python: expose at least underscored Matrix[34]._translation property.

Still need to figure out a way to expose the property with the same name
as a static function, but this has to suffice for now.

src/python/magnum/math.matrix.h

@@ -558,6 +558,10 @@ template<class T> void matrices(
             static_cast<Math::Vector2<T>(Math::Matrix3<T>::*)() const>(&Math::Matrix3<T>::up),
             [](Math::Matrix3<T>& self, const Math::Vector2<T>& value) { self.up() = value; },
             "Up-pointing 2D vector")
+        .def_property("_translation", // TODO
+            static_cast<Math::Vector2<T>(Math::Matrix3<T>::*)() const>(&Math::Matrix3<T>::translation),
+            [](Math::Matrix3<T>& self, const Math::Vector2<T>& value) { self.translation() = value; },
+            "2D translation part of the matrix")
 
         /* Static/member scaling(). Pybind doesn't support that natively, so
            we create a scaling(*args, **kwargs) and dispatch ourselves. */
@@ -688,6 +692,10 @@ template<class T> void matrices(
             static_cast<Math::Vector3<T>(Math::Matrix4<T>::*)() const>(&Math::Matrix4<T>::backward),
             [](Math::Matrix4<T>& self, const Math::Vector3<T>& value) { self.backward() = value; },
             "Backward-pointing 3D vector")
+        .def_property("_translation", // TODO
+            static_cast<Math::Vector3<T>(Math::Matrix4<T>::*)() const>(&Math::Matrix4<T>::translation),
+            [](Math::Matrix4<T>& self, const Math::Vector3<T>& value) { self.translation() = value; },
+            "3D translation part of the matrix")
 
         /* Static/member scaling(). Pybind doesn't support that natively, so
            we create a scaling(*args, **kwargs) and dispatch ourselves. */

src/python/magnum/test/test_math.py

@@ -649,15 +649,15 @@ class Matrix3_(unittest.TestCase):
         self.assertEqual(c.scaling(), Vector2(1.0, 2.0))
 
     def test_properties(self):
-        a = Matrix3.rotation(Deg(45.0))
+        a = Matrix3.translation(Vector2.y_axis(-5.0))@Matrix3.rotation(Deg(45.0))
         self.assertEqual(a.right, Vector2(0.707107, 0.707107))
         self.assertEqual(a.up, Vector2(-0.707107, 0.707107))
-        # TODO: a.translation
+        self.assertEqual(a._translation, Vector2.y_axis(-5.0)) # TODO
 
         a.right = Vector2.x_axis(2.0)
         a.up = -Vector2.y_axis()
+        a._translation = Vector2(0.0) # TODO
         self.assertEqual(a, Matrix3.from_diagonal((2.0, -1.0, 1.0)))
-        # TODO: a.translation
 
     def test_methods(self):
         self.assertEqual(Matrix3.rotation(Deg(45.0)).transposed(),
@@ -750,17 +750,17 @@ class Matrix4_(unittest.TestCase):
         self.assertEqual(c.scaling(), Vector3(1.0, 2.0, 3.5))
 
     def test_properties(self):
-        a = Matrix4.rotation_z(Deg(45.0))
+        a = Matrix4.translation(Vector3.y_axis(-5.0))@Matrix4.rotation_z(Deg(45.0))
         self.assertEqual(a.right, Vector3(0.707107, 0.707107, 0.0))
         self.assertEqual(a.up, Vector3(-0.707107, 0.707107, 0.0))
         self.assertEqual(a.backward, Vector3(0.0, 0.0, 1.0))
-        # TODO: a.translation
+        self.assertEqual(a._translation, Vector3.y_axis(-5.0)) # TODO
 
         a.right = Vector3.x_axis(3.0)
         a.up = -Vector3.y_axis()
         a.backward = Vector3.z_axis(2.0)
+        a._translation = Vector3(0.0) # TODO
         self.assertEqual(a, Matrix4.from_diagonal((3.0, -1.0, 2.0, 1.0)))
-        # TODO: a.translation
 
     def test_methods(self):
         self.assertEqual(Matrix4.rotation_y(Deg(45.0)).transposed(),