PR Summary

At the moment, Tk does not support updating the 'scaling' value when the monitor pixel ratio changes, or the window is moved to a different one. Thus this needs a patch in the C extension to catch that window message and propagate it to Python. Due to thread locking issues, this needs to be done via a polled queue.

This is waiting for the pixel ratio refactor, #19126.

PR Checklist

• Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (run flake8 on changed files to check).
• New features are documented, with examples if plot related.
• Documentation is sphinx and numpydoc compliant (the docs should build without error).
• Conforms to Matplotlib style conventions (install flake8-docstrings and run flake8 --docstring-convention=all).
• New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• [n/a] API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).