Cleanup OpenPype Qt widgets on Substance Painter shutdown

openpype/hosts/substancepainter/deploy/plugins/openpype_plugin.py

@@ -1,13 +1,34 @@
 
+
+def cleanup_openpype_qt_widgets():
+    """
+        Workaround for Substance failing to shut down correctly
+        when a Qt window was still open at the time of shutting down.
+
+        This seems to work sometimes, but not all the time.
+
+    """
+    # TODO: Create a more reliable method to close down all OpenPype Qt widgets
+    from PySide2 import QtWidgets
+    import substance_painter.ui
+
+    # Kill OpenPype Qt widgets
+    print("Killing OpenPype Qt widgets..")
+    for widget in QtWidgets.QApplication.topLevelWidgets():
+        if widget.__module__.startswith("openpype."):
+            print(f"Deleting widget: {widget.__class__.__name__}")
+            substance_painter.ui.delete_ui_element(widget)
+
+
 def start_plugin():
     from openpype.pipeline import install_host
     from openpype.hosts.substancepainter.api import SubstanceHost
-
     install_host(SubstanceHost())
 
 
 def close_plugin():
     from openpype.pipeline import uninstall_host
+    cleanup_openpype_qt_widgets()
     uninstall_host()