[wip] the null fields/mappings are a PAIN

Author: mosra

src/Magnum/Trade/Implementation/sceneTools.h

@@ -305,6 +305,8 @@ inline SceneData sceneConvertToSingleFunctionObjects(const SceneData& scene, Con
             -   fields that don't actually get their object mapping touched
                 during the process (and then all fields that share object
                 mapping with them) */
+#warning removing implicit mapping from here will mean the null will get treated as a placeholder by copy(), not wanted
+#warning it needs to restore the field instead
         } else fields[i] = SceneFieldData{field.name(), field.mappingType(), field.mappingData(), field.fieldType(), field.fieldData(), field.fieldArraySize(), field.flags() & ~SceneFieldFlag::ImplicitMapping};
     }
 

src/Magnum/Trade/Test/SceneToolsTest.cpp

@@ -41,6 +41,8 @@ struct SceneToolsTest: TestSuite::Tester {
     void combineObjectsShared();
     void combineObjectsPlaceholderFieldPlaceholder();
     void combineObjectSharedFieldPlaceholder();
+    void combineImplicitNullMapping();
+    void combineTrivialNullParent();
 
     void convertToSingleFunctionObjects();
     void convertToSingleFunctionObjectsFieldsToCopy();
@@ -80,7 +82,10 @@ SceneToolsTest::SceneToolsTest() {
     addTests({&SceneToolsTest::combineAlignment,
               &SceneToolsTest::combineObjectsShared,
               &SceneToolsTest::combineObjectsPlaceholderFieldPlaceholder,
-              &SceneToolsTest::combineObjectSharedFieldPlaceholder});
+              &SceneToolsTest::combineObjectSharedFieldPlaceholder,
+
+              &SceneToolsTest::combineImplicitNullMapping,
+              &SceneToolsTest::combineTrivialNullParent});
 
     addInstancedTests({&SceneToolsTest::convertToSingleFunctionObjects},
         Containers::arraySize(ConvertToSingleFunctionObjectsData));
@@ -349,6 +354,47 @@ void SceneToolsTest::combineObjectSharedFieldPlaceholder() {
     CORRADE_COMPARE(scene.field(SceneField::MeshMaterial).stride()[0], 4);
 }
 
+void SceneToolsTest::combineImplicitNullMapping() {
+    const Short parentFieldData[]{-1, 0, 0};
+    const UnsignedByte meshFieldData[]{3, 5};
+
+    SceneData scene = Implementation::sceneCombine(SceneMappingType::UnsignedShort, 167, Containers::arrayView({
+        /* If the field has any flags, it shouldn't be treated as a
+           placeholder */
+#warning or maybe it should be preserved? yeah
+        SceneFieldData{SceneField::Mesh, Containers::ArrayView<UnsignedByte>{nullptr, Containers::arraySize(meshFieldData)}, Containers::arrayView(meshFieldData), SceneFieldFlag::ImplicitMapping},
+        SceneFieldData{SceneField::Parent, Containers::ArrayView<UnsignedShort>{nullptr, Containers::arraySize(parentFieldData)}, Containers::arrayView(parentFieldData), SceneFieldFlag::ImplicitMapping}
+    }));
+
+    CORRADE_COMPARE(scene.mappingBound(), 167);
+    CORRADE_COMPARE(scene.fieldCount(), 2);
+
+    CORRADE_COMPARE(scene.fieldName(0), SceneField::Mesh);
+    CORRADE_COMPARE(scene.fieldFlags(0), SceneFieldFlag::ImplicitMapping);
+    CORRADE_COMPARE(scene.fieldType(0), SceneFieldType::UnsignedByte);
+    CORRADE_COMPARE(scene.fieldArraySize(0), 0);
+    CORRADE_COMPARE_AS(scene.mapping<UnsignedShort>(0), Containers::arrayView<UnsignedShort>({
+        0, 1, 2
+    }), TestSuite::Compare::Container);
+    CORRADE_COMPARE_AS(scene.field<UnsignedByte>(0),
+        Containers::arrayView(meshFieldData),
+        TestSuite::Compare::Container);
+
+    CORRADE_COMPARE(scene.fieldName(1), SceneField::Parent);
+    CORRADE_COMPARE(scene.fieldFlags(1), SceneFieldFlag::ImplicitMapping);
+    CORRADE_COMPARE(scene.fieldType(1), SceneFieldType::Short);
+    CORRADE_COMPARE(scene.fieldArraySize(1), 0);
+    CORRADE_COMPARE_AS(scene.mapping<UnsignedShort>(1), Containers::arrayView<UnsignedShort>({
+        0, 1
+    }), TestSuite::Compare::Container);
+    CORRADE_COMPARE_AS(scene.field<UnsignedByte>(1),
+        Containers::arrayView(meshFieldData),
+        TestSuite::Compare::Container);
+}
+
+void SceneToolsTest::combineTrivialNullParent() {
+}
+
 void SceneToolsTest::convertToSingleFunctionObjects() {
     auto&& data = ConvertToSingleFunctionObjectsData[testCaseInstanceId()];
     setTestCaseDescription(data.name);