Fix T63794: duplicating an armature clears B-Bones' custom handle references.

This patch fixes T63794 by updating duplicated bones' custom handle references
to point to the new armature's bones.

The problem occurs because B-Bones of a duplicated armature keep pointing to
the old armature's bones. The references are cleared upon entering Edit Mode
because there are no matching `EditBone` for such bones, and `find_ebone_link`
just returns `NULL` in such cases.

Reviewers: mont29, angavrilov

Maniphest Tasks: T63794

Differential Revision: https://developer.blender.org/D4726

1 files changed, 33 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/armature.c b/source/blender/blenkernel/intern/armature.c
index 97238020f29..7f374c1d66e 100644
--- a/source/blender/blenkernel/intern/armature.c
+++ b/source/blender/blenkernel/intern/armature.c
@@ -169,6 +169,28 @@ static void copy_bonechildren(Bone *bone_dst,
   }
 }
 
+static void copy_bonechildren_custom_handles(Bone *bone_dst, bArmature *arm_dst, GHash **bone_hash)
+{
+  Bone *bone_dst_child;
+
+  /* Lazily create the name -> bone hashtable. */
+  if ((bone_dst->bbone_prev || bone_dst->bbone_next) && *bone_hash == NULL) {
+    *bone_hash = BKE_armature_bone_from_name_map(arm_dst);
+  }
+
+  if (bone_dst->bbone_prev) {
+    bone_dst->bbone_prev = BLI_ghash_lookup(*bone_hash, bone_dst->bbone_prev->name);
+  }
+  if (bone_dst->bbone_next) {
+    bone_dst->bbone_next = BLI_ghash_lookup(*bone_hash, bone_dst->bbone_next->name);
+  }
+
+  for (bone_dst_child = bone_dst->childbase.first; bone_dst_child;
+       bone_dst_child = bone_dst_child->next) {
+    copy_bonechildren_custom_handles(bone_dst_child, arm_dst, bone_hash);
+  }
+}
+
 /**
  * Only copy internal data of Armature ID from source
  * to already allocated/initialized destination.
@@ -202,6 +224,17 @@ void BKE_armature_copy_data(Main *UNUSED(bmain),
 
   arm_dst->act_bone = bone_dst_act;
 
+  /* Fix custom handle references. */
+  GHash *bone_hash = NULL; /* lazily created */
+
+  for (bone_dst = arm_dst->bonebase.first; bone_dst; bone_dst = bone_dst->next) {
+    copy_bonechildren_custom_handles(bone_dst, arm_dst, &bone_hash);
+  }
+
+  if (bone_hash) {
+    BLI_ghash_free(bone_hash, NULL, NULL);
+  }
+
   arm_dst->edbo = NULL;
   arm_dst->act_edbone = NULL;
 }