(Wayland): support wp_fractional_scale_v1

[wakira]

Description

Introduce wp_fractional_scale_v1 protocol for proper fractional scaling under wayland.

For compositors supporting wp_fractional_scale_v1, RetroArch is now pixel-accurate when using a non-integer scale.

Tested using KDE 5.27.5

[ColinKinloch]

You should apply the same scaling to active_touch_positions.

[wakira]

You should apply the same scaling to active_touch_positions.

fixed

[ColinKinloch]

I just tested it on gnome desktop and it seems to work fine.
Just a nitpick, I feel that the fractional_scale_num variables should just be fractional_scale.

[wakira]

Just a nitpick, I feel that the fractional_scale_num variables should just be fractional_scale.

The reasoning is that while buffer_scale is just the integer scale factor (1 for 1x, 2 for 2x ...), the fractional one is different (120 for 1x, 180 for 1.5x ...). I think similar names (buffer_scale and fractional_scale) might be error-prune.

I'm fine with just fractional_scale if that is not a concern.

[ColinKinloch]

The sent scale is the numerator of a fraction with a denominator of 120.

https://wayland.app/protocols/fractional-scale-v1#wp_fractional_scale_v1:event:preferred_scale

Yeah, it's okay. So long as num is short for numerator. 😄

[ColinKinloch]

@LibretroAdmin
This works well. It also still seems to rebase without conflicts.

[zoltanvb]

May we have this? :) Although I could not apply the patch version any more to current RA code, so maybe it is again a merge conflict that is not visible here.
https://github.com/wakira/RetroArch/commit/3c9a2f4fc3dbd7d9af96b9ff8dcb56a10bcd446a.patch/