Mesh: Move runtime data out of DNA

This commit replaces the `Mesh_Runtime` struct embedded in `Mesh`
with `blender::bke::MeshRuntime`. This has quite a few benefits:
- It's possible to use C++ types like `std::mutex`, `Array`,
  `BitVector`, etc. more easily
- Meshes saved in files are slightly smaller
- Copying and writing meshes is a bit more obvious without
  clearing of runtime data, etc.

The first is by far the most important. It will allows us to avoid a
bunch of manual memory management boilerplate that is error-prone and
annoying. It should also simplify future CoW improvements for runtime
data.

This patch doesn't change anything besides changing `mesh.runtime.data`
to `mesh.runtime->data`. The cleanups above will happen separately.

Differential Revision: https://developer.blender.org/D16180

1 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/modifiers/intern/MOD_multires.cc b/source/blender/modifiers/intern/MOD_multires.cc
index a23ab73c651..2bc3763c46b 100644
--- a/source/blender/modifiers/intern/MOD_multires.cc
+++ b/source/blender/modifiers/intern/MOD_multires.cc
@@ -230,7 +230,7 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
   if ((ctx->object->mode & OB_MODE_SCULPT) && !for_orco && !for_render && !sculpt_base_mesh) {
     /* NOTE: CCG takes ownership over Subdiv. */
     result = multires_as_ccg(mmd, ctx, mesh, subdiv);
-    result->runtime.subdiv_ccg_tot_level = mmd->totlvl;
+    result->runtime->subdiv_ccg_tot_level = mmd->totlvl;
     /* TODO(sergey): Usually it is sculpt stroke's update variants which
      * takes care of this, but is possible that we need this before the
      * stroke: i.e. when exiting blender right after stroke is done.
@@ -238,7 +238,7 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
      * surely there is a better way of solving this. */
     if (ctx->object->sculpt != nullptr) {
       SculptSession *sculpt_session = ctx->object->sculpt;
-      sculpt_session->subdiv_ccg = result->runtime.subdiv_ccg;
+      sculpt_session->subdiv_ccg = result->runtime->subdiv_ccg;
       sculpt_session->multires.active = true;
       sculpt_session->multires.modifier = mmd;
       sculpt_session->multires.level = mmd->sculptlvl;