python: expose scenetools.combine_fields().

Finally it's possible to create scenes from scratch from Python.

doc/python/magnum.trade.rst

@@ -705,8 +705,10 @@
 .. py:class:: magnum.trade.SceneFieldData
 
     Associates a pair of typed data views with a name, type and other scene
-    field properties. The mapping data view is always one-dimensional. The
-    field data view can be either one-dimensional, for example a NumPy array:
+    field properties, which can be subsequently put into a :ref:`SceneData`
+    instance, for example with :ref:`scenetools.combine_fields()`. The mapping
+    data view is always one-dimensional. The field data view can be either
+    one-dimensional, for example a NumPy array:
 
     ..
         Just to verify the snippet below actually works (don't want the arrows

src/python/magnum/scenetools.cpp

@@ -32,6 +32,7 @@
 #include <Corrade/Containers/Pair.h>
 #include <Magnum/Math/Matrix3.h>
 #include <Magnum/Math/Matrix4.h>
+#include <Magnum/SceneTools/Combine.h>
 #include <Magnum/SceneTools/Filter.h>
 #include <Magnum/SceneTools/Hierarchy.h>
 #include <Magnum/Trade/SceneData.h>
@@ -53,6 +54,9 @@ void scenetools(py::module_& m) {
     #endif
 
     m
+        .def("combine_fields", [](const Trade::SceneMappingType mappingType, UnsignedLong mappingBound, const std::vector<Trade::SceneFieldData>& fields) {
+            return SceneTools::combineFields(mappingType, mappingBound, fields);
+        }, "Combine scene fields together", py::arg("mapping_type"), py::arg("mapping_bound"), py::arg("fields"))
         .def("filter_fields", [](const Trade::SceneData& scene, const Containers::BitArrayView fieldsToKeep) {
             if(fieldsToKeep.size() != scene.fieldCount()) {
                 PyErr_Format(PyExc_AssertionError, "expected %u bits but got %zu", scene.fieldCount(), fieldsToKeep.size());

src/python/magnum/test/test_scenetools.py

@@ -23,6 +23,7 @@
 #   DEALINGS IN THE SOFTWARE.
 #
 
+import array
 import os
 import sys
 import unittest
@@ -32,6 +33,36 @@ from magnum import *
 from magnum import scenetools, trade
 import magnum
 
+class Combine(unittest.TestCase):
+    def test(self):
+        mapping = array.array('I', [0, 176, 35])
+        meshes = array.array('H', [26, 17, 2])
+        materials = array.array('b', [-1, 104, 8])
+
+        scene = scenetools.combine_fields(trade.SceneMappingType.UNSIGNED_LONG, 180, [
+            trade.SceneFieldData(trade.SceneField.MESH,
+                trade.SceneMappingType.UNSIGNED_INT, mapping,
+                trade.SceneFieldType.UNSIGNED_SHORT, meshes),
+            trade.SceneFieldData(trade.SceneField.MESH_MATERIAL,
+                trade.SceneMappingType.UNSIGNED_INT, mapping,
+                trade.SceneFieldType.BYTE, materials),
+        ])
+        self.assertEqual(scene.mapping_type, trade.SceneMappingType.UNSIGNED_LONG)
+        self.assertEqual(scene.mapping_bound, 180)
+        self.assertEqual(scene.field_count, 2)
+
+        self.assertEqual(scene.field_size(0), 3)
+        self.assertEqual(scene.field_name(0), trade.SceneField.MESH)
+        self.assertEqual(scene.field_type(0), trade.SceneFieldType.UNSIGNED_SHORT)
+        self.assertEqual(list(scene.mapping(0)), [0, 176, 35])
+        self.assertEqual(list(scene.field(0)), [26, 17, 2])
+
+        self.assertEqual(scene.field_size(1), 3)
+        self.assertEqual(scene.field_name(1), trade.SceneField.MESH_MATERIAL)
+        self.assertEqual(scene.field_type(1), trade.SceneFieldType.BYTE)
+        self.assertEqual(list(scene.mapping(1)), [0, 176, 35])
+        self.assertEqual(list(scene.field(1)), [-1, 104, 8])
+
 class Filter(unittest.TestCase):
     def test_fields(self):
         # Static builds with non-static plugins cause assertions with non-owned