UV Island support for vertex & edge slide

This ensures slide with `Correct UVs` enabled, keeps UV's (any loop custom-data) contiguous.

Adds 2 key functions `BM_vert_loop_groups_data_layer_create` and `BM_vert_loop_groups_data_layer_merge`

They work by collecting matching loop custom-data around the vertices loop-fan,
and merging the custom-data after edits are made.

Thanks to @mont29 for review!

1 files changed, 22 insertions, 1 deletions

diff --git a/source/blender/editors/transform/transform.h b/source/blender/editors/transform/transform.h
index 2330ec6e79e..84a81e8b3d8 100644
--- a/source/blender/editors/transform/transform.h
+++ b/source/blender/editors/transform/transform.h
@@ -200,9 +200,19 @@ typedef struct TransDataNla {
 struct LinkNode;
 struct GHash;
 
+/* header of TransDataEdgeSlideVert, TransDataEdgeSlideEdge */
+typedef struct TransDataGenericSlideVert {
+	struct BMVert *v;
+	struct LinkNode **cd_loop_groups;
+} TransDataGenericSlideVert;
+
 typedef struct TransDataEdgeSlideVert {
-	struct BMVert *v_a, *v_b;
+	/* TransDataGenericSlideVert */
 	struct BMVert *v;
+	struct LinkNode **cd_loop_groups;
+	/* end generic */
+
+	struct BMVert *v_a, *v_b;
 	float v_co_orig[3];
 
 	float edge_len;
@@ -220,6 +230,13 @@ typedef struct SlideOrigData {
 	bool use_origfaces;
 	struct GHash    *origfaces;
 	struct BMesh *bm_origfaces;
+
+	struct MemArena *arena;
+	/* number of math BMLoop layers */
+	int  layer_math_map_num;
+	/* array size of 'layer_math_map_num'
+	 * maps TransDataVertSlideVert.cd_group index to absolute CustomData layer index */
+	int *layer_math_map;
 } SlideOrigData;
 
 typedef struct EdgeSlideData {
@@ -241,7 +258,11 @@ typedef struct EdgeSlideData {
 
 
 typedef struct TransDataVertSlideVert {
+	/* TransDataGenericSlideVert */
 	BMVert *v;
+	struct LinkNode **cd_loop_groups;
+	/* end generic */
+
 	float   co_orig_3d[3];
 	float   co_orig_2d[2];
 	float (*co_link_orig_3d)[3];