SG-30534: First step to supporting PySide6 (#898)

* First step to supporting PySide6.

* Provide a patch for PySide6 to work using the PySide (Qt4) interface
* Create a new qt6 module to import PySide6 directly (unpatched)
* Next step, deprecate PySide/Qt4 and make PySide6/Qt6 the default base

* Black style

python/tank/platform/engine.py

@@ -49,6 +49,7 @@
 from . import events
 from . import qt
 from . import qt5
+from . import qt6
 from .bundle import TankBundle
 from .framework import setup_frameworks
 from .engine_logging import ToolkitEngineHandler, ToolkitEngineLegacyHandler
@@ -92,6 +93,7 @@ def __init__(self, tk, context, engine_instance_name, env):
         self.__created_qt_dialogs = []
         self.__qt_debug_info = {}
         self.__has_qt5 = False
+        self.__has_qt6 = False
 
         self.__commands_that_need_prefixing = []
 
@@ -179,6 +181,11 @@ def __init__(self, tk, context, engine_instance_name, env):
         for name, value in qt5_base.items():
             setattr(qt5, name, value)
 
+        qt6_base = self.__define_qt6_base()
+        self.__has_qt6 = len(qt6_base) > 0
+        for name, value in qt6_base.items():
+            setattr(qt6, name, value)
+
         # Update the authentication module to use the engine's Qt.
         # @todo: can this import be untangled? Code references internal part of the auth module
         from ..authentication.ui import qt_abstraction
@@ -623,6 +630,16 @@ def has_qt5(self):
         """
         return self.__has_qt5
 
+    @property
+    def has_qt6(self):
+        """
+        Indicates that the host application has access to Qt 6 and that the ``sgtk.platform.qt6`` module
+        has been populated with the Qt 6 modules and information.
+
+        :returns bool: boolean value indicating if Qt 6 is available.
+        """
+        return self.__has_qt6
+
     @property
     def has_qt4(self):
         """
@@ -2167,6 +2184,17 @@ def __define_qt5_base(self):
         """
         return QtImporter(interface_version_requested=QtImporter.QT5).base
 
+    def __define_qt6_base(self):
+        """
+        This will be called at initialization to discover every PySide6 module. It should provide
+        every Qt modules available as well as two extra attributes, ``__name__`` and
+        ``__version__``, which refer to the name of the binding and it's version, e.g.
+        PySide6 and 6.2.7
+
+        :returns: A dictionary with all the modules, __version__ and __name__.
+        """
+        return QtImporter(interface_version_requested=QtImporter.QT6).base
+
     def _initialize_dark_look_and_feel(self):
         """
         Initializes a standard toolkit look and feel using a combination of

python/tank/platform/qt6/__init__.py

@@ -0,0 +1,12 @@
+# Copyright (c) 2016 Shotgun Software Inc.
+#
+# CONFIDENTIAL AND PROPRIETARY
+#
+# This work is provided "AS IS" and subject to the Shotgun Pipeline Toolkit
+# Source Code License included in this distribution package. See LICENSE.
+# By accessing, using, copying or modifying this work you indicate your
+# agreement to the Shotgun Pipeline Toolkit Source Code License. All rights
+# not expressly granted therein are reserved by Shotgun Software Inc.
+
+# This module will be populated during engine initialization with modules available for Qt 6 if
+# PySide6 is accessible.