Implement Native Audio Switching for Element Call Widget on iOS/Android

[toger5]

Background

Element Call is implemented on our mobile platform via a one-fits-all widget approach. Web views on mobile platforms (Android, iOS) do not support properly selecting an audio output device from within the web view. Those mobile platforms "try" to find a "smart" auto selection.

Plan

In order to workaround the above constraints, on mobile we do not want to change the audio output/input via the web view, but instead do this all natively through the widget hosting native messenger app.

We still want that the control/change action of input/outbut audio lives in the widget / web view. In order to allow this we use js<->swift/cotlin web ffi calls.

Note the operating system can also change the audio input/output devices which is also signaled to the widget.

See FFI calls defined in: controlledOutput

The implementation wrt. Element Call widget is carried out in: #3270

Current state:

• Element Call Audio device controls for mobile native audio device selection #3270
• iOS
  • set the url flag to use controlled audio
  • audio output works (in general. the call audio is audible)
  • changing the output in the os (wither by connecting bt headphones or by using a native dialog) also updates the ui in EC
  • (ios specific) Earpiece mode is only delectable when on default audio output device
  • (ios specific) Earpiece mode works as good as it can.
  • changing the output in app also changes the actual audible output. (on ios this means that the button in the ui forwards us to the native picker)
  • initial list of devices is correct (on ios this is only about showing the earpice when starting with speaker mode)
  • all related PRs merged
    • EC: Native switch for audio outputs/inputs and earpiece element-x-ios#4136
• android
  • set the url flag to use controlled audio
  • audio output works (in general. the call audio is audible)
  • changing the output in the os (wither by connecting bt headphones or by using a native dialog) also updates the ui in EC
  • changing the output in app also changes the actual audible output.
  • initial list of devices is correct (we had issues with the timing of sending over the initial devices)
  • all related PRs merged
    • EC: Add PoC for native audio output selector element-x-android#4663

[toger5]

I will reopen this since it also tracks the mobile progress.