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, 5 insertions, 0 deletions

diff --git a/source/blender/bmesh/intern/bmesh_interp.h b/source/blender/bmesh/intern/bmesh_interp.h
index c605ad31ae7..cd6d5e2731d 100644
--- a/source/blender/bmesh/intern/bmesh_interp.h
+++ b/source/blender/bmesh/intern/bmesh_interp.h
@@ -27,6 +27,9 @@
  *  \ingroup bmesh
  */
 
+struct LinkNode;
+struct MemArena;
+
 void  BM_loop_interp_multires(BMesh *bm, BMLoop *target, BMFace *source);
 void  BM_vert_interp_from_face(BMesh *bm, BMVert *v, BMFace *source);
 
@@ -49,5 +52,7 @@ 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);
 
 #endif /* __BMESH_INTERP_H__ */