Selection highlighting, picking of MhFootPrint node, with test.

lib/mayaHydra/flowViewportAPIExamples/footPrintNode/mhFootPrintNode.cpp

@@ -42,6 +42,14 @@
 #include <maya/MGlobal.h>
 #include <maya/MFnDagNode.h>
 #include <maya/MModelMessage.h>
+#include <maya/MDagPath.h>
+#include <maya/MSelectionList.h>
+#include <maya/MPointArray.h>
+
+// MayaHydra headers.
+#include <mayaHydraLib/pick/mhPickHandler.h>
+#include <mayaHydraLib/pick/mhPickHandlerRegistry.h>
+#include <ufeExtensions/Global.h>
 
 //Flow viewport headers
 #include <flowViewport/API/fvpVersionInterface.h>
@@ -50,6 +58,7 @@
 //Hydra headers
 #include <pxr/base/vt/array.h>
 #include <pxr/base/gf/vec3f.h>
+#include <pxr/imaging/hdx/pickTask.h>
 #include <pxr/imaging/hd/tokens.h>
 #include <pxr/imaging/hd/retainedSceneIndex.h>
 #include <pxr/imaging/hd/retainedDataSource.h>
@@ -63,6 +72,40 @@ PXR_NAMESPACE_USING_DIRECTIVE
 namespace {
 void nodeAddedToModel(MObject& node, void* clientData);
 void nodeRemovedFromModel(MObject& node, void* clientData);
+
+// Pick handler for the footprint node.
+
+class FootPrintPickHandler : public MayaHydra::PickHandler {
+public:
+
+    FootPrintPickHandler(MObject& footPrintObj) : _footPrintObj(footPrintObj) {}
+
+    bool handlePickHit(
+        const Input& pickInput, Output& pickOutput
+    ) const override
+    {
+        // Foot print parts are not selectable individually: only the complete
+        // Maya shape object is selectable.
+        //
+        // Conceptually we could append a picked Maya object either to the
+        // classic Maya MSelectionList selection or to the "MayaSelectTool"
+        // named UFE selection (which provides input for the global selection).
+        // However, the Maya select context filters out Maya items added to the
+        // "MayaSelectTool" named UFE selection, so add to the MSelectionList.
+        MDagPath dagPath;
+        TF_AXIOM(MDagPath::getAPathTo(_footPrintObj, dagPath) == MS::kSuccess);
+        pickOutput.mayaSelection.add(dagPath);
+        const auto& wsPt = pickInput.pickHit.worldSpaceHitPoint;
+        pickOutput.mayaWorldSpaceHitPts.append(wsPt[0], wsPt[1], wsPt[2]);
+
+        return true;
+    }
+
+private:
+
+    MObject _footPrintObj;
+};
+
 }
 
 //---------------------------------------------------------------------------
@@ -131,6 +174,8 @@ class MhFootPrint : public MPxLocatorNode
 
     MCallbackId _nodeAddedToModelCbId{0};
     MCallbackId _nodeRemovedFromModelCbId{0};
+
+    SdfPath _pathPrefix;
 };
 
 namespace 
@@ -409,7 +454,8 @@ namespace {
         //Trigger a call to compute so that everything is initialized
         MhFootPrint* footPrintInstance = reinterpret_cast<MhFootPrint*>(clientData);
         footPrintInstance->updateFootPrintPrims();
-        footPrintInstance->addedToModelCb();
+        // No need to call footPrintInstance->addedToModelCb(), as reading the
+        // file will add the node to the model.
     }
 }
 
@@ -552,19 +598,30 @@ void* MhFootPrint::creator()
 
 void MhFootPrint::addedToModelCb()
 {
-    static const SdfPath noPrefix = SdfPath::AbsoluteRootPath();
+    _pathPrefix = SdfPath(TfStringPrintf("/MhFootPrint_%p", this));
 
     //Add the callback when an attribute of this node changes
     MObject obj = thisMObject();
     _cbAttributeChangedId = MNodeMessage::addAttributeChangedCallback(obj, attributeChangedCallback, ((void*)this));
 
     //Data producer scene index interface is used to add the retained scene index to all viewports with all render delegates
     auto& dataProducerSceneIndexInterface = Fvp::DataProducerSceneIndexInterface::get();
-    dataProducerSceneIndexInterface.addDataProducerSceneIndex(_retainedSceneIndex, noPrefix, (void*)&obj, FvpViewportAPITokens->allViewports,FvpViewportAPITokens->allRenderers);
+    dataProducerSceneIndexInterface.addDataProducerSceneIndex(_retainedSceneIndex, _pathPrefix, (void*)&obj);
+
+    // Register a pick handler for our prefix with the pick handler registry.
+    auto pickHandler = std::make_shared<FootPrintPickHandler>(obj);
+    TF_AXIOM(MayaHydra::PickHandlerRegistry::Instance().Register(_pathPrefix, pickHandler));
+
+    // No need for a path mapper: the parts of the footprint are not selectable
+    // individually, only the Maya shape, so the built-in Maya path mapper does
+    // the job of path mapping for the footprint node.
 }
 
 void MhFootPrint::removedFromModelCb()
 {
+    // Unregister our pick handler.
+    TF_AXIOM(MayaHydra::PickHandlerRegistry::Instance().Unregister(_pathPrefix));
+
     //Remove the callback
     if (_cbAttributeChangedId){
         CHECK_MSTATUS(MMessage::removeCallback(_cbAttributeChangedId));

test/lib/mayaUsd/render/mayaToHydra/cpp/testHydraPrim.cpp

@@ -20,8 +20,12 @@
 #include <ufe/path.h>
 #include <ufe/pathString.h>
 
+#include <pxr/imaging/hd/sceneIndexPrimView.h>
+
 #include <gtest/gtest.h>
 
+#include <regex>
+
 PXR_NAMESPACE_USING_DIRECTIVE
 
 using namespace MayaHydra;
@@ -108,3 +112,29 @@ TEST(TestHydraPrim, translation)
     constexpr double epsilon{1e-7};
     ASSERT_TRUE(GfIsClose(primTranslation, expectedTranslation, epsilon));
 }
+
+TEST(TestHydraPrim, countPrims)
+{
+    const auto& sceneIndices = GetTerminalSceneIndices();
+    auto siRoot = sceneIndices.front();
+
+    auto [argc, argv] = getTestingArgs();
+    ASSERT_EQ(argc, 2);
+
+    const std::regex r{argv[0]};
+    std::smatch m;
+    const int expectedNbMatches{std::stoi(argv[1])};
+    int nbMatches{0};
+
+    for (const auto& primPath : 
+             HdSceneIndexPrimView(siRoot, SdfPath::AbsoluteRootPath())) {
+        // Can't match temporary string, see
+        // https://stackoverflow.com/questions/27391016
+        const std::string element = primPath.GetElementString();
+        if (std::regex_search(element, m, r)) {
+            ++nbMatches;
+        }
+    }
+
+    ASSERT_EQ(nbMatches, expectedNbMatches);
+}

test/lib/mayaUsd/render/mayaToHydra/testFootPrintNode.py

@@ -34,6 +34,8 @@ class TestFootPrintNode(mtohUtils.MayaHydraBaseTestCase): #Subclassing mtohUtils
     IMAGE_DIFF_FAIL_PERCENT = 0.1
     imageVersion = None
 
+    _requiredPlugins = ['mayaHydraCppTests']
+
     @classmethod
     def setUpClass(cls):
         super(TestFootPrintNode, cls).setUpClass()
@@ -257,5 +259,38 @@ def test_Load(self):
             #using imageVersion as the color is different for this image under usd 24.11+
             self.assertSnapshotClose("loadingFootPrintScene.png", self.IMAGE_DIFF_FAIL_THRESHOLD, self.IMAGE_DIFF_FAIL_PERCENT, self.imageVersion)
 
+    # Test selection highlighting.  When the footprint node is selected, only
+    # its two Hydra scene index prims (heel and sole) should have a
+    # _SelectionHighlight mirror hierarchy, and no other prim.
+    def test_selectionHighlight(self):
+        with PluginLoaded('mayaHydraFootPrintNode'):
+            # Create a cube.
+            cmds.polyCube()
+
+            cmds.refresh()
+
+            # Create a footprint node.  It will be selected.
+            cmds.createNode('MhFootPrint')
+
+            cmds.refresh()
+
+            # Traverse the scene starting at the root, and count the number
+            # of _SelectionHighlight mirror hierarchies.  There should be 2,
+            # one for the heel and one for the sole of the footprint node.
+            cmds.mayaHydraCppTest('.*_SelectionHighlight', 2, f="TestHydraPrim.countPrims")
+
+    # Test picking.  Once picked, the footprint node must appear in the global
+    # selection.
+    def test_picking(self):
+        with PluginLoaded('mayaHydraFootPrintNode'):
+
+            cmds.createNode('MhFootPrint')
+
+            cmds.refresh()
+
+            cmds.mayaHydraCppTest('|transform1|MhFootPrint1', f="TestUsdPicking.pickPrim")
+
+            self.assertEqual(['MhFootPrint1'], cmds.ls(sl=True))
+
 if __name__ == '__main__':
     fixturesUtils.runTests(globals())