Fix T40324: Checker deselect fails for edge-rings

1 files changed, 24 insertions, 1 deletions

diff --git a/source/blender/editors/mesh/editmesh_select.c b/source/blender/editors/mesh/editmesh_select.c
index 7e58f3fb018..cd39d4a0776 100644
--- a/source/blender/editors/mesh/editmesh_select.c
+++ b/source/blender/editors/mesh/editmesh_select.c
@@ -2433,6 +2433,27 @@ void MESH_OT_select_less(wmOperatorType *ot)
 	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 }
 
+/**
+ * Check if we're connected to another selected efge.
+ */
+static bool bm_edge_is_select_isolated(BMEdge *e)
+{
+	BMIter viter;
+	BMVert *v;
+
+	BM_ITER_ELEM (v, &viter, e, BM_VERTS_OF_EDGE) {
+		BMIter eiter;
+		BMEdge *e_other;
+
+		BM_ITER_ELEM (e_other, &eiter, v, BM_EDGES_OF_VERT) {
+			if ((e_other != e) && BM_elem_flag_test(e_other, BM_ELEM_SELECT)) {
+				return false;
+			}
+		}
+	}
+	return true;
+}
+
 /* Walk all reachable elements of the same type as h_act in breadth-first
  * order, starting from h_act. Deselects elements if the depth when they
  * are reached is not a multiple of "nth". */
@@ -2460,8 +2481,10 @@ static void walker_deselect_nth(BMEditMesh *em, int nth, int offset, BMHeader *h
 			mask_vert = BMO_ELE_TAG;
 			break;
 		case BM_EDGE:
+			/* When an edge has no connected-selected edges,
+			 * use face-stepping (supports edge-rings) */
 			itertype = BM_EDGES_OF_MESH;
-			walktype = BMW_VERT_SHELL;
+			walktype = bm_edge_is_select_isolated((BMEdge *)h_act) ? BMW_FACE_SHELL : BMW_VERT_SHELL;
 			flushtype = SCE_SELECT_EDGE;
 			mask_edge = BMO_ELE_TAG;
 			break;