Anim: add Action Slot selector to Action Constraint

Add slotted Actions support to Action constraints.

The user interface can be improved once #127751 lands.

Ref: #120406
Pull Request: https://projects.blender.org/blender/blender/pulls/127749

scripts/startup/bl_operators/anim.py

@@ -731,7 +731,28 @@ class ANIM_OT_slot_unassign_from_id(Operator):
         return {'FINISHED'}
 
 
-class ANIM_OT_slot_unassign_from_nla_strip(Operator):
+class generic_slot_unassign_mixin():
+    context_property_name = ""
+    """Which context attribute to use to get the to-be-manipulated data-block."""
+
+    @classmethod
+    def poll(cls, context):
+        slot_user = getattr(context, cls.context_property_name, None)
+        if not slot_user:
+            return False
+
+        if not slot_user.action_slot:
+            cls.poll_message_set("No Action slot is assigned, so there is nothing to un-assign")
+            return False
+        return True
+
+    def execute(self, context):
+        slot_user = getattr(context, self.context_property_name, None)
+        slot_user.action_slot = None
+        return {'FINISHED'}
+
+
+class ANIM_OT_slot_unassign_from_nla_strip(generic_slot_unassign_mixin, Operator):
     """Un-assign the assigned Action Slot from an NLA strip.
 
     Note that _which_ NLA strip should get this slot unassigned must be set in
@@ -744,21 +765,23 @@ class ANIM_OT_slot_unassign_from_nla_strip(Operator):
     bl_description = "Un-assign the action slot from this NLA strip, effectively making it non-animated"
     bl_options = {'REGISTER', 'UNDO'}
 
-    @classmethod
-    def poll(cls, context):
-        nla_strip = getattr(context, "nla_strip", None)
-        if not nla_strip:
-            return False
+    context_property_name = "nla_strip"
 
-        if not nla_strip.action or not nla_strip.action_slot:
-            cls.poll_message_set("This NLA strip has no Action slot assigned")
-            return False
-        return True
 
-    def execute(self, context):
-        nla_strip = getattr(context, "nla_strip", None)
-        nla_strip.action_slot = None
-        return {'FINISHED'}
+class ANIM_OT_slot_unassign_from_constraint(generic_slot_unassign_mixin, Operator):
+    """Un-assign the assigned Action Slot from an Action constraint.
+
+    Note that _which_ constraint should get this slot unassigned must be set in
+    the "constraint" context pointer, using:
+
+    >>> layout.context_pointer_set("constraint", constraint)
+    """
+    bl_idname = "anim.slot_unassign_from_constraint"
+    bl_label = "Unassign Slot"
+    bl_description = "Un-assign the action slot from this constraint"
+    bl_options = {'REGISTER', 'UNDO'}
+
+    context_property_name = "constraint"
 
 
 classes = (
@@ -773,4 +796,5 @@ classes = (
     ANIM_OT_slot_new_for_id,
     ANIM_OT_slot_unassign_from_id,
     ANIM_OT_slot_unassign_from_nla_strip,
+    ANIM_OT_slot_unassign_from_constraint,
 )

scripts/startup/bl_ui/properties_constraint.py

@@ -1126,7 +1126,17 @@ class ConstraintButtonsSubPanel:
         layout.use_property_split = True
         layout.use_property_decorate = True
 
-        layout.prop(con, "action")
+        col = layout.column(align=True)
+        col.prop(con, "action")
+        if context.preferences.experimental.use_animation_baklava and con.action and con.action.is_action_layered:
+            col.context_pointer_set("animated_id", con.id_data)
+            col.template_search(
+                con, "action_slot",
+                con, "action_slots",
+                new="",  # No use in making a new slot here.
+                unlink="anim.slot_unassign_from_constraint",
+            )
+
         layout.prop(con, "use_bone_object_action")
 
         col = layout.column(align=True)

source/blender/animrig/intern/action_iterators.cc

@@ -14,6 +14,8 @@
 #include "BKE_anim_data.hh"
 #include "BKE_nla.hh"
 
+#include "DNA_constraint_types.h"
+
 namespace blender::animrig {
 
 void action_foreach_fcurve(Action &action,
@@ -73,6 +75,48 @@ bool foreach_action_slot_use(
     }
   }
 
+  /* The rest of the code deals with constraints, so only relevant when this is an Object. */
+  if (GS(animated_id.name) != ID_OB) {
+    return true;
+  }
+
+  const Object &object = reinterpret_cast<const Object &>(animated_id);
+
+  /**
+   * Visit a constraint, and call the callback if it's an Action constraint.
+   *
+   * \returns whether to continue looping over possible uses of Actions, i.e.
+   * the return value of the callback.
+   */
+  auto visit_constraint = [&](const bConstraint &constraint) -> bool {
+    if (constraint.type != CONSTRAINT_TYPE_ACTION) {
+      return true;
+    }
+    bActionConstraint *constraint_data = static_cast<bActionConstraint *>(constraint.data);
+    if (!constraint_data->act) {
+      return true;
+    }
+    return callback(constraint_data->act->wrap(), constraint_data->action_slot_handle);
+  };
+
+  /* Visit Object constraints. */
+  LISTBASE_FOREACH (bConstraint *, con, &object.constraints) {
+    if (!visit_constraint(*con)) {
+      return false;
+    }
+  }
+
+  /* Visit Pose Bone constraints. */
+  if (object.type == OB_ARMATURE) {
+    LISTBASE_FOREACH (bPoseChannel *, pchan, &object.pose->chanbase) {
+      LISTBASE_FOREACH (bConstraint *, con, &pchan->constraints) {
+        if (!visit_constraint(*con)) {
+          return false;
+        }
+      }
+    }
+  }
+
   return true;
 }
 

source/blender/blenkernel/intern/anim_sys.cc

@@ -854,7 +854,7 @@ void animsys_evaluate_action_group(PointerRNA *ptr,
 
   const auto visit_fcurve = [&](FCurve *fcu) {
     /* check if this curve should be skipped */
-    if ((fcu->flag & (FCURVE_MUTED | FCURVE_DISABLED)) == 0 && !BKE_fcurve_is_empty(fcu)) {
+    if ((fcu->flag & FCURVE_MUTED) == 0 && !BKE_fcurve_is_empty(fcu)) {
       PathResolvedRNA anim_rna;
       if (BKE_animsys_rna_path_resolve(ptr, fcu->rna_path, fcu->array_index, &anim_rna)) {
         const float curval = calculate_fcurve(&anim_rna, fcu, anim_eval_context);

source/blender/blenkernel/intern/constraint.cc

@@ -2982,18 +2982,19 @@ static void actcon_get_tarmat(Depsgraph *depsgraph,
              (cob->pchan) ? cob->pchan->name : nullptr);
     }
 
-    /* TODO: add an action slot selector to the constraint settings. */
-    const blender::animrig::slot_handle_t slot_handle = blender::animrig::first_slot_handle(
-        *data->act);
-
     /* Get the appropriate information from the action */
     if (cob->type == CONSTRAINT_OBTYPE_OBJECT || (data->flag & ACTCON_BONE_USE_OBJECT_ACTION)) {
       Object workob;
 
       /* evaluate using workob */
       /* FIXME: we don't have any consistent standards on limiting effects on object... */
-      what_does_obaction(
-          cob->ob, &workob, nullptr, data->act, slot_handle, nullptr, &anim_eval_context);
+      what_does_obaction(cob->ob,
+                         &workob,
+                         nullptr,
+                         data->act,
+                         data->action_slot_handle,
+                         nullptr,
+                         &anim_eval_context);
       BKE_object_to_mat4(&workob, ct->matrix);
     }
     else if (cob->type == CONSTRAINT_OBTYPE_BONE) {
@@ -3010,8 +3011,13 @@ static void actcon_get_tarmat(Depsgraph *depsgraph,
       tchan->rotmode = pchan->rotmode;
 
       /* evaluate action using workob (it will only set the PoseChannel in question) */
-      what_does_obaction(
-          cob->ob, &workob, &pose, data->act, slot_handle, pchan->name, &anim_eval_context);
+      what_does_obaction(cob->ob,
+                         &workob,
+                         &pose,
+                         data->act,
+                         data->action_slot_handle,
+                         pchan->name,
+                         &anim_eval_context);
 
       /* convert animation to matrices for use here */
       BKE_pchan_calc_mat(tchan);
@@ -6673,3 +6679,11 @@ void BKE_constraint_blend_read_data(BlendDataReader *reader, ID *id_owner, ListB
     }
   }
 }
+
+/* Some static asserts to ensure that the bActionConstraint data is using the expected types for
+ * some of the fields. This check is done here instead of in DNA_constraint_types.h to avoid the
+ * inclusion of an DNA_anim_types.h in DNA_constraint_types.h just for this assert. */
+static_assert(
+    std::is_same_v<decltype(ActionSlot::handle), decltype(bActionConstraint::action_slot_handle)>);
+static_assert(
+    std::is_same_v<decltype(ActionSlot::name), decltype(bActionConstraint::action_slot_name)>);

source/blender/editors/object/object_constraint.cc

@@ -357,10 +357,23 @@ static void test_constraint(
       /* must have action */
       con->flag |= CONSTRAINT_DISABLE;
     }
-    else if (data->act->idroot != ID_OB) {
-      /* only object-rooted actions can be used */
-      data->act = nullptr;
-      con->flag |= CONSTRAINT_DISABLE;
+    else {
+      animrig::Action &action = data->act->wrap();
+      if (action.is_action_legacy()) {
+        if (data->act->idroot != ID_OB) {
+          /* Only object-rooted actions can be used. */
+          data->act = nullptr;
+          con->flag |= CONSTRAINT_DISABLE;
+        }
+      }
+      else {
+        /* The slot was assigned, so assume that it is suitable to animate the
+         * owner (only suitable slots appear in the drop-down). */
+        animrig::Slot *slot = action.slot_for_handle(data->action_slot_handle);
+        if (!slot) {
+          con->flag |= CONSTRAINT_DISABLE;
+        }
+      }
     }
 
     /* Skip target checking if we're not using it */

source/blender/makesdna/DNA_constraint_types.h

@@ -335,6 +335,9 @@ typedef struct bActionConstraint {
   char _pad[3];
   float eval_time; /* Only used when flag ACTCON_USE_EVAL_TIME is set. */
   struct bAction *act;
+  int32_t action_slot_handle;
+  char action_slot_name[66]; /* MAX_ID_NAME */
+  char _pad1[2];
   /** MAX_ID_NAME-2. */
   char subtarget[64];
 } bActionConstraint;

source/blender/makesrna/intern/rna_constraint.cc

@@ -29,6 +29,11 @@
 
 #include "ED_object.hh"
 
+#ifdef WITH_ANIM_BAKLAVA
+#  include "ANIM_action.hh"
+#  include "rna_action_tools.hh"
+#endif
+
 /* Please keep the names in sync with `constraint.cc`. */
 const EnumPropertyItem rna_enum_constraint_type_items[] = {
     RNA_ENUM_ITEM_HEADING(N_("Motion Tracking"), nullptr),
@@ -707,6 +712,49 @@ static void rna_ActionConstraint_minmax_range(
   }
 }
 
+#  ifdef WITH_ANIM_BAKLAVA
+static void rna_ActionConstraint_action_slot_handle_set(
+    PointerRNA *ptr, const blender::animrig::slot_handle_t new_slot_handle)
+{
+  bConstraint *con = (bConstraint *)ptr->data;
+  bActionConstraint *acon = (bActionConstraint *)con->data;
+
+  rna_generic_action_slot_handle_set(new_slot_handle,
+                                     *ptr->owner_id,
+                                     acon->act,
+                                     acon->action_slot_handle,
+                                     acon->action_slot_name);
+}
+
+static PointerRNA rna_ActionConstraint_action_slot_get(PointerRNA *ptr)
+{
+  bConstraint *con = (bConstraint *)ptr->data;
+  bActionConstraint *acon = (bActionConstraint *)con->data;
+
+  return rna_generic_action_slot_get(acon->act, acon->action_slot_handle);
+}
+
+static void rna_ActionConstraint_action_slot_set(PointerRNA *ptr,
+                                                 PointerRNA value,
+                                                 ReportList *reports)
+{
+  bConstraint *con = (bConstraint *)ptr->data;
+  bActionConstraint *acon = (bActionConstraint *)con->data;
+
+  rna_generic_action_slot_set(
+      value, *ptr->owner_id, acon->act, acon->action_slot_handle, acon->action_slot_name, reports);
+}
+
+static void rna_iterator_ActionConstraint_action_slots_begin(CollectionPropertyIterator *iter,
+                                                             PointerRNA *ptr)
+{
+  bConstraint *con = (bConstraint *)ptr->data;
+  bActionConstraint *acon = (bActionConstraint *)con->data;
+
+  rna_iterator_generic_action_slots_begin(iter, acon->act);
+}
+#  endif /* WITH_ANIM_BAKLAVA */
+
 static int rna_SplineIKConstraint_joint_bindings_get_length(const PointerRNA *ptr,
                                                             int length[RNA_MAX_ARRAY_DIMENSION])
 {
@@ -1859,6 +1907,71 @@ static void rna_def_constraint_action(BlenderRNA *brna)
   RNA_def_property_flag(prop, PROP_EDITABLE | PROP_ID_REFCOUNT);
   RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
 
+#  ifdef WITH_ANIM_BAKLAVA
+  /* This property is not necessary for the Python API (that is better off using
+   * slot references/pointers directly), but it is needed for library overrides
+   * to work. */
+  prop = RNA_def_property(srna, "action_slot_handle", PROP_INT, PROP_NONE);
+  RNA_def_property_int_sdna(prop, nullptr, "action_slot_handle");
+  RNA_def_property_int_funcs(
+      prop, nullptr, "rna_ActionConstraint_action_slot_handle_set", nullptr);
+  RNA_def_property_ui_text(prop,
+                           "Action Slot Handle",
+                           "A number that identifies which sub-set of the Action is considered "
+                           "to be for this Action Constraint");
+  RNA_def_property_override_flag(prop, PROPOVERRIDE_OVERRIDABLE_LIBRARY);
+  RNA_def_property_update(prop, NC_ANIMATION | ND_NLA_ACTCHANGE, "rna_Constraint_update");
+
+  prop = RNA_def_property(srna, "action_slot_name", PROP_STRING, PROP_NONE);
+  RNA_def_property_string_sdna(prop, nullptr, "action_slot_name");
+  RNA_def_property_ui_text(
+      prop,
+      "Action Slot Name",
+      "The name of the action slot. The slot identifies which sub-set of the Action "
+      "is considered to be for this constraint, and its name is used to find the right slot "
+      "when assigning an Action.");
+
+  prop = RNA_def_property(srna, "action_slot", PROP_POINTER, PROP_NONE);
+  RNA_def_property_struct_type(prop, "ActionSlot");
+  RNA_def_property_flag(prop, PROP_EDITABLE);
+  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_ui_text(
+      prop,
+      "Action Slot",
+      "The slot identifies which sub-set of the Action is considered to be for this "
+      "strip, and its name is used to find the right slot when assigning another Action");
+  RNA_def_property_pointer_funcs(prop,
+                                 "rna_ActionConstraint_action_slot_get",
+                                 "rna_ActionConstraint_action_slot_set",
+                                 nullptr,
+                                 nullptr);
+  RNA_def_property_update(prop, NC_ANIMATION | ND_NLA_ACTCHANGE, "rna_Constraint_update");
+  /* `strip.action_slot` is exposed to RNA as a pointer for things like the action slot selector in
+   * the GUI. The ground truth of the assigned slot, however, is `action_slot_handle` declared
+   * above. That property is used for library override operations, and this pointer property should
+   * just be ignored.
+   *
+   * This needs PROPOVERRIDE_IGNORE; PROPOVERRIDE_NO_COMPARISON is not suitable here. This property
+   * should act as if it is an overridable property (as from the user's perspective, it is), but an
+   * override operation should not be created for it. It will be created for `action_slot_handle`,
+   * and that's enough. */
+  RNA_def_property_override_flag(prop, PROPOVERRIDE_IGNORE);
+
+  prop = RNA_def_property(srna, "action_slots", PROP_COLLECTION, PROP_NONE);
+  RNA_def_property_struct_type(prop, "ActionSlot");
+  RNA_def_property_collection_funcs(prop,
+                                    "rna_iterator_ActionConstraint_action_slots_begin",
+                                    "rna_iterator_array_next",
+                                    "rna_iterator_array_end",
+                                    "rna_iterator_array_dereference_get",
+                                    nullptr,
+                                    nullptr,
+                                    nullptr,
+                                    nullptr);
+  RNA_def_property_ui_text(
+      prop, "Action Slots", "The list of action slots suitable for this NLA strip");
+#  endif /* WITH_ANIM_BAKLAVA */
+
   prop = RNA_def_property(srna, "use_bone_object_action", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, nullptr, "flag", ACTCON_BONE_USE_OBJECT_ACTION);
   RNA_def_property_ui_text(prop,

tests/python/bl_rigging_symmetrize.py

@@ -116,6 +116,10 @@ def check_constraints(self, input_arm, expected_arm, bone, exp_bone):
                              "Mismatching constraint value types in pose.bones[%s].constraints[%s].%s" % (
                              bone.name, const_name, var))
 
+            if isinstance(value, bpy.types.bpy_prop_collection):
+                # Don't compare collection properties.
+                continue
+
             if isinstance(value, str):
                 self.assertEqual(value, exp_value,
                                  "Mismatching constraint value in pose.bones[%s].constraints[%s].%s" % (
@@ -133,10 +137,19 @@ def check_constraints(self, input_arm, expected_arm, bone, exp_bone):
                 self.assertEqual(value, exp_value,
                                  "Mismatching constraint boolean in pose.bones[%s].constraints[%s].%s" % (
                                      bone.name, const_name, var))
-            else:
+            elif isinstance(value, float):
                 msg = "Mismatching constraint value in pose.bones[%s].constraints[%s].%s" % (
                     bone.name, const_name, var)
                 self.assertAlmostEqual(value, exp_value, places=6, msg=msg)
+            elif isinstance(value, int):
+                msg = "Mismatching constraint value in pose.bones[%s].constraints[%s].%s" % (
+                    bone.name, const_name, var)
+                self.assertEqual(value, exp_value, msg=msg)
+            elif value is None:
+                # Since above the types were compared already, if value is none, so is exp_value.
+                pass
+            else:
+                self.fail(f"unexpected value type: {value!r} is of type {type(value)}")
 
 
 class AbstractAnimationTest: