Expose isRootChild as DCC function.

Author: deboisj

lib/usdUfe/ufe/Global.cpp

@@ -75,6 +75,8 @@ Ufe::Rtid initialize(
         UsdUfe::setIsAttributeLockedFn(dccFunctions.isAttributeLockedFn);
     if (dccFunctions.saveStageLoadRulesFn)
         UsdUfe::setSaveStageLoadRulesFn(dccFunctions.saveStageLoadRulesFn);
+    if (dccFunctions.isRootChildFn)
+        UsdUfe::setIsRootChildFn(dccFunctions.isRootChildFn);
 
     // Create a default stages subject if none is provided.
     if (nullptr == ss) {

lib/usdUfe/ufe/Global.h

@@ -46,6 +46,7 @@ struct USDUFE_PUBLIC DCCFunctions
     // Optional: default values will be used if no function is supplied.
     IsAttributeLockedFn  isAttributeLockedFn = nullptr;
     SaveStageLoadRulesFn saveStageLoadRulesFn = nullptr;
+    IsRootChildFn isRootChildFn = nullptr;
 };
 
 /*! Ufe runtime handlers used to initialize the plugin.

lib/usdUfe/ufe/Utils.cpp

@@ -90,6 +90,7 @@ UsdUfe::UfePathToPrimFn      gUfePathToPrimFn = nullptr;
 UsdUfe::TimeAccessorFn       gTimeAccessorFn = nullptr;
 UsdUfe::IsAttributeLockedFn  gIsAttributeLockedFn = nullptr;
 UsdUfe::SaveStageLoadRulesFn gSaveStageLoadRulesFn = nullptr;
+UsdUfe::IsRootChildFn        gIsRootChildFn = nullptr;
 
 } // anonymous namespace
 
@@ -231,6 +232,29 @@ void saveStageLoadRules(const PXR_NS::UsdStageRefPtr& stage)
         gSaveStageLoadRulesFn(stage);
 }
 
+void setIsRootChildFn(IsRootChildFn fn)
+{
+    // This function is allowed to be null in which case, the default implementation
+    // is used (isRootChildDefault()).
+    gIsRootChildFn = fn;
+}
+
+bool isRootChild(const Ufe::Path& path)
+{
+    return gIsRootChildFn ? gIsRootChildFn(path) : isRootChildDefault(path);
+}
+
+bool isRootChildDefault(const Ufe::Path& path)
+{
+    // When called we make the assumption that we are given a valid
+    // path and we are only testing whether or not we are a root child.
+    auto segments = path.getSegments();
+    if (segments.size() != 2) {
+        TF_RUNTIME_ERROR(kIllegalUFEPath, path.string().c_str());
+    }
+    return (segments[1].size() == 1);
+}
+
 int ufePathToInstanceIndex(const Ufe::Path& path, UsdPrim* prim)
 {
     int instanceIndex = UsdImagingDelegate::ALL_INSTANCES;
@@ -254,17 +278,6 @@ int ufePathToInstanceIndex(const Ufe::Path& path, UsdPrim* prim)
     return instanceIndex;
 }
 
-bool isRootChild(const Ufe::Path& path)
-{
-    // When called we make the assumption that we are given a valid
-    // path and we are only testing whether or not we are a root child.
-    auto segments = path.getSegments();
-    if (segments.size() != 2) {
-        TF_RUNTIME_ERROR(kIllegalUFEPath, path.string().c_str());
-    }
-    return (segments[1].size() == 1);
-}
-
 std::string uniqueName(const TfToken::HashSet& existingNames, std::string srcName)
 {
     // Compiled regular expression to find a numerical suffix to a path component.

lib/usdUfe/ufe/Utils.h

@@ -44,6 +44,7 @@ typedef PXR_NS::UsdPrim (*UfePathToPrimFn)(const Ufe::Path&);
 typedef PXR_NS::UsdTimeCode (*TimeAccessorFn)(const Ufe::Path&);
 typedef bool (*IsAttributeLockedFn)(const PXR_NS::UsdAttribute& attr, std::string* errMsg);
 typedef void (*SaveStageLoadRulesFn)(const PXR_NS::UsdStageRefPtr&);
+typedef bool (*IsRootChildFn)(const Ufe::Path& path);
 
 //------------------------------------------------------------------------------
 // Helper functions
@@ -137,9 +138,22 @@ void saveStageLoadRules(const PXR_NS::UsdStageRefPtr& stage);
 USDUFE_PUBLIC
 int ufePathToInstanceIndex(const Ufe::Path& path, PXR_NS::UsdPrim* prim = nullptr);
 
+//! Set the DCC specific "isRootChild" test function.
+//! Use of this function is optional, if one is not supplied then
+//! a default implementation of isRootChild is used..
+USDUFE_PUBLIC
+void setIsRootChildFn(IsRootChildFn fn);
+
+//! Returns true if the path corresponds to an item at the root of a runtime.
+//! Implementation can be set by the DCC.
 USDUFE_PUBLIC
 bool isRootChild(const Ufe::Path& path);
 
+//! Default isRootChild() implementation. Assumes 2 segments. Will report a root child
+//! if the second segment has a single component.
+USDUFE_PUBLIC
+bool isRootChildDefault(const Ufe::Path& path);
+
 //! Split the source name into a base name and a numerical suffix (set to
 //! 1 if absent).  Increment the numerical suffix until name is unique.
 USDUFE_PUBLIC