Loading mayaHydra should not set scene as modified.

lib/mayaHydra/mayaPlugin/plugin.cpp

@@ -33,6 +33,7 @@
 #include <maya/MFnPlugin.h>
 #include <maya/MGlobal.h>
 #include <maya/MSceneMessage.h>
+#include <maya/MCommandResult.h>
 
 #include <memory>
 #include <vector>
@@ -78,6 +79,44 @@ namespace {
     setenv(name.c_str(), value.c_str(), 1);
     #endif
     }
+
+class SceneModifiedGuard
+{
+public:
+
+    // Read modified state before
+    SceneModifiedGuard() : _wasModified(sceneModified())
+    {}
+
+    ~SceneModifiedGuard()
+    {
+        // If modified flag became true, clear it.
+        if (sceneModified() && !_wasModified) {
+            MGlobal::executeCommand("file -modified 0");
+        }
+    }
+
+private:
+
+    bool _wasModified{false};
+
+    // Scene modified query.
+    static bool sceneModified()
+    {
+        MCommandResult result;
+        auto status = MGlobal::executeCommand("file -query -modified", result);
+        if (status != MStatus::kSuccess) {
+            throw std::runtime_error("File modified query error in mayaHydra plugin load.");
+        }
+        int typedResult{0};
+        status = result.getResult(typedResult);
+        if (status != MStatus::kSuccess) {
+            throw std::runtime_error("Command result access error in mayaHydra plugin load.");
+        }
+        return (typedResult != 0);
+    }
+};
+
 }
 
 void initialize()
@@ -132,6 +171,8 @@ void beforePluginUnloadCallback( const MStringArray& strs, void* clientData )
 
 PLUGIN_EXPORT MStatus initializePlugin(MObject obj)
 {
+    SceneModifiedGuard guard;
+
     MString experimental("mayaHydra is experimental.");
     MGlobal::displayWarning(experimental);
 

test/lib/mayaUsd/render/mayaToHydra/CMakeLists.txt

@@ -56,6 +56,7 @@ set(INTERACTIVE_TEST_SCRIPT_FILES
     testCustomShadersNode.py
     testMayaDefaultMaterial.py
     testMayaLightingModes.py
+    testSceneModified.py
     cpp/testColorPreferences.py
     cpp/testCppFramework.py
     cpp/testDataProducerExample.py

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

@@ -26,6 +26,8 @@ class TestPolygonPrimitives(mtohUtils.MayaHydraBaseTestCase):
     IMAGE_DIFF_FAIL_THRESHOLD = 0.05
     IMAGE_DIFF_FAIL_PERCENT = 1.5
 
+    _requiredPlugins = ['modelingToolkit']
+
     def compareSnapshot(self, referenceFilename, cameraDistance=15, imageVersion=None):
         self.setBasicCam(cameraDistance)
         cmds.refresh()

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

@@ -0,0 +1,32 @@
+# Copyright 2024 Autodesk
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+import maya.cmds as cmds
+import fixturesUtils
+import mtohUtils
+
+class TestSceneModified(mtohUtils.MayaHydraBaseTestCase):
+    _file = __file__
+
+    # Base class setUp() defines HdStorm as the renderer.
+
+    def test_sceneModified(self):
+        # Though it modifies node 'defaultRenderGlobals' (as reported by
+        # 'ls -modified'), loading the mayaHydra plugin should not cause
+        # a scene modified warning, which causes spurious dialogs on file
+        # new or open to save what is essentially an empty file.
+        self.assertFalse(cmds.file(query=True, modified=True))
+
+if __name__ == '__main__':
+    fixturesUtils.runTests(globals())

test/testUtils/fixturesUtils.py

@@ -19,9 +19,6 @@
 import sys
 import unittest
 
-# Plugins that are bundled and loaded by default in a Maya installation
-DEFAULT_PLUGINS = ['ArubaTessellator', 'modelingToolkit']
-
 def _setUpClass(modulePathName, pluginName, initializeStandalone):
     '''
     Common code for setUpClass() and readOnlySetUpClass()
@@ -32,10 +29,10 @@ def _setUpClass(modulePathName, pluginName, initializeStandalone):
 
     if pluginName:
         import maya.cmds as cmds
+        wasModified = cmds.file(query=True, modified=True)
         cmds.loadPlugin(pluginName, quiet=True)
-
-    for defaultPlugin in DEFAULT_PLUGINS:
-        cmds.loadPlugin(defaultPlugin, quiet=True)
+        isModified = cmds.file(query=True, modified=True)
+        assert isModified == wasModified, ('Loading plugin %s modified the scene' % pluginName)
 
     realPath = os.path.realpath(modulePathName)
     return os.path.split(realPath)

test/testUtils/mayaUtils.py

@@ -43,61 +43,6 @@
 HD_STORM = "HdStormRendererPlugin"
 HD_STORM_OVERRIDE = "mayaHydraRenderOverride_" + HD_STORM
 
-def loadPlugin(pluginName):
-    """ 
-        Load all given plugins created or needed by maya-ufe-plugin 
-        Args:
-            pluginName (str): The plugin name to load
-        Returns:
-            True if all plugins are loaded. False if a plugin failed to load
-    """
-    try:
-        if not isPluginLoaded(pluginName):
-            cmds.loadPlugin( pluginName, quiet = True )
-        return True
-    except:
-        print(sys.exc_info()[1])
-        print("Unable to load %s" % pluginName)
-        return False
-
-def isPluginLoaded(pluginName):
-    """ 
-        Verifies that the given plugin is loaded
-        Args:
-            pluginName (str): The plugin name to verify
-        Returns:
-            True if the plugin is loaded. False if a plugin failed to load
-    """
-    return cmds.pluginInfo( pluginName, loaded=True, query=True)
-
-def isMayaUsdPluginLoaded():
-    """ 
-        Load plugins needed by UFE tests.
-        Returns:
-            True if plugins loaded successfully. False if a plugin failed to load
-    """
-    # Load the mayaUsdPlugin first.
-    if not loadPlugin("mayaUsdPlugin"):
-        return False
-
-    # Load the UFE support plugin, for ufeSelectCmd support.  If this plugin
-    # isn't included in the distribution of Maya (e.g. Maya 2019 or 2020), use
-    # fallback test plugin.
-    if not (loadPlugin("ufeSupport") or loadPlugin("ufeTestCmdsPlugin")):
-        return False
-
-    # The renderSetup Python plugin registers a file new callback to Maya.  On
-    # test application exit (in TbaseApp::cleanUp()), a file new is done and
-    # thus the file new callback is invoked.  Unfortunately, this occurs after
-    # the Python interpreter has been finalized, which causes a crash.  Since
-    # renderSetup is not needed for mayaUsd tests, unload it.
-    rs = 'renderSetup'
-    if cmds.pluginInfo(rs, q=True, loaded=True):
-        unloaded = cmds.unloadPlugin(rs)
-        return (unloaded[0] == rs)
-
-    return True
-
 def createUfePathSegment(mayaPath):
     """
         Create a UFE path from a given maya path and return the first segment.
@@ -152,6 +97,8 @@ def openNewScene(useTestSettings=True):
     cmds.file(new=True, force=True)
     if useTestSettings:
         applyTestSettings()
+        # As this conceptually opens a new scene, set the file to unmodified.
+        cmds.file(modified=False)
 
 def openTestScene(*args, useTestSettings=True):
     filePath = testUtils.getTestScene(*args)

test/testUtils/mtohUtils.py

@@ -35,13 +35,6 @@
 HD_STORM_OVERRIDE = "mayaHydraRenderOverride_" + HD_STORM
 MAYAUSD_PLUGIN_NAME = 'mayaUsdPlugin'
 
-def checkForPlugin(pluginName: str):
-    try:
-        cmds.loadPlugin(pluginName)
-    except:
-        return False
-    return True
-
 class MayaHydraBaseTestCase(unittest.TestCase, ImageDiffingTestCase):
     '''Base class for mayaHydra unit tests.'''
 
@@ -60,7 +53,9 @@ class MayaHydraBaseTestCase(unittest.TestCase, ImageDiffingTestCase):
     # Unloading mayaHydraFlowViewportAPILocator crashes Maya (HYDRA-1304).
     # Unloading mtoa succeeds on Linux, but fails on Windows and macOS
     # with "cannot be unloaded because it is still in use" error.
-    _pluginsCantUnload = ['mayaHydraFlowViewportAPILocator', 'mtoa']
+    # Unloading modelingToolkit fails with a
+    # "Dynamic unloading is not currently supported." error
+    _pluginsCantUnload = ['mayaHydraFlowViewportAPILocator', 'mtoa', 'modelingToolkit']
 
     @classmethod
     def setUpClass(cls):
@@ -106,8 +101,17 @@ def setUp(self):
         # so open a new file before each test to minimize leftovers
         # from previous tests.
         mayaUtils.openNewScene()
+        modified = cmds.file(query=True, modified=True)
+        assert not modified, 'Internal test framework error: scene left as modified by mayaUtils.openNewScene()'
+
         self.setHdStormRenderer()
 
+        # We've just opened a new scene, so we should not be modified.  Setting
+        # Storm as the renderer should conceptually not change that status, but
+        # unfortunately in automated tests it does (see setHdStormRender()
+        # method documentation).  Restore modified status to false.
+        cmds.file(modified=False)
+
     @classmethod
     def tearDownClass(cls):
         # Clean out the scene to allow all plugins to unload cleanly.
@@ -131,6 +135,10 @@ def setHdStormRenderer(self):
         cmds.modelEditor(
             self.activeEditor, e=1,
             rendererOverrideName=HD_STORM_OVERRIDE)
+        # During automated tests, tracing demonstrates that the following call
+        # to refresh marks the scene as modified, with the modified node being
+        # defaultRenderGlobals.  This behavior cannot be reproduced in a
+        # non-automated interactive Maya.
         cmds.refresh(f=1)
         self.delegateId = cmds.mayaHydra(renderer=HD_STORM,
                                     sceneDelegateId="MayaHydraSceneDelegate")