Fix T48290: Hook fails after deleting geometry

Now CD_SHAPEKEY_INDEX customdata is stored in edit-mode when hooks and vertex parents are used.

This also fixes a bug where undo would loose key-index data.

Move to structs for BM_mesh_bm_to/from_me to avoid passing many argument, which mostly aren't used.

source/blender/blenkernel/BKE_mesh.h

@@ -69,7 +69,7 @@ extern "C" {
 
 /* *** mesh.c *** */
 
-struct BMesh *BKE_mesh_to_bmesh(struct Mesh *me, struct Object *ob);
+struct BMesh *BKE_mesh_to_bmesh(struct Mesh *me, struct Object *ob, const bool add_key_index);
 
 int poly_find_loop_from_vert(
         const struct MPoly *poly,

source/blender/blenkernel/intern/mesh.c

@@ -595,14 +595,17 @@ Mesh *BKE_mesh_copy(Mesh *me)
 	return BKE_mesh_copy_ex(G.main, me);
 }
 
-BMesh *BKE_mesh_to_bmesh(Mesh *me, Object *ob)
+BMesh *BKE_mesh_to_bmesh(Mesh *me, Object *ob, const bool add_key_index)
 {
 	BMesh *bm;
 	const BMAllocTemplate allocsize = BMALLOC_TEMPLATE_FROM_ME(me);
 
 	bm = BM_mesh_create(&allocsize);
 
-	BM_mesh_bm_from_me(bm, me, false, true, ob->shapenr);
+	BM_mesh_bm_from_me(
+	        bm, me, (&(struct BMeshFromMeshParams){
+	            .add_key_index = add_key_index, .use_shapekey = true, .active_shapekey = ob->shapenr,
+	        }));
 
 	return bm;
 }

source/blender/blenkernel/intern/paint.c

@@ -635,7 +635,7 @@ static void sculptsession_bm_to_me_update_data_only(Object *ob, bool reorder)
 			}
 			if (reorder)
 				BM_log_mesh_elems_reorder(ss->bm, ss->bm_log);
-			BM_mesh_bm_to_me(ss->bm, ob->data, false);
+			BM_mesh_bm_to_me(ss->bm, ob->data, (&(struct BMeshToMeshParams){0}));
 		}
 	}
 }

source/blender/blenkernel/intern/scene.c

@@ -1774,7 +1774,7 @@ static void prepare_mesh_for_viewport_render(Main *bmain, Scene *scene)
 		{
 			if (check_rendered_viewport_visible(bmain)) {
 				BMesh *bm = mesh->edit_btmesh->bm;
-				BM_mesh_bm_to_me(bm, mesh, false);
+				BM_mesh_bm_to_me(bm, mesh, (&(struct BMeshToMeshParams){0}));
 				DAG_id_tag_update(&mesh->id, 0);
 			}
 		}

source/blender/bmesh/intern/bmesh_mesh_conv.c

@@ -224,7 +224,7 @@ static BMFace *bm_face_create_from_mpoly(
  */
 void BM_mesh_bm_from_me(
         BMesh *bm, Mesh *me,
-        const bool calc_face_normal, const bool set_key, int act_key_nr)
+        const struct BMeshFromMeshParams *params)
 {
 	MVert *mvert;
 	MEdge *medge;
@@ -273,8 +273,8 @@ void BM_mesh_bm_from_me(
 		CustomData_set_layer_name(&bm->ldata, CD_MLOOPUV, i, bm->pdata.layers[li].name);
 	}
 
-	if ((act_key_nr != 0) && (me->key != NULL)) {
-		actkey = BLI_findlink(&me->key->block, act_key_nr - 1);
+	if ((params->active_shapekey != 0) && (me->key != NULL)) {
+		actkey = BLI_findlink(&me->key->block, params->active_shapekey - 1);
 	}
 	else {
 		actkey = NULL;
@@ -283,9 +283,11 @@ void BM_mesh_bm_from_me(
 	const int tot_shape_keys = me->key ? BLI_listbase_count(&me->key->block) : 0;
 	const float (**shape_key_table)[3] = tot_shape_keys ? BLI_array_alloca(shape_key_table, tot_shape_keys) : NULL;
 
-	if (tot_shape_keys) {
+	if (tot_shape_keys || params->add_key_index) {
 		CustomData_add_layer(&bm->vdata, CD_SHAPE_KEYINDEX, CD_ASSIGN, NULL, 0);
+	}
 
+	if (tot_shape_keys) {
 		/* check if we need to generate unique ids for the shapekeys.
 		 * this also exists in the file reading code, but is here for
 		 * a sanity check */
@@ -303,7 +305,7 @@ void BM_mesh_bm_from_me(
 
 		if (actkey && actkey->totelem == me->totvert) {
 			keyco = actkey->data;
-			bm->shapenr = act_key_nr;
+			bm->shapenr = params->active_shapekey;
 		}
 
 		for (i = 0, block = me->key->block.first; block; block = block->next, i++) {
@@ -328,10 +330,13 @@ void BM_mesh_bm_from_me(
 	const int cd_edge_bweight_offset = CustomData_get_offset(&bm->edata, CD_BWEIGHT);
 	const int cd_edge_crease_offset  = CustomData_get_offset(&bm->edata, CD_CREASE);
 	const int cd_shape_key_offset = me->key ? CustomData_get_offset(&bm->vdata, CD_SHAPEKEY) : -1;
-	const int cd_shape_keyindex_offset = me->key ? CustomData_get_offset(&bm->vdata, CD_SHAPE_KEYINDEX) : -1;
+	const int cd_shape_keyindex_offset = (tot_shape_keys || params->add_key_index) ?
+	          CustomData_get_offset(&bm->vdata, CD_SHAPE_KEYINDEX) : -1;
 
 	for (i = 0, mvert = me->mvert; i < me->totvert; i++, mvert++) {
-		v = vtable[i] = BM_vert_create(bm, keyco && set_key ? keyco[i] : mvert->co, NULL, BM_CREATE_SKIP_CD);
+		v = vtable[i] = BM_vert_create(
+		        bm, keyco && params->use_shapekey ? keyco[i] : mvert->co, NULL,
+		        BM_CREATE_SKIP_CD);
 		BM_elem_index_set(v, i); /* set_ok */
 
 		/* transfer flag */
@@ -349,11 +354,11 @@ void BM_mesh_bm_from_me(
 
 		if (cd_vert_bweight_offset != -1) BM_ELEM_CD_SET_FLOAT(v, cd_vert_bweight_offset, (float)mvert->bweight / 255.0f);
 
+		/* set shape key original index */
+		if (cd_shape_keyindex_offset != -1) BM_ELEM_CD_SET_INT(v, cd_shape_keyindex_offset, i);
+
 		/* set shapekey data */
 		if (tot_shape_keys) {
-			/* set shape key original index */
-			if (cd_shape_keyindex_offset != -1) BM_ELEM_CD_SET_INT(v, cd_shape_keyindex_offset, i);
-
 			float (*co_dst)[3] = BM_ELEM_CD_GET_VOID_P(v, cd_shape_key_offset);
 			for (j = 0; j < tot_shape_keys; j++, co_dst++) {
 				copy_v3_v3(*co_dst, shape_key_table[j][i]);
@@ -436,7 +441,7 @@ void BM_mesh_bm_from_me(
 		/* Copy Custom Data */
 		CustomData_to_bmesh_block(&me->pdata, &bm->pdata, i, &f->head.data, true);
 
-		if (calc_face_normal) {
+		if (params->calc_face_normal) {
 			BM_face_normal_update(f);
 		}
 	}
@@ -571,7 +576,9 @@ BLI_INLINE void bmesh_quick_edgedraw_flag(MEdge *med, BMEdge *e)
 	}
 }
 
-void BM_mesh_bm_to_me(BMesh *bm, Mesh *me, bool do_tessface)
+void BM_mesh_bm_to_me(
+        BMesh *bm, Mesh *me,
+        const struct BMeshToMeshParams *params)
 {
 	MLoop *mloop;
 	MPoly *mpoly;
@@ -632,10 +639,13 @@ void BM_mesh_bm_to_me(BMesh *bm, Mesh *me, bool do_tessface)
 	me->totface = 0;
 	me->act_face = -1;
 
-	CustomData_copy(&bm->vdata, &me->vdata, CD_MASK_MESH, CD_CALLOC, me->totvert);
-	CustomData_copy(&bm->edata, &me->edata, CD_MASK_MESH, CD_CALLOC, me->totedge);
-	CustomData_copy(&bm->ldata, &me->ldata, CD_MASK_MESH, CD_CALLOC, me->totloop);
-	CustomData_copy(&bm->pdata, &me->pdata, CD_MASK_MESH, CD_CALLOC, me->totpoly);
+	{
+		const CustomDataMask mask = CD_MASK_MESH | params->cd_mask_extra;
+		CustomData_copy(&bm->vdata, &me->vdata, mask, CD_CALLOC, me->totvert);
+		CustomData_copy(&bm->edata, &me->edata, mask, CD_CALLOC, me->totedge);
+		CustomData_copy(&bm->ldata, &me->ldata, mask, CD_CALLOC, me->totloop);
+		CustomData_copy(&bm->pdata, &me->pdata, mask, CD_CALLOC, me->totpoly);
+	}
 
 	CustomData_add_layer(&me->vdata, CD_MVERT, CD_ASSIGN, mvert, me->totvert);
 	CustomData_add_layer(&me->edata, CD_MEDGE, CD_ASSIGN, medge, me->totedge);
@@ -784,11 +794,11 @@ void BM_mesh_bm_to_me(BMesh *bm, Mesh *me, bool do_tessface)
 		if (vertMap) MEM_freeN(vertMap);
 	}
 
-	if (do_tessface) {
+	if (params->calc_tessface) {
 		BKE_mesh_tessface_calc(me);
 	}
 
-	BKE_mesh_update_customdata_pointers(me, do_tessface);
+	BKE_mesh_update_customdata_pointers(me, params->calc_tessface);
 
 	{
 		BMEditSelection *selected;

source/blender/bmesh/intern/bmesh_mesh_conv.h

@@ -39,9 +39,28 @@ void BM_mesh_cd_flag_ensure(BMesh *bm, struct Mesh *mesh, const char cd_flag);
 void BM_mesh_cd_flag_apply(BMesh *bm, const char cd_flag);
 char BM_mesh_cd_flag_from_bmesh(BMesh *bm);
 
+
+struct BMeshFromMeshParams {
+	unsigned int calc_face_normal : 1;
+	/* add a vertex CD_SHAPE_KEYINDEX layer */
+	unsigned int add_key_index : 1;
+	/* set vertex coordinates from the shapekey */
+	unsigned int use_shapekey : 1;
+	/* define the active shape key (index + 1) */
+	int active_shapekey;
+};
 void BM_mesh_bm_from_me(
         BMesh *bm, struct Mesh *me,
-        const bool calc_face_normal, const bool set_key, int act_key_nr);
-void BM_mesh_bm_to_me(BMesh *bm, struct Mesh *me, bool do_tessface);
+        const struct BMeshFromMeshParams *params)
+ATTR_NONNULL(1, 2, 3);
+
+struct BMeshToMeshParams {
+	unsigned int calc_tessface : 1;
+	int64_t cd_mask_extra;
+};
+void BM_mesh_bm_to_me(
+        BMesh *bm, struct Mesh *me,
+        const struct BMeshToMeshParams *params)
+ATTR_NONNULL(1, 2, 3);
 
 #endif /* __BMESH_MESH_CONV_H__ */

source/blender/bmesh/operators/bmo_mesh_conv.c

@@ -45,7 +45,10 @@ void bmo_mesh_to_bmesh_exec(BMesh *bm, BMOperator *op)
 	Mesh *me     = BMO_slot_ptr_get(op->slots_in,  "mesh");
 	bool set_key = BMO_slot_bool_get(op->slots_in, "use_shapekey");
 
-	BM_mesh_bm_from_me(bm, me, false, set_key, ob->shapenr);
+	BM_mesh_bm_from_me(
+	        bm, me, (&(struct BMeshFromMeshParams){
+	             .use_shapekey = set_key, .active_shapekey = ob->shapenr,
+	        }));
 
 	if (me->key && ob->shapenr > me->key->totkey) {
 		ob->shapenr = me->key->totkey - 1;
@@ -69,5 +72,5 @@ void bmo_bmesh_to_mesh_exec(BMesh *bm, BMOperator *op)
 	/* Object *ob = BMO_slot_ptr_get(op, "object"); */
 	const bool dotess = !BMO_slot_bool_get(op->slots_in, "skip_tessface");
 
-	BM_mesh_bm_to_me(bm, me, dotess);
+	BM_mesh_bm_to_me(bm, me, (&(struct BMeshToMeshParams){ .calc_tessface = dotess, }));
 }

source/blender/editors/include/ED_mesh.h

@@ -80,7 +80,7 @@ void EDBM_mesh_normals_update(struct BMEditMesh *em);
 void EDBM_mesh_clear(struct BMEditMesh *em);
 
 void EDBM_selectmode_to_scene(struct bContext *C);
-void EDBM_mesh_make(struct ToolSettings *ts, struct Object *ob);
+void EDBM_mesh_make(struct ToolSettings *ts, struct Object *ob, const bool add_key_index);
 void EDBM_mesh_free(struct BMEditMesh *em);
 void EDBM_mesh_load(struct Object *ob);
 struct DerivedMesh *EDBM_mesh_deform_dm_get(struct BMEditMesh *em);

source/blender/editors/mesh/editmesh_tools.c

@@ -3011,7 +3011,7 @@ static Base *mesh_separate_tagged(Main *bmain, Scene *scene, Base *base_old, BMe
 
 	BM_mesh_normals_update(bm_new);
 
-	BM_mesh_bm_to_me(bm_new, base_new->object->data, false);
+	BM_mesh_bm_to_me(bm_new, base_new->object->data, (&(struct BMeshToMeshParams){0}));
 
 	BM_mesh_free(bm_new);
 	((Mesh *)base_new->object->data)->edit_btmesh = NULL;
@@ -3294,7 +3294,7 @@ static int edbm_separate_exec(bContext *C, wmOperator *op)
 
 					bm_old = BM_mesh_create(&bm_mesh_allocsize_default);
 
-					BM_mesh_bm_from_me(bm_old, me, false, false, 0);
+					BM_mesh_bm_from_me(bm_old, me, (&(struct BMeshFromMeshParams){0}));
 
 					switch (type) {
 						case MESH_SEPARATE_MATERIAL:
@@ -3309,7 +3309,7 @@ static int edbm_separate_exec(bContext *C, wmOperator *op)
 					}
 
 					if (retval_iter) {
-						BM_mesh_bm_to_me(bm_old, me, false);
+						BM_mesh_bm_to_me(bm_old, me, (&(struct BMeshToMeshParams){0}));
 
 						DAG_id_tag_update(&me->id, OB_RECALC_DATA);
 						WM_event_add_notifier(C, NC_GEOM | ND_DATA, me);

source/blender/editors/mesh/editmesh_utils.c

@@ -347,7 +347,7 @@ void EDBM_selectmode_to_scene(bContext *C)
 	WM_event_add_notifier(C, NC_SCENE | ND_TOOLSETTINGS, scene);
 }
 
-void EDBM_mesh_make(ToolSettings *ts, Object *ob)
+void EDBM_mesh_make(ToolSettings *ts, Object *ob, const bool add_key_index)
 {
 	Mesh *me = ob->data;
 	BMesh *bm;
@@ -356,7 +356,7 @@ void EDBM_mesh_make(ToolSettings *ts, Object *ob)
 		BKE_mesh_convert_mfaces_to_mpolys(me);
 	}
 
-	bm = BKE_mesh_to_bmesh(me, ob);
+	bm = BKE_mesh_to_bmesh(me, ob, add_key_index);
 
 	if (me->edit_btmesh) {
 		/* this happens when switching shape keys */
@@ -395,7 +395,7 @@ void EDBM_mesh_load(Object *ob)
 		bm->shapenr = 1;
 	}
 
-	BM_mesh_bm_to_me(bm, me, false);
+	BM_mesh_bm_to_me(bm, me, (&(struct BMeshToMeshParams){0}));
 
 #ifdef USE_TESSFACE_DEFAULT
 	BKE_mesh_tessface_calc(me);
@@ -533,7 +533,10 @@ static void *editbtMesh_to_undoMesh(void *emv, void *obdata)
 
 	/* BM_mesh_validate(em->bm); */ /* for troubleshooting */
 
-	BM_mesh_bm_to_me(em->bm, &um->me, false);
+	BM_mesh_bm_to_me(
+	        em->bm, &um->me, (&(struct BMeshToMeshParams){
+	            .cd_mask_extra = CD_MASK_SHAPE_KEYINDEX,
+	        }));
 
 	um->selectmode = em->selectmode;
 	um->shapenr = em->bm->shapenr;
@@ -557,7 +560,10 @@ static void undoMesh_to_editbtMesh(void *umv, void *em_v, void *obdata)
 
 	bm = BM_mesh_create(&allocsize);
 
-	BM_mesh_bm_from_me(bm, &um->me, true, false, um->shapenr);
+	BM_mesh_bm_from_me(
+	        bm, &um->me, (&(struct BMeshFromMeshParams){
+	            .calc_face_normal = true, .active_shapekey = um->shapenr,
+	        }));
 
 	em_tmp = BKE_editmesh_create(bm, true);
 	*em = *em_tmp;

source/blender/editors/mesh/mesh_data.c

@@ -582,7 +582,7 @@ static int drop_named_image_invoke(bContext *C, wmOperator *op, const wmEvent *e
 	obedit = base->object;
 	me = obedit->data;
 	if (me->edit_btmesh == NULL) {
-		EDBM_mesh_make(scene->toolsettings, obedit);
+		EDBM_mesh_make(scene->toolsettings, obedit, false);
 		exitmode = 1;
 	}
 	if (me->edit_btmesh == NULL)

source/blender/editors/mesh/meshtools.c

@@ -572,7 +572,7 @@ int join_mesh_exec(bContext *C, wmOperator *op)
 	ED_object_editmode_exit(C, EM_FREEDATA | EM_WAITCURSOR | EM_DO_UNDO);
 #else
 	/* toggle editmode using lower level functions so this can be called from python */
-	EDBM_mesh_make(scene->toolsettings, ob);
+	EDBM_mesh_make(scene->toolsettings, ob, false);
 	EDBM_mesh_load(ob);
 	EDBM_mesh_free(me->edit_btmesh);
 	MEM_freeN(me->edit_btmesh);

source/blender/editors/object/object_edit.c

@@ -316,6 +316,27 @@ void OBJECT_OT_hide_render_set(wmOperatorType *ot)
 
 /* ******************* toggle editmode operator  ***************** */
 
+static bool mesh_needs_keyindex(const Mesh *me)
+{
+	if (me->key) {
+		return false;  /* will be added */
+	}
+
+	for (const Object *ob = G.main->object.first; ob; ob = ob->id.next) {
+		if ((ob->parent) && (ob->parent->data == me) && ELEM(ob->partype, PARVERT1, PARVERT3)) {
+			return true;
+		}
+		if (ob->data == me) {
+			for (const ModifierData *md = ob->modifiers.first; md; md = md->next) {
+				if (md->type == eModifierType_Hook) {
+					return true;
+				}
+			}
+		}
+	}
+	return false;
+}
+
 /**
  * Load EditMode data back into the object,
  * optionally freeing the editmode data.
@@ -494,7 +515,9 @@ void ED_object_editmode_enter(bContext *C, int flag)
 		ok = 1;
 		scene->obedit = ob;  /* context sees this */
 
-		EDBM_mesh_make(scene->toolsettings, ob);
+		const bool use_key_index = mesh_needs_keyindex(ob->data);
+
+		EDBM_mesh_make(scene->toolsettings, ob, use_key_index);
 
 		em = BKE_editmesh_from_object(ob);
 		if (LIKELY(em)) {

source/blender/editors/object/object_hook.c

@@ -316,7 +316,7 @@ static bool object_hook_index_array(Scene *scene, Object *obedit,
 			BMEditMesh *em;
 
 			EDBM_mesh_load(obedit);
-			EDBM_mesh_make(scene->toolsettings, obedit);
+			EDBM_mesh_make(scene->toolsettings, obedit, true);
 
 			DAG_id_tag_update(obedit->data, 0);
 

source/blender/editors/object/object_relations.c

@@ -136,7 +136,7 @@ static int vertex_parent_set_exec(bContext *C, wmOperator *op)
 		BMEditMesh *em;
 
 		EDBM_mesh_load(obedit);
-		EDBM_mesh_make(scene->toolsettings, obedit);
+		EDBM_mesh_make(scene->toolsettings, obedit, true);
 
 		DAG_id_tag_update(obedit->data, 0);
 

source/blender/editors/sculpt_paint/paint_image_proj.c

@@ -5866,15 +5866,17 @@ static int add_simple_uvs_exec(bContext *C, wmOperator *UNUSED(op))
 
 	ED_mesh_uv_texture_ensure(me, NULL);
 
-	BM_mesh_bm_from_me(bm, me, true, false, 0);
-
+	BM_mesh_bm_from_me(
+	        bm, me,(&(struct BMeshFromMeshParams){
+	            .calc_face_normal = true,
+	        }));
 	/* select all uv loops first - pack parameters needs this to make sure charts are registered */
 	ED_uvedit_select_all(bm);
 	ED_uvedit_unwrap_cube_project(ob, bm, 1.0, false);
 	/* set the margin really quickly before the packing operation*/
 	scene->toolsettings->uvcalc_margin = 0.001f;
 	ED_uvedit_pack_islands(scene, ob, bm, false, false, true);
-	BM_mesh_bm_to_me(bm, me, false);
+	BM_mesh_bm_to_me(bm, me, (&(struct BMeshToMeshParams){0}));
 	BM_mesh_free(bm);
 
 	if (synch_selection)

source/blender/editors/sculpt_paint/sculpt.c

@@ -5003,7 +5003,10 @@ void sculpt_dynamic_topology_enable(bContext *C)
 	/* Create triangles-only BMesh */
 	ss->bm = BM_mesh_create(&allocsize);
 
-	BM_mesh_bm_from_me(ss->bm, me, true, true, ob->shapenr);
+	BM_mesh_bm_from_me(
+	        ss->bm, me, (&(struct BMeshFromMeshParams){
+	            .calc_face_normal = true, .use_shapekey = true, .active_shapekey = ob->shapenr,
+	        }));
 	sculpt_dynamic_topology_triangulate(ss->bm);
 	BM_data_layer_add(ss->bm, &ss->bm->vdata, CD_PAINT_MASK);
 	sculpt_dyntopo_node_layers_add(ss);

source/blender/makesrna/intern/rna_object.c

@@ -267,7 +267,7 @@ static void rna_Object_active_shape_update(Main *bmain, Scene *scene, PointerRNA
 		switch (ob->type) {
 			case OB_MESH:
 				EDBM_mesh_load(ob);
-				EDBM_mesh_make(scene->toolsettings, ob);
+				EDBM_mesh_make(scene->toolsettings, ob, true);
 
 				DAG_id_tag_update(ob->data, 0);
 

source/blender/python/bmesh/bmesh_py_types.c

@@ -916,7 +916,7 @@ static PyObject *bpy_bmesh_to_mesh(BPy_BMesh *self, PyObject *args)
 	/* python won't ensure matching uv/mtex */
 	BM_mesh_cd_validate(bm);
 
-	BM_mesh_bm_to_me(bm, me, false);
+	BM_mesh_bm_to_me(bm, me, (&(struct BMeshToMeshParams){0}));
 
 	/* we could have the user do this but if they forget blender can easy crash
 	 * since the references arrays for the objects derived meshes are now invalid */
@@ -1075,7 +1075,10 @@ static PyObject *bpy_bmesh_from_mesh(BPy_BMesh *self, PyObject *args, PyObject *
 
 	bm = self->bm;
 
-	BM_mesh_bm_from_me(bm, me, use_fnorm, use_shape_key, shape_key_index + 1);
+	BM_mesh_bm_from_me(
+	        bm, me, (&(struct BMeshFromMeshParams){
+	            .calc_face_normal = use_fnorm, .use_shapekey = use_shape_key, .active_shapekey = shape_key_index + 1,
+	        }));
 
 	Py_RETURN_NONE;
 }

source/blenderplayer/bad_level_call_stubs/stubs.c

@@ -221,7 +221,7 @@ bool BPY_string_is_keyword(const char *str) { return false; }
 /*new render funcs */
 void EDBM_selectmode_set(struct BMEditMesh *em) RET_NONE
 void EDBM_mesh_load(struct Object *ob) RET_NONE
-void EDBM_mesh_make(struct ToolSettings *ts, struct Object *ob) RET_NONE
+void EDBM_mesh_make(struct ToolSettings *ts, struct Object *ob, const bool use_key_index) RET_NONE
 void EDBM_mesh_normals_update(struct BMEditMesh *em) RET_NONE
 void *g_system;
 bool EDBM_mtexpoly_check(struct BMEditMesh *em) RET_ZERO