iOS Retina support for GetCurrentDisplayMode

[flibitijibibo]

See: f660aec fd41ed1

This may be an SDL issue though?

@TheSpydog @kiates

[TheSpydog]

Whatever logic we add for this, should it go into GetGraphicsAdapters as well? I don't remember why the retina logic was only in GetCurrentDisplayMode since both deal with DisplayModes.

[flibitijibibo]

I would think so... the thing that throws me off is how uikit doesn't give you the full unscaled res, so you can't know the maximum drawable size. I did this for Wayland and it's totally fine:

https://github.com/flibitijibibo/SDL/blob/main/src/video/wayland/SDL_waylandvideo.c#L381

[TheSpydog]

For some reason SDL's UIKit driver seems pretty deliberate in choosing to use "points" over pixels for display modes. I don't really understand the rationale.

I think we could take the existing code and multiply w/h by data.uiscreen.nativeScale at the end to get the full raw size of the screen, although that'd be a breaking change for applications. Alternatively we could introduce a new SDL hint to request a full retina resolution instead of points.

[TheSpydog]

SDL issue filed: libsdl-org/SDL#5290