[usdImaging] fix _GetDirtyBitsForPrimvarChange for PrimvarChangeAdd

It was observed that primvars such as widths for UsdGeomPoints would not
update in hdSt from the usdImagingDelegate. If the widths primvar was
not read from disk it would always display with it's default value. The
change here is that with a PrimvarChangeAdd it will set the incoming
dirty bit instead of just DirtyPrimvar

pxr/usdImaging/bin/testusdview/CMakeLists.txt

@@ -325,6 +325,11 @@ pxr_install_test_dir(
     DEST testUsdviewVariantSelection
 )
 
+pxr_install_test_dir(
+    SRC testenv/testUsdviewPointWidths
+    DEST testUsdviewPointWidths
+)
+
 
 pxr_register_test(testUsdviewAlive
     PRE_COMMAND "${PYTHON_EXECUTABLE} testUsdviewAliveSetup.py"
@@ -961,6 +966,21 @@ pxr_register_test(testUsdviewVariantSelection
     EXPECTED_RETURN_CODE 0
 )
 
+pxr_register_test(testUsdviewPointWidths
+    PYTHON
+    COMMAND "${CMAKE_INSTALL_PREFIX}/bin/testusdview --testScript testUsdviewPointWidths.py points.usda"
+    IMAGE_DIFF_COMPARE
+        start.png
+        set_point_widths_025.png
+        set_point_widths_050.png
+        set_point_widths_primvar_075.png
+        end.png
+    FAIL 1
+    FAIL_PERCENT 0.002
+    PERCEPTUAL
+    EXPECTED_RETURN_CODE 0
+)
+
 if(OPENCOLORIO_FOUND AND ${PXR_BUILD_OPENCOLORIO_PLUGIN})
     pxr_register_test(testUsdviewColorManagement
         PYTHON

pxr/usdImaging/bin/testusdview/testenv/testUsdviewPointWidths/points.usda

@@ -0,0 +1,8 @@
+#usda 1.0
+(
+    defaultPrim = "World"
+    upAxis = "Y"
+)
+
+def Xform "Scene" {
+}

pxr/usdImaging/bin/testusdview/testenv/testUsdviewPointWidths/testUsdviewPointWidths.py

@@ -0,0 +1,93 @@
+#!/pxrpythonsubst
+#
+# Copyright 2020 Pixar
+#
+# Licensed under the Apache License, Version 2.0 (the "Apache License")
+# with the following modification; you may not use this file except in
+# compliance with the Apache License and the following modification to it:
+# Section 6. Trademarks. is deleted and replaced with:
+#
+# 6. Trademarks. This License does not grant permission to use the trade
+#    names, trademarks, service marks, or product names of the Licensor
+#    and its affiliates, except as required to comply with Section 4(c) of
+#    the License and to reproduce the content of the NOTICE file.
+#
+# You may obtain a copy of the Apache License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the Apache License with the above modification is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the Apache License for the specific
+# language governing permissions and limitations under the Apache License.
+#
+from __future__ import print_function
+
+from pxr.Usdviewq.common import Usd, UsdGeom
+from pxr import Vt, Gf, Sdf
+
+# Remove any unwanted visuals from the view, and enable autoClip
+def _modifySettings(appController):
+    appController._dataModel.viewSettings.showBBoxes = False
+    appController._dataModel.viewSettings.showHUD = False
+    appController._dataModel.viewSettings.autoComputeClippingPlanes = True
+
+def _createPoints(stage):
+    # define the points Prim on the stage
+    points = UsdGeom.Points.Define(stage, Sdf.Path("/Scene/points"))
+
+    positions = []
+    for x in range(-5, 5):
+        positions.append(Gf.Vec3f(x, 0, 10))
+
+    points.CreatePointsAttr().Set(Vt.Vec3fArray(positions))
+    return points
+
+def _createWidths(points, widthSize):
+    # initialize the widths attribute to a specific value
+    widths = []
+    for _ in range(0, len(points.GetPointsAttr().Get())):
+        widths.append(widthSize)
+
+    points.CreateWidthsAttr().Set(widths)
+
+def _createWidthsPrimvar(points, widthSize):
+    widths = []
+    for _ in range(0, len(points.GetPointsAttr().Get())):
+        widths.append(widthSize)
+
+    api = UsdGeom.PrimvarsAPI(points)
+    api.CreatePrimvar(UsdGeom.Tokens.widths, Sdf.ValueTypeNames.FloatArray).Set(widths)
+
+def _removeWidthsPrimvar(points):
+    api = UsdGeom.PrimvarsAPI(points)
+    api.RemovePrimvar(UsdGeom.Tokens.widths)
+
+def _testPointsWidthsAttr(appController):
+    # create the initial set of points that we will be changing the widths on
+    points = _createPoints(appController._dataModel.stage)
+
+    # take a screen shot of the points with their default widths
+    appController._takeShot("start.png")
+
+    # now author the widths attribute to a non-default width size
+    _createWidths(points, 0.25)
+    appController._takeShot("set_point_widths_025.png")
+
+    # change widths to a different value
+    _createWidths(points, 0.5)
+    appController._takeShot("set_point_widths_050.png")
+
+    # now author the widths primvar to override the widths attr
+    _createWidthsPrimvar(points, 0.75)
+    appController._takeShot("set_point_widths_primvar_075.png")
+
+    # remove the widths primvar to revert back to the widths attr
+    _removeWidthsPrimvar(points)
+    appController._takeShot("end.png")
+
+# This test adds and removes primvars that are used/unused by the material.
+def testUsdviewInputFunction(appController):
+    _modifySettings(appController)
+    _testPointsWidthsAttr(appController)

pxr/usdImaging/usdImaging/primAdapter.cpp

@@ -870,7 +870,6 @@ _GetDirtyBitsForPrimvarChange(
     HdDirtyBits dirty = HdChangeTracker::Clean;
 
     switch (changeType) {
-        case PrimvarChangeAdd:
         case PrimvarChangeRemove:
         case PrimvarChangeDesc:
         {
@@ -879,6 +878,7 @@ _GetDirtyBitsForPrimvarChange(
             dirty = HdChangeTracker::DirtyPrimvar;
             break;
         }
+        case PrimvarChangeAdd:
         case PrimvarChangeValue:
         {
             dirty = valueChangeDirtyBit;