Fix: Joining armatures loses drivers

Currently, when joining two armatures, the drivers of the armatures being merged
in are lost. This commit introduces a new AnimData API function for merging
animation data into another AnimData block.

NOTE:
* For now, this only copies the drivers over. As a result, manual effort will
  still be needed to go through and fix the drivers.

  I am working on automating that process, but it's more important that the
  drivers don't have to be created from scratch for now (since this is needed
  for the Goosberry rigging work).

2 files changed, 29 insertions, 0 deletions

diff --git a/source/blender/editors/armature/armature_naming.c b/source/blender/editors/armature/armature_naming.c
index 9afc45955bd..f984bf071fa 100644
--- a/source/blender/editors/armature/armature_naming.c
+++ b/source/blender/editors/armature/armature_naming.c
@@ -267,6 +267,7 @@ void ED_armature_bone_rename(bArmature *arm, const char *oldnamep, const char *n
 		/* Fix all animdata that may refer to this bone - we can't just do the ones attached to objects, since
 		 * other ID-blocks may have drivers referring to this bone [#29822]
 		 */
+		// XXX: the ID here is for armatures, but most bone drivers are actually on the object instead...
 		{
 			
 			BKE_all_animdata_fix_paths_rename(&arm->id, "pose.bones", oldname, newname);
diff --git a/source/blender/editors/armature/armature_relations.c b/source/blender/editors/armature/armature_relations.c
index 3e226c39c8c..2a19d7a0bec 100644
--- a/source/blender/editors/armature/armature_relations.c
+++ b/source/blender/editors/armature/armature_relations.c
@@ -40,6 +40,7 @@
 #include "BLF_translation.h"
 
 #include "BKE_action.h"
+#include "BKE_animsys.h"
 #include "BKE_constraint.h"
 #include "BKE_context.h"
 #include "BKE_depsgraph.h"
@@ -200,6 +201,33 @@ int join_armature_exec(bContext *C, wmOperator *op)
 		if ((base->object->type == OB_ARMATURE) && (base->object != ob)) {
 			bArmature *curarm = base->object->data;
 			
+			/* we assume that each armature datablock is only used in a single place */
+			BLI_assert(ob->data != base->object->data);
+			
+			/* copy over animdata first, so that the link fixing can access and fix the links */
+			if (base->object->adt) {
+				if (ob->adt == NULL) {
+					/* no animdata, so just use a copy of the whole thing */
+					ob->adt = BKE_copy_animdata(base->object->adt, false);
+				}
+				else {
+					/* merge in data - we'll fix the drivers manually */
+					BKE_animdata_merge_copy(&ob->id, &base->object->id, ADT_MERGECOPY_KEEP_DST, false);
+				}
+			}
+			
+			if (curarm->adt) {
+				if (arm->adt == NULL) {
+					/* no animdata, so just use a copy of the whole thing */
+					arm->adt = BKE_copy_animdata(curarm->adt, false);
+				}
+				else {
+					/* merge in data - we'll fix the drivers manually */
+					BKE_animdata_merge_copy(&arm->id, &curarm->id, ADT_MERGECOPY_KEEP_DST, false);
+				}
+			}
+			
+			
 			/* Make a list of editbones in current armature */
 			ED_armature_to_edit(base->object->data);