wp-fractional-scale-v1: New protocol for fractional scaling

Previously wp-surface-scale-v1.

This protocols allows for communicating preferred fractional scales to surfaces, which in combination with wp_viewport can be used to render surfaces at fractional scales when applicable.

This protocol behaves similar to wl_surface.scale in wayland!220 (merged), but with a fractional scale rather than an integer.

• 3 implementations:
  • Compositor implementation: wlroots/wlroots!3511 (merged) (includes test client), https://github.com/swaywm/sway/pull/6929, https://github.com/mahkoh/jay/commit/e52a60b3b69e2f67025da467a46d8073c0484147 , https://invent.kde.org/plasma/kwin/-/merge_requests/2598
  • Client implementation: https://codereview.qt-project.org/c/qt/qtwayland/+/420041, https://codeberg.org/dnkl/foot/pulls/1006, https://github.com/libsdl-org/SDL/pull/5906, https://github.com/rust-windowing/winit/pull/2369
• Reviewer: @davidedmundson
• 3 ACKs from members
  • KDE: @davidedmundson
  • wlroots: @emersion
  • Qt: @eskilblomfeldt

More test clients available here: https://gitlab.freedesktop.org/kennylevinsen/fractional-scaling