Transform/Snap: EditMesh/BKE_bvhutils API improvements

Separate the creation of trees from EditMesh from the creation of trees from DerivedMesh.
This was meant to simplify the API, but didn't work out so well.

`bvhtree_from_mesh_*` actually is working as `bvhtree_from_derivedmesh_*`.
This is inconsistent with the trees created from EditMesh. Since for create them does not use the DerivedMesh.

In such cases the dm is being used only to cache the tree in the struct DerivedMesh. What is immediately released once
bvhtree is being used in functions that change(tag) the DM cleaning the cache.

- Use a filter function so users of SnapObjectContext can define how edit-mesh elements are handled.
- Remove em_evil.
- bvhtree of EditMesh is now really cached in the snap functions.
- Code becomes organized and easier to maintain.

This is an important patch for future improvements in snapping functions.

1 files changed, 2 insertions, 1 deletions

diff --git a/source/blender/editors/transform/transform.h b/source/blender/editors/transform/transform.h
index 5858210cd4f..11151a9c65a 100644
--- a/source/blender/editors/transform/transform.h
+++ b/source/blender/editors/transform/transform.h
@@ -59,6 +59,7 @@ struct wmTimer;
 struct ARegion;
 struct ReportList;
 struct EditBone;
+struct SnapObjectContext;
 
 /* transinfo->redraw */
 typedef enum {
@@ -105,7 +106,7 @@ typedef struct TransSnap {
 	/**
 	 * Re-usable snap context data.
 	 */
-	SnapObjectContext *object_context;
+	struct SnapObjectContext *object_context;
 } TransSnap;
 
 typedef struct TransCon {