source/blender/blenkernel/BKE_main.h

@@ -198,6 +198,7 @@ typedef struct Main {
   ListBase paintcurves;
   ListBase wm;       /* Singleton (exception). */
   ListBase gpencils; /* Legacy Grease Pencil. */
+  ListBase grease_pencils;
   ListBase movieclips;
   ListBase masks;
   ListBase linestyles;
@@ -211,7 +212,6 @@ typedef struct Main {
   ListBase pointclouds;
   ListBase volumes;
   ListBase simulations;
-  ListBase grease_pencils;
 
   /**
    * Must be generated, used and freed by same code - never assume this is valid data unless you

source/blender/makesrna/intern/CMakeLists.txt

@@ -90,8 +90,10 @@ set(DEFSRC
 
 if(WITH_EXPERIMENTAL_FEATURES)
   add_definitions(-DWITH_SIMULATION_DATABLOCK)
+  add_definitions(-DWITH_GREASE_PENCIL_V3)
   list(APPEND DEFSRC
     rna_simulation.c
+    rna_grease_pencil.c
   )
 endif()
 

source/blender/makesrna/intern/makesrna.c

@@ -4509,6 +4509,9 @@ static RNAProcessItem PROCESS_ITEMS[] = {
     {"rna_dynamicpaint.c", NULL, RNA_def_dynamic_paint},
     {"rna_fcurve.c", "rna_fcurve_api.c", RNA_def_fcurve},
     {"rna_gpencil_legacy.c", NULL, RNA_def_gpencil},
+#ifdef WITH_GREASE_PENCIL_V3
+    {"rna_grease_pencil.c", NULL, RNA_def_grease_pencil},
+#endif
     {"rna_curves.c", NULL, RNA_def_curves},
     {"rna_image.c", "rna_image_api.c", RNA_def_image},
     {"rna_key.c", NULL, RNA_def_key},

source/blender/makesrna/intern/rna_ID.c

@@ -489,7 +489,11 @@ StructRNA *ID_code_to_RNA_type(short idcode)
     case ID_GD_LEGACY:
       return &RNA_GreasePencil;
     case ID_GP:
-      /* TODO. */
+#  ifdef WITH_GREASE_PENCIL_V3
+      return &RNA_GreasePencilv3;
+#  else
+      return &RNA_ID;
+#  endif
       break;
     case ID_GR:
       return &RNA_Collection;

source/blender/makesrna/intern/rna_grease_pencil.c

@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright 2023 Blender Foundation. */
+
+/** \file
+ * \ingroup RNA
+ */
+
+#include "DNA_grease_pencil_types.h"
+
+#include "RNA_access.h"
+#include "RNA_define.h"
+#include "RNA_enum_types.h"
+
+#include "rna_internal.h"
+
+#ifdef RNA_RUNTIME
+
+#else
+
+static void rna_def_grease_pencil_data(BlenderRNA *brna)
+{
+  StructRNA *srna;
+
+  srna = RNA_def_struct(brna, "GreasePencilv3", "ID");
+  RNA_def_struct_sdna(srna, "GreasePencil");
+  RNA_def_struct_ui_text(srna, "Grease Pencil", "Grease Pencil data-block");
+  RNA_def_struct_ui_icon(srna, ICON_OUTLINER_DATA_GREASEPENCIL);
+
+  /* Animation Data */
+  rna_def_animdata_common(srna);
+}
+
+void RNA_def_grease_pencil(BlenderRNA *brna)
+{
+  rna_def_grease_pencil_data(brna);
+}
+
+#endif

source/blender/makesrna/intern/rna_internal.h

@@ -156,6 +156,9 @@ void RNA_def_depsgraph(struct BlenderRNA *brna);
 void RNA_def_dynamic_paint(struct BlenderRNA *brna);
 void RNA_def_fcurve(struct BlenderRNA *brna);
 void RNA_def_gpencil(struct BlenderRNA *brna);
+#ifdef WITH_GREASE_PENCIL_V3
+void RNA_def_grease_pencil(struct BlenderRNA *brna);
+#endif
 void RNA_def_greasepencil_modifier(struct BlenderRNA *brna);
 void RNA_def_shader_fx(struct BlenderRNA *brna);
 void RNA_def_curves(struct BlenderRNA *brna);
@@ -502,6 +505,9 @@ void RNA_def_main_actions(BlenderRNA *brna, PropertyRNA *cprop);
 void RNA_def_main_particles(BlenderRNA *brna, PropertyRNA *cprop);
 void RNA_def_main_palettes(BlenderRNA *brna, PropertyRNA *cprop);
 void RNA_def_main_gpencil(BlenderRNA *brna, PropertyRNA *cprop);
+#ifdef WITH_GREASE_PENCIL_V3
+void RNA_def_main_grease_pencil(BlenderRNA *brna, PropertyRNA *cprop);
+#endif
 void RNA_def_main_movieclips(BlenderRNA *brna, PropertyRNA *cprop);
 void RNA_def_main_masks(BlenderRNA *brna, PropertyRNA *cprop);
 void RNA_def_main_linestyles(BlenderRNA *brna, PropertyRNA *cprop);

source/blender/makesrna/intern/rna_main.c

@@ -96,6 +96,9 @@ RNA_MAIN_LISTBASE_FUNCS_DEF(collections)
 RNA_MAIN_LISTBASE_FUNCS_DEF(curves)
 RNA_MAIN_LISTBASE_FUNCS_DEF(fonts)
 RNA_MAIN_LISTBASE_FUNCS_DEF(gpencils)
+#  ifdef WITH_GREASE_PENCIL_V3
+RNA_MAIN_LISTBASE_FUNCS_DEF(grease_pencils)
+#  endif
 RNA_MAIN_LISTBASE_FUNCS_DEF(hair_curves)
 RNA_MAIN_LISTBASE_FUNCS_DEF(images)
 RNA_MAIN_LISTBASE_FUNCS_DEF(lattices)
@@ -340,6 +343,14 @@ void RNA_def_main(BlenderRNA *brna)
        "Grease Pencil data-blocks",
 #  endif
        RNA_def_main_gpencil},
+#  ifdef WITH_GREASE_PENCIL_V3
+      {"grease_pencils_v3",
+       "GreasePencilv3",
+       "rna_Main_grease_pencils_begin",
+       "Grease Pencil",
+       "Grease Pencil data-blocks",
+       RNA_def_main_grease_pencil},
+#  endif
       {"movieclips",
        "MovieClip",
        "rna_Main_movieclips_begin",

source/blender/makesrna/intern/rna_main_api.c

@@ -2058,6 +2058,18 @@ void RNA_def_main_gpencil(BlenderRNA *brna, PropertyRNA *cprop)
       func, "do_ui_user", true, "", "Make sure interface does not reference this grease pencil");
 }
 
+#ifdef WITH_GREASE_PENCIL_V3
+void RNA_def_main_grease_pencil(BlenderRNA *brna, PropertyRNA *cprop)
+{
+  StructRNA *srna;
+
+  RNA_def_property_srna(cprop, "BlendDataGreasePencilsV3");
+  srna = RNA_def_struct(brna, "BlendDataGreasePencilsV3", NULL);
+  RNA_def_struct_sdna(srna, "Main");
+  RNA_def_struct_ui_text(srna, "Main Grease Pencils", "Collection of grease pencils");
+}
+#endif
+
 void RNA_def_main_movieclips(BlenderRNA *brna, PropertyRNA *cprop)
 {
   StructRNA *srna;

source/blender/makesrna/intern/rna_object.c

@@ -606,6 +606,12 @@ static StructRNA *rna_Object_data_typef(PointerRNA *ptr)
       return &RNA_LightProbe;
     case OB_GPENCIL_LEGACY:
       return &RNA_GreasePencil;
+    case OB_GREASE_PENCIL:
+#  ifdef WITH_GREASE_PENCIL_V3
+      return &RNA_GreasePencilv3;
+#  else
+      return &RNA_ID;
+#  endif
     case OB_CURVES:
       return &RNA_Curves;
     case OB_POINTCLOUD: