[Bf-blender-cvs] [4c7ea01cbdc] temp-sculpt-colors: temp-sculpt-colors: Fix crash in redoing after undoing first stroke of paint brush.

[Joseph Eagar]

Commit: 4c7ea01cbdc3ed0c37c9ea8e5cc223ee2fa1926b
Author: Joseph Eagar
Date:   Tue Mar 22 09:54:27 2022 -0700
Branches: temp-sculpt-colors
https://developer.blender.org/rB4c7ea01cbdc3ed0c37c9ea8e5cc223ee2fa1926b

temp-sculpt-colors: Fix crash in redoing after
                    undoing first stroke of
		    paint brush.

===================================================================

M	source/blender/draw/intern/draw_cache_impl_mesh.c
M	source/blender/editors/sculpt_paint/sculpt_undo.c

===================================================================

diff --git a/source/blender/draw/intern/draw_cache_impl_mesh.c b/source/blender/draw/intern/draw_cache_impl_mesh.c
index 2e1881b0346..2fa49d3025c 100644
--- a/source/blender/draw/intern/draw_cache_impl_mesh.c
+++ b/source/blender/draw/intern/draw_cache_impl_mesh.c
@@ -693,6 +693,8 @@ static DRW_MeshCDMask mesh_cd_calc_used_gpu_layers(const Object *object,
               break;
             }
 
+            /* Note: this is the logical index into the color attribute list,
+               not the customdata index. */
             int layer_i = BKE_id_attribute_to_index(
                 (ID *)&query_mesh, layer, ATTR_DOMAIN_MASK_COLOR, CD_MASK_COLOR_ALL);
 
diff --git a/source/blender/editors/sculpt_paint/sculpt_undo.c b/source/blender/editors/sculpt_paint/sculpt_undo.c
index d6ee1a91a1f..fcdce9a59b1 100644
--- a/source/blender/editors/sculpt_paint/sculpt_undo.c
+++ b/source/blender/editors/sculpt_paint/sculpt_undo.c
@@ -1562,6 +1562,15 @@ static void sculpt_undo_set_active_layer(struct bContext *C, SculptAttrRef *attr
   CustomDataLayer *layer;
   layer = BKE_id_attribute_find(&me->id, attr->name, attr->type, attr->domain);
 
+  if (!layer) {
+    /* memfile undo killed the layer; re-create it */
+    CustomData *cdata = attr->domain == ATTR_DOMAIN_POINT ? &me->vdata : &me->ldata;
+    int totelem = attr->domain == ATTR_DOMAIN_POINT ? me->totvert : me->totloop;
+
+    CustomData_add_layer_named(cdata, attr->type, CD_DEFAULT, NULL, totelem, attr->name);
+    layer = BKE_id_attribute_find(&me->id, attr->name, attr->type, attr->domain);
+  }
+
   if (layer) {
     BKE_id_attributes_active_color_set(&me->id, layer);