fix(present): black video flashes and other bugs linked to Qt

[jeertmans]

See #464 for original pull request. I did some mistakes but by pushing on my main branch instead of @PeculiarProgrammer 's main branch.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.83%. Comparing base (3b23c77) to head (0da32ad).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #465      +/-   ##
==========================================
- Coverage   80.54%   77.83%   -2.72%     
==========================================
  Files          22       22              
  Lines        1835     1827       -8     
==========================================
- Hits         1478     1422      -56     
- Misses        357      405      +48     

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[jeertmans]

@PeculiarProgrammer: did you check that #315 was fixed on Windows?

[PeculiarProgrammer]

Yep. #315 was fixed.

[jeertmans]

Thanks @PeculiarProgrammer, I also ran some tests on Windows, both with PySide6 and PyQt6, and it worked (for PyQt6, I had to bump the minimal version, but looks good).