Add API to allow input reordering on node graphs

source/MaterialXCore/Node.cpp

@@ -717,6 +717,38 @@ void NodeGraph::modifyInterfaceName(const string& inputPath, const string& inter
     }
 }
 
+void NodeGraph::setInputOrdering(const StringVec& inputNames)
+{
+    StringSet childInputNames;
+    std::vector<unsigned int> childInputIndicies;
+
+    for (ElementPtr child : _childOrder)
+    {
+        InputPtr input = child->asA<Input>();
+        if (!input)
+            continue;
+
+        const string& inputName = input->getName();
+        childInputNames.insert(inputName);
+        childInputIndicies.push_back(getChildIndex(inputName));
+    }
+
+    // Check that all names exist in the inputs
+    StringSet orderedInputNames(inputNames.begin(), inputNames.end());
+    if (childInputNames != orderedInputNames)
+    {
+        throw Exception("The set of names provided does not match the existing set of input names");
+    }
+
+    // Use the existing input child indices to set the locations for the
+    // named list. Pre-sort to add from lowest index to highest
+    std::sort(childInputIndicies.begin(), childInputIndicies.end());
+    for (size_t i = 0; i < childInputIndicies.size(); i++)
+    {
+        setChildIndex(inputNames[i], childInputIndicies[i]);
+    }
+}
+
 NodeDefPtr NodeGraph::getNodeDef() const
 {
     NodeDefPtr nodedef = resolveNameReference<NodeDef>(getNodeDefString());

source/MaterialXCore/Node.h

@@ -379,6 +379,10 @@ class MX_CORE_API NodeGraph : public GraphElement
     /// @param interfaceName The new interface name.
     void modifyInterfaceName(const string& inputPath, const string& interfaceName);
 
+    /// Set the ordering of inputs
+    /// @param inputNames List of names of all inputs in the desired order from start to end.
+    void setInputOrdering(const StringVec& inputNames);
+
     /// @}
     /// @name Validation
     /// @{

source/MaterialXTest/MaterialXCore/Node.cpp

@@ -825,3 +825,41 @@ TEST_CASE("Node Definition Creation", "[nodedef]")
 
     REQUIRE(doc->validate());
 }
+
+TEST_CASE("Input Ordering", "[nodegraph]")
+{
+    mx::DocumentPtr doc = mx::createDocument();
+    mx::NodeGraphPtr graph = doc->addNodeGraph("graph1");
+    mx::StringVec childNames = { "one", "node_0", "two", "node_1", "three", "node_3", "four" };
+    for (const std::string& childName : childNames)
+    {
+        if (childName.rfind("node", 0) == 0)
+            graph->addNode("constant", childName);
+        else
+            graph->addInput(childName, "color3");
+    }
+
+    mx::StringVec incorrectInputOrdering = { "two2", "one", "four", "three" };
+    bool haveIncorrectNames = true;
+    try
+    {
+        graph->setInputOrdering(incorrectInputOrdering);
+        haveIncorrectNames = false;
+    }
+    catch (mx::Exception& e)
+    {
+        INFO(e.what())
+    }
+    REQUIRE(haveIncorrectNames);
+
+    mx::StringVec desiredInputOrdering = { "two", "one", "four", "three" };
+    graph->setInputOrdering(desiredInputOrdering);
+
+    mx::StringVec desiredChildOrdering = { "two", "node_0", "one", "node_1", "four", "node_3", "three" };
+    mx::StringVec resultingChildOrdering;
+    for (auto child : graph->getChildren())
+    {
+        resultingChildOrdering.push_back(child->getName());
+    }
+    REQUIRE((resultingChildOrdering == desiredChildOrdering));
+}