Anim: allow appending bone collections with liboverrides

source/blender/animrig/ANIM_bone_collections.h

@@ -74,6 +74,17 @@ void ANIM_armature_runtime_free(struct bArmature *armature);
  */
 struct BoneCollection *ANIM_armature_bonecoll_new(struct bArmature *armature, const char *name);
 
+/**
+ * Add a bone collection to the Armature.
+ *
+ * NOTE: this should not typically be used. It is only used by the library overrides system to
+ * apply override operations.
+ */
+struct BoneCollection *ANIM_armature_bonecoll_insert_copy_after(
+    struct bArmature *armature,
+    struct BoneCollection *anchor,
+    const struct BoneCollection *bcoll_to_copy);
+
 /**
  * Remove a bone collection from the armature.
  */

source/blender/animrig/intern/bone_collections.cc

@@ -7,6 +7,7 @@
  */
 
 #include "BLI_linklist.h"
+#include "BLI_listbase.h"
 #include "BLI_map.hh"
 #include "BLI_math_color.h"
 #include "BLI_string.h"
@@ -113,6 +114,31 @@ BoneCollection *ANIM_armature_bonecoll_new(bArmature *armature, const char *name
   return bcoll;
 }
 
+BoneCollection *ANIM_armature_bonecoll_insert_copy_after(bArmature *armature,
+                                                         BoneCollection *anchor,
+                                                         const BoneCollection *bcoll_to_copy)
+{
+  BoneCollection *bcoll = static_cast<BoneCollection *>(MEM_dupallocN(bcoll_to_copy));
+
+  /* Remap the bone pointers to the given armature, as `bcoll_to_copy` will
+   * likely be owned by another copy of the armature. */
+  BLI_duplicatelist(&bcoll->bones, &bcoll->bones);
+  BKE_armature_bone_hash_make(armature);
+  LISTBASE_FOREACH (BoneCollectionMember *, member, &bcoll->bones) {
+    member->bone = BKE_armature_find_bone_name(armature, member->bone->name);
+  }
+
+  if (bcoll_to_copy->prop) {
+    bcoll->prop = IDP_CopyProperty_ex(bcoll_to_copy->prop,
+                                      0 /*do_id_user ? 0 : LIB_ID_CREATE_NO_USER_REFCOUNT*/);
+  }
+
+  BLI_insertlinkafter(&armature->collections, anchor, bcoll);
+  bonecoll_ensure_name_unique(armature, bcoll);
+
+  return bcoll;
+}
+
 static void armature_bonecoll_active_clear(bArmature *armature)
 {
   armature->runtime.active_collection_index = -1;

source/blender/editors/armature/bone_collections.cc

@@ -66,6 +66,27 @@ static bool bone_collection_poll(bContext *C)
   return true;
 }
 
+static bool bone_collection_add_poll(bContext *C)
+{
+  Object *ob = ED_object_context(C);
+  if (ob == nullptr) {
+    return false;
+  }
+
+  if (ob->type != OB_ARMATURE) {
+    CTX_wm_operator_poll_msg_set(C, "Bone collections can only be added to an Armature");
+    return false;
+  }
+
+  if (ID_IS_LINKED(ob->data)) {
+    CTX_wm_operator_poll_msg_set(
+        C, "Cannot add bone collections to a linked Armature without an override");
+    return false;
+  }
+
+  return true;
+}
+
 static bool active_bone_collection_poll(bContext *C)
 {
   if (!bone_collection_poll(C)) {
@@ -109,7 +130,7 @@ void ARMATURE_OT_collection_add(wmOperatorType *ot)
 
   /* api callbacks */
   ot->exec = bone_collection_add_exec;
-  ot->poll = bone_collection_poll;
+  ot->poll = bone_collection_add_poll;
 
   /* flags */
   ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;

source/blender/makesrna/intern/rna_armature.cc

@@ -299,6 +299,31 @@ static void rna_EditBone_collections_begin(CollectionPropertyIterator *iter, Poi
   rna_iterator_listbase_begin(iter, &bone_collection_refs, nullptr);
 }
 
+/* Armature.collections library override support. */
+static bool rna_Armature_collections_override_apply(Main *bmain,
+                                                    RNAPropertyOverrideApplyContext &rnaapply_ctx)
+{
+  PointerRNA *ptr_dst = &rnaapply_ctx.ptr_dst;
+  PropertyRNA *prop_dst = rnaapply_ctx.prop_dst;
+  PointerRNA *ptr_item_dst = &rnaapply_ctx.ptr_item_dst;
+  PointerRNA *ptr_item_src = &rnaapply_ctx.ptr_item_src;
+  IDOverrideLibraryPropertyOperation *opop = rnaapply_ctx.liboverride_operation;
+
+  if (opop->operation != LIBOVERRIDE_OP_INSERT_AFTER) {
+    printf("Unsupported RNA override operation on armature collections, ignoring\n");
+    return false;
+  }
+
+  bArmature *arm_dst = (bArmature *)ptr_dst->owner_id;
+  BoneCollection *bcoll_anchor = static_cast<BoneCollection *>(ptr_item_dst->data);
+  BoneCollection *bcoll_src = static_cast<BoneCollection *>(ptr_item_src->data);
+
+  ANIM_armature_bonecoll_insert_copy_after(arm_dst, bcoll_anchor, bcoll_src);
+
+  RNA_property_update_main(bmain, nullptr, ptr_dst, prop_dst);
+  return true;
+}
+
 static char *rna_BoneColor_path_posebone(const PointerRNA *ptr)
 {
   /* Find the bPoseChan that owns this BoneColor. */
@@ -1907,6 +1932,10 @@ static void rna_def_armature(BlenderRNA *brna)
   RNA_def_property_collection_sdna(prop, nullptr, "collections", nullptr);
   RNA_def_property_struct_type(prop, "BoneCollection");
   RNA_def_property_ui_text(prop, "Bone Collections", "");
+  RNA_def_property_override_funcs(
+      prop, nullptr, nullptr, "rna_Armature_collections_override_apply");
+  RNA_def_property_override_flag(
+      prop, PROPOVERRIDE_OVERRIDABLE_LIBRARY | PROPOVERRIDE_LIBRARY_INSERTION);
   rna_def_armature_collections(brna, prop);
 
   /* Enum values */