[libsdl] SDL3 onboarding status

[nephros]

This issue is inspired by sailfishos/libsdl#8 (comment)

Some tasks, and the opportunity for discussion of getting SDL3 into Sailfish OS.

Packages (packaging repos required):

• SDL3 https://github.com/libsdl-org/SDL/tree/release-3.4.x
• SDL3_ttf https://github.com/libsdl-org/SDL_ttf
• SDL3_sound https://github.com/icculus/SDL_sound
• SDL3_net https://github.com/libsdl-org/SDL_net
• SDL3_mixer https://github.com/libsdl-org/SDL_mixer
• SDL3_image https://github.com/libsdl-org/SDL_image

Optional but useful:

• sdl2-compat https://github.com/libsdl-org/sdl2-compat

Others:

• sdk-sdl-project-example https://github.com/sailfishos/sdk-sdl-project-example.git
• SDL3pp https://talesm.github.io/SDL3pp/

[nephros]

I have prepared some work that may be useful to make SDL3 feel at home on Sailfish OS. I'd be prepared to prepare PRs on these after we have a dedicated repo:

1. introducing SailfishOS as an "SDL Platform" (could go upstream).
   This allows for CMake configuration of switching features on and off, and makes #ifdef SDL_PLATFORM_SAILFISHOS available in the code.
   SDL makes some assumptions on what a "Linux" system can do, usally targets mainstream desktop uses rather than mobile, and of course does some if ANDROID || iOS things which can be expanded by if SFOS.

Based on 1.:

• using sailjail-compliant user-dirs per default.
• defaulting SDL Pulseaudio role to x-meego (avoids full-blown sound and enables volume control)
• detecting SailJail as a sandbox
• detecting devices as phone or tablet

OS-specific features:

• droidmedia camera support (working, needs polishing)
• sensorfw sensor support (WIP, non-working)
• Maliit IME integration (WIP, half-working, needs glib which is bad, needs rewrite)

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Anyone interested may watch these:

• https://build.sailfishos.org/package/show/home:nephros:devel:sdl3/SDL3
• https://github.com/nephros/libsdl.git (packaging, additional features as patches)
• https://github.com:nephros/SDL.git (fork, includes the feature branches)

[nephros]

Just for completeness, these are the top 3 problems someone faces when trying to port any SDL app to SFOS:

1. Portrait/Landscape/Rotation support, major problem, see the discussion link above
2. Lack of Maliit IME input: depending on whether the application offers their own on-screen keyboard, (often they do not), this makes text input require a hardware keyboard.
3. Pulseaudio policy: without explicitly setting the pulseaudio role to x-meego, applications use audio at full volume with no way to control it. Fix is easy, but it is a very annoying default behavior.