SDL: Add DS3 button pressure

[Megamouse]

• Add DS3 button pressure to SDL pad handler

This seems very hacky, but it's supposedly the only way to make it work.
The code changes are inspired by non-existent documentation and some bold PRs in other projects.

NOTE: It won't work on windows, since our CI builds SDL without hidapi support.

Fixes #16824

[ItsLaguna]

I know it's still a draft but tried it and thought I'd mention the behavior so far:

• The controller isn't picked (regardless of bluetooth/wired) unless it was turned on/plugged before booting the emulator or before pressing Pads (meaning that if you pressed pads and it wasn't turned on, even refreshing inside Pads won't make it appear)

• None of the buttons that should have pressure sensitivity work (again regardless of bluetooth/wired), tried pressing harder too (😂) but there's no input registered.

That's all, really appreciate you working on this, Megamouse 🙂

[Megamouse]

This works now!
It needs to wait for the next SDL update, but at least it can be tested already.

The SDL implementation is a bit strange, but whatever...

[ItsLaguna]

You work fast!

Was going to report earlier that simply pressing was giving no input (but hard pressing did) and in the middle of compressing the video I saw a new push and was glad to see that it works now. However there's still a minor hiccup that can occur while going from regular to full press, check the following vid (this is from the latest commit, starts at 0:04):

2025-04-10.21-02-56.trimmed.trimmed.mp4

I'm just pressing harder / loosening it but never letting go, again something minor but thought I'd report it.

Amazing work Megamouse, thanks again 🙏🏻

[Megamouse]

@ItsLaguna can you try again ?

[ItsLaguna]

@Megamouse working perfectly now, no more hiccups but comparing between DS3 handler and the current SDL I've noticed you gotta push a bit more than usual.

2025-04-10.22-15-52.trimmed.mp4

Here I'm switching between both and as you can see it goes back to the other regular press despite applying the same amount of force to the button.

[Megamouse]

I know. but that's just how SDL reports the value...
Maybe there's some sort of hidden SDL deadzone applied... idk

[ItsLaguna]

Ah that's a shame, hopefully they can sort that out.
Leaving that aside, it works great and once again, thanks 🙏🏻

[Megamouse]

Turns out I was dropping negative values, which means the whole weaker half of the button press.
Should be fine now

[ItsLaguna]

Yeah, now it matches 👍🏻

Noticed that upon changing handlers, there's a weird input (R1+Triangle?) but honestly no one is going to be doing that.
Just letting you know for the sake of it lmao.

2025-04-10.23-01-42.mp4

[Megamouse]

I couldn't reproduce this. Maybe it's specific to mgs.
But I can try to take a more thorough look when I have the time.