Add PyQt6 support

[MHendricks]

Add the binding information for PyQt6 support.

PyQt6 seems to have removed a lot of backwards compatible support that PySide6 has not. This introduces a few issues that should be figured out before this is merged. I will add additional notes calling out the specifics.

[MHendricks]

I wanted to ask how to solve the two failing PyQt6 tests. It looks like PyQt6 is capturing the FileNotFoundError error that is getting raised and these tests are looking for and wrapping it in a generic PyQt6.uic.exceptions.UIFileException that only inherits from Exception not from FileNotFoundError. This breaks the test, but also makes it so if a Qt.py user wanted to handle missing file exceptions they now have to account for if you are using PyQt6.

Do we accept this limitation and I just update the tests so they pass, or should I look into extracting the original exception and raise it in the _loadUi function?

The exception raised by the test:

ERROR: tests.test_load_ui_invalidpath
Tests to see if loadUi successfully fails on invalid paths
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/runner/.local/lib/python3.10/site-packages/PyQt6/uic/ui_file.py", line 35, in __init__
    document = ElementTree.parse(ui_file)
  File "/usr/lib/python3.10/xml/etree/ElementTree.py", line 1222, in parse
    tree.parse(source, parser)
  File "/usr/lib/python3.10/xml/etree/ElementTree.py", line 569, in parse
    source = open(source, "rb")
FileNotFoundError: [Errno 2] No such file or directory: 'made/up/path'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/runner/work/Qt.py/Qt.py/tests.py", line 622, in test_load_ui_invalidpath
    assert_raises(IOError, QtCompat.loadUi, 'made/up/path')
  File "/usr/lib/python3.10/unittest/case.py", line 738, in assertRaises
    return context.handle('assertRaises', args, kwargs)
  File "/usr/lib/python3.10/unittest/case.py", line 201, in handle
    callable_obj(*args, **kwargs)
  File "/home/runner/work/Qt.py/Qt.py/Qt.py", line 798, in _loadUi
    return Qt._uic.loadUi(uifile, baseinstance)
  File "/home/runner/.local/lib/python3.10/site-packages/PyQt6/uic/load_ui.py", line 86, in loadUi
    return DynamicUILoader(package).loadUi(uifile, baseinstance)
  File "/home/runner/.local/lib/python3.10/site-packages/PyQt6/uic/Loader/loader.py", line 62, in loadUi
    return self.parse(filename)
  File "/home/runner/.local/lib/python3.10/site-packages/PyQt6/uic/uiparser.py", line 995, in parse
    ui_file = UIFile(filename)
  File "/home/runner/.local/lib/python3.10/site-packages/PyQt6/uic/ui_file.py", line 37, in __init__
    self._raise_exception("invalid Qt Designer file", detail=str(e))
  File "/home/runner/.local/lib/python3.10/site-packages/PyQt6/uic/ui_file.py", line 92, in _raise_exception
    raise UIFileException(self._ui_file, message, detail=detail)
PyQt6.uic.exceptions.UIFileException: made/up/path: invalid Qt Designer file: [Errno 2] No such file or directory: 'made/up/path'

[MHendricks]

I see this as the biggest issue with PyQt6 in Qt.py. From experience as one of the few people using PyQt bindings most devs only test their code in PySide and won't run into the missing short enum's.

Once I got into running the tests, I discovered that Qt4 and the older versions of Qt5 in the VFXPLATFORM docker images don't support the new enum names. So this can't just be solved by dropping Qt4 support, we would have to consider dropping support for older versions of Qt5.

I considered building some sort of compatibility mapping of all enums, but it's not just QtCore.Qt that has this enum issue. A lot of classes have their own Enums like QFont.Weight.Bold. Alternatively, adding a enum lookup method like get_enum in test.py could work but seems unlikely to be used by users unless somehow forced.

[MHendricks]

Just read up on #413 (comment) and looks like we are planning to drop Qt4 support. If we also drop support for older versions of Qt5 then we can just encourage using the fully qualified enum names.

[MHendricks]

I've been using the https://stackoverflow.com/a/72658216 and ran into problems with it not supporting sub-classes. For example it didn't find QTreeWidget.ScrollPerPixel because that is defined on its superclass QAbstractItemView.ScrollMode.ScrollPerPixel.

We have a lot of code we will need to convert so I'm working on improving it using ast to parse the .pyi file and adding support for using PySide6 which the original would not have supported.

I found out that Qt.py has a cli that I never noticed so I'm thinking of adding it there. Though this may be its own merge request.

[MHendricks]

Makes it possible to take a font string saved in Qt6 easily be loaded in Qt5. By default it would log a warning and not load the font.

>>> fs = "Arial,7,-1,5,400,0,0,0,0,0,0,0,0,0,0,1"
>>> from PySide2.QtGui import QFont
>>> f = QFont()
>>> f.fromString(fs)
QFont::fromString: Invalid description 'Arial,7,-1,5,400,0,0,0,0,0,0,0,0,0,0,1'
False
>>> f
<PySide2.QtGui.QFont(,-1,-1,5,50,0,0,0,0,0) at 0x000001196C664480>
>>> from PyQt5.QtGui import QFont
>>> f = QFont()
>>> f.fromString(fs)
QFont::fromString: Invalid description 'Arial,7,-1,5,400,0,0,0,0,0,0,0,0,0,0,1'
False
>>> f
<PyQt5.QtGui.QFont object at 0x00000119698EFD80>

[MHendricks]

Another PyQt6 only issue. When building keyboard shortcuts, the PyQt6 bindings don't accept the new QKeyCombination objects so you have to cast them to QKeySequence before passing them.

PySide6:

>>> from PySide6 import QtCore, QtGui
>>> act = QtGui.QAction()
>>> act.setShortcut(QtCore.Qt.Modifier.SHIFT | QtCore.Qt.Key.Key_Backspace)

PyQt6:

>>> from PySide6 import QtCore, QtGui
>>> QtGui.QAction().setShortcut(QtCore.Qt.Modifier.SHIFT | QtCore.Qt.Key.Key_Backspace)
>>> from PyQt6 import QtCore, QtGui
>>> QtGui.QAction().setShortcut(QtCore.Qt.Modifier.SHIFT | QtCore.Qt.Key.Key_Backspace)

Traceback (most recent call last):
  File "C:\blur\dev\preditor\preditor\gui\console.py", line 586, in keyPressEvent
    self.executeCommand()
  File "C:\blur\dev\preditor\preditor\gui\console.py", line 469, in executeCommand
    cmdresult, wasEval = self.executeString(commandText)
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\blur\dev\preditor\preditor\gui\console.py", line 422, in executeString
    cmdresult = eval(compiled, __main__.__dict__, __main__.__dict__)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<ConsolePrEdit>", line 1, in <module>
TypeError: setShortcut(self, shortcut: Union[QKeySequence, QKeySequence.StandardKey, Optional[str], int]): argument 1 has unexpected type 'QKeyCombination'

PyQt6 fix:

>>> QtGui.QAction().setShortcut(QtGui.QKeySequence(QtCore.Qt.Modifier.SHIFT | QtCore.Qt.Key.Key_Backspace))

[MHendricks]

I added a compatibility function to convert enums to int values.

For user prefs I often store the int value of flags and enums in prefs files and restore them. The new enum implementation for both PySide6 and PyQt6 require converting to int differently. For PyQt4/5 you can just cast them to ints(for some bindings they are already ints). In Qt6 you have to call enum.value to get the enum value.

>>> from PySide6 import QtCore 
>>> int(QtCore.Qt.WindowState.WindowActive)

Traceback (most recent call last):
  File "C:\blur\dev\preditor\preditor\gui\console.py", line 586, in keyPressEvent
    self.executeCommand()
  File "C:\blur\dev\preditor\preditor\gui\console.py", line 469, in executeCommand
    cmdresult, wasEval = self.executeString(commandText)
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\blur\dev\preditor\preditor\gui\console.py", line 422, in executeString
    cmdresult = eval(compiled, __main__.__dict__, __main__.__dict__)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<ConsolePrEdit>", line 1, in <module>
TypeError: int() argument must be a string, a bytes-like object or a real number, not 'WindowState'
>>> QtCore.Qt.WindowState.WindowActive.value
8

[mottosso]

Great initiative. I'm in the start of a house-move at the moment and will be slow to reply, but I would like invite others to join in on the conversation too so if you are reading this, do chime in.

[MHendricks]

I wanted to ask how to solve the two failing PyQt6 tests. It looks like PyQt6 is capturing the FileNotFoundError error that is getting raised and these tests are looking for and wrapping it in a generic PyQt6.uic.exceptions.UIFileException that only inherits from Exception not from FileNotFoundError. This breaks the test, but also makes it so if a Qt.py user wanted to handle missing file exceptions they now have to account for if you are using PyQt6.

Do we accept this limitation and I just update the tests so they pass, or should I look into extracting the original exception and raise it in the _loadUi function?

I chose the latter. For known exceptions we are testing for IOError and xml.etree.ElementTree.ParseError it will raise the generic exception(error.__context__). Otherwise it will raise the original PyQt6 specific errors, but for now I'm guessing it's unlikely that devs will be handling those errors in code.