Fix #147796: Animated Transforms to Deltas resets non-animated props

Instead of always resetting the 'standard' transform, only reset those
array elements that were actually animated (and whose animation has
thus been transfered to the corresponding 'delta' transform).

This approach also has the advantage of using the defaults from RNA,
rather than hard-coding defaults based on the property name.

Pull Request: https://projects.blender.org/blender/blender/pulls/147982

scripts/startup/bl_operators/object.py

@@ -881,24 +881,23 @@ class TransformsToDeltasAnim(Operator):
                     # no conflict yet
                     existingFCurves[dpath] = [fcu.array_index]
 
-            # if F-Curve uses standard transform path
-            # just append "delta_" to this path
+            # Move the 'standard' to the 'delta' data paths.
             for fcu in channelbag.fcurves:
-                if fcu.data_path == "location":
-                    fcu.data_path = "delta_location"
-                    obj.location.zero()
-                elif fcu.data_path == "rotation_euler":
-                    fcu.data_path = "delta_rotation_euler"
-                    obj.rotation_euler.zero()
-                elif fcu.data_path == "rotation_quaternion":
-                    fcu.data_path = "delta_rotation_quaternion"
-                    obj.rotation_quaternion.identity()
-                # XXX: currently not implemented
-                # ~ elif fcu.data_path == "rotation_axis_angle":
-                # ~    fcu.data_path = "delta_rotation_axis_angle"
-                elif fcu.data_path == "scale":
-                    fcu.data_path = "delta_scale"
-                    obj.scale = 1.0, 1.0, 1.0
+                standard_path = fcu.data_path
+                array_index = fcu.array_index
+                try:
+                    delta_path = STANDARD_TO_DELTA_PATHS[standard_path]
+                except KeyError:
+                    # Not a standard transform path.
+                    continue
+
+                # Just change the F-Curve's data path. The array index should remain the same.
+                fcu.data_path = delta_path
+
+                # Reset the now-no-longer-animated property to its default value.
+                default_array = obj.bl_rna.properties[standard_path].default_array
+                property_array = getattr(obj, standard_path)
+                property_array[array_index] = default_array[array_index]
 
         # hack: force animsys flush by changing frame, so that deltas get run
         context.scene.frame_set(context.scene.frame_current)