python: expose trade.MeshData.index_data and .vertex_data.

Useful for rudimentary data size stats queries, not much else as the
other APIs are not exposed yet.

src/python/magnum/test/test_trade.py

@@ -105,10 +105,27 @@ class MeshData(unittest.TestCase):
         importer = trade.ImporterManager().load_and_instantiate('GltfImporter')
         importer.open_file(os.path.join(os.path.dirname(__file__), 'mesh.glb'))
 
-        mesh = importer.mesh(0)
+        mesh = importer.mesh(1)
+        mesh_refcount = sys.getrefcount(mesh)
         self.assertEqual(mesh.primitive, MeshPrimitive.TRIANGLES)
         # TODO: test more, once it's exposed
 
+        index_data = mesh.index_data
+        self.assertEqual(len(index_data), 3)
+        self.assertIs(index_data.owner, mesh)
+        self.assertEqual(sys.getrefcount(mesh), mesh_refcount + 1)
+
+        del index_data
+        self.assertEqual(sys.getrefcount(mesh), mesh_refcount)
+
+        vertex_data = mesh.vertex_data
+        self.assertEqual(len(vertex_data), 72)
+        self.assertIs(vertex_data.owner, mesh)
+        self.assertEqual(sys.getrefcount(mesh), mesh_refcount + 1)
+
+        del vertex_data
+        self.assertEqual(sys.getrefcount(mesh), mesh_refcount)
+
 class Importer(unittest.TestCase):
     def test(self):
         manager = trade.ImporterManager()

src/python/magnum/trade.cpp

@@ -307,9 +307,15 @@ void trade(py::module_& m) {
 
     py::class_<Trade::MeshData>{m, "MeshData", "Mesh data"}
         .def_property_readonly("primitive", &Trade::MeshData::primitive, "Primitive")
+        .def_property_readonly("index_data", [](Trade::MeshData& self) {
+            return Containers::pyArrayViewHolder(self.indexData(), py::cast(self));
+        }, "Raw index data")
+        .def_property_readonly("vertex_data", [](Trade::MeshData& self) {
+            return Containers::pyArrayViewHolder(self.vertexData(), py::cast(self));
+        }, "Raw vertex data")
         .def_property_readonly("is_indexed", &Trade::MeshData::isIndexed, "Whether the mesh is indexed")
-        .def_property_readonly("vertex_count", &Trade::MeshData::vertexCount)
         .def_property_readonly("index_count", &Trade::MeshData::indexCount)
+        .def_property_readonly("vertex_count", &Trade::MeshData::vertexCount)
         .def_property_readonly("attribute_count", static_cast<UnsignedInt(Trade::MeshData::*)() const>(&Trade::MeshData::attributeCount));
 
     py::class_<Trade::ImageData1D> imageData1D{m, "ImageData1D", "One-dimensional image data"};