[Feature Request] Allow to map gamepad buttons to emulator function keys

[casasfernando]

It would be really handy to add the possibility to map gamepad buttons or button combinations to emulator function keys (e.g.: exit emulator).
When running supermodel on dedicated gaming platforms (Steam Deck, RetroPie, etc.) where the main if not the only interface between the user and the system is just a gamepad it can be really useful to be able to access some emulator functions using just that.

Probably the best approach would be to be able to define a "special button" (e.g.: mode button) in the gamepad that when pressed in combination with other buttons (start, select, etc.) can trigger different actions like Exit, Pause, Reset, etc.

Thanks!

[casasfernando]

@trzy I have a couple of questions related to this FR that could use your comments/feedback:

1. Are there any reasons why this wasn’t implemented in the past and/or shouldn’t be implemented in the future?
2. If this would be implemented which would be the preferred approach?
3. I’m thinking on only a subset of keys that would highly benefit from being accesible with the gamepad: exit, pause, load, save, change slot and screenshot.
4. Looking at the code since INPUT_UI is not user configurable should this change to configurable? Would be better to create a new one (eg: INPUT_UI_CUSTOM) for the subset of UI keys that would be user configurable? Or add them to the existing INPUT_COMMON?

Thanks

[trzy]

It's not unusual for someone to accidentally delete their config file and we wouldn't want a situation where there is no way to use core emulator functions because all keys appear unbound. I think the preferred approach would be that these functions remain permanently bound to the given keys but that optionally, additional bindings can be introduced.

This is a little different than how inputs currently work (they can be cleared). There are probably a couple ways of achieving this. One way would be to create "alt" mappings for all the emulator functions that by default are unbound. Or, we can add a property to inputs that allows a hard-coded binding that cannot be cleared but only added to.

[casasfernando]

Thanks for sharing the motivation behind the current implementation. It makes sense.

I acknowledge that this feature is not a top priority hence why I wouldn't mind giving it a try and and see if I can implement it myself.
Will take a closer look at the code and see if/what I can do following the guidance above.