Fix face-creation with existing hidden geometry

- face-create-extend option could add hidden verts and edges into
  the selection history (invalid state).
- faces could be created that included existing hidden edges
  that remained hidden (invalid state too).
- newly created faces could copy hidden flag from surrounding faces,
  giving very confusing results (looks as if face creation failed).

Surprising nobody noticed these years old bugs!

1 files changed, 26 insertions, 7 deletions

diff --git a/source/blender/editors/mesh/editmesh_tools.c b/source/blender/editors/mesh/editmesh_tools.c
index c57b0215d46..8f004bcf72b 100644
--- a/source/blender/editors/mesh/editmesh_tools.c
+++ b/source/blender/editors/mesh/editmesh_tools.c
@@ -684,27 +684,38 @@ static void edbm_add_edge_face_exec__tricky_finalize_sel(BMesh *bm, BMElem *ele_
 	/* now we need to find the edge that isnt connected to this element */
 	BM_select_history_clear(bm);
 
+	/* Notes on hidden geometry:
+	 * - un-hide the face since its possible hidden was copied when copying surrounding face attributes.
+	 * - un-hide before adding to select history
+	 *   since we may extend into an existing, hidden vert/edge.
+	 */
+
+	BM_elem_flag_disable(f, BM_ELEM_HIDDEN);
+	BM_face_select_set(bm, f, false);
+
 	if (ele_desel->head.htype == BM_VERT) {
 		BMLoop *l = BM_face_vert_share_loop(f, (BMVert *)ele_desel);
 		BLI_assert(f->len == 3);
-		BM_face_select_set(bm, f, false);
 		BM_vert_select_set(bm, (BMVert *)ele_desel, false);
-
 		BM_edge_select_set(bm, l->next->e, true);
 		BM_select_history_store(bm, l->next->e);
 	}
 	else {
 		BMLoop *l = BM_face_edge_share_loop(f, (BMEdge *)ele_desel);
 		BLI_assert(f->len == 4 || f->len == 3);
-		BM_face_select_set(bm, f, false);
+
 		BM_edge_select_set(bm, (BMEdge *)ele_desel, false);
 		if (f->len == 4) {
-			BM_edge_select_set(bm, l->next->next->e, true);
-			BM_select_history_store(bm, l->next->next->e);
+			BMEdge *e_active = l->next->next->e;
+			BM_elem_flag_disable(e_active, BM_ELEM_HIDDEN);
+			BM_edge_select_set(bm, e_active, true);
+			BM_select_history_store(bm, e_active);
 		}
 		else {
-			BM_vert_select_set(bm, l->next->next->v, true);
-			BM_select_history_store(bm, l->next->next->v);
+			BMVert *v_active = l->next->next->v;
+			BM_elem_flag_disable(v_active, BM_ELEM_HIDDEN);
+			BM_vert_select_set(bm, v_active, true);
+			BM_select_history_store(bm, v_active);
 		}
 	}
 }
@@ -758,6 +769,14 @@ static int edbm_add_edge_face_exec(bContext *C, wmOperator *op)
 	else
 #endif
 	{
+		/* Newly created faces may include existing hidden edges,
+		 * copying face data from surrounding, may have copied hidden face flag too.
+		 *
+		 * Important that faces use flushing since 'edges.out' wont include hidden edges that already existed.
+		 */
+		BMO_slot_buffer_hflag_disable(em->bm, bmop.slots_out, "faces.out", BM_FACE, BM_ELEM_HIDDEN, true);
+		BMO_slot_buffer_hflag_disable(em->bm, bmop.slots_out, "edges.out", BM_EDGE, BM_ELEM_HIDDEN, false);
+
 		BMO_slot_buffer_hflag_enable(em->bm, bmop.slots_out, "faces.out", BM_FACE, BM_ELEM_SELECT, true);
 		BMO_slot_buffer_hflag_enable(em->bm, bmop.slots_out, "edges.out", BM_EDGE, BM_ELEM_SELECT, true);
 	}