void write_paintcurve(BlendWriter *writer, PaintCurve *pc, const void *id
 {
   if (pc->id.us > 0 || BLO_write_is_undo(writer)) {
     BLO_write_id_struct(writer, PaintCurve, id_address, &pc->id);
-    write_iddata(writer, &pc->id);
+    BKE_id_blend_write(writer, &pc->id);
 
     BLO_write_struct_array(writer, PaintCurvePoint, pc->tot_points, pc->points);
   }
@@ -2946,7 +2890,7 @@ static void write_movieclip(BlendWriter *writer, MovieClip *clip, const void *id
     MovieTrackingObject *object;
 
     BLO_write_id_struct(writer, MovieClip, id_address, &clip->id);
-    write_iddata(writer, &clip->id);
+    BKE_id_blend_write(writer, &clip->id);
 
     if (clip->adt) {
       BKE_animdata_blend_write(writer, clip->adt);
@@ -2975,7 +2919,7 @@ static void write_mask(BlendWriter *writer, Mask *mask, const void *id_address)
     MaskLayer *masklay;
 
     BLO_write_id_struct(writer, Mask, id_address, &mask->id);
-    write_iddata(writer, &mask->id);
+    BKE_id_blend_write(writer, &mask->id);
 
     if (mask->adt) {
       BKE_animdata_blend_write(writer, mask->adt);
@@ -3285,7 +3229,7 @@ static void write_linestyle(BlendWriter *writer,
 {
   if (linestyle->id.us > 0 || BLO_write_is_undo(writer)) {
     BLO_write_id_struct(writer, FreestyleLineStyle, id_address, &linestyle->id);
-    write_iddata(writer, &linestyle->id);
+    BKE_id_blend_write(writer, &linestyle->id);
 
     if (linestyle->adt) {
       BKE_animdata_blend_write(writer, linestyle->adt);
@@ -3327,7 +3271,7 @@ static void write_cachefile(BlendWriter *writer, CacheFile *cache_file, const vo
 static void write_workspace(BlendWriter *writer, WorkSpace *workspace, const void *id_address)
 {
   BLO_write_id_struct(writer, WorkSpace, id_address, &workspace->id);
-  write_iddata(writer, &workspace->id);
+  BKE_id_blend_write(writer, &workspace->id);
   BLO_write_struct_list(writer, WorkSpaceLayout, &workspace->layouts);
   BLO_write_struct_list(writer, WorkSpaceDataRelation, &workspace->hook_layout_relations);
   BLO_write_struct_list(writer, wmOwnerID, &workspace->owner_ids);
@@ -3344,7 +3288,7 @@ static void write_hair(BlendWriter *writer, Hair *hair, const void *id_address)
   if (hair->id.us > 0 || BLO_write_is_undo(writer)) {
     /* Write LibData */
     BLO_write_id_struct(writer, Hair, id_address, &hair->id);
-    write_iddata(writer, &hair->id);
+    BKE_id_blend_write(writer, &hair->id);
 
     /* Direct data */
     CustomData_blend_write(writer, &hair->pdata, hair->totpoint, CD_MASK_ALL, &hair->id);
@@ -3365,7 +3309,7 @@ static void write_pointcloud(BlendWriter *writer, PointCloud *pointcloud, const
 
     /* Write LibData */
     BLO_write_id_struct(writer, PointCloud, id_address, &pointcloud->id);
-    write_iddata(writer, &pointcloud->id);
+    BKE_id_blend_write(writer, &pointcloud->id);
 
     /* Direct data */
     CustomData_blend_write(
@@ -3390,7 +3334,7 @@ static void write_volume(BlendWriter *writer, Volume *volume, const void *id_add
 
     /* write LibData */
     BLO_write_id_struct(writer, Volume, id_address, &volume->id);
-    write_iddata(writer, &volume->id);
+    BKE_id_blend_write(writer, &volume->id);
 
     /* direct data */
     BLO_write_pointer_array(writer, volume->totcol, volume->mat);
@@ -3410,7 +3354,7 @@ static void write_simulation(BlendWriter *writer, Simulation *simulation, const
 {
   if (simulation->id.us > 0 || BLO_write_is_undo(writer)) {
     BLO_write_id_struct(writer, Simulation, id_address, &simulation->id);
-    write_iddata(writer, &simulation->id);
+    BKE_id_blend_write(writer, &simulation->id);
 
     if (simulation->adt) {
       BKE_animdata_blend_write(writer, simulation->adt);
@@ -3490,7 +3434,7 @@ static void write_libraries(WriteData *wd, Main *main)
 
       BlendWriter writer = {wd};
       writestruct(wd, ID_LI, Library, 1, main->curlib);
-      write_iddata(&writer, &main->curlib->id);
+      BKE_id_blend_write(&writer, &main->curlib->id);
 
       if (main->curlib->packedfile) {
         PackedFile *pf = main->curlib->packedfile;
@@ -3782,9 +3726,6 @@ static bool write_file_handle(Main *mainvar,
           case ID_TE:
             write_texture(&writer, (Tex *)id_buffer, id);
             break;
-          case ID_ME:
-            write_mesh(&writer, (Mesh *)id_buffer, id);
-            break;
           case ID_PA:
             write_particlesettings(&writer, (ParticleSettings *)id_buffer, id);
             break;
@@ -3821,6 +3762,9 @@ static bool write_file_handle(Main *mainvar,
           case ID_SIM:
             write_simulation(&writer, (Simulation *)id_buffer, id);
             break;
+          case ID_ME:
+            /* Do nothing, handled in IDTypeInfo callback. */
+            break;
           case ID_LI:
             /* Do nothing, handled below - and should never be reached. */
             BLI_assert(0);