Cleanup/refactor: remove BKE_idcode, in favour of BKE_idtype.

Mpving utils from idcode to idtype proved to be somewhat painful for
some reasons, but now all looks good.

Had to add a fake/empty shell for the special snowflake too,
`ID_LINK_PLACEHOLDER/INDEX_ID_NULL`...

7 files changed, 368 insertions, 451 deletions

diff --git a/source/blender/blenkernel/intern/idcode.c b/source/blender/blenkernel/intern/idcode.c
deleted file mode 100644
index 454be246ad9..00000000000
--- a/source/blender/blenkernel/intern/idcode.c
+++ /dev/null
@@ -1,432 +0,0 @@
-/*
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
- *
- * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
- * All rights reserved.
- * return info about ID types
- */
-
-/** \file
- * \ingroup bke
- */
-
-#include <stdlib.h>
-#include <string.h>
-
-#include "DNA_ID.h"
-
-#include "BLI_utildefines.h"
-
-#include "BLT_translation.h"
-
-#include "BKE_idcode.h"
-#include "BKE_main.h"
-
-typedef struct {
-  unsigned short code;
-  const char *name, *plural;
-
-  const char *i18n_context;
-
-  int flags;
-#define IDTYPE_FLAGS_ISLINKABLE (1 << 0)
-} IDType;
-
-/* Keep alignment for readability. */
-/* clang-format off */
-/**
- * When editing ensure that:
- * - Plural needs to match rna_main.c's #MainCollectionDef.
- * - Keep it in sync with i18n contexts in BLT_translation.h
- */
-static IDType idtypes[] = {
-  /** ID's directly below must all be in #Main, and be kept in sync with #MAX_LIBARRAY (membership, not order) */
-  {ID_AC,   "Action",             "actions",         BLT_I18NCONTEXT_ID_ACTION,             IDTYPE_FLAGS_ISLINKABLE},
-  {ID_AR,   "Armature",           "armatures",       BLT_I18NCONTEXT_ID_ARMATURE,           IDTYPE_FLAGS_ISLINKABLE},
-  {ID_BR,   "Brush",              "brushes",         BLT_I18NCONTEXT_ID_BRUSH,              IDTYPE_FLAGS_ISLINKABLE},
-  {ID_CA,   "Camera",             "cameras",         BLT_I18NCONTEXT_ID_CAMERA,             IDTYPE_FLAGS_ISLINKABLE},
-  {ID_CF,   "CacheFile",          "cache_files",     BLT_I18NCONTEXT_ID_CACHEFILE,          IDTYPE_FLAGS_ISLINKABLE},
-  {ID_GR,   "Collection",         "collections",     BLT_I18NCONTEXT_ID_COLLECTION,         IDTYPE_FLAGS_ISLINKABLE},
-  {ID_CU,   "Curve",              "curves",          BLT_I18NCONTEXT_ID_CURVE,              IDTYPE_FLAGS_ISLINKABLE},
-  {ID_GD,   "GPencil",            "grease_pencils",  BLT_I18NCONTEXT_ID_GPENCIL,            IDTYPE_FLAGS_ISLINKABLE}, /* rename gpencil */
-	{ID_HA,   "Hair",               "hair",            BLT_I18NCONTEXT_ID_HAIR,               IDTYPE_FLAGS_ISLINKABLE},
-  {ID_IM,   "Image",              "images",          BLT_I18NCONTEXT_ID_IMAGE,              IDTYPE_FLAGS_ISLINKABLE},
-  {ID_IP,   "Ipo",                "ipos",            "",                                    IDTYPE_FLAGS_ISLINKABLE}, /* deprecated */
-  {ID_KE,   "Key",                "shape_keys",      BLT_I18NCONTEXT_ID_SHAPEKEY,           0                      },
-  {ID_LA,   "Light",              "lights",          BLT_I18NCONTEXT_ID_LIGHT,              IDTYPE_FLAGS_ISLINKABLE},
-  {ID_LI,   "Library",            "libraries",       BLT_I18NCONTEXT_ID_LIBRARY,            0                      },
-  {ID_LS,   "FreestyleLineStyle", "linestyles",      BLT_I18NCONTEXT_ID_FREESTYLELINESTYLE, IDTYPE_FLAGS_ISLINKABLE},
-  {ID_LT,   "Lattice",            "lattices",        BLT_I18NCONTEXT_ID_LATTICE,            IDTYPE_FLAGS_ISLINKABLE},
-  {ID_MA,   "Material",           "materials",       BLT_I18NCONTEXT_ID_MATERIAL,           IDTYPE_FLAGS_ISLINKABLE},
-  {ID_MB,   "Metaball",           "metaballs",       BLT_I18NCONTEXT_ID_METABALL,           IDTYPE_FLAGS_ISLINKABLE},
-  {ID_MC,   "MovieClip",          "movieclips",      BLT_I18NCONTEXT_ID_MOVIECLIP,          IDTYPE_FLAGS_ISLINKABLE},
-  {ID_ME,   "Mesh",               "meshes",          BLT_I18NCONTEXT_ID_MESH,               IDTYPE_FLAGS_ISLINKABLE},
-  {ID_MSK,  "Mask",               "masks",           BLT_I18NCONTEXT_ID_MASK,               IDTYPE_FLAGS_ISLINKABLE},
-  {ID_NT,   "NodeTree",           "node_groups",     BLT_I18NCONTEXT_ID_NODETREE,           IDTYPE_FLAGS_ISLINKABLE},
-  {ID_OB,   "Object",             "objects",         BLT_I18NCONTEXT_ID_OBJECT,             IDTYPE_FLAGS_ISLINKABLE},
-  {ID_PA,   "ParticleSettings",   "particles",       BLT_I18NCONTEXT_ID_PARTICLESETTINGS,   IDTYPE_FLAGS_ISLINKABLE},
-  {ID_PAL,  "Palettes",           "palettes",        BLT_I18NCONTEXT_ID_PALETTE,            IDTYPE_FLAGS_ISLINKABLE},
-  {ID_PC,   "PaintCurve",         "paint_curves",    BLT_I18NCONTEXT_ID_PAINTCURVE,         IDTYPE_FLAGS_ISLINKABLE},
-  {ID_LP,   "LightProbe",         "lightprobes",     BLT_I18NCONTEXT_ID_LIGHTPROBE,         IDTYPE_FLAGS_ISLINKABLE},
-	{ID_PT,   "PointCloud",         "pointclouds",     BLT_I18NCONTEXT_ID_POINTCLOUD,         IDTYPE_FLAGS_ISLINKABLE},
-  {ID_SCE,  "Scene",              "scenes",          BLT_I18NCONTEXT_ID_SCENE,              IDTYPE_FLAGS_ISLINKABLE},
-  {ID_SCR,  "Screen",             "screens",         BLT_I18NCONTEXT_ID_SCREEN,             IDTYPE_FLAGS_ISLINKABLE},
-  {ID_SEQ,  "Sequence",           "sequences",       BLT_I18NCONTEXT_ID_SEQUENCE,           0                      }, /* not actually ID data */
-  {ID_SPK,  "Speaker",            "speakers",        BLT_I18NCONTEXT_ID_SPEAKER,            IDTYPE_FLAGS_ISLINKABLE},
-  {ID_SO,   "Sound",              "sounds",          BLT_I18NCONTEXT_ID_SOUND,              IDTYPE_FLAGS_ISLINKABLE},
-  {ID_TE,   "Texture",            "textures",        BLT_I18NCONTEXT_ID_TEXTURE,            IDTYPE_FLAGS_ISLINKABLE},
-  {ID_TXT,  "Text",               "texts",           BLT_I18NCONTEXT_ID_TEXT,               IDTYPE_FLAGS_ISLINKABLE},
-  {ID_VF,   "VFont",              "fonts",           BLT_I18NCONTEXT_ID_VFONT,              IDTYPE_FLAGS_ISLINKABLE},
-	{ID_VO,   "Volume",             "volumes",         BLT_I18NCONTEXT_ID_VOLUME,             IDTYPE_FLAGS_ISLINKABLE},
-  {ID_WO,   "World",              "worlds",          BLT_I18NCONTEXT_ID_WORLD,              IDTYPE_FLAGS_ISLINKABLE},
-  {ID_WM,   "WindowManager",      "window_managers", BLT_I18NCONTEXT_ID_WINDOWMANAGER,      0                       },
-  {ID_WS,   "WorkSpace",          "workspaces",      BLT_I18NCONTEXT_ID_WORKSPACE,          IDTYPE_FLAGS_ISLINKABLE},
-
-  /** Keep last, not an ID exactly, only include for completeness */
-  {ID_LINK_PLACEHOLDER, "Link Placeholder", "link_placeholders", BLT_I18NCONTEXT_ID_ID, 0}, /* plural is fake */
-};
-/* clang-format on */
-
-/* -1 for ID_LINK_PLACEHOLDER */
-BLI_STATIC_ASSERT((ARRAY_SIZE(idtypes) - 1 == MAX_LIBARRAY), "Missing IDType");
-
-static IDType *idtype_from_name(const char *str)
-{
-  int i = ARRAY_SIZE(idtypes);
-
-  while (i--) {
-    if (STREQ(str, idtypes[i].name)) {
-      return &idtypes[i];
-    }
-  }
-
-  return NULL;
-}
-static IDType *idtype_from_code(short idcode)
-{
-  int i = ARRAY_SIZE(idtypes);
-
-  while (i--) {
-    if (idcode == idtypes[i].code) {
-      return &idtypes[i];
-    }
-  }
-
-  return NULL;
-}
-
-/**
- * Return if the ID code is a valid ID code.
- *
- * \param idcode: The code to check.
- * \return Boolean, 0 when invalid.
- */
-bool BKE_idcode_is_valid(short idcode)
-{
-  return idtype_from_code(idcode) ? true : false;
-}
-
-/**
- * Return non-zero when an ID type is linkable.
- *
- * \param idcode: The code to check.
- * \return Boolean, 0 when non linkable.
- */
-bool BKE_idcode_is_linkable(short idcode)
-{
-  IDType *idt = idtype_from_code(idcode);
-  BLI_assert(idt);
-  return idt ? ((idt->flags & IDTYPE_FLAGS_ISLINKABLE) != 0) : false;
-}
-
-/**
- * Convert an idcode into a name.
- *
- * \param idcode: The code to convert.
- * \return A static string representing the name of
- * the code.
- */
-const char *BKE_idcode_to_name(short idcode)
-{
-  IDType *idt = idtype_from_code(idcode);
-  BLI_assert(idt);
-  return idt ? idt->name : NULL;
-}
-
-/**
- * Convert a name into an idcode (ie. ID_SCE)
- *
- * \param name: The name to convert.
- * \return The code for the name, or 0 if invalid.
- */
-short BKE_idcode_from_name(const char *name)
-{
-  IDType *idt = idtype_from_name(name);
-  BLI_assert(idt);
-  return idt ? idt->code : 0;
-}
-
-/**
- * Convert an idcode into an idfilter (e.g. ID_OB -> FILTER_ID_OB).
- */
-uint64_t BKE_idcode_to_idfilter(const short idcode)
-{
-#define CASE_IDFILTER(_id) \
-  case ID_##_id: \
-    return FILTER_ID_##_id
-
-  switch (idcode) {
-    CASE_IDFILTER(AC);
-    CASE_IDFILTER(AR);
-    CASE_IDFILTER(BR);
-    CASE_IDFILTER(CA);
-    CASE_IDFILTER(CF);
-    CASE_IDFILTER(CU);
-    CASE_IDFILTER(GD);
-    CASE_IDFILTER(GR);
-    CASE_IDFILTER(IM);
-    CASE_IDFILTER(LA);
-    CASE_IDFILTER(LS);
-    CASE_IDFILTER(LT);
-    CASE_IDFILTER(MA);
-    CASE_IDFILTER(MB);
-    CASE_IDFILTER(MC);
-    CASE_IDFILTER(ME);
-    CASE_IDFILTER(MSK);
-    CASE_IDFILTER(NT);
-    CASE_IDFILTER(OB);
-    CASE_IDFILTER(PA);
-    CASE_IDFILTER(PAL);
-    CASE_IDFILTER(PC);
-    CASE_IDFILTER(LP);
-    CASE_IDFILTER(SCE);
-    CASE_IDFILTER(SPK);
-    CASE_IDFILTER(SO);
-    CASE_IDFILTER(TE);
-    CASE_IDFILTER(TXT);
-    CASE_IDFILTER(VF);
-    CASE_IDFILTER(HA);
-    CASE_IDFILTER(PT);
-    CASE_IDFILTER(VO);
-    CASE_IDFILTER(WO);
-    CASE_IDFILTER(WS);
-    default:
-      return 0;
-  }
-
-#undef CASE_IDFILTER
-}
-
-/**
- * Convert an idfilter into an idcode (e.g. FILTER_ID_OB -> ID_OB).
- */
-short BKE_idcode_from_idfilter(const uint64_t idfilter)
-{
-#define CASE_IDFILTER(_id) \
-  case FILTER_ID_##_id: \
-    return ID_##_id
-
-  switch (idfilter) {
-    CASE_IDFILTER(AC);
-    CASE_IDFILTER(AR);
-    CASE_IDFILTER(BR);
-    CASE_IDFILTER(CA);
-    CASE_IDFILTER(CF);
-    CASE_IDFILTER(CU);
-    CASE_IDFILTER(GD);
-    CASE_IDFILTER(GR);
-    CASE_IDFILTER(HA);
-    CASE_IDFILTER(IM);
-    CASE_IDFILTER(LA);
-    CASE_IDFILTER(LP);
-    CASE_IDFILTER(LS);
-    CASE_IDFILTER(LT);
-    CASE_IDFILTER(MA);
-    CASE_IDFILTER(MB);
-    CASE_IDFILTER(MC);
-    CASE_IDFILTER(ME);
-    CASE_IDFILTER(MSK);
-    CASE_IDFILTER(NT);
-    CASE_IDFILTER(OB);
-    CASE_IDFILTER(PA);
-    CASE_IDFILTER(PAL);
-    CASE_IDFILTER(PC);
-    CASE_IDFILTER(PT);
-    CASE_IDFILTER(SCE);
-    CASE_IDFILTER(SPK);
-    CASE_IDFILTER(SO);
-    CASE_IDFILTER(TE);
-    CASE_IDFILTER(TXT);
-    CASE_IDFILTER(VF);
-    CASE_IDFILTER(VO);
-    CASE_IDFILTER(WO);
-    default:
-      return 0;
-  }
-
-#undef CASE_IDFILTER
-}
-
-/**
- * Convert an idcode into an index (e.g. ID_OB -> INDEX_ID_OB).
- */
-int BKE_idcode_to_index(const short idcode)
-{
-#define CASE_IDINDEX(_id) \
-  case ID_##_id: \
-    return INDEX_ID_##_id
-
-  switch ((ID_Type)idcode) {
-    CASE_IDINDEX(AC);
-    CASE_IDINDEX(AR);
-    CASE_IDINDEX(BR);
-    CASE_IDINDEX(CA);
-    CASE_IDINDEX(CF);
-    CASE_IDINDEX(CU);
-    CASE_IDINDEX(GD);
-    CASE_IDINDEX(GR);
-    CASE_IDINDEX(HA);
-    CASE_IDINDEX(IM);
-    CASE_IDINDEX(KE);
-    CASE_IDINDEX(IP);
-    CASE_IDINDEX(LA);
-    CASE_IDINDEX(LI);
-    CASE_IDINDEX(LP);
-    CASE_IDINDEX(LS);
-    CASE_IDINDEX(LT);
-    CASE_IDINDEX(MA);
-    CASE_IDINDEX(MB);
-    CASE_IDINDEX(MC);
-    CASE_IDINDEX(ME);
-    CASE_IDINDEX(MSK);
-    CASE_IDINDEX(NT);
-    CASE_IDINDEX(OB);
-    CASE_IDINDEX(PA);
-    CASE_IDINDEX(PAL);
-    CASE_IDINDEX(PC);
-    CASE_IDINDEX(PT);
-    CASE_IDINDEX(SCE);
-    CASE_IDINDEX(SCR);
-    CASE_IDINDEX(SPK);
-    CASE_IDINDEX(SO);
-    CASE_IDINDEX(TE);
-    CASE_IDINDEX(TXT);
-    CASE_IDINDEX(VF);
-    CASE_IDINDEX(VO);
-    CASE_IDINDEX(WM);
-    CASE_IDINDEX(WO);
-    CASE_IDINDEX(WS);
-  }
-
-  BLI_assert(0);
-  return -1;
-
-#undef CASE_IDINDEX
-}
-
-/**
- * Get an idcode from an index (e.g. INDEX_ID_OB -> ID_OB).
- */
-short BKE_idcode_from_index(const int index)
-{
-#define CASE_IDCODE(_id) \
-  case INDEX_ID_##_id: \
-    return ID_##_id
-
-  switch (index) {
-    CASE_IDCODE(AC);
-    CASE_IDCODE(AR);
-    CASE_IDCODE(BR);
-    CASE_IDCODE(CA);
-    CASE_IDCODE(CF);
-    CASE_IDCODE(CU);
-    CASE_IDCODE(GD);
-    CASE_IDCODE(GR);
-    CASE_IDCODE(HA);
-    CASE_IDCODE(IM);
-    CASE_IDCODE(KE);
-    CASE_IDCODE(IP);
-    CASE_IDCODE(LA);
-    CASE_IDCODE(LI);
-    CASE_IDCODE(LP);
-    CASE_IDCODE(LS);
-    CASE_IDCODE(LT);
-    CASE_IDCODE(MA);
-    CASE_IDCODE(MB);
-    CASE_IDCODE(MC);
-    CASE_IDCODE(ME);
-    CASE_IDCODE(MSK);
-    CASE_IDCODE(NT);
-    CASE_IDCODE(OB);
-    CASE_IDCODE(PA);
-    CASE_IDCODE(PAL);
-    CASE_IDCODE(PC);
-    CASE_IDCODE(PT);
-    CASE_IDCODE(SCE);
-    CASE_IDCODE(SCR);
-    CASE_IDCODE(SPK);
-    CASE_IDCODE(SO);
-    CASE_IDCODE(TE);
-    CASE_IDCODE(TXT);
-    CASE_IDCODE(VF);
-    CASE_IDCODE(VO);
-    CASE_IDCODE(WM);
-    CASE_IDCODE(WO);
-    CASE_IDCODE(WS);
-  }
-
-  BLI_assert(0);
-  return -1;
-
-#undef CASE_IDCODE
-}
-
-/**
- * Convert an idcode into a name (plural).
- *
- * \param idcode: The code to convert.
- * \return A static string representing the name of
- * the code.
- */
-const char *BKE_idcode_to_name_plural(short idcode)
-{
-  IDType *idt = idtype_from_code(idcode);
-  BLI_assert(idt);
-  return idt ? idt->plural : NULL;
-}
-
-/**
- * Convert an idcode into its translations' context.
- *
- * \param idcode: The code to convert.
- * \return A static string representing the i18n context of the code.
- */
-const char *BKE_idcode_to_translation_context(short idcode)
-{
-  IDType *idt = idtype_from_code(idcode);
-  BLI_assert(idt);
-  return idt ? idt->i18n_context : BLT_I18NCONTEXT_DEFAULT;
-}
-
-/**
- * Return an ID code and steps the index forward 1.
- *
- * \param index: start as 0.
- * \return the code, 0 when all codes have been returned.
- */
-short BKE_idcode_iter_step(int *index)
-{
-  return (*index < ARRAY_SIZE(idtypes)) ? idtypes[(*index)++].code : 0;
-}
diff --git a/source/blender/blenkernel/intern/idprop_utils.c b/source/blender/blenkernel/intern/idprop_utils.c
index c966838171d..a7dd6afd10d 100644
--- a/source/blender/blenkernel/intern/idprop_utils.c
+++ b/source/blender/blenkernel/intern/idprop_utils.c
@@ -25,8 +25,8 @@
 #include "BLI_string.h"
 #include "BLI_utildefines.h"
 
-#include "BKE_idcode.h"
 #include "BKE_idprop.h"
+#include "BKE_idtype.h"
 
 #include "MEM_guardedalloc.h"
 
@@ -181,7 +181,7 @@ static void idp_repr_fn_recursive(struct ReprState *state, const IDProperty *pro
       const ID *id = prop->data.pointer;
       if (id != NULL) {
         STR_APPEND_STR("bpy.data.");
-        STR_APPEND_STR(BKE_idcode_to_name_plural(GS(id->name)));
+        STR_APPEND_STR(BKE_idtype_idcode_to_name_plural(GS(id->name)));
         STR_APPEND_STR("[");
         STR_APPEND_STR_QUOTE(id->name + 2);
         STR_APPEND_STR("]");
diff --git a/source/blender/blenkernel/intern/idtype.c b/source/blender/blenkernel/intern/idtype.c
index ce2835717a0..5ec5dc4b4cd 100644
--- a/source/blender/blenkernel/intern/idtype.c
+++ b/source/blender/blenkernel/intern/idtype.c
@@ -24,6 +24,8 @@
  * \ingroup bke
  */
 
+#include <string.h>
+
 #include "MEM_guardedalloc.h"
 
 #include "BLI_utildefines.h"
@@ -34,13 +36,13 @@
 
 #include "DNA_ID.h"
 
-#include "BKE_idcode.h"
+#include "BKE_main.h"
 
 #include "BKE_idtype.h"
 
 // static CLG_LogRef LOG = {"bke.idtype"};
 
-static IDTypeInfo *id_types[INDEX_ID_MAX] = {NULL};
+static IDTypeInfo *id_types[MAX_LIBARRAY] = {NULL};
 
 static void id_type_init(void)
 {
@@ -91,6 +93,10 @@ static void id_type_init(void)
   INIT_TYPE(ID_PT);
   INIT_TYPE(ID_VO);
 
+  /* Special naughty boy... */
+  BLI_assert(IDType_ID_LINK_PLACEHOLDER.main_listbase_index == INDEX_ID_NULL);
+  id_types[INDEX_ID_NULL] = &IDType_ID_LINK_PLACEHOLDER;
+
 #undef INIT_TYPE
 }
 
@@ -102,9 +108,9 @@ void BKE_idtype_init(void)
 
 const IDTypeInfo *BKE_idtype_get_info_from_idcode(const short id_code)
 {
-  int id_index = BKE_idcode_to_index(id_code);
+  int id_index = BKE_idtype_idcode_to_index(id_code);
 
-  if (id_index >= 0 && id_index < INDEX_ID_MAX && id_types[id_index] != NULL &&
+  if (id_index >= 0 && id_index < ARRAY_SIZE(id_types) && id_types[id_index] != NULL &&
       id_types[id_index]->name[0] != '\0') {
     return id_types[id_index];
   }
@@ -117,3 +123,329 @@ const IDTypeInfo *BKE_idtype_get_info_from_id(const ID *id)
 {
   return BKE_idtype_get_info_from_idcode(GS(id->name));
 }
+
+static const IDTypeInfo *idtype_get_info_from_name(const char *str)
+{
+  for (int i = ARRAY_SIZE(id_types); i--;) {
+    if (id_types[i] != NULL && STREQ(str, id_types[i]->name)) {
+      return id_types[i];
+    }
+  }
+
+  return NULL;
+}
+
+/* Various helpers/wrappers around IDTypeInfo structure. */
+
+/**
+ * Convert an idcode into a name.
+ *
+ * \param idcode: The code to convert.
+ * \return A static string representing the name of
+ * the code.
+ */
+const char *BKE_idtype_idcode_to_name(const short idcode)
+{
+  const IDTypeInfo *id_type = BKE_idtype_get_info_from_idcode(idcode);
+  BLI_assert(id_type != NULL);
+  return id_type != NULL ? id_type->name : NULL;
+}
+
+/**
+ * Convert an idcode into a name (plural).
+ *
+ * \param idcode: The code to convert.
+ * \return A static string representing the name of
+ * the code.
+ */
+const char *BKE_idtype_idcode_to_name_plural(const short idcode)
+{
+  const IDTypeInfo *id_type = BKE_idtype_get_info_from_idcode(idcode);
+  BLI_assert(id_type != NULL);
+  return id_type != NULL ? id_type->name_plural : NULL;
+}
+
+/**
+ * Convert an idcode into its translations' context.
+ *
+ * \param idcode: The code to convert.
+ * \return A static string representing the i18n context of the code.
+ */
+const char *BKE_idtype_idcode_to_translation_context(const short idcode)
+{
+  const IDTypeInfo *id_type = BKE_idtype_get_info_from_idcode(idcode);
+  BLI_assert(id_type != NULL);
+  return id_type != NULL ? id_type->translation_context : BLT_I18NCONTEXT_DEFAULT;
+}
+
+/**
+ * Convert a name into an idcode (ie. ID_SCE)
+ *
+ * \param name: The name to convert.
+ * \return The code for the name, or 0 if invalid.
+ */
+short BKE_idtype_idcode_from_name(const char *name)
+{
+  const IDTypeInfo *id_type = idtype_get_info_from_name(name);
+  BLI_assert(id_type);
+  return id_type != NULL ? id_type->id_code : 0;
+}
+
+/**
+ * Return if the ID code is a valid ID code.
+ *
+ * \param idcode: The code to check.
+ * \return Boolean, 0 when invalid.
+ */
+bool BKE_idtype_idcode_is_valid(const short idcode)
+{
+  return BKE_idtype_get_info_from_idcode(idcode) != NULL ? true : false;
+}
+
+/**
+ * Return non-zero when an ID type is linkable.
+ *
+ * \param idcode: The code to check.
+ * \return Boolean, 0 when non linkable.
+ */
+bool BKE_idtype_idcode_is_linkable(const short idcode)
+{
+  const IDTypeInfo *id_type = BKE_idtype_get_info_from_idcode(idcode);
+  BLI_assert(id_type != NULL);
+  return id_type != NULL ? (id_type->flags & IDTYPE_FLAGS_NO_LIBLINKING) == 0 : false;
+}
+
+/**
+ * Convert an idcode into an idfilter (e.g. ID_OB -> FILTER_ID_OB).
+ */
+uint64_t BKE_idtype_idcode_to_idfilter(const short idcode)
+{
+#define CASE_IDFILTER(_id) \
+  case ID_##_id: \
+    return FILTER_ID_##_id
+
+  switch (idcode) {
+    CASE_IDFILTER(AC);
+    CASE_IDFILTER(AR);
+    CASE_IDFILTER(BR);
+    CASE_IDFILTER(CA);
+    CASE_IDFILTER(CF);
+    CASE_IDFILTER(CU);
+    CASE_IDFILTER(GD);
+    CASE_IDFILTER(GR);
+    CASE_IDFILTER(HA);
+    CASE_IDFILTER(IM);
+    CASE_IDFILTER(LA);
+    CASE_IDFILTER(LS);
+    CASE_IDFILTER(LT);
+    CASE_IDFILTER(MA);
+    CASE_IDFILTER(MB);
+    CASE_IDFILTER(MC);
+    CASE_IDFILTER(ME);
+    CASE_IDFILTER(MSK);
+    CASE_IDFILTER(NT);
+    CASE_IDFILTER(OB);
+    CASE_IDFILTER(PA);
+    CASE_IDFILTER(PAL);
+    CASE_IDFILTER(PC);
+    CASE_IDFILTER(PT);
+    CASE_IDFILTER(LP);
+    CASE_IDFILTER(SCE);
+    CASE_IDFILTER(SPK);
+    CASE_IDFILTER(SO);
+    CASE_IDFILTER(TE);
+    CASE_IDFILTER(TXT);
+    CASE_IDFILTER(VF);
+    CASE_IDFILTER(VO);
+    CASE_IDFILTER(WO);
+    CASE_IDFILTER(WS);
+    default:
+      return 0;
+  }
+
+#undef CASE_IDFILTER
+}
+
+/**
+ * Convert an idfilter into an idcode (e.g. FILTER_ID_OB -> ID_OB).
+ */
+short BKE_idtype_idcode_from_idfilter(const uint64_t idfilter)
+{
+#define CASE_IDFILTER(_id) \
+  case FILTER_ID_##_id: \
+    return ID_##_id
+
+  switch (idfilter) {
+    CASE_IDFILTER(AC);
+    CASE_IDFILTER(AR);
+    CASE_IDFILTER(BR);
+    CASE_IDFILTER(CA);
+    CASE_IDFILTER(CF);
+    CASE_IDFILTER(CU);
+    CASE_IDFILTER(GD);
+    CASE_IDFILTER(GR);
+    CASE_IDFILTER(HA);
+    CASE_IDFILTER(IM);
+    CASE_IDFILTER(LA);
+    CASE_IDFILTER(LS);
+    CASE_IDFILTER(LT);
+    CASE_IDFILTER(MA);
+    CASE_IDFILTER(MB);
+    CASE_IDFILTER(MC);
+    CASE_IDFILTER(ME);
+    CASE_IDFILTER(MSK);
+    CASE_IDFILTER(NT);
+    CASE_IDFILTER(OB);
+    CASE_IDFILTER(PA);
+    CASE_IDFILTER(PAL);
+    CASE_IDFILTER(PC);
+    CASE_IDFILTER(PT);
+    CASE_IDFILTER(LP);
+    CASE_IDFILTER(SCE);
+    CASE_IDFILTER(SPK);
+    CASE_IDFILTER(SO);
+    CASE_IDFILTER(TE);
+    CASE_IDFILTER(TXT);
+    CASE_IDFILTER(VF);
+    CASE_IDFILTER(VO);
+    CASE_IDFILTER(WO);
+    default:
+      return 0;
+  }
+
+#undef CASE_IDFILTER
+}
+
+/**
+ * Convert an idcode into an index (e.g. ID_OB -> INDEX_ID_OB).
+ */
+int BKE_idtype_idcode_to_index(const short idcode)
+{
+#define CASE_IDINDEX(_id) \
+  case ID_##_id: \
+    return INDEX_ID_##_id
+
+  switch ((ID_Type)idcode) {
+    CASE_IDINDEX(AC);
+    CASE_IDINDEX(AR);
+    CASE_IDINDEX(BR);
+    CASE_IDINDEX(CA);
+    CASE_IDINDEX(CF);
+    CASE_IDINDEX(CU);
+    CASE_IDINDEX(GD);
+    CASE_IDINDEX(GR);
+    CASE_IDINDEX(HA);
+    CASE_IDINDEX(IM);
+    CASE_IDINDEX(IP);
+    CASE_IDINDEX(KE);
+    CASE_IDINDEX(LA);
+    CASE_IDINDEX(LI);
+    CASE_IDINDEX(LS);
+    CASE_IDINDEX(LT);
+    CASE_IDINDEX(MA);
+    CASE_IDINDEX(MB);
+    CASE_IDINDEX(MC);
+    CASE_IDINDEX(ME);
+    CASE_IDINDEX(MSK);
+    CASE_IDINDEX(NT);
+    CASE_IDINDEX(OB);
+    CASE_IDINDEX(PA);
+    CASE_IDINDEX(PAL);
+    CASE_IDINDEX(PC);
+    CASE_IDINDEX(PT);
+    CASE_IDINDEX(LP);
+    CASE_IDINDEX(SCE);
+    CASE_IDINDEX(SCR);
+    CASE_IDINDEX(SPK);
+    CASE_IDINDEX(SO);
+    CASE_IDINDEX(TE);
+    CASE_IDINDEX(TXT);
+    CASE_IDINDEX(VF);
+    CASE_IDINDEX(VO);
+    CASE_IDINDEX(WM);
+    CASE_IDINDEX(WO);
+    CASE_IDINDEX(WS);
+  }
+
+  /* Special naughty boy... */
+  if (idcode == ID_LINK_PLACEHOLDER) {
+    return INDEX_ID_NULL;
+  }
+
+  return -1;
+
+#undef CASE_IDINDEX
+}
+
+/**
+ * Get an idcode from an index (e.g. INDEX_ID_OB -> ID_OB).
+ */
+short BKE_idtype_idcode_from_index(const int index)
+{
+#define CASE_IDCODE(_id) \
+  case INDEX_ID_##_id: \
+    return ID_##_id
+
+  switch (index) {
+    CASE_IDCODE(AC);
+    CASE_IDCODE(AR);
+    CASE_IDCODE(BR);
+    CASE_IDCODE(CA);
+    CASE_IDCODE(CF);
+    CASE_IDCODE(CU);
+    CASE_IDCODE(GD);
+    CASE_IDCODE(GR);
+    CASE_IDCODE(HA);
+    CASE_IDCODE(IM);
+    CASE_IDCODE(IP);
+    CASE_IDCODE(KE);
+    CASE_IDCODE(LA);
+    CASE_IDCODE(LI);
+    CASE_IDCODE(LS);
+    CASE_IDCODE(LT);
+    CASE_IDCODE(MA);
+    CASE_IDCODE(MB);
+    CASE_IDCODE(MC);
+    CASE_IDCODE(ME);
+    CASE_IDCODE(MSK);
+    CASE_IDCODE(NT);
+    CASE_IDCODE(OB);
+    CASE_IDCODE(PA);
+    CASE_IDCODE(PAL);
+    CASE_IDCODE(PC);
+    CASE_IDCODE(PT);
+    CASE_IDCODE(LP);
+    CASE_IDCODE(SCE);
+    CASE_IDCODE(SCR);
+    CASE_IDCODE(SPK);
+    CASE_IDCODE(SO);
+    CASE_IDCODE(TE);
+    CASE_IDCODE(TXT);
+    CASE_IDCODE(VF);
+    CASE_IDCODE(VO);
+    CASE_IDCODE(WM);
+    CASE_IDCODE(WO);
+    CASE_IDCODE(WS);
+  }
+
+  /* Special naughty boy... */
+  if (index == INDEX_ID_NULL) {
+    return ID_LINK_PLACEHOLDER;
+  }
+
+  return -1;
+
+#undef CASE_IDCODE
+}
+
+/**
+ * Return an ID code and steps the index forward 1.
+ *
+ * \param index: start as 0.
+ * \return the code, 0 when all codes have been returned.
+ */
+short BKE_idtype_idcode_iter_step(int *index)
+{
+  printf("%d: %d\n", *index, BKE_idtype_idcode_from_index((*index)));
+  return (*index < ARRAY_SIZE(id_types)) ? BKE_idtype_idcode_from_index((*index)++) : 0;
+}
diff --git a/source/blender/blenkernel/intern/lib_id.c b/source/blender/blenkernel/intern/lib_id.c
index 3e779c92a4a..a9a2ad31ee0 100644
--- a/source/blender/blenkernel/intern/lib_id.c
+++ b/source/blender/blenkernel/intern/lib_id.c
@@ -93,7 +93,6 @@
 #include "BKE_global.h"
 #include "BKE_gpencil.h"
 #include "BKE_hair.h"
-#include "BKE_idcode.h"
 #include "BKE_idprop.h"
 #include "BKE_idtype.h"
 #include "BKE_image.h"
@@ -139,6 +138,23 @@
 
 static CLG_LogRef LOG = {.identifier = "bke.lib_id"};
 
+/* Empty shell mostly, but needed for read code. */
+IDTypeInfo IDType_ID_LINK_PLACEHOLDER = {
+    .id_code = ID_LINK_PLACEHOLDER,
+    .id_filter = 0,
+    .main_listbase_index = INDEX_ID_NULL,
+    .struct_size = sizeof(ID),
+    .name = "LinkPlaceholder",
+    .name_plural = "link_placeholders",
+    .translation_context = BLT_I18NCONTEXT_ID_ID,
+    .flags = IDTYPE_FLAGS_NO_COPY | IDTYPE_FLAGS_NO_LIBLINKING | IDTYPE_FLAGS_NO_MAKELOCAL,
+
+    .init_data = NULL,
+    .copy_data = NULL,
+    .free_data = NULL,
+    .make_local = NULL,
+};
+
 /* GS reads the memory pointed at in a specific ordering.
  * only use this definition, makes little and big endian systems
  * work fine, in conjunction with MAKE_ID */
@@ -204,7 +220,7 @@ void BKE_lib_id_clear_library_data(Main *bmain, ID *id)
 void id_lib_extern(ID *id)
 {
   if (id && ID_IS_LINKED(id)) {
-    BLI_assert(BKE_idcode_is_linkable(GS(id->name)));
+    BLI_assert(BKE_idtype_idcode_is_linkable(GS(id->name)));
     if (id->tag & LIB_TAG_INDIRECT) {
       id->tag &= ~LIB_TAG_INDIRECT;
       id->flag &= ~LIB_INDIRECT_WEAK_LINK;
@@ -217,7 +233,7 @@ void id_lib_extern(ID *id)
 void id_lib_indirect_weak_link(ID *id)
 {
   if (id && ID_IS_LINKED(id)) {
-    BLI_assert(BKE_idcode_is_linkable(GS(id->name)));
+    BLI_assert(BKE_idtype_idcode_is_linkable(GS(id->name)));
     if (id->tag & LIB_TAG_INDIRECT) {
       id->flag |= LIB_INDIRECT_WEAK_LINK;
     }
@@ -355,7 +371,8 @@ static int lib_id_expand_local_cb(LibraryIDLinkCallbackData *cb_data)
    * (through drivers)...
    * Just skip it, shape key can only be either indirectly linked, or fully local, period.
    * And let's curse one more time that stupid useless shapekey ID type! */
-  if (*id_pointer && *id_pointer != id_self && BKE_idcode_is_linkable(GS((*id_pointer)->name))) {
+  if (*id_pointer && *id_pointer != id_self &&
+      BKE_idtype_idcode_is_linkable(GS((*id_pointer)->name))) {
     id_lib_extern(*id_pointer);
   }
 
@@ -1154,7 +1171,7 @@ void *BKE_id_new(Main *bmain, const short type, const char *name)
   BLI_assert(bmain != NULL);
 
   if (name == NULL) {
-    name = DATA_(BKE_idcode_to_name(type));
+    name = DATA_(BKE_idtype_idcode_to_name(type));
   }
 
   ID *id = BKE_libblock_alloc(bmain, type, name, 0);
@@ -1171,7 +1188,7 @@ void *BKE_id_new(Main *bmain, const short type, const char *name)
 void *BKE_id_new_nomain(const short type, const char *name)
 {
   if (name == NULL) {
-    name = DATA_(BKE_idcode_to_name(type));
+    name = DATA_(BKE_idtype_idcode_to_name(type));
   }
 
   ID *id = BKE_libblock_alloc(NULL,
@@ -1670,7 +1687,7 @@ bool BKE_id_new_name_validate(ListBase *lb, ID *id, const char *tname)
 
   if (name[0] == '\0') {
     /* Disallow empty names. */
-    BLI_strncpy(name, DATA_(BKE_idcode_to_name(GS(id->name))), sizeof(name));
+    BLI_strncpy(name, DATA_(BKE_idtype_idcode_to_name(GS(id->name))), sizeof(name));
   }
   else {
     /* disallow non utf8 chars,
@@ -1875,7 +1892,7 @@ void BKE_library_make_local(Main *bmain,
 
     /* Do not explicitly make local non-linkable IDs (shapekeys, in fact),
      * they are assumed to be handled by real data-blocks responsible of them. */
-    const bool do_skip = (id && !BKE_idcode_is_linkable(GS(id->name)));
+    const bool do_skip = (id && !BKE_idtype_idcode_is_linkable(GS(id->name)));
 
     for (; id; id = id->next) {
       ID *ntree = (ID *)ntreeFromID(id);
diff --git a/source/blender/blenkernel/intern/main_idmap.c b/source/blender/blenkernel/intern/main_idmap.c
index 0936e1f399f..d5499374e06 100644
--- a/source/blender/blenkernel/intern/main_idmap.c
+++ b/source/blender/blenkernel/intern/main_idmap.c
@@ -25,7 +25,7 @@
 
 #include "DNA_ID.h"
 
-#include "BKE_idcode.h"
+#include "BKE_idtype.h"
 #include "BKE_lib_id.h"
 #include "BKE_main.h"
 #include "BKE_main_idmap.h" /* own include */
@@ -110,7 +110,7 @@ struct IDNameLib_Map *BKE_main_idmap_create(struct Main *bmain,
   while (index < MAX_LIBARRAY) {
     struct IDNameLib_TypeMap *type_map = &id_map->type_maps[index];
     type_map->map = NULL;
-    type_map->id_type = BKE_idcode_iter_step(&index);
+    type_map->id_type = BKE_idtype_idcode_iter_step(&index);
     BLI_assert(type_map->id_type != 0);
   }
   BLI_assert(index == MAX_LIBARRAY);
diff --git a/source/blender/blenkernel/intern/mesh.c b/source/blender/blenkernel/intern/mesh.c
index 600f6b8a3ec..a59337bc4a2 100644
--- a/source/blender/blenkernel/intern/mesh.c
+++ b/source/blender/blenkernel/intern/mesh.c
@@ -44,7 +44,6 @@
 #include "BKE_animsys.h"
 #include "BKE_editmesh.h"
 #include "BKE_global.h"
-#include "BKE_idcode.h"
 #include "BKE_idtype.h"
 #include "BKE_key.h"
 #include "BKE_lib_id.h"
@@ -672,7 +671,8 @@ static void mesh_ensure_cdlayers_primary(Mesh *mesh, bool do_tessface)
 Mesh *BKE_mesh_new_nomain(
     int verts_len, int edges_len, int tessface_len, int loops_len, int polys_len)
 {
-  Mesh *mesh = BKE_libblock_alloc(NULL, ID_ME, BKE_idcode_to_name(ID_ME), LIB_ID_COPY_LOCALIZE);
+  Mesh *mesh = BKE_libblock_alloc(
+      NULL, ID_ME, BKE_idtype_idcode_to_name(ID_ME), LIB_ID_COPY_LOCALIZE);
   BKE_libblock_init_empty(&mesh->id);
 
   /* don't use CustomData_reset(...); because we dont want to touch customdata */
diff --git a/source/blender/blenkernel/intern/modifier.c b/source/blender/blenkernel/intern/modifier.c
index 92cfc90ec3d..43e246bb342 100644
--- a/source/blender/blenkernel/intern/modifier.c
+++ b/source/blender/blenkernel/intern/modifier.c
@@ -51,7 +51,7 @@
 #include "BKE_appdir.h"
 #include "BKE_editmesh.h"
 #include "BKE_global.h"
-#include "BKE_idcode.h"
+#include "BKE_idtype.h"
 #include "BKE_key.h"
 #include "BKE_lib_id.h"
 #include "BKE_lib_query.h"