Cleanup: Use const when retrieving custom data layers

Knowing when layers are retrieved for write access will be essential
when adding proper copy-on-write support. This commit makes that
clearer by adding `const` where the retrieved data is not modified.

Ref T95842

8 files changed, 20 insertions, 22 deletions

diff --git a/source/blender/editors/curves/intern/curves_ops.cc b/source/blender/editors/curves/intern/curves_ops.cc
index a2945e8b7e6..5588f7440a8 100644
--- a/source/blender/editors/curves/intern/curves_ops.cc
+++ b/source/blender/editors/curves/intern/curves_ops.cc
@@ -195,7 +195,7 @@ static void try_convert_single_object(Object &curves_ob,
 
   /* Prepare utility data structure to map hair roots to mfaces. */
   const Span<int> mface_to_poly_map{
-      static_cast<int *>(CustomData_get_layer(&surface_me.fdata, CD_ORIGINDEX)),
+      static_cast<const int *>(CustomData_get_layer(&surface_me.fdata, CD_ORIGINDEX)),
       surface_me.totface};
   Array<Vector<int>> poly_to_mface_map(surface_me.totpoly);
   for (const int mface_i : mface_to_poly_map.index_range()) {
diff --git a/source/blender/editors/mesh/mesh_data.c b/source/blender/editors/mesh/mesh_data.c
index d11f0b490c1..6b857fccec7 100644
--- a/source/blender/editors/mesh/mesh_data.c
+++ b/source/blender/editors/mesh/mesh_data.c
@@ -549,9 +549,9 @@ int ED_mesh_sculpt_color_add(
     }
 
     if (CustomData_has_layer(&me->vdata, CD_PROP_COLOR) && do_init) {
-      MPropCol *color_data = CustomData_get_layer(&me->vdata, CD_PROP_COLOR);
+      const MPropCol *color_data = CustomData_get_layer(&me->vdata, CD_PROP_COLOR);
       CustomData_add_layer_named(
-          &me->vdata, CD_PROP_COLOR, CD_DUPLICATE, color_data, me->totvert, name);
+          &me->vdata, CD_PROP_COLOR, CD_DUPLICATE, (MPropCol *)color_data, me->totvert, name);
     }
     else {
       CustomData_add_layer_named(&me->vdata, CD_PROP_COLOR, CD_DEFAULT, NULL, me->totvert, name);
diff --git a/source/blender/editors/mesh/meshtools.c b/source/blender/editors/mesh/meshtools.c
index 9575fde68f0..d4ed49de34a 100644
--- a/source/blender/editors/mesh/meshtools.c
+++ b/source/blender/editors/mesh/meshtools.c
@@ -1273,7 +1273,6 @@ bool ED_mesh_pick_face_vert(
     MLoop *me_eval_mloop;
     MVert *me_eval_mvert;
     uint me_eval_mpoly_len;
-    const int *index_mp_to_orig;
 
     me_eval_mpoly = me_eval->mpoly;
     me_eval_mloop = me_eval->mloop;
@@ -1281,7 +1280,7 @@ bool ED_mesh_pick_face_vert(
 
     me_eval_mpoly_len = me_eval->totpoly;
 
-    index_mp_to_orig = CustomData_get_layer(&me_eval->pdata, CD_ORIGINDEX);
+    const int *index_mp_to_orig = CustomData_get_layer(&me_eval->pdata, CD_ORIGINDEX);
 
     /* tag all verts using this face */
     if (index_mp_to_orig) {
@@ -1313,8 +1312,7 @@ bool ED_mesh_pick_face_vert(
 
     /* map 'dm -> me' r_index if possible */
     if (v_idx_best != ORIGINDEX_NONE) {
-      const int *index_mv_to_orig;
-      index_mv_to_orig = CustomData_get_layer(&me_eval->vdata, CD_ORIGINDEX);
+      const int *index_mv_to_orig = CustomData_get_layer(&me_eval->vdata, CD_ORIGINDEX);
       if (index_mv_to_orig) {
         v_idx_best = index_mv_to_orig[v_idx_best];
       }
diff --git a/source/blender/editors/object/object_bake_api.c b/source/blender/editors/object/object_bake_api.c
index a7379d7e492..114b2ce8102 100644
--- a/source/blender/editors/object/object_bake_api.c
+++ b/source/blender/editors/object/object_bake_api.c
@@ -446,9 +446,9 @@ static bool bake_object_check(ViewLayer *view_layer,
   }
 
   if (target == R_BAKE_TARGET_VERTEX_COLORS) {
-    MPropCol *mcol = CustomData_get_layer(&me->vdata, CD_PROP_COLOR);
+    const MPropCol *mcol = CustomData_get_layer(&me->vdata, CD_PROP_COLOR);
     const bool mcol_valid = (mcol != NULL);
-    MLoopCol *mloopcol = CustomData_get_layer(&me->ldata, CD_PROP_BYTE_COLOR);
+    const MLoopCol *mloopcol = CustomData_get_layer(&me->ldata, CD_PROP_BYTE_COLOR);
     if (mloopcol == NULL && !mcol_valid) {
       BKE_reportf(reports,
                   RPT_ERROR,
@@ -943,9 +943,9 @@ static bool bake_targets_init_vertex_colors(BakeTargets *targets, Object *ob, Re
   }
 
   Mesh *me = ob->data;
-  MPropCol *mcol = CustomData_get_layer(&me->vdata, CD_PROP_COLOR);
+  const MPropCol *mcol = CustomData_get_layer(&me->vdata, CD_PROP_COLOR);
   const bool mcol_valid = (mcol != NULL);
-  MLoopCol *mloopcol = CustomData_get_layer(&me->ldata, CD_PROP_BYTE_COLOR);
+  const MLoopCol *mloopcol = CustomData_get_layer(&me->ldata, CD_PROP_BYTE_COLOR);
   if (mloopcol == NULL && !mcol_valid) {
     BKE_report(reports, RPT_ERROR, "No vertex colors layer found to bake to");
     return false;
diff --git a/source/blender/editors/sculpt_paint/sculpt_face_set.c b/source/blender/editors/sculpt_paint/sculpt_face_set.c
index 7171c241534..67bf7b3286c 100644
--- a/source/blender/editors/sculpt_paint/sculpt_face_set.c
+++ b/source/blender/editors/sculpt_paint/sculpt_face_set.c
@@ -60,7 +60,7 @@
 
 int ED_sculpt_face_sets_find_next_available_id(struct Mesh *mesh)
 {
-  int *face_sets = CustomData_get_layer(&mesh->pdata, CD_SCULPT_FACE_SETS);
+  const int *face_sets = CustomData_get_layer(&mesh->pdata, CD_SCULPT_FACE_SETS);
   if (!face_sets) {
     return SCULPT_FACE_SET_NONE;
   }
diff --git a/source/blender/editors/sculpt_paint/sculpt_ops.c b/source/blender/editors/sculpt_paint/sculpt_ops.c
index 5aa1dbef74c..9c4ae446125 100644
--- a/source/blender/editors/sculpt_paint/sculpt_ops.c
+++ b/source/blender/editors/sculpt_paint/sculpt_ops.c
@@ -639,14 +639,14 @@ static int vertex_to_loop_colors_exec(bContext *C, wmOperator *UNUSED(op))
   }
   MPropCol *vertcols = CustomData_get_layer_n(&mesh->vdata, CD_PROP_COLOR, MPropCol_layer_n);
 
-  MLoop *loops = CustomData_get_layer(&mesh->ldata, CD_MLOOP);
-  MPoly *polys = CustomData_get_layer(&mesh->pdata, CD_MPOLY);
+  const MLoop *loops = CustomData_get_layer(&mesh->ldata, CD_MLOOP);
+  const MPoly *polys = CustomData_get_layer(&mesh->pdata, CD_MPOLY);
 
   for (int i = 0; i < mesh->totpoly; i++) {
-    MPoly *c_poly = &polys[i];
+    const MPoly *c_poly = &polys[i];
     for (int j = 0; j < c_poly->totloop; j++) {
       int loop_index = c_poly->loopstart + j;
-      MLoop *c_loop = &loops[c_poly->loopstart + j];
+      const MLoop *c_loop = &loops[c_poly->loopstart + j];
       float srgb_color[4];
       linearrgb_to_srgb_v4(srgb_color, vertcols[c_loop->v].color);
       loopcols[loop_index].r = (char)(srgb_color[0] * 255);
@@ -719,14 +719,14 @@ static int loop_to_vertex_colors_exec(bContext *C, wmOperator *UNUSED(op))
   }
   MPropCol *vertcols = CustomData_get_layer_n(&mesh->vdata, CD_PROP_COLOR, MPropCol_layer_n);
 
-  MLoop *loops = CustomData_get_layer(&mesh->ldata, CD_MLOOP);
-  MPoly *polys = CustomData_get_layer(&mesh->pdata, CD_MPOLY);
+  const MLoop *loops = CustomData_get_layer(&mesh->ldata, CD_MLOOP);
+  const MPoly *polys = CustomData_get_layer(&mesh->pdata, CD_MPOLY);
 
   for (int i = 0; i < mesh->totpoly; i++) {
-    MPoly *c_poly = &polys[i];
+    const MPoly *c_poly = &polys[i];
     for (int j = 0; j < c_poly->totloop; j++) {
       int loop_index = c_poly->loopstart + j;
-      MLoop *c_loop = &loops[c_poly->loopstart + j];
+      const MLoop *c_loop = &loops[c_poly->loopstart + j];
       vertcols[c_loop->v].color[0] = (loopcols[loop_index].r / 255.0f);
       vertcols[c_loop->v].color[1] = (loopcols[loop_index].g / 255.0f);
       vertcols[c_loop->v].color[2] = (loopcols[loop_index].b / 255.0f);
diff --git a/source/blender/editors/sculpt_paint/sculpt_undo.c b/source/blender/editors/sculpt_paint/sculpt_undo.c
index 5867dc558de..1fee20444e7 100644
--- a/source/blender/editors/sculpt_paint/sculpt_undo.c
+++ b/source/blender/editors/sculpt_paint/sculpt_undo.c
@@ -1265,7 +1265,7 @@ static SculptUndoNode *sculpt_undo_face_sets_push(Object *ob, SculptUndoType typ
 
   unode->face_sets = MEM_callocN(me->totpoly * sizeof(int), "sculpt face sets");
 
-  int *face_sets = CustomData_get_layer(&me->pdata, CD_SCULPT_FACE_SETS);
+  const int *face_sets = CustomData_get_layer(&me->pdata, CD_SCULPT_FACE_SETS);
   for (int i = 0; i < me->totpoly; i++) {
     unode->face_sets[i] = face_sets[i];
   }
diff --git a/source/blender/editors/space_spreadsheet/spreadsheet_data_source_geometry.cc b/source/blender/editors/space_spreadsheet/spreadsheet_data_source_geometry.cc
index 66eced27b32..7f696efabf7 100644
--- a/source/blender/editors/space_spreadsheet/spreadsheet_data_source_geometry.cc
+++ b/source/blender/editors/space_spreadsheet/spreadsheet_data_source_geometry.cc
@@ -256,7 +256,7 @@ IndexMask GeometryDataSource::apply_selection_filter(Vector<int64_t> &indices) c
   BMesh *bm = mesh_orig->edit_mesh->bm;
   BM_mesh_elem_table_ensure(bm, BM_VERT);
 
-  int *orig_indices = (int *)CustomData_get_layer(&mesh_eval->vdata, CD_ORIGINDEX);
+  const int *orig_indices = (int *)CustomData_get_layer(&mesh_eval->vdata, CD_ORIGINDEX);
   if (orig_indices != nullptr) {
     /* Use CD_ORIGINDEX layer if it exists. */
     VArray<bool> selection = mesh_component->attribute_try_adapt_domain<bool>(