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

2 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/editors/sculpt_paint/paint_image_proj.c b/source/blender/editors/sculpt_paint/paint_image_proj.c
index 8ffa78cd457..41d5090b38c 100644
--- a/source/blender/editors/sculpt_paint/paint_image_proj.c
+++ b/source/blender/editors/sculpt_paint/paint_image_proj.c
@@ -4074,7 +4074,7 @@ static bool proj_paint_state_mesh_eval_init(const bContext *C, ProjPaintState *p
   ps->totloop_eval = ps->me_eval->totloop;
 
   ps->mlooptri_eval = BKE_mesh_runtime_looptri_ensure(ps->me_eval);
-  ps->totlooptri_eval = ps->me_eval->runtime.looptris.len;
+  ps->totlooptri_eval = BKE_mesh_runtime_looptri_len(ps->me_eval);
 
   ps->poly_to_loop_uv = MEM_mallocN(ps->totpoly_eval * sizeof(MLoopUV *), "proj_paint_mtfaces");
 
diff --git a/source/blender/editors/sculpt_paint/paint_utils.c b/source/blender/editors/sculpt_paint/paint_utils.c
index cb981a3bfb1..ce4a5151a20 100644
--- a/source/blender/editors/sculpt_paint/paint_utils.c
+++ b/source/blender/editors/sculpt_paint/paint_utils.c
@@ -286,7 +286,7 @@ static void imapaint_pick_uv(
   const ePaintCanvasSource mode = scene->toolsettings->imapaint.mode;
 
   const MLoopTri *lt = BKE_mesh_runtime_looptri_ensure(me_eval);
-  const int tottri = me_eval->runtime.looptris.len;
+  const int tottri = BKE_mesh_runtime_looptri_len(me_eval);
 
   const MVert *mvert = BKE_mesh_verts(me_eval);
   const MLoop *mloop = BKE_mesh_loops(me_eval);