DNA: initial DNA defaults support

This provides an API to access structs
with their members set to default values:

- DNA_struct_default_get(name)
- DNA_struct_default_alloc(name)

Currently this is only used for scene & view shading initialization,
eventually it can be used for RNA defaults and initializing
DNA struct members on file reading.

1 files changed, 112 insertions, 0 deletions

diff --git a/source/blender/makesdna/intern/dna_defaults.c b/source/blender/makesdna/intern/dna_defaults.c
new file mode 100644
index 00000000000..327411ab17f
--- /dev/null
+++ b/source/blender/makesdna/intern/dna_defaults.c
@@ -0,0 +1,112 @@
+/*
+ * 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.
+ *
+ * DNA default value access.
+ */
+
+/** \file
+ * \ingroup DNA
+ *
+ * This API provides direct access to DNA default structs
+ * to avoid duplicating values for initialization, versioning and RNA.
+ * This allows DNA default definitions to be defined in a single header along side the types.
+ * So each `DNA_{name}_types.h` can have an optional `DNA_{name}_defaults.h` file along side it.
+ *
+ * Defining the defaults is optional since it doesn't make sense for some structs to have defaults.
+ *
+ * To create these defaults there is a GDB script which can be handy to get started:
+ * `./source/tools/utils/gdb_struct_repr_c99.py`
+ *
+ * Magic numbers should be replaced with flags before committing.
+ *
+ * The main functions to access these are:
+ * - #DNA_struct_default_get
+ * - #DNA_struct_default_alloc
+ *
+ * These access the struct table #DNA_default_table using the struct number.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+
+#include "MEM_guardedalloc.h"
+
+#include "BLI_utildefines.h"
+#include "BLI_endian_switch.h"
+#include "BLI_memarena.h"
+#include "BLI_math.h"
+
+#include "DNA_defaults.h"
+#include "DNA_scene_types.h"
+#include "DNA_curve_types.h"
+
+#include "DNA_scene_defaults.h"
+
+const Scene DNA_DEFAULT_Scene = _DNA_DEFAULT_Scene;
+const ToolSettings DNA_DEFAULT_ToolSettings = _DNA_DEFAULT_ToolSettings;
+
+/**
+ * Prevent assigning the wrong struct types since all elements in #DNA_default_table are `void *`.
+ */
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
+#  define SDNA_TYPE_CHECKED(v, t) (&(v) + (_Generic((v), t : 0)))
+#else
+#  define SDNA_TYPE_CHECKED(v, t) (&(v))
+#endif
+
+/*  */
+#define SDNA_DEFAULT_DECL(struct_name) \
+  [SDNA_TYPE_FROM_STRUCT(struct_name)] = SDNA_TYPE_CHECKED(DNA_DEFAULT_##struct_name, struct_name)
+
+#define SDNA_DEFAULT_DECL_EX(struct_name, struct_path) \
+  [SDNA_TYPE_FROM_STRUCT(struct_name)] = SDNA_TYPE_CHECKED(DNA_DEFAULT_##struct_path, struct_name)
+
+/** Keep headers sorted. */
+const void *DNA_default_table[SDNA_TYPE_MAX] = {
+    /* DNA_scene_defaults.h */
+    SDNA_DEFAULT_DECL(Scene),
+    SDNA_DEFAULT_DECL_EX(RenderData, Scene.r),
+    SDNA_DEFAULT_DECL_EX(ImageFormatData, Scene.r.im_format),
+    SDNA_DEFAULT_DECL_EX(BakeData, Scene.r.bake),
+    SDNA_DEFAULT_DECL_EX(FFMpegCodecData, Scene.r.ffcodecdata),
+    SDNA_DEFAULT_DECL_EX(DisplaySafeAreas, Scene.safe_areas),
+    SDNA_DEFAULT_DECL_EX(AudioData, Scene.audio),
+    SDNA_DEFAULT_DECL_EX(PhysicsSettings, Scene.physics_settings),
+    SDNA_DEFAULT_DECL_EX(SceneDisplay, Scene.display),
+
+    SDNA_DEFAULT_DECL(ToolSettings),
+    SDNA_DEFAULT_DECL_EX(CurvePaintSettings, ToolSettings.curve_paint_settings),
+    SDNA_DEFAULT_DECL_EX(ImagePaintSettings, ToolSettings.imapaint),
+    SDNA_DEFAULT_DECL_EX(ParticleEditSettings, ToolSettings.particle),
+    SDNA_DEFAULT_DECL_EX(ParticleBrushData, ToolSettings.particle.brush[0]),
+    SDNA_DEFAULT_DECL_EX(MeshStatVis, ToolSettings.statvis),
+    SDNA_DEFAULT_DECL_EX(GP_Sculpt_Settings, ToolSettings.gp_sculpt),
+    SDNA_DEFAULT_DECL_EX(GP_Sculpt_Guide, ToolSettings.gp_sculpt.guide),
+
+    /* DNA_view3d_defaults.h */
+    SDNA_DEFAULT_DECL_EX(View3DShading, Scene.display.shading),
+    SDNA_DEFAULT_DECL_EX(View3DCursor, Scene.cursor),
+};
+#undef SDNA_DEFAULT_DECL
+#undef SDNA_DEFAULT_DECL_EX
+
+char *_DNA_struct_default_alloc_impl(const char *data_src, size_t size, const char *alloc_str)
+{
+  char *data_dst = MEM_mallocN(size, alloc_str);
+  memcpy(data_dst, data_src, size);
+  return data_dst;
+}