Fix: selecting bones of pose assets not respecting multiple slots

The code for selecting bones from a pose was still using the legacy api,
thus it didn't work properly for selecting bones of all slots.

Pull Request: https://projects.blender.org/blender/blender/pulls/134912

scripts/addons_core/pose_library/operators.py

@@ -272,8 +272,8 @@ class POSELIB_OT_pose_asset_select_bones(PoseAssetUser, Operator):
     flipped: BoolProperty(name="Flipped", default=False)  # type: ignore
 
     def use_pose(self, context: Context, pose_asset: Action) -> Set[str]:
-        arm_object: Object = context.object
-        pose_usage.select_bones(arm_object, pose_asset, select=self.select, flipped=self.flipped)
+        for object in context.selected_objects:
+            pose_usage.select_bones(object, pose_asset, select=self.select, flipped=self.flipped)
         if self.select:
             msg = tip_("Selected bones from %s") % pose_asset.name
         else:

scripts/addons_core/pose_library/pose_usage.py

@@ -9,26 +9,59 @@ Pose Library - usage functions.
 from typing import Set
 import re
 import bpy
+from bpy_extras import anim_utils
 
 from bpy.types import (
     Action,
     Object,
+    ActionSlot,
 )
 
 
+def _find_best_slot(action: Action, object: Object) -> ActionSlot | None:
+    """
+    Trying to find a slot that is the best match for the given object.
+    The best slot is either
+    the slot of the given object if that exists in the action,
+    or the first slot of type object
+    """
+    if not action.slots:
+        return None
+    # For the selection code, the object doesn't need to be animated yet, so anim_data may be None.
+    anim_data = object.animation_data
+
+    # last_slot_identifier will equal to the current slot identifier if one is assigned.
+    if anim_data and anim_data.last_slot_identifier in action.slots:
+        return action.slots[anim_data.last_slot_identifier]
+
+    for slot in action.slots:
+        if slot.target_id_type == 'OBJECT':
+            return slot
+    return None
+
+
 def select_bones(arm_object: Object, action: Action, *, select: bool, flipped: bool) -> None:
-    pose_bone_re = re.compile(r'pose.bones\["([^"]+)"\]')
     pose = arm_object.pose
+    if not pose:
+        return
+
+    slot = _find_best_slot(action, arm_object)
+    if not slot:
+        return
 
     seen_bone_names: Set[str] = set()
+    channelbag = anim_utils.action_get_channelbag_for_slot(action, slot)
+    if not channelbag:
+        return
 
-    for fcurve in action.fcurves:
+    pose_bone_re = re.compile(r'pose.bones\["([^"]+)"\]')
+    for fcurve in channelbag.fcurves:
         data_path: str = fcurve.data_path
-        match = pose_bone_re.match(data_path)
-        if not match:
+        regex_match = pose_bone_re.match(data_path)
+        if not regex_match:
             continue
 
-        bone_name = match.group(1)
+        bone_name = regex_match.group(1)
 
         if bone_name in seen_bone_names:
             continue

scripts/modules/bpy_extras/anim_utils.py

@@ -13,7 +13,7 @@ __all__ = (
 )
 
 import bpy
-from bpy.types import Action, ActionSlot
+from bpy.types import Action, ActionSlot, ActionChannelbag
 from dataclasses import dataclass
 
 from collections.abc import (
@@ -75,14 +75,18 @@ class BakeOptions:
     """Bake custom properties."""
 
 
-def _get_channelbag_for_slot(action: Action, slot: ActionSlot):
-    # This is on purpose limited to the first layer and strip. To support more
-    # than 1 layer, a rewrite of this operator is needed which ideally would
-    # happen in C++.
+def action_get_channelbag_for_slot(action: Action, slot: ActionSlot) -> ActionChannelbag | None:
+    """
+    Returns the first channelbag found for the slot.
+    In case there are multiple layers or strips they are iterated until a
+    channelbag for that slot is found. In case no matching channelbag is found, returns None.
+    """
     for layer in action.layers:
         for strip in layer.strips:
             channelbag = strip.channelbag(slot)
-            return channelbag
+            if channelbag:
+                return channelbag
+    return None
 
 
 def _ensure_channelbag_exists(action: Action, slot: ActionSlot):
@@ -409,7 +413,7 @@ def bake_action_iter(
     # pose
     lookup_fcurves = {}
     assert action.is_action_layered
-    channelbag = _get_channelbag_for_slot(action, atd.action_slot)
+    channelbag = action_get_channelbag_for_slot(action, atd.action_slot)
     if channelbag:
         # channelbag can be None if no layers or strips exist in the action.
         lookup_fcurves = {(fcurve.data_path, fcurve.array_index): fcurve for fcurve in channelbag.fcurves}