arealights: disable Y-flip in the DDS importer.

The example was made back when DDS files were loaded without Y flipping,
so when they actually got flipped, it broke the example.

src/arealights/AreaLightsExample.cpp

@@ -36,6 +36,7 @@
 #include <Corrade/Containers/StringView.h>
 #include <Corrade/Containers/StringStl.h>
 #include <Corrade/PluginManager/PluginManager.h>
+#include <Corrade/Utility/ConfigurationGroup.h>
 #include <Corrade/Utility/FormatStl.h>
 #include <Corrade/Utility/Resource.h>
 #include <Magnum/ImageView.h>
@@ -338,10 +339,12 @@ AreaLightsExample::AreaLightsExample(const Arguments& arguments): Platform::Appl
     _projection = Matrix4::perspectiveProjection(60.0_degf, 4.0f/3.0f, 0.1f, 50.0f);
     _transformation = Matrix4::rotationX(-90.0_degf)*Matrix4::scaling(Vector3{25.0f});
 
-    /* Load LTC matrix and BRDF textures */
+    /* Load LTC matrix and BRDF textures. The shader assumes the data is
+       Y-down, so disable Y-flipping in the importer. */
     PluginManager::Manager<Trade::AbstractImporter> manager;
     Containers::Pointer<Trade::AbstractImporter> importer = manager.loadAndInstantiate("DdsImporter");
     if(!importer) std::exit(1);
+    importer->configuration().setValue("assumeYUpZBackward", true);
 
     const Utility::Resource rs{"arealights-data"};
     if(!importer->openData(rs.getRaw("ltc_amp.dds")))