[RFC PATCH] dinput: Introduce new HID joystick backend.

[Rémi Bernon]

On 6/17/21 6:40 PM, Zebediah Figura (she/her) wrote:
> On 6/1/21 4:09 AM, Rémi Bernon wrote:
>> Sending this as RFC because I'm not completely sure how to proceed (and
>> also because ideally it would depend on 206872 which is not merged yet).
>>
>> The problem is that this new backend will fail most dinput(8) tests
>> until it's more properly implemented, although the testbot doesn't have
>> HID devices to test with.
>>
>> It could also cause issues if the new backend is enumerated and somehow
>> is selected by default for some reason.
>>
>> Either we don't really care, or the new backend could be conditionally
>> enabled with a configure flag?
> 
> For whatever it's worth, this strikes me as a good idea.
> 
> Probably what should be done is to deprioritize or even explicitly 
> disable this backend in the registry until it's ready to work, at which 
> point we can make it the default, keeping the old backends around until 
> all the bugs get ironed out. I don't know whether it's worth completely 
> disabling it just to make the tests pass for the TestBot and Alexandre; 
> I guess I'll leave that one to them.

I don't think there's a registry entry for that? The backends are just 
enumerated in order. It could be added I guess but I'm not even sure 
it's worth it. I think the way it usually works is that each backend 
lists their device, creating physically duplicated devices but with 
different features (like the linux and linuxinput joysticks).

> 
> Of course, introducing a switch like that is a good way to ensure that 
> concerned users always turn it off, and that the new backend never 
> really gets tested, but it would be unfair to offer no way to revert to 
> the old behaviour...
> 

I don't even think the TestBot will notice, as it doesn't have any 
joysticks.

> (Side note: looking at this patch shows me just how ugly the 
> IDirectInputDevice8WVtbl implementation is. If it's really worth sharing 
> all that code, I'd advocate for using a struct dinput_device_ops 
> instead...)
> 

Yeah although that would require cleaning up all the other joystick 
backend code, which I understand will ultimately be removed so it's a 
bit of a waste of time. Finishing the cleanup after the HID backend is 
complete is probably simpler.
-- 
Rémi Bernon <rbernon at codeweavers.com>