Primitives: fix empty Icosphere position array.

Positions and normals have the same data, thus the data were simply
copied to positions and then moved to normals in return to save one
needless copying. However it seems that these two operations were
swapped by the compiler (C++ standard?) and thus there were no positions
to be copied.

Now explicitly creating copy of position array and then moving them in
return. While at it, renamed also `vertices` to `positions` to be
consistent with the rest of the engine.  Also added simple (count only)
unit test to avoid this error in the future.

src/Primitives/Icosphere.cpp

@@ -55,7 +55,7 @@ Trade::MeshData3D Icosphere::solid(const UnsignedInt subdivisions) {
         4, 8, 0
     };
 
-    std::vector<Vector3> vertices{
+    std::vector<Vector3> positions{
         {0.0f, -0.525731f, 0.850651f},
         {0.850651f, 0.0f, 0.525731f},
         {0.850651f, 0.0f, -0.525731f},
@@ -71,12 +71,14 @@ Trade::MeshData3D Icosphere::solid(const UnsignedInt subdivisions) {
     };
 
     for(std::size_t i = 0; i != subdivisions; ++i)
-        MeshTools::subdivide(indices, vertices, [](const Vector3& a, const Vector3& b) {
+        MeshTools::subdivide(indices, positions, [](const Vector3& a, const Vector3& b) {
             return (a+b).normalized();
         });
 
-    MeshTools::removeDuplicates(indices, vertices);
-    return Trade::MeshData3D(Mesh::Primitive::Triangles, std::move(indices), {vertices}, {std::move(vertices)}, {});
+    MeshTools::removeDuplicates(indices, positions);
+
+    std::vector<Vector3> normals(positions);
+    return Trade::MeshData3D(Mesh::Primitive::Triangles, std::move(indices), {std::move(positions)}, {std::move(normals)}, {});
 }
 
 }}

src/Primitives/Test/CMakeLists.txt

@@ -25,4 +25,5 @@
 corrade_add_test(PrimitivesCapsuleTest CapsuleTest.cpp LIBRARIES MagnumPrimitives)
 corrade_add_test(PrimitivesCircleTest CircleTest.cpp LIBRARIES MagnumPrimitives)
 corrade_add_test(PrimitivesCylinderTest CylinderTest.cpp LIBRARIES MagnumPrimitives)
+corrade_add_test(PrimitivesIcosphereTest IcosphereTest.cpp LIBRARIES MagnumPrimitives)
 corrade_add_test(PrimitivesUVSphereTest UVSphereTest.cpp LIBRARIES MagnumPrimitives)

src/Primitives/Test/IcosphereTest.cpp

@@ -0,0 +1,57 @@
+/*
+    This file is part of Magnum.
+
+    Copyright © 2010, 2011, 2012, 2013 Vladimír Vondruš <mosra@centrum.cz>
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included
+    in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+*/
+
+#include <TestSuite/Tester.h>
+
+#include "Math/Vector3.h"
+#include "Primitives/Icosphere.h"
+#include "Trade/MeshData3D.h"
+
+namespace Magnum { namespace Primitives { namespace Test {
+
+class IcosphereTest: public TestSuite::Tester {
+    public:
+        explicit IcosphereTest();
+
+        void count();
+};
+
+IcosphereTest::IcosphereTest() {
+    addTests({&IcosphereTest::count});
+}
+
+void IcosphereTest::count() {
+    Trade::MeshData3D data = Primitives::Icosphere::solid(2);
+
+    CORRADE_COMPARE(data.positionArrayCount(), 1);
+    CORRADE_COMPARE(data.normalArrayCount(), 1);
+
+    CORRADE_COMPARE(data.indices().size(), 960);
+    CORRADE_COMPARE(data.positions(0).size(), 162);
+    CORRADE_COMPARE(data.normals(0).size(), 162);
+}
+
+}}}
+
+CORRADE_TEST_MAIN(Magnum::Primitives::Test::IcosphereTest)