Re: [AD] ex_joystick_hotplugging.c

[Peter Wang <novalazy@xxxxxxxxxx>]

On 2010-08-21, Trent Gamblin <trent@xxxxxxxxxx> wrote:
> On 2010-08-21, at 6:39 PM, Peter Wang wrote:
> > Hi,
> > 
> > I still think it's a bad idea that al_get_num_joysticks can now
> > invalidate existing ALLEGRO_JOYSTICK structures.
> 
> Yeah, I agree.
> 
> > curr_joy is invalid at this point.
> > 
> > It crashes when I unplug a joystick.  (I will fix it while fixing some
> > issues with the linux joystick driver)
> 
> Alright. I wanted to get it into SVN because I have
> other commitments that aren't going to leave me much
> time to tune this how I'd like right now. I think the
> issues are pretty minor and shouldn't be too hard to
> fix.

Ok.  The Linux joystick driver is much improved now.
The other drivers seem to require similar changes.


I think we should not require Allegro programs to put in extra effort to
cope with hotplugging.  Anything that requires the program to remember
an old id/index/whatever, in addition to ALLEGRO_JOYSTICK handles, is
too much work.  I have a feeling most programs wouldn't bother.

Rather, ALLEGRO_JOYSTICK handles should persist after reconfiguration,
and they should continue to refer to the same physical devices (which
are still plugged in).  No re-getting of handles required.

Handles for devices which have been unplugged should *also* persist, so
nothing will crash.  Inactive handles should be reused when devices are
plugged in.  That would make this common situation just work:
if I pull out device A during a game and plug in device B, I probably
wanted to use device B in place of device A.  Since the old
ALLEGRO_JOYSTICK handle is valid, a program that doesn't do anything
special will work as expected.

We can add a function:
    bool al_get_joystick_active(ALLEGRO_JOYSTICK *joy);
to tell if the handle has a physical device associated with it.

Comments?

Peter