Fix T44589: No way to add a skin data layer manualy.

There are several ways to end up with an object with skin modifier, but no
skin data on the geometry. So we need an operator to add it by hands.

Also tweaked a bit UI of this modifier.

3 files changed, 42 insertions, 1 deletions

diff --git a/source/blender/editors/mesh/mesh_data.c b/source/blender/editors/mesh/mesh_data.c
index 86991d7dfeb..1d0cd6a2934 100644
--- a/source/blender/editors/mesh/mesh_data.c
+++ b/source/blender/editors/mesh/mesh_data.c
@@ -804,7 +804,7 @@ void MESH_OT_customdata_clear_mask(wmOperatorType *ot)
 }
 
 /* Clear Skin */
-static int mesh_customdata_clear_skin_poll(bContext *C)
+static bool mesh_customdata_skin_has(bContext *C)
 {
 	Object *ob = ED_object_context(C);
 
@@ -819,6 +819,45 @@ static int mesh_customdata_clear_skin_poll(bContext *C)
 	}
 	return false;
 }
+
+static int mesh_customdata_skin_add_poll(bContext *C)
+{
+	return !mesh_customdata_skin_has(C);
+}
+
+static int mesh_customdata_skin_add_exec(bContext *C, wmOperator *UNUSED(op))
+{
+	Object *ob = ED_object_context(C);
+	Mesh *me = ob->data;
+
+	BKE_mesh_ensure_skin_customdata(me);
+
+	DAG_id_tag_update(&me->id, 0);
+	WM_event_add_notifier(C, NC_GEOM | ND_DATA, me);
+
+	return OPERATOR_FINISHED;
+}
+
+void MESH_OT_customdata_skin_add(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name = "Add Skin Data";
+	ot->idname = "MESH_OT_customdata_skin_add";
+	ot->description = "Add a vertex skin layer";
+
+	/* api callbacks */
+	ot->exec = mesh_customdata_skin_add_exec;
+	ot->poll = mesh_customdata_skin_add_poll;
+
+	/* flags */
+	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+}
+
+static int mesh_customdata_clear_skin_poll(bContext *C)
+{
+	return mesh_customdata_skin_has(C);
+}
+
 static int mesh_customdata_clear_skin_exec(bContext *C, wmOperator *UNUSED(op))
 {
 	return mesh_customdata_clear_exec__internal(C, BM_VERT, CD_MVERT_SKIN);
diff --git a/source/blender/editors/mesh/mesh_intern.h b/source/blender/editors/mesh/mesh_intern.h
index c7355120a57..de7d0f32f6f 100644
--- a/source/blender/editors/mesh/mesh_intern.h
+++ b/source/blender/editors/mesh/mesh_intern.h
@@ -233,6 +233,7 @@ void MESH_OT_vertex_color_add(struct wmOperatorType *ot);
 void MESH_OT_vertex_color_remove(struct wmOperatorType *ot);
 /* no create_mask yet */
 void MESH_OT_customdata_clear_mask(struct wmOperatorType *ot);
+void MESH_OT_customdata_skin_add(struct wmOperatorType *ot);
 void MESH_OT_customdata_clear_skin(struct wmOperatorType *ot);
 void MESH_OT_customdata_custom_splitnormals_add(struct wmOperatorType *ot);
 void MESH_OT_customdata_custom_splitnormals_clear(struct wmOperatorType *ot);
diff --git a/source/blender/editors/mesh/mesh_ops.c b/source/blender/editors/mesh/mesh_ops.c
index 2855af063c0..31d3f019585 100644
--- a/source/blender/editors/mesh/mesh_ops.c
+++ b/source/blender/editors/mesh/mesh_ops.c
@@ -152,6 +152,7 @@ void ED_operatortypes_mesh(void)
 	WM_operatortype_append(MESH_OT_vertex_color_add);
 	WM_operatortype_append(MESH_OT_vertex_color_remove);
 	WM_operatortype_append(MESH_OT_customdata_clear_mask);
+	WM_operatortype_append(MESH_OT_customdata_skin_add);
 	WM_operatortype_append(MESH_OT_customdata_clear_skin);
 	WM_operatortype_append(MESH_OT_customdata_custom_splitnormals_add);
 	WM_operatortype_append(MESH_OT_customdata_custom_splitnormals_clear);