IDTypeInfo: add .blend file io callbacks

This is part of T76372.
It adds the `blend_write`, `blend_read_data`, `blend_read_lib`
and `blend_read_expand` which correspond to the various
steps when reading and writing .blend files.
Having these callbacks allows us to decentralize the blenloader
code a lot more. This has the affect that code related to any
specific ID type is less scattered.

Reviewers: mont29

Differential Revision: https://developer.blender.org/D8670

source/blender/blenkernel/BKE_idtype.h

@@ -34,6 +34,10 @@ extern "C" {
 struct ID;
 struct LibraryForeachIDData;
 struct Main;
+struct BlendWriter;
+struct BlendDataReader;
+struct BlendLibReader;
+struct BlendExpander;
 
 /** IDTypeInfo.flags. */
 enum {
@@ -89,6 +93,13 @@ typedef void (*IDTypeForeachCacheFunction)(struct ID *id,
                                            IDTypeForeachCacheFunctionCallback function_callback,
                                            void *user_data);
 
+typedef void (*IDTypeBlendWriteFunction)(struct BlendWriter *writer,
+                                         struct ID *id,
+                                         const void *id_address);
+typedef void (*IDTypeBlendReadDataFunction)(struct BlendDataReader *reader, struct ID *id);
+typedef void (*IDTypeBlendReadLibFunction)(struct BlendLibReader *reader, struct ID *id);
+typedef void (*IDTypeBlendReadExpandFunction)(struct BlendExpander *expander, struct ID *id);
+
 typedef struct IDTypeInfo {
   /* ********** General IDType data. ********** */
 
@@ -161,6 +172,26 @@ typedef struct IDTypeInfo {
    * Iterator over all cache pointers of given ID.
    */
   IDTypeForeachCacheFunction foreach_cache;
+
+  /**
+   * Write all structs that should be saved in a .blend file.
+   */
+  IDTypeBlendWriteFunction blend_write;
+
+  /**
+   * Update pointers for all structs directly owned by this data block.
+   */
+  IDTypeBlendReadDataFunction blend_read_data;
+
+  /**
+   * Update pointers to other id data blocks.
+   */
+  IDTypeBlendReadLibFunction blend_read_lib;
+
+  /**
+   * Specify which other id data blocks should be loaded when the current one is loaded.
+   */
+  IDTypeBlendReadExpandFunction blend_read_expand;
 } IDTypeInfo;
 
 /* ********** Declaration of each IDTypeInfo. ********** */

source/blender/blenkernel/intern/action.c

@@ -184,6 +184,12 @@ IDTypeInfo IDType_ID_AC = {
     .free_data = action_free_data,
     .make_local = NULL,
     .foreach_id = action_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /* ***************** Library data level operations on action ************** */

source/blender/blenkernel/intern/armature.c

@@ -180,6 +180,12 @@ IDTypeInfo IDType_ID_AR = {
     .free_data = armature_free_data,
     .make_local = NULL,
     .foreach_id = armature_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /** \} */

source/blender/blenkernel/intern/brush.c

@@ -210,6 +210,12 @@ IDTypeInfo IDType_ID_BR = {
     .free_data = brush_free_data,
     .make_local = brush_make_local,
     .foreach_id = brush_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 static RNG *brush_rng;

source/blender/blenkernel/intern/cachefile.c

@@ -100,6 +100,12 @@ IDTypeInfo IDType_ID_CF = {
     .free_data = cache_file_free_data,
     .make_local = NULL,
     .foreach_id = NULL,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /* TODO: make this per cache file to avoid global locks. */

source/blender/blenkernel/intern/camera.c

@@ -128,6 +128,12 @@ IDTypeInfo IDType_ID_CA = {
     .free_data = camera_free_data,
     .make_local = camera_make_local,
     .foreach_id = camera_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /** \} */

source/blender/blenkernel/intern/collection.c

@@ -173,6 +173,12 @@ IDTypeInfo IDType_ID_GR = {
     .free_data = collection_free_data,
     .make_local = NULL,
     .foreach_id = collection_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /** \} */

source/blender/blenkernel/intern/curve.c

@@ -146,6 +146,12 @@ IDTypeInfo IDType_ID_CU = {
     .free_data = curve_free_data,
     .make_local = NULL,
     .foreach_id = curve_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 static int cu_isectLL(const float v1[3],

source/blender/blenkernel/intern/font.c

@@ -135,6 +135,12 @@ IDTypeInfo IDType_ID_VF = {
     .free_data = vfont_free_data,
     .make_local = NULL,
     .foreach_id = NULL,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /***************************** VFont *******************************/

source/blender/blenkernel/intern/gpencil.c

@@ -126,6 +126,12 @@ IDTypeInfo IDType_ID_GD = {
     .free_data = greasepencil_free_data,
     .make_local = NULL,
     .foreach_id = greasepencil_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /* ************************************************** */

source/blender/blenkernel/intern/hair.c

@@ -119,6 +119,12 @@ IDTypeInfo IDType_ID_HA = {
     .free_data = hair_free_data,
     .make_local = NULL,
     .foreach_id = hair_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 static void hair_random(Hair *hair)

source/blender/blenkernel/intern/image.c

@@ -232,6 +232,11 @@ IDTypeInfo IDType_ID_IM = {
     .make_local = NULL,
     .foreach_id = NULL,
     .foreach_cache = image_foreach_cache,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /* prototypes */

source/blender/blenkernel/intern/ipo.c

@@ -124,6 +124,12 @@ IDTypeInfo IDType_ID_IP = {
     .free_data = ipo_free_data,
     .make_local = NULL,
     .foreach_id = NULL,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /* *************************************************** */

source/blender/blenkernel/intern/key.c

@@ -113,6 +113,12 @@ IDTypeInfo IDType_ID_KE = {
     .free_data = shapekey_free_data,
     .make_local = NULL,
     .foreach_id = shapekey_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 #define KEY_MODE_DUMMY 0 /* use where mode isn't checked for */

source/blender/blenkernel/intern/lattice.c

@@ -139,6 +139,12 @@ IDTypeInfo IDType_ID_LT = {
     .free_data = lattice_free_data,
     .make_local = NULL,
     .foreach_id = lattice_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 int BKE_lattice_index_from_uvw(Lattice *lt, const int u, const int v, const int w)

source/blender/blenkernel/intern/library.c

@@ -75,6 +75,12 @@ IDTypeInfo IDType_ID_LI = {
     .free_data = library_free_data,
     .make_local = NULL,
     .foreach_id = library_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 void BKE_library_filepath_set(Main *bmain, Library *lib, const char *filepath)

source/blender/blenkernel/intern/light.c

@@ -134,6 +134,12 @@ IDTypeInfo IDType_ID_LA = {
     .free_data = light_free_data,
     .make_local = NULL,
     .foreach_id = light_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 Light *BKE_light_add(Main *bmain, const char *name)

source/blender/blenkernel/intern/lightprobe.c

@@ -69,6 +69,12 @@ IDTypeInfo IDType_ID_LP = {
     .free_data = NULL,
     .make_local = NULL,
     .foreach_id = lightprobe_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 void BKE_lightprobe_type_set(LightProbe *probe, const short lightprobe_type)

source/blender/blenkernel/intern/linestyle.c

@@ -204,6 +204,12 @@ IDTypeInfo IDType_ID_LS = {
     .free_data = linestyle_free_data,
     .make_local = NULL,
     .foreach_id = linestyle_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 static const char *modifier_name[LS_MODIFIER_NUM] = {

source/blender/blenkernel/intern/mask.c

@@ -109,6 +109,12 @@ IDTypeInfo IDType_ID_MSK = {
     .free_data = mask_free_data,
     .make_local = NULL,
     .foreach_id = mask_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 static struct {

source/blender/blenkernel/intern/material.c

@@ -175,6 +175,12 @@ IDTypeInfo IDType_ID_MA = {
     .free_data = material_free_data,
     .make_local = NULL,
     .foreach_id = material_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 void BKE_gpencil_material_attr_init(Material *ma)

source/blender/blenkernel/intern/mball.c

@@ -125,6 +125,12 @@ IDTypeInfo IDType_ID_MB = {
     .free_data = metaball_free_data,
     .make_local = NULL,
     .foreach_id = metaball_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /* Functions */

source/blender/blenkernel/intern/mesh.c

@@ -178,6 +178,12 @@ IDTypeInfo IDType_ID_ME = {
     .free_data = mesh_free_data,
     .make_local = NULL,
     .foreach_id = mesh_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 enum {

source/blender/blenkernel/intern/movieclip.c

@@ -162,6 +162,11 @@ IDTypeInfo IDType_ID_MC = {
     .make_local = NULL,
     .foreach_id = movie_clip_foreach_id,
     .foreach_cache = movie_clip_foreach_cache,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /*********************** movieclip buffer loaders *************************/

source/blender/blenkernel/intern/node.c

@@ -359,6 +359,11 @@ IDTypeInfo IDType_ID_NT = {
     .make_local = NULL,
     .foreach_id = node_foreach_id,
     .foreach_cache = node_foreach_cache,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 static void node_add_sockets_from_type(bNodeTree *ntree, bNode *node, bNodeType *ntype)

source/blender/blenkernel/intern/object.c

@@ -528,6 +528,12 @@ IDTypeInfo IDType_ID_OB = {
     .free_data = object_free_data,
     .make_local = object_make_local,
     .foreach_id = object_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 void BKE_object_workob_clear(Object *workob)

source/blender/blenkernel/intern/paint.c

@@ -117,6 +117,12 @@ IDTypeInfo IDType_ID_PAL = {
     .free_data = palette_free_data,
     .make_local = NULL,
     .foreach_id = NULL,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 static void paint_curve_copy_data(Main *UNUSED(bmain),
@@ -155,6 +161,12 @@ IDTypeInfo IDType_ID_PC = {
     .free_data = paint_curve_free_data,
     .make_local = NULL,
     .foreach_id = NULL,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 const char PAINT_CURSOR_SCULPT[3] = {255, 100, 100};

source/blender/blenkernel/intern/particle.c

@@ -209,6 +209,12 @@ IDTypeInfo IDType_ID_PA = {
     .free_data = particle_settings_free_data,
     .make_local = NULL,
     .foreach_id = particle_settings_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 unsigned int PSYS_FRAND_SEED_OFFSET[PSYS_FRAND_COUNT];

source/blender/blenkernel/intern/pointcloud.c

@@ -113,6 +113,12 @@ IDTypeInfo IDType_ID_PT = {
     .free_data = pointcloud_free_data,
     .make_local = NULL,
     .foreach_id = pointcloud_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 static void pointcloud_random(PointCloud *pointcloud)

source/blender/blenkernel/intern/scene.c

@@ -606,6 +606,11 @@ IDTypeInfo IDType_ID_SCE = {
     .make_local = NULL,
     .foreach_id = scene_foreach_id,
     .foreach_cache = scene_foreach_cache,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 const char *RE_engine_id_BLENDER_EEVEE = "BLENDER_EEVEE";

source/blender/blenkernel/intern/screen.c

@@ -245,6 +245,12 @@ IDTypeInfo IDType_ID_SCR = {
     .free_data = screen_free_data,
     .make_local = NULL,
     .foreach_id = screen_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /* ************ Spacetype/regiontype handling ************** */

source/blender/blenkernel/intern/simulation.cc

@@ -160,6 +160,12 @@ IDTypeInfo IDType_ID_SIM = {
     /* free_data */ simulation_free_data,
     /* make_local */ nullptr,
     /* foreach_id */ simulation_foreach_id,
+    /* foreach_cache */ NULL,
+
+    /* blend_write */ NULL,
+    /* blend_read_data */ NULL,
+    /* blend_read_lib */ NULL,
+    /* blend_read_expand */ NULL,
 };
 
 void *BKE_simulation_add(Main *bmain, const char *name)

source/blender/blenkernel/intern/sound.c

@@ -143,6 +143,11 @@ IDTypeInfo IDType_ID_SO = {
     .make_local = NULL,
     .foreach_id = NULL,
     .foreach_cache = sound_foreach_cache,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 #ifdef WITH_AUDASPACE

source/blender/blenkernel/intern/speaker.c

@@ -65,6 +65,12 @@ IDTypeInfo IDType_ID_SPK = {
     .free_data = NULL,
     .make_local = NULL,
     .foreach_id = speaker_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 void *BKE_speaker_add(Main *bmain, const char *name)

source/blender/blenkernel/intern/text.c

@@ -182,6 +182,12 @@ IDTypeInfo IDType_ID_TXT = {
     .free_data = text_free_data,
     .make_local = NULL,
     .foreach_id = NULL,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /** \} */

source/blender/blenkernel/intern/texture.c

@@ -149,6 +149,12 @@ IDTypeInfo IDType_ID_TE = {
     .free_data = texture_free_data,
     .make_local = NULL,
     .foreach_id = texture_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /* Utils for all IDs using those texture slots. */

source/blender/blenkernel/intern/volume.cc

@@ -525,6 +525,11 @@ IDTypeInfo IDType_ID_VO = {
     /* make_local */ nullptr,
     /* foreach_id */ volume_foreach_id,
     /* foreach_cache */ volume_foreach_cache,
+
+    /* blend_write */ NULL,
+    /* blend_read_data */ NULL,
+    /* blend_read_lib */ NULL,
+    /* blend_read_expand */ NULL,
 };
 
 void BKE_volume_init_grids(Volume *volume)

source/blender/blenkernel/intern/workspace.c

@@ -90,6 +90,12 @@ IDTypeInfo IDType_ID_WS = {
     .free_data = workspace_free_data,
     .make_local = NULL,
     .foreach_id = workspace_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 /** \name Internal Utils

source/blender/blenkernel/intern/world.c

@@ -137,6 +137,12 @@ IDTypeInfo IDType_ID_WO = {
     .free_data = world_free_data,
     .make_local = NULL,
     .foreach_id = world_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 World *BKE_world_add(Main *bmain, const char *name)

source/blender/blenloader/intern/readfile.c

@@ -8240,6 +8240,9 @@ static bool direct_link_id(FileData *fd, Main *main, const int tag, ID *id, ID *
   }
 
   const IDTypeInfo *id_type = BKE_idtype_get_info_from_id(id);
+  if (id_type->blend_read_data != NULL) {
+    id_type->blend_read_data(&reader, id);
+  }
 
   /* XXX Very weakly handled currently, see comment in read_libblock() before trying to
    * use it for anything new. */
@@ -8959,6 +8962,11 @@ static void lib_link_all(FileData *fd, Main *bmain)
 
     lib_link_id(&reader, id);
 
+    const IDTypeInfo *id_type = BKE_idtype_get_info_from_id(id);
+    if (id_type->blend_read_lib != NULL) {
+      id_type->blend_read_lib(&reader, id);
+    }
+
     /* Note: ID types are processed in reverse order as defined by INDEX_ID_XXX enums in DNA_ID.h.
      * This ensures handling of most dependencies in proper order, as elsewhere in code.
      * Please keep order of entries in that switch matching that order, it's easier to quickly see
@@ -10372,6 +10380,11 @@ void BLO_expand_main(void *fdhandle, Main *mainvar)
         if (id->tag & LIB_TAG_NEED_EXPAND) {
           expand_id(&expander, id);
 
+          const IDTypeInfo *id_type = BKE_idtype_get_info_from_id(id);
+          if (id_type->blend_read_expand != NULL) {
+            id_type->blend_read_expand(&expander, id);
+          }
+
           switch (GS(id->name)) {
             case ID_OB:
               expand_object(&expander, (Object *)id);

source/blender/blenloader/intern/writefile.c

@@ -3865,6 +3865,11 @@ static bool write_file_handle(Main *mainvar,
         ((ID *)id_buffer)->prev = NULL;
         ((ID *)id_buffer)->next = NULL;
 
+        const IDTypeInfo *id_type = BKE_idtype_get_info_from_id(id);
+        if (id_type->blend_write != NULL) {
+          id_type->blend_write(&writer, (ID *)id_buffer, id);
+        }
+
         switch ((ID_Type)GS(id->name)) {
           case ID_WM:
             write_windowmanager(&writer, (wmWindowManager *)id_buffer, id);

source/blender/windowmanager/intern/wm.c

@@ -113,6 +113,12 @@ IDTypeInfo IDType_ID_WM = {
     .free_data = window_manager_free_data,
     .make_local = NULL,
     .foreach_id = window_manager_foreach_id,
+    .foreach_cache = NULL,
+
+    .blend_write = NULL,
+    .blend_read_data = NULL,
+    .blend_read_lib = NULL,
+    .blend_read_expand = NULL,
 };
 
 #define MAX_OP_REGISTERED 32