Fix error in recent vert/edge-slide commits

`CustomData_bmesh_interp_n` was expecting the 'dest' arg not to have its offset applied.

This was a bit confusing since the source args have it applied,
and in some cases we only have the destination with the offset.

6 files changed, 75 insertions, 58 deletions

diff --git a/source/blender/blenkernel/BKE_customdata.h b/source/blender/blenkernel/BKE_customdata.h
index 508784273bc..e2e4a7a08ec 100644
--- a/source/blender/blenkernel/BKE_customdata.h
+++ b/source/blender/blenkernel/BKE_customdata.h
@@ -204,7 +204,7 @@ void CustomData_copy_data(const struct CustomData *source,
 void CustomData_copy_data_named(const struct CustomData *source,
                           struct CustomData *dest, int source_index,
                           int dest_index, int count);
-void CustomData_copy_elements(int type, void *source, void *dest, int count);
+void CustomData_copy_elements(int type, void *src_data_ofs, void *dst_data_ofs, int count);
 void CustomData_bmesh_copy_data(const struct CustomData *source, 
                                 struct CustomData *dest, void *src_block, 
                                 void **dest_block);
@@ -232,11 +232,11 @@ void CustomData_interp(
         int count, int dest_index);
 void CustomData_bmesh_interp_n(
         struct CustomData *data, const void **src_blocks, const float *weights,
-        const float *sub_weights, int count, void *dest_block_ofs, int n);
+        const float *sub_weights, int count, void *dst_block_ofs, int n);
 void CustomData_bmesh_interp(
         struct CustomData *data, const void **src_blocks,
         const float *weights, const float *sub_weights, int count,
-        void *dest_block);
+        void *dst_block);
 
 
 /* swaps the data in the element corners, to new corners with indices as
diff --git a/source/blender/blenkernel/intern/customdata.c b/source/blender/blenkernel/intern/customdata.c
index 585ae905013..1362c55f49c 100644
--- a/source/blender/blenkernel/intern/customdata.c
+++ b/source/blender/blenkernel/intern/customdata.c
@@ -1790,7 +1790,8 @@ static CustomDataLayer *customData_add_layer__internal(CustomData *data, int typ
                                                        int totelem, const char *name)
 {
 	const LayerTypeInfo *typeInfo = layerType_getInfo(type);
-	int size = typeInfo->size * totelem, flag = 0, index = data->totlayer;
+	const int size = totelem * typeInfo->size;
+	int flag = 0, index = data->totlayer;
 	void *newlayerdata = NULL;
 
 	/* Passing a layerdata to copy from with an alloctype that won't copy is
@@ -2003,7 +2004,7 @@ static void *customData_duplicate_referenced_layer_index(CustomData *data, const
 		const LayerTypeInfo *typeInfo = layerType_getInfo(layer->type);
 
 		if (typeInfo->copy) {
-			void *dst_data = MEM_mallocN(typeInfo->size * totelem, "CD duplicate ref layer");
+			void *dst_data = MEM_mallocN(totelem * typeInfo->size, "CD duplicate ref layer");
 			typeInfo->copy(layer->data, dst_data, totelem);
 			layer->data = dst_data;
 		}
@@ -2104,14 +2105,14 @@ void CustomData_set_only_copy(const struct CustomData *data,
 			data->layers[i].flag |= CD_FLAG_NOCOPY;
 }
 
-void CustomData_copy_elements(int type, void *source, void *dest, int count)
+void CustomData_copy_elements(int type, void *src_data_ofs, void *dst_data_ofs, int count)
 {
 	const LayerTypeInfo *typeInfo = layerType_getInfo(type);
 
 	if (typeInfo->copy)
-		typeInfo->copy(source, dest, count);
+		typeInfo->copy(src_data_ofs, dst_data_ofs, count);
 	else
-		memcpy(dest, source, typeInfo->size * count);
+		memcpy(dst_data_ofs, src_data_ofs, count * typeInfo->size);
 }
 
 static void CustomData_copy_data_layer(
@@ -2123,28 +2124,28 @@ static void CustomData_copy_data_layer(
 	int dst_offset;
 
 	const void *src_data = source->layers[src_i].data;
-	void *dest_data = dest->layers[dst_i].data;
+	void *dst_data = dest->layers[dst_i].data;
 
 	typeInfo = layerType_getInfo(source->layers[src_i].type);
 
 	src_offset = src_index * typeInfo->size;
 	dst_offset = dst_index * typeInfo->size;
 
-	if (!src_data || !dest_data) {
-		if (!(src_data == NULL && dest_data == NULL)) {
+	if (!src_data || !dst_data) {
+		if (!(src_data == NULL && dst_data == NULL)) {
 			printf("%s: warning null data for %s type (%p --> %p), skipping\n",
 				   __func__, layerType_getName(source->layers[src_i].type),
-				   (void *)src_data, (void *)dest_data);
+				   (void *)src_data, (void *)dst_data);
 		}
 		return;
 	}
 
 	if (typeInfo->copy)
 		typeInfo->copy(POINTER_OFFSET(src_data, src_offset),
-		               POINTER_OFFSET(dest_data, dst_offset),
+		               POINTER_OFFSET(dst_data, dst_offset),
 		               count);
 	else
-		memcpy(POINTER_OFFSET(dest_data, dst_offset),
+		memcpy(POINTER_OFFSET(dst_data, dst_offset),
 		       POINTER_OFFSET(src_data, src_offset),
 		       count * typeInfo->size);
 }
@@ -2208,7 +2209,7 @@ void CustomData_free_elem(CustomData *data, int index, int count)
 			typeInfo = layerType_getInfo(data->layers[i].type);
 
 			if (typeInfo->free) {
-				int offset = typeInfo->size * index;
+				int offset = index * typeInfo->size;
 
 				typeInfo->free(POINTER_OFFSET(data->layers[i].data, offset), count, typeInfo->size);
 			}
@@ -2223,7 +2224,6 @@ void CustomData_interp(const CustomData *source, CustomData *dest,
                        int count, int dest_index)
 {
 	int src_i, dest_i;
-	int dest_offset;
 	int j;
 	const void *source_buf[SOURCE_BUF_SIZE];
 	const void **sources = source_buf;
@@ -2255,13 +2255,11 @@ void CustomData_interp(const CustomData *source, CustomData *dest,
 			void *src_data = source->layers[src_i].data;
 
 			for (j = 0; j < count; ++j) {
-				sources[j] = POINTER_OFFSET(src_data, typeInfo->size * src_indices[j]);
+				sources[j] = POINTER_OFFSET(src_data, src_indices[j] * typeInfo->size);
 			}
 
-			dest_offset = dest_index * typeInfo->size;
-
 			typeInfo->interp(sources, weights, sub_weights, count,
-			                 POINTER_OFFSET(dest->layers[dest_i].data, dest_offset));
+			                 POINTER_OFFSET(dest->layers[dest_i].data, dest_index * typeInfo->size));
 
 			/* if there are multiple source & dest layers of the same type,
 			 * we don't want to copy all source layers to the same dest, so
@@ -2283,7 +2281,7 @@ void CustomData_swap(struct CustomData *data, int index, const int *corner_indic
 		typeInfo = layerType_getInfo(data->layers[i].type);
 
 		if (typeInfo->swap) {
-			int offset = typeInfo->size * index;
+			const int offset = index * typeInfo->size;
 
 			typeInfo->swap(POINTER_OFFSET(data->layers[i].data, offset), corner_indices);
 		}
@@ -2986,24 +2984,24 @@ void CustomData_bmesh_set_layer_n(CustomData *data, void *block, int n, void *so
 }
 
 /**
- * \param src_blocks must be pointers to the data, offset by layer->offset already.
+ * \note src_blocks_ofs & dst_block_ofs
+ * must be pointers to the data, offset by layer->offset already.
  */
 void CustomData_bmesh_interp_n(
-        CustomData *data, const void **src_blocks,
+        CustomData *data, const void **src_blocks_ofs,
         const float *weights, const float *sub_weights,
-        int count, void *dest_block, int n)
+        int count, void *dst_block_ofs, int n)
 {
 	CustomDataLayer *layer = &data->layers[n];
 	const LayerTypeInfo *typeInfo = layerType_getInfo(layer->type);
 
-	typeInfo->interp(src_blocks, weights, sub_weights, count,
-	                 POINTER_OFFSET(dest_block, layer->offset));
+	typeInfo->interp(src_blocks_ofs, weights, sub_weights, count, dst_block_ofs);
 }
 
 void CustomData_bmesh_interp(
         CustomData *data, const void **src_blocks,
         const float *weights, const float *sub_weights,
-        int count, void *dest_block)
+        int count, void *dst_block)
 {
 	int i, j;
 	void *source_buf[SOURCE_BUF_SIZE];
@@ -3023,7 +3021,10 @@ void CustomData_bmesh_interp(
 			for (j = 0; j < count; ++j) {
 				sources[j] = POINTER_OFFSET(src_blocks[j], layer->offset);
 			}
-			CustomData_bmesh_interp_n(data, sources, weights, sub_weights, count, dest_block, i);
+			CustomData_bmesh_interp_n(
+			        data, sources,
+			        weights, sub_weights, count,
+			        POINTER_OFFSET(dst_block, layer->offset), i);
 		}
 	}
 
diff --git a/source/blender/bmesh/intern/bmesh_interp.c b/source/blender/bmesh/intern/bmesh_interp.c
index 1d8c6f5c041..af4bc90d695 100644
--- a/source/blender/bmesh/intern/bmesh_interp.c
+++ b/source/blender/bmesh/intern/bmesh_interp.c
@@ -202,8 +202,8 @@ void BM_face_interp_from_face(BMesh *bm, BMFace *target, BMFace *source, const b
 	BMLoop *l_iter;
 	BMLoop *l_first;
 
-	void **blocks_l    = BLI_array_alloca(blocks_l, source->len);
-	void **blocks_v    = do_vertex ? BLI_array_alloca(blocks_v, source->len) : NULL;
+	const void **blocks_l    = BLI_array_alloca(blocks_l, source->len);
+	const void **blocks_v    = do_vertex ? BLI_array_alloca(blocks_v, source->len) : NULL;
 	float (*cos_2d)[2] = BLI_array_alloca(cos_2d, source->len);
 	float axis_mat[3][3];  /* use normal to transform into 2d xy coords */
 	int i;
@@ -220,10 +220,8 @@ void BM_face_interp_from_face(BMesh *bm, BMFace *target, BMFace *source, const b
 		if (do_vertex) blocks_v[i] = l_iter->v->head.data;
 	} while (i++, (l_iter = l_iter->next) != l_first);
 
-	BM_face_interp_from_face_ex(
-	        bm, target, source, do_vertex,
-	        (const void **)blocks_l, (const void **)blocks_v,
-	        cos_2d, axis_mat);
+	BM_face_interp_from_face_ex(bm, target, source, do_vertex,
+	                            blocks_l, blocks_v, cos_2d, axis_mat);
 }
 
 /**
@@ -1056,25 +1054,31 @@ LinkNode *BM_vert_loop_groups_data_layer_create(BMesh *bm, BMVert *v, int layer_
 }
 
 static void bm_vert_loop_groups_data_layer_merge__single(
-        BMesh *bm, void *lf_p, void *data, int type)
+        BMesh *bm, void *lf_p, int layer_n,
+        void *data_tmp)
 {
 	struct LoopGroupCD *lf = lf_p;
+	const int type = bm->ldata.layers[layer_n].type;
 	int i;
 	const float *data_weights;
 
 	data_weights = lf->data_weights;
 
-	CustomData_bmesh_interp(&bm->ldata, (const void **)lf->data, data_weights, NULL, lf->data_len, data);
+	CustomData_bmesh_interp_n(
+	        &bm->ldata, (const void **)lf->data,
+	        data_weights, NULL, lf->data_len, data_tmp, layer_n);
 
 	for (i = 0; i < lf->data_len; i++) {
-		CustomData_copy_elements(type, data, lf->data[i], 1);
+		CustomData_copy_elements(type, data_tmp, lf->data[i], 1);
 	}
 }
 
 static void bm_vert_loop_groups_data_layer_merge_weights__single(
-        BMesh *bm, void *lf_p, void *data, int type, const float *loop_weights)
+        BMesh *bm, void *lf_p, const int layer_n, void *data_tmp,
+        const float *loop_weights)
 {
 	struct LoopGroupCD *lf = lf_p;
+	const int type = bm->ldata.layers[layer_n].type;
 	int i;
 	const float *data_weights;
 
@@ -1096,25 +1100,28 @@ static void bm_vert_loop_groups_data_layer_merge_weights__single(
 		data_weights = lf->data_weights;
 	}
 
-	CustomData_bmesh_interp(&bm->ldata, (const void **)lf->data, data_weights, NULL, lf->data_len, data);
+	CustomData_bmesh_interp_n(
+	        &bm->ldata, (const void **)lf->data,
+	        data_weights, NULL, lf->data_len, data_tmp, layer_n);
 
 	for (i = 0; i < lf->data_len; i++) {
-		CustomData_copy_elements(type, data, lf->data[i], 1);
+		CustomData_copy_elements(type, data_tmp, lf->data[i], 1);
 	}
 }
 
 /**
  * Take existing custom data and merge each fan's data.
  */
-void BM_vert_loop_groups_data_layer_merge(BMesh *bm, LinkNode *groups, int layer_n)
+void BM_vert_loop_groups_data_layer_merge(BMesh *bm, LinkNode *groups, const int layer_n)
 {
-	int type = bm->ldata.layers[layer_n].type;
-	int size = CustomData_sizeof(type);
-	void *data = alloca(size);
+	const int type = bm->ldata.layers[layer_n].type;
+	const int size = CustomData_sizeof(type);
+	void *data_tmp = malloc(size);
 
 	do {
-		bm_vert_loop_groups_data_layer_merge__single(bm, groups->link, data, type);
+		bm_vert_loop_groups_data_layer_merge__single(bm, groups->link, layer_n, data_tmp);
 	} while ((groups = groups->next));
+	free(data_tmp);
 }
 
 /**
@@ -1123,13 +1130,14 @@ void BM_vert_loop_groups_data_layer_merge(BMesh *bm, LinkNode *groups, int layer
  */
 void BM_vert_loop_groups_data_layer_merge_weights(BMesh *bm, LinkNode *groups, int layer_n, const float *loop_weights)
 {
-	int type = bm->ldata.layers[layer_n].type;
-	int size = CustomData_sizeof(type);
-	void *data = alloca(size);
+	const int type = bm->ldata.layers[layer_n].type;
+	const int size = CustomData_sizeof(type);
+	void *data_tmp = malloc(size);
 
 	do {
-		bm_vert_loop_groups_data_layer_merge_weights__single(bm, groups->link, data, type, loop_weights);
+		bm_vert_loop_groups_data_layer_merge_weights__single(bm, groups->link, layer_n, data_tmp, loop_weights);
 	} while ((groups = groups->next));
+	free(data_tmp);
 }
 
 /** \} */
\ No newline at end of file
diff --git a/source/blender/bmesh/intern/bmesh_interp.h b/source/blender/bmesh/intern/bmesh_interp.h
index 3be6dcdace3..117333b52e3 100644
--- a/source/blender/bmesh/intern/bmesh_interp.h
+++ b/source/blender/bmesh/intern/bmesh_interp.h
@@ -54,8 +54,13 @@ void  BM_loop_interp_from_face(BMesh *bm, BMLoop *target, BMFace *source,
                                const bool do_vertex, const bool do_multires);
 
 void  BM_face_multires_bounds_smooth(BMesh *bm, BMFace *f);
-struct LinkNode *BM_vert_loop_groups_data_layer_create(BMesh *bm, BMVert *v, int layer_n, struct MemArena *arena);
-void BM_vert_loop_groups_data_layer_merge(BMesh *bm, struct LinkNode *groups, int layer_n);
-void BM_vert_loop_groups_data_layer_merge_weights(BMesh *bm, struct LinkNode *groups, int layer_n, const float *loop_weights);
+
+struct LinkNode *BM_vert_loop_groups_data_layer_create(
+        BMesh *bm, BMVert *v, const int layer_n, struct MemArena *arena);
+void BM_vert_loop_groups_data_layer_merge(
+        BMesh *bm, struct LinkNode *groups, const int layer_n);
+void BM_vert_loop_groups_data_layer_merge_weights(
+        BMesh *bm, struct LinkNode *groups, const int layer_n,
+        const float *loop_weights);
 
 #endif /* __BMESH_INTERP_H__ */
diff --git a/source/blender/bmesh/tools/bmesh_decimate_collapse.c b/source/blender/bmesh/tools/bmesh_decimate_collapse.c
index 85402544396..230cb302d28 100644
--- a/source/blender/bmesh/tools/bmesh_decimate_collapse.c
+++ b/source/blender/bmesh/tools/bmesh_decimate_collapse.c
@@ -527,7 +527,9 @@ static void bm_edge_collapse_loop_customdata(BMesh *bm, BMLoop *l, BMVert *v_cle
 
 					/* detect seams */
 					if (CustomData_data_equals(type, cd_src[0], cd_iter)) {
-						CustomData_bmesh_interp_n(&bm->ldata, cd_src, w, NULL, 2, l_iter->head.data, i);
+						CustomData_bmesh_interp_n(
+						        &bm->ldata, cd_src, w, NULL, ARRAY_SIZE(cd_src),
+						        POINTER_OFFSET(l_iter->head.data, offset), i);
 #ifdef USE_SEAM
 						is_seam = false;
 #endif
diff --git a/source/blender/editors/transform/transform.c b/source/blender/editors/transform/transform.c
index 58ef2958f37..8421f4dd3fe 100644
--- a/source/blender/editors/transform/transform.c
+++ b/source/blender/editors/transform/transform.c
@@ -5317,16 +5317,17 @@ static void slide_origdata_interp_data_vert(
         TransDataGenericSlideVert *sv)
 {
 	BMIter liter;
-	BMLoop *l;
-	int j;
+	int j, l_num;
 	float *loop_weights;
 	const bool do_loop_weight = (len_squared_v3v3(sv->v->co, sv->co_orig_3d) > FLT_EPSILON);
 
 	// BM_ITER_ELEM (l, &liter, sv->v, BM_LOOPS_OF_VERT) {
-	l = BM_iter_new(&liter, bm, BM_LOOPS_OF_VERT, sv->v);
-	loop_weights = do_loop_weight ? BLI_array_alloca(loop_weights, liter.count) : NULL;
-	for (j = 0 ; l; l = BM_iter_step(&liter), j++) {
+	BM_iter_init(&liter, bm, BM_LOOPS_OF_VERT, sv->v);
+	l_num = liter.count;
+	loop_weights = do_loop_weight ? BLI_array_alloca(loop_weights, l_num) : NULL;
+	for (j = 0; j < l_num; j++) {
 		BMFace *f_copy;  /* the copy of 'f' */
+		BMLoop *l = BM_iter_step(&liter);
 
 		f_copy = BLI_ghash_lookup(sod->origfaces, l->f);