BPY: Implement get_transform and set_transform for runtime-defined RNA properties.

Improve handling of runtime defined python RNA properties. Mainly:
* Add `get_transform` and `set_transform` new callbacks.
  These allow to edit the value, while still using the default
  (IDProperty-based) storage system.
* Read-only properties should now be defined using a new `options` flag,
  `READ_ONLY`.
* `get`/`set` should only be used when storing data outside of the
  default system now.
  * Having a `get` without a `set` defined forces property to be
    read-only (same behavior as before).
  * Having a `set` without a `get` is now an error.
* Just like with existing `get/set` callbacks, `get_/set_transform`
  callbacks must always generate values matching the constraints defined
  by their `bpy.props` property definition (same type, within required
  range, same dimensions/sizes for the `Vector` properties, etc.).
* To simplify handling of non-statically sized strings, the relevant
  RNA API has been modified, to use `std::string` instead of
  (allocated) char arrays.

Relevant unittests and benchmarking have been added or updated as part
of this project.

Note: From initial benchmarking, 'transform' versions of get/set are
several times faster than 'real' get/set.

Implements #141042.

Pull Request: https://projects.blender.org/blender/blender/pulls/141303

tests/python/bl_pyapi_prop_array.py

@@ -147,32 +147,71 @@ class TestPropArrayIndex(unittest.TestCase):
 
         self.test_array_b_2d_storage = [[bool(v) for v in range(self.size_2d[1])] for i in range(self.size_2d[0])]
 
-        def set_(s, v):
+        def bool_set_(s, v):
             self.test_array_b_2d_storage = v
-        id_type.test_array_b_2d_getset = BoolVectorProperty(
-            size=self.size_2d,
-            get=lambda s: self.test_array_b_2d_storage,
-            set=set_,
-        )
 
         self.test_array_i_2d_storage = [[int(v) for v in range(self.size_2d[1])] for i in range(self.size_2d[0])]
 
-        def set_(s, v):
+        def int_set_(s, v):
             self.test_array_i_2d_storage = v
-        id_type.test_array_i_2d_getset = IntVectorProperty(
-            size=self.size_2d,
-            get=lambda s: self.test_array_i_2d_storage,
-            set=set_,
-        )
 
         self.test_array_f_2d_storage = [[float(v) for v in range(self.size_2d[1])] for i in range(self.size_2d[0])]
 
-        def set_(s, v):
+        def float_set_(s, v):
             self.test_array_f_2d_storage = v
+
+        id_type.test_array_b_2d_getset = BoolVectorProperty(
+            size=self.size_2d,
+            get=lambda s: self.test_array_b_2d_storage,
+            set=bool_set_,
+        )
+        id_type.test_array_i_2d_getset = IntVectorProperty(
+            size=self.size_2d,
+            get=lambda s: self.test_array_i_2d_storage,
+            set=int_set_,
+        )
         id_type.test_array_f_2d_getset = FloatVectorProperty(
             size=self.size_2d,
             get=lambda s: self.test_array_f_2d_storage,
-            set=set_,
+            set=float_set_,
+        )
+
+        id_type.test_array_b_3d_transform = BoolVectorProperty(
+            size=self.size_3d,
+            get_transform=lambda s, c_v, isset: seq_items_xform(c_v, lambda v: not v),
+            set_transform=lambda s, n_v, c_v, isset: seq_items_xform(n_v, lambda v: not v),
+        )
+        id_type.test_array_i_3d_transform = IntVectorProperty(
+            size=self.size_3d,
+            get_transform=lambda s, c_v, isset: seq_items_xform(c_v, lambda v: v + 1),
+            set_transform=lambda s, n_v, c_v, isset: seq_items_xform(n_v, lambda v: v - 1),
+        )
+        id_type.test_array_f_3d_transform = FloatVectorProperty(
+            size=self.size_3d,
+            get_transform=lambda s, c_v, isset: seq_items_xform(c_v, lambda v: v * 2.0),
+            set_transform=lambda s, n_v, c_v, isset: seq_items_xform(n_v, lambda v: v / 2.0),
+        )
+
+        id_type.test_array_b_2d_getset_transform = BoolVectorProperty(
+            size=self.size_2d,
+            get=lambda s: self.test_array_b_2d_storage,
+            set=bool_set_,
+            get_transform=lambda s, c_v, isset: seq_items_xform(c_v, lambda v: not v),
+            set_transform=lambda s, n_v, c_v, isset: seq_items_xform(n_v, lambda v: not v),
+        )
+        id_type.test_array_i_2d_getset_transform = IntVectorProperty(
+            size=self.size_2d,
+            get=lambda s: self.test_array_i_2d_storage,
+            set=int_set_,
+            get_transform=lambda s, c_v, isset: seq_items_xform(c_v, lambda v: v + 1),
+            set_transform=lambda s, n_v, c_v, isset: seq_items_xform(n_v, lambda v: v - 1),
+        )
+        id_type.test_array_f_2d_getset_transform = FloatVectorProperty(
+            size=self.size_2d,
+            get=lambda s: self.test_array_f_2d_storage,
+            set=float_set_,
+            get_transform=lambda s, c_v, isset: seq_items_xform(c_v, lambda v: v * 2.0),
+            set_transform=lambda s, n_v, c_v, isset: seq_items_xform(n_v, lambda v: v / 2.0),
         )
 
     def tearDown(self):
@@ -190,6 +229,14 @@ class TestPropArrayIndex(unittest.TestCase):
         del id_type.test_array_i_2d_getset
         del id_type.test_array_b_2d_getset
 
+        del id_type.test_array_f_3d_transform
+        del id_type.test_array_i_3d_transform
+        del id_type.test_array_b_3d_transform
+
+        del id_type.test_array_f_2d_getset_transform
+        del id_type.test_array_i_2d_getset_transform
+        del id_type.test_array_b_2d_getset_transform
+
     @staticmethod
     def compute_slice_len(s):
         if not isinstance(s, slice):
@@ -297,6 +344,36 @@ class TestPropArrayIndex(unittest.TestCase):
             id_inst.test_array_f_2d_getset, self.size_2d, self.valid_indices_2d, self.invalid_indices_2d
         )
 
+    def test_indices_access_b_3d_transform(self):
+        self.do_test_indices_access(
+            id_inst.test_array_b_3d_transform, self.size_3d, self.valid_indices_3d, self.invalid_indices_3d
+        )
+
+    def test_indices_access_i_3d_transform(self):
+        self.do_test_indices_access(
+            id_inst.test_array_i_3d_transform, self.size_3d, self.valid_indices_3d, self.invalid_indices_3d
+        )
+
+    def test_indices_access_f_3d_transform(self):
+        self.do_test_indices_access(
+            id_inst.test_array_f_3d_transform, self.size_3d, self.valid_indices_3d, self.invalid_indices_3d
+        )
+
+    def test_indices_access_b_2d_getset_transform(self):
+        self.do_test_indices_access(
+            id_inst.test_array_b_2d_getset_transform, self.size_2d, self.valid_indices_2d, self.invalid_indices_2d
+        )
+
+    def test_indices_access_i_2d_getset_transform(self):
+        self.do_test_indices_access(
+            id_inst.test_array_i_2d_getset_transform, self.size_2d, self.valid_indices_2d, self.invalid_indices_2d
+        )
+
+    def test_indices_access_f_2d_getset_transform(self):
+        self.do_test_indices_access(
+            id_inst.test_array_f_2d_getset_transform, self.size_2d, self.valid_indices_2d, self.invalid_indices_2d
+        )
+
 
 class TestPropArrayForeach(unittest.TestCase):
     # Test foreach_get/_set access of Int and Float vector properties (bool ones do not support this).
@@ -499,12 +576,37 @@ class TestPropArrayMultiDimensional(unittest.TestCase):
         def set_fn(id_arg, value):
             local_data["array"] = value
 
+        def get_tx_fn(id_arg, curr_value, is_set):
+            return seq_items_xform(curr_value, lambda v: v + 1.0)
+
+        def set_tx_fn(id_arg, new_value, curr_value, is_set):
+            return seq_items_xform(new_value, lambda v: v - 1.0)
+
         id_type.temp = FloatVectorProperty(size=(dim_x, dim_y), subtype='MATRIX', get=get_fn, set=set_fn)
         id_inst.temp = data_native
         data_as_tuple = seq_items_as_tuple(id_inst.temp)
         self.assertEqual(data_as_tuple, data_native)
         del id_type.temp
 
+        id_type.temp = FloatVectorProperty(
+            size=(dim_x, dim_y), subtype='MATRIX', get_transform=get_tx_fn, set_transform=set_tx_fn)
+        id_inst.temp = data_native
+        data_as_tuple = seq_items_as_tuple(id_inst.temp)
+        self.assertEqual(data_as_tuple, data_native)
+        del id_type.temp
+
+        id_type.temp = FloatVectorProperty(
+            size=(dim_x, dim_y),
+            subtype='MATRIX',
+            get=get_fn,
+            set=set_fn,
+            get_transform=get_tx_fn,
+            set_transform=set_tx_fn)
+        id_inst.temp = data_native
+        data_as_tuple = seq_items_as_tuple(id_inst.temp)
+        self.assertEqual(data_as_tuple, data_native)
+        del id_type.temp
+
     def test_matrix_3x3(self):
         self._test_matrix(3, 3)