Fix T78242: Crash when using a Sculpt color tools that needs connectivity for the first time

When there is no color layer available,
BKE_sculpt_update_object_for_edit creates a new one and tags the mesh
with ID_RECLAC_GEOMETRY, so this layer is inmediatly available when the
tool starts. This also deletes the PBVH and when it is created again in
BKE_sculpt_update_object_after_eval, the pmap is not initialized, making
the tool crash.

This moves the color layer creation to a separate function outside
BKE_sculpt_update_object_for_edit, which now runs after the color
layer is available, so it won't need to update again and the pmap will
still be available when the tool is used.

Reviewed By: sergey

Maniphest Tasks: T78242

Differential Revision: https://developer.blender.org/D8135

source/blender/blenkernel/BKE_paint.h

@@ -451,6 +451,10 @@ void BKE_sculptsession_free_vwpaint_data(struct SculptSession *ss);
 void BKE_sculptsession_bm_to_me(struct Object *ob, bool reorder);
 void BKE_sculptsession_bm_to_me_for_render(struct Object *object);
 
+/* Create new color layer on object if it doesn't have one and if experimental feature set has
+ * sculpt vertex color enabled. Returns truth if new layer has been added, false otherwise. */
+void BKE_sculpt_color_layer_create_if_needed(struct Object *object);
+
 void BKE_sculpt_update_object_for_edit(struct Depsgraph *depsgraph,
                                        struct Object *ob_orig,
                                        bool need_pmap,

source/blender/blenkernel/intern/paint.c

@@ -1484,7 +1484,7 @@ static void sculpt_update_object(Depsgraph *depsgraph,
                                  Mesh *me_eval,
                                  bool need_pmap,
                                  bool need_mask,
-                                 bool need_colors)
+                                 bool UNUSED(need_colors))
 {
   Scene *scene = DEG_get_input_scene(depsgraph);
   Sculpt *sd = scene->toolsettings->sculpt;
@@ -1514,16 +1514,6 @@ static void sculpt_update_object(Depsgraph *depsgraph,
     }
   }
 
-  /* Add a color layer if a color tool is used. */
-  Mesh *orig_me = BKE_object_get_original_mesh(ob);
-  if (need_colors && U.experimental.use_sculpt_vertex_colors) {
-    if (!CustomData_has_layer(&orig_me->vdata, CD_PROP_COLOR)) {
-      CustomData_add_layer(&orig_me->vdata, CD_PROP_COLOR, CD_DEFAULT, NULL, orig_me->totvert);
-      BKE_mesh_update_customdata_pointers(orig_me, true);
-      DEG_id_tag_update(&orig_me->id, ID_RECALC_GEOMETRY);
-    }
-  }
-
   /* tessfaces aren't used and will become invalid */
   BKE_mesh_tessface_clear(me);
 
@@ -1684,10 +1674,26 @@ void BKE_sculpt_update_object_after_eval(Depsgraph *depsgraph, Object *ob_eval)
   Mesh *me_eval = BKE_object_get_evaluated_mesh(ob_eval);
 
   BLI_assert(me_eval != NULL);
-
   sculpt_update_object(depsgraph, ob_orig, me_eval, false, false, false);
 }
 
+void BKE_sculpt_color_layer_create_if_needed(struct Object *object)
+{
+  Mesh *orig_me = BKE_object_get_original_mesh(object);
+  if (!U.experimental.use_sculpt_vertex_colors) {
+    return;
+  }
+
+  if (CustomData_has_layer(&orig_me->vdata, CD_PROP_COLOR)) {
+    return;
+  }
+
+  CustomData_add_layer(&orig_me->vdata, CD_PROP_COLOR, CD_DEFAULT, NULL, orig_me->totvert);
+  BKE_mesh_update_customdata_pointers(orig_me, true);
+  DEG_id_tag_update(&orig_me->id, ID_RECALC_GEOMETRY);
+  return;
+}
+
 void BKE_sculpt_update_object_for_edit(
     Depsgraph *depsgraph, Object *ob_orig, bool need_pmap, bool need_mask, bool need_colors)
 {

source/blender/editors/sculpt_paint/sculpt.c

@@ -7140,7 +7140,6 @@ static void sculpt_brush_init_tex(const Scene *scene, Sculpt *sd, SculptSession
 
 static void sculpt_brush_stroke_init(bContext *C, wmOperator *op)
 {
-  Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
   Scene *scene = CTX_data_scene(C);
   Object *ob = CTX_data_active_object(C);
   Sculpt *sd = CTX_data_tool_settings(C)->sculpt;
@@ -7163,6 +7162,14 @@ static void sculpt_brush_stroke_init(bContext *C, wmOperator *op)
 
   is_smooth = sculpt_needs_connectivity_info(sd, brush, ss, mode);
   needs_colors = ELEM(brush->sculpt_tool, SCULPT_TOOL_PAINT, SCULPT_TOOL_SMEAR);
+
+  if (needs_colors) {
+    BKE_sculpt_color_layer_create_if_needed(ob);
+  }
+
+  /* CTX_data_ensure_evaluated_depsgraph should be used at the end to include the updates of
+   * earlier steps modifying the data. */
+  Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
   BKE_sculpt_update_object_for_edit(depsgraph, ob, is_smooth, need_mask, needs_colors);
 }
 

source/blender/editors/sculpt_paint/sculpt_filter_color.c

@@ -265,7 +265,6 @@ static int sculpt_color_filter_modal(bContext *C, wmOperator *op, const wmEvent
 static int sculpt_color_filter_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event))
 {
   Object *ob = CTX_data_active_object(C);
-  Depsgraph *depsgraph = CTX_data_depsgraph_pointer(C);
   Sculpt *sd = CTX_data_tool_settings(C)->sculpt;
   SculptSession *ss = ob->sculpt;
   int mode = RNA_enum_get(op->ptr, "type");
@@ -285,6 +284,11 @@ static int sculpt_color_filter_invoke(bContext *C, wmOperator *op, const wmEvent
 
   SCULPT_undo_push_begin("color filter");
 
+  BKE_sculpt_color_layer_create_if_needed(ob);
+
+  /* CTX_data_ensure_evaluated_depsgraph should be used at the end to include the updates of
+   * earlier steps modifying the data. */
+  Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
   bool needs_pmap = mode == COLOR_FILTER_SMOOTH;
   BKE_sculpt_update_object_for_edit(depsgraph, ob, needs_pmap, false, true);