From fff84622f8867df28c3d29dee5004c5920cfc90d Mon Sep 17 00:00:00 2001
From: Chris Rydalch <chrisrydalch@users.noreply.github.com>
Date: Thu, 24 Sep 2020 21:40:23 -0400
Subject: [PATCH] Add BlockVariantSelection to VariantSets

---
 pxr/usd/sdf/primSpec.cpp               | 12 ++++++++++++
 pxr/usd/sdf/primSpec.h                 |  5 +++++
 pxr/usd/sdf/wrapPrimSpec.cpp           |  1 +
 pxr/usd/usd/testenv/testUsdVariants.py | 13 +++++++++++++
 pxr/usd/usd/variantSets.cpp            | 11 +++++++++++
 pxr/usd/usd/variantSets.h              |  5 +++++
 pxr/usd/usd/wrapVariantSets.cpp        |  1 +
 7 files changed, 48 insertions(+)

diff --git a/pxr/usd/sdf/primSpec.cpp b/pxr/usd/sdf/primSpec.cpp
index 5936a9e5c2..6e38a8b2ac 100644
--- a/pxr/usd/sdf/primSpec.cpp
+++ b/pxr/usd/sdf/primSpec.cpp
@@ -762,6 +762,18 @@ SdfPrimSpec::SetVariantSelection(const std::string& variantSetName,
     }
 }
 
+void
+SdfPrimSpec::BlockVariantSelection(const std::string& variantSetName)
+{
+    if (_ValidateEdit(SdfFieldKeys->VariantSelection)) {
+        SdfVariantSelectionProxy proxy = GetVariantSelections();
+        if (proxy) {
+            SdfChangeBlock block;
+            proxy[variantSetName] = std::string();
+        }
+    }
+}
+
 //
 // Relocates
 //
diff --git a/pxr/usd/sdf/primSpec.h b/pxr/usd/sdf/primSpec.h
index e70daf7fdd..204b1458e5 100644
--- a/pxr/usd/sdf/primSpec.h
+++ b/pxr/usd/sdf/primSpec.h
@@ -695,6 +695,11 @@ class SdfPrimSpec : public SdfSpec
     void SetVariantSelection(const std::string& variantSetName,
                              const std::string& variantName);
 
+    /// Blocks the variant selected for the given variant set by setting
+    /// the variant selection to empty.
+    SDF_API
+    void BlockVariantSelection(const std::string& variantSetName);
+
     /// @}
     /// \name Relocates
     /// @{
diff --git a/pxr/usd/sdf/wrapPrimSpec.cpp b/pxr/usd/sdf/wrapPrimSpec.cpp
index d37ff9102c..cca945e94d 100644
--- a/pxr/usd/sdf/wrapPrimSpec.cpp
+++ b/pxr/usd/sdf/wrapPrimSpec.cpp
@@ -361,6 +361,7 @@ void wrapPrimSpec()
         .def("GetAttributeAtPath", &This::GetAttributeAtPath)
         .def("GetRelationshipAtPath", &This::GetRelationshipAtPath)
         .def("GetVariantNames", &This::GetVariantNames)
+        .def("BlockVariantSelection", &This::BlockVariantSelection)
 
         .add_property("variantSelections",
             &This::GetVariantSelections,
diff --git a/pxr/usd/usd/testenv/testUsdVariants.py b/pxr/usd/usd/testenv/testUsdVariants.py
index c6e8f218a4..90901d8c8b 100644
--- a/pxr/usd/usd/testenv/testUsdVariants.py
+++ b/pxr/usd/usd/testenv/testUsdVariants.py
@@ -62,6 +62,19 @@ def test_VariantSetAPI(self):
                          "localDanglingVariant"))
         self.assertFalse(prim.GetVariantSets().HasVariantSet(
                          "referencedDanglingVariant"))
+        # ClearVariantSelection clears the variant set selection from the edit target,
+        # permitting any weaker layer selection to take effect
+        stage.SetEditTarget(stage.GetSessionLayer())
+        prim.GetVariantSet('modelingVariant').SetVariantSelection('Carton_Sealed')
+        self.assertEqual(prim.GetVariantSet('modelingVariant').GetVariantSelection(),
+                        'Carton_Sealed')
+        prim.GetVariantSet('modelingVariant').ClearVariantSelection()
+        self.assertEqual(prim.GetVariantSet('modelingVariant').GetVariantSelection(),
+                        'Carton_Opened')
+        # BlockVariantSelection sets the selection to empty, which blocks weaker variant
+        # selection opinions
+        prim.GetVariantSet('modelingVariant').BlockVariantSelection()
+        self.assertEqual(prim.GetVariantSet('modelingVariant').GetVariantSelection(), '')
 
     def test_VariantSelectionPathAbstraction(self):
         for fmt in allFormats:
diff --git a/pxr/usd/usd/variantSets.cpp b/pxr/usd/usd/variantSets.cpp
index 01a43d741e..a66646f6f4 100644
--- a/pxr/usd/usd/variantSets.cpp
+++ b/pxr/usd/usd/variantSets.cpp
@@ -148,6 +148,17 @@ UsdVariantSet::ClearVariantSelection()
     return SetVariantSelection(string());
 }
 
+bool
+UsdVariantSet::BlockVariantSelection()
+{
+    if (SdfPrimSpecHandle spec = _CreatePrimSpecForEditing()) {
+        spec->BlockVariantSelection(_variantSetName);
+        return true;
+    }
+
+    return false;
+}
+
 UsdEditTarget
 UsdVariantSet::GetVariantEditTarget(const SdfLayerHandle &layer) const
 {
diff --git a/pxr/usd/usd/variantSets.h b/pxr/usd/usd/variantSets.h
index 7cdd530aa6..5397577774 100644
--- a/pxr/usd/usd/variantSets.h
+++ b/pxr/usd/usd/variantSets.h
@@ -110,6 +110,11 @@ class UsdVariantSet {
     USD_API
     bool ClearVariantSelection();
 
+    /// Blocks any weaker selection for this VariantSet, setting it to empty in
+    /// the stage's current EditTarget. Return true on success, false otherwise.
+    USD_API
+    bool BlockVariantSelection();
+
     /// Return a \a UsdEditTarget that edits the currently selected variant in
     /// this VariantSet in \a layer.  If there is no currently
     /// selected variant in this VariantSet, return an invalid EditTarget.
diff --git a/pxr/usd/usd/wrapVariantSets.cpp b/pxr/usd/usd/wrapVariantSets.cpp
index a05edc4319..2567e88199 100644
--- a/pxr/usd/usd/wrapVariantSets.cpp
+++ b/pxr/usd/usd/wrapVariantSets.cpp
@@ -83,6 +83,7 @@ void wrapUsdVariantSets()
         .def("SetVariantSelection", &UsdVariantSet::SetVariantSelection,
              arg("variantName"))
         .def("ClearVariantSelection", &UsdVariantSet::ClearVariantSelection)
+        .def("BlockVariantSelection", &UsdVariantSet::BlockVariantSelection)
         .def("GetVariantEditTarget", &UsdVariantSet::GetVariantEditTarget,
              arg("layer")=SdfLayerHandle())
         .def("GetVariantEditContext", _GetVariantEditContext,