Add support for PyQt6 and PySide6 (<6.4) to Qt backends

[astrofrog]

Work in progress!

[dhomeier]

@astrofrog I have added CI envs for PyQt6 and PySide6 in #2320 if you want to test those here. The setup is taken from the working one in glue-viz/echo#34; pyqt63 is failing on collection with the get_qapp error that is probably fixed here, pyside63 is running all tests with 3 failures.

[astrofrog]

The PySide6 6.4 errors are due to spyder-ide/qtpy#373

[dhomeier]

Testing PySide6 6.4.0 with spyder-ide/qtpy#374 installed from git+https://github.com/astrofrog/qtpy.git@ad9d386 seems to get a bit further, but then fails on the matplotlib side with

    from glue.viewers.matplotlib.qt.widget import MplWidget
../../opt/mambax86/envs/pyside6/lib/python3.10/site-packages/glue/viewers/matplotlib/qt/widget.py:13: in <module>
    from matplotlib.backends.backend_qt5 import FigureManagerQT
../../opt/mambax86/envs/pyside6/lib/python3.10/site-packages/matplotlib/backends/backend_qt5.py:6: in <module>
    from .backend_qt import (  # noqa
../../opt/mambax86/envs/pyside6/lib/python3.10/site-packages/matplotlib/backends/backend_qt.py:72: in <module>
    _MODIFIER_KEYS = [
../../opt/mambax86/envs/pyside6/lib/python3.10/site-packages/matplotlib/backends/backend_qt.py:73: in <listcomp>
    (_to_int(getattr(_enum("QtCore.Qt.KeyboardModifier"), mod)),
E   TypeError: int() argument must be a string, a bytes-like object or a real number, not 'KeyboardModifier'

There was a change in type from 6.3.2

type(PySide6.QtCore.Qt.KeyboardModifier.ControlModifier)
<class 'PySide6.QtCore.Qt.KeyboardModifier'>

which supports __int__(), in 6.4.0 to

type(PySide6.QtCore.Qt.KeyboardModifier.ControlModifier)
<enum 'KeyboardModifier'>

which has no __int__(), but does provide a value returning the same.

Matplotlib may need to define something like

_to_int = operator.attrgetter("value") if QT_API in ("PyQt6", "PySide64") else int

[astrofrog]

@dhomeier - thanks for investigating! Could you report that upstream to Matplotlib?

[astrofrog]

@dhomeier - I think this is ready for now, happy to merge? (the pyside63 failure that is not an allowed failure is a non-deterministic error).

[dhomeier]

Yes; I could get MplWidget to load and the test session to start patching that in my matplotlib installation, but starting the app fails at

GlueApplication(self.data_collection)

../../opt/mambax86/envs/pyside6/lib/python3.10/site-packages/glue/viewers/image/qt/tests/test_python_export.py:18: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../../opt/mambax86/envs/pyside6/lib/python3.10/site-packages/glue/app/qt/application.py:303: in __init__
    self._setup_ui()
../../opt/mambax86/envs/pyside6/lib/python3.10/site-packages/glue/app/qt/application.py:369: in _setup_ui
    lw = LayerTreeWidget(session=self._session)
../../opt/mambax86/envs/pyside6/lib/python3.10/site-packages/glue/app/qt/layer_tree_widget.py:519: in __init__
    self._create_actions()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <glue.app.qt.layer_tree_widget.LayerTreeWidget(0x6000031be160) at 0x1924ffb00>

    def _create_actions(self):
>       tree = self.ui.layerTree
E       AttributeError: 'PySide6.QtWidgets.QWidget' object has no attribute 'layerTree'

../../opt/mambax86/envs/pyside6/lib/python3.10/site-packages/glue/app/qt/layer_tree_widget.py:582: AttributeError
-------------------------------------------------------------------- Captured stderr setup ---------------------------------------------------------------------
qt.pysideplugin: Environment variable PYSIDE_DESIGNER_PLUGINS is not set, bailing out.
qt.pysideplugin: No instance of QPyDesignerCustomWidgetCollection was found.
Qt WebEngine seems to be initialized from a plugin. Please set Qt::AA_ShareOpenGLContexts using QCoreApplication::setAttribute and QSGRendererInterface::OpenGLRhi using QQuickWindow::setGraphicsApi before constructing QGuiApplication.
qt.pysideplugin: No instance of QPyDesignerCustomWidgetCollection was found.
Traceback (most recent call last):
  File "/Users/derek/opt/mambax86/envs/pyside6/lib/python3.10/site-packages/qtpy/uic.py", line 166, in createWidget
    widget = self.customWidgets[class_name](parent)
  File "/Users/derek/opt/mambax86/envs/pyside6/lib/python3.10/site-packages/glue/core/qt/data_collection_model.py", line 455, in __init__
    self.setEditTriggers(self.NoEditTriggers)
AttributeError: 'DataCollectionView' object has no attribute 'NoEditTriggers'. Did you mean: 'editTriggers'?
"Empty widget item in QVBoxLayout 'layout'."

so I'd also recommend to wait for the qtpy and matplotlib errors to be fixed, and then continue to work on PySide 6.4 support.

I also noticed when launching pytest directly, I am getting the environment listing as

                glue:	0.1.dev6471+g2d83dd8

               PYTHON
              Python:	INSTALLED (3.10.6)

        GUI FRAMEWORK
               PyQt5:	NOT INSTALLED
             PySide2:	NOT INSTALLED

             REQUIRED

and so on, but no report on the PyQt6 and PySide6 installations; could not figure out where that printout is generated though.

[dhomeier]

@dhomeier - I think this is ready for now, happy to merge? (the pyside63 failure that is not an allowed failure is a non-deterministic error).

Should it not still be better in allowed_failures so as not to block the publish job?

How about a more changelog-usable title like "Add support for PyQt6 and PySide6 backends"?

[dhomeier]

Ah, mpl is already fixed in matplotlib/matplotlib#24158 (GH search is just performing very awkwardly)!