bmesh api: minor simplify & cleanup

- add BM_face_edge_share_loop(f, e) -- edge version of existing BM_face_vert_share_loop(f, v)
- simplify BM_edge_ordered_verts_ex(), check could be reduced.
- use BM_ELEM_INTERNAL_TAG for bmesh_jfke(), not BM_ELEM_TAG to avoid clobbering tagged data tools might use.

source/blender/bmesh/intern/bmesh_core.c

@@ -1618,7 +1618,6 @@ BMFace *bmesh_jfke(BMesh *bm, BMFace *f1, BMFace *f2, BMEdge *e)
 {
 	BMLoop *l_iter, *f1loop = NULL, *f2loop = NULL;
 	int newlen = 0, i, f1len = 0, f2len = 0, radlen = 0, edok, shared;
-	BMIter iter;
 
 	/* can't join a face to itsel */
 	if (f1 == f2) {
@@ -1628,19 +1627,10 @@ BMFace *bmesh_jfke(BMesh *bm, BMFace *f1, BMFace *f2, BMEdge *e)
 	/* verify that e is in both f1 and f2 */
 	f1len = f1->len;
 	f2len = f2->len;
-	BM_ITER(l_iter, &iter, bm, BM_LOOPS_OF_FACE, f1) {
-		if (l_iter->e == e) {
-			f1loop = l_iter;
-			break;
-		}
-	}
-	BM_ITER(l_iter, &iter, bm, BM_LOOPS_OF_FACE, f2) {
-		if (l_iter->e == e) {
-			f2loop = l_iter;
-			break;
-		}
-	}
-	if (!(f1loop && f2loop)) {
+
+	if (!((f1loop = BM_face_edge_share_loop(f1, e)) &&
+	      (f2loop = BM_face_edge_share_loop(f2, e))))
+	{
 		return NULL;
 	}
 	
@@ -1673,21 +1663,21 @@ BMFace *bmesh_jfke(BMesh *bm, BMFace *f1, BMFace *f2, BMEdge *e)
 
 	/* validate no internal join */
 	for (i = 0, l_iter = BM_FACE_FIRST_LOOP(f1); i < f1len; i++, l_iter = l_iter->next) {
-		BM_elem_flag_disable(l_iter->v, BM_ELEM_TAG);
+		BM_elem_flag_disable(l_iter->v, BM_ELEM_INTERNAL_TAG);
 	}
 	for (i = 0, l_iter = BM_FACE_FIRST_LOOP(f2); i < f2len; i++, l_iter = l_iter->next) {
-		BM_elem_flag_disable(l_iter->v, BM_ELEM_TAG);
+		BM_elem_flag_disable(l_iter->v, BM_ELEM_INTERNAL_TAG);
 	}
 
 	for (i = 0, l_iter = BM_FACE_FIRST_LOOP(f1); i < f1len; i++, l_iter = l_iter->next) {
 		if (l_iter != f1loop) {
-			BM_elem_flag_enable(l_iter->v, BM_ELEM_TAG);
+			BM_elem_flag_enable(l_iter->v, BM_ELEM_INTERNAL_TAG);
 		}
 	}
 	for (i = 0, l_iter = BM_FACE_FIRST_LOOP(f2); i < f2len; i++, l_iter = l_iter->next) {
 		if (l_iter != f2loop) {
 			/* as soon as a duplicate is found, bail out */
-			if (BM_elem_flag_test(l_iter->v, BM_ELEM_TAG)) {
+			if (BM_elem_flag_test(l_iter->v, BM_ELEM_INTERNAL_TAG)) {
 				return NULL;
 			}
 		}

source/blender/bmesh/intern/bmesh_queries.c

@@ -652,7 +652,7 @@ BMVert *BM_edge_share_vert(BMEdge *e1, BMEdge *e2)
 }
 
 /**
- * \brief Radial Find a Vertex Loop in Face
+ * \brief Return the Loop Shared by Face and Vertex
  *
  * Finds the loop used which uses \a v in face loop \a l
  *
@@ -674,6 +674,29 @@ BMLoop *BM_face_vert_share_loop(BMFace *f, BMVert *v)
 	return NULL;
 }
 
+/**
+ * \brief Return the Loop Shared by Face and Edge
+ *
+ * Finds the loop used which uses \a e in face loop \a l
+ *
+ * \note currenly this just uses simple loop in future may be speeded up
+ * using radial vars
+ */
+BMLoop *BM_face_edge_share_loop(BMFace *f, BMEdge *e)
+{
+	BMLoop *l_first;
+	BMLoop *l_iter;
+
+	l_iter = l_first = e->l;
+	do {
+		if (l_iter->f == f) {
+			return l_iter;
+		}
+	} while ((l_iter = l_iter->radial_next) != l_first);
+
+	return NULL;
+}
+
 /**
  * Returns the verts of an edge as used in a face
  * if used in a face at all, otherwise just assign as used in the edge.
@@ -681,24 +704,16 @@ BMLoop *BM_face_vert_share_loop(BMFace *f, BMVert *v)
  * Useful to get a deterministic winding order when calling
  * BM_face_create_ngon() on an arbitrary array of verts,
  * though be sure to pick an edge which has a face.
+ *
+ * \note This is infact quite a simple check, mainly include this function so the intent is more obvious.
+ * We know these 2 verts will _always_ make up the loops edge
  */
 void BM_edge_ordered_verts_ex(BMEdge *edge, BMVert **r_v1, BMVert **r_v2,
                               BMLoop *edge_loop)
 {
 	BLI_assert(edge_loop->e == edge);
-
-	if ((edge_loop == NULL) ||
-	    (((edge_loop->prev->v == edge->v1) && (edge_loop->v == edge->v2)) ||
-	     ((edge_loop->v == edge->v1) && (edge_loop->next->v == edge->v2)))
-	    )
-	{
-		*r_v1 = edge->v1;
-		*r_v2 = edge->v2;
-	}
-	else {
-		*r_v1 = edge->v2;
-		*r_v2 = edge->v1;
-	}
+	*r_v1 = edge_loop->v;
+	*r_v2 = edge_loop->next->v;
 }
 
 void BM_edge_ordered_verts(BMEdge *edge, BMVert **r_v1, BMVert **r_v2)

source/blender/bmesh/intern/bmesh_queries.h

@@ -79,6 +79,7 @@ int     BM_edge_share_vert_count(BMEdge *e1, BMEdge *e2);
 
 BMVert *BM_edge_share_vert(BMEdge *e1, BMEdge *e2);
 BMLoop *BM_face_vert_share_loop(BMFace *f, BMVert *v);
+BMLoop *BM_face_edge_share_loop(BMFace *f, BMEdge *e);
 
 void    BM_edge_ordered_verts(BMEdge *edge, BMVert **r_v1, BMVert **r_v2);
 void    BM_edge_ordered_verts_ex(BMEdge *edge, BMVert **r_v1, BMVert **r_v2,