Gaffer : Support for Python 3.11 and Qt/PySide 6.5.3

[boberfly]

Generally describe what this PR will do, and why it is needed

• This allows Gaffer to compile against Python 3.11 and Qt 6.5.3 (windows-tested)
• Aligns with VFX Platform 2024
• Very WIP, probably best to treat this PR as a guide for a better one...

Related issues

• N/A

Dependencies

• Python 3.11.x, Qt 6.5.3, PySide 6.5.3, Qt.py 1.4.1

Breaking changes

• Anything dependent upon old Qt 5.15 or PySide2 functionality eg. OpenGL widget creation

Checklist

• I have read the contribution guidelines.
• I have updated the documentation, if applicable.
• I have tested my change(s) in the test suite, and added new test cases where necessary.
• My code follows the Gaffer project's prevailing coding style and conventions.

This is very much a WIP and more designed as a guide for when Gaffer officially wants to support Python 3.11/Qt 6.5.x/PySide6. There are some issues still that I'm seeing eg. with spreadsheets:

Traceback (most recent call last):
  File "c:\Users\alex.fuller\local_packages\gaffer\1.5.2.0\platform-windows\arch-AMD64\python-3.11\ext\python\GafferUI\SpreadsheetUI\_ProxySelectionModel.py", line 119, in __modelChanged
    self.__initModelChain()
  File "c:\Users\alex.fuller\local_packages\gaffer\1.5.2.0\platform-windows\arch-AMD64\python-3.11\ext\python\GafferUI\SpreadsheetUI\_ProxySelectionModel.py", line 125, in __initModelChain
    assert( self.model() )
            ^^^^^^^^^^^^
AssertionError

Also some calls to self.qtWidget.update() require an argument which I'm not too sure on how to solve. Maybe the whole region of the widget needs to be passed to it?

Cheers

[johnhaddon]

Thanks Alex. What are your hopes for this in terms of timeframe? We're currently discussing when we might move the official builds over to a newer VFXPlatform, but that's likely to be led by version updates in other DCCs our main clients use - it's easier for them if everything aligns. Are you looking to get the official builds moved over, or just to have the capability to make your own with newer dependencies?

[boberfly]

Hi John some scheduling here is prepping for deploying Maya 2025 by around May but I'm not too fussed, it was to see if I should just go to this earlier than later to have less build variants, but I will probably stick to vfxplatform 2023 dependencies for now. The capability to DIY build is what I'm after more yep.