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Bug 1944 - Linux events, joysticks having only hat are not read
Summary: Linux events, joysticks having only hat are not read
Status: RESOLVED FIXED
Alias: None
Product: SDL
Classification: Unclassified
Component: joystick (show other bugs)
Version: 2.0.0
Hardware: x86 Linux
: P2 normal
Assignee: Ryan C. Gordon
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2013-07-07 15:31 UTC by Nicolas Adenis-Lamarre
Modified: 2013-11-06 12:49 UTC (History)
1 user (show)

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Description Nicolas Adenis-Lamarre 2013-07-07 15:31:06 UTC 
EV_IsJoystick(int fd) is too restritive :

In sdl 1.x
same problem as in SDL2 +

in the function static int EV_IsJoystick(int fd)
you do:
(test_bit(BTN_TRIGGER, keybit) || test_bit(BTN_A, keybit) || test_bit(BTN_1, keybit))
doesn't work for the wii guitar hero guitar driver i've wrotten for linux 3.11 because this guitar has no TRIGGER nor A nor 1 button.

In sdl 2.x
in the function static int EV_IsJoystick(int fd)
you do:

test_bit(ABS_X, absbit) && test_bit(ABS_Y, absbit)

but some joysticks have only hat.
so, it should be

(test_bit(ABS_X, absbit) && test_bit(ABS_Y, absbit))
||
test_bit(ABS_HAT0X, absbit) && test_bit(ABS_HAT0Y, absbit)
||
test_bit(ABS_HAT1X, absbit) && test_bit(ABS_HAT1Y, absbit)
||
test_bit(ABS_HAT2X, absbit) && test_bit(ABS_HAT2Y, absbit)
Comment 1 Nicolas Adenis-Lamarre 2013-07-07 16:09:49 UTC 
some other devices not detected :  "Nintendo Wii Remote IR" and "Nintendo Wii Remote Acceleromete"
because they are just axes. (i can however understand that it's not joysticks, and in my own opinion, the 3 devices should be only 1 because it's physically only 1 )

name    : "Nintendo Wii Remote IR"
   bits ev : EV_SYN EV_ABS

name    : "Nintendo Wii Remote"
   bits ev : EV_SYN EV_KEY EV_FF

name    : "Nintendo Wii Remote Acceleromete"
   bits ev : EV_SYN EV_ABS
Comment 2 Nicolas Adenis-Lamarre 2013-07-12 06:19:29 UTC 
the worst effect making this test less restrictive is to have some non joystick devices recognized as a joystick.
not really a keyboard, because a keyboard with axes could be considered as a joystick, but the question is more not detect a mouse as a joystick.
I could think this test has been added to difference a joystick and a mouse ; but in my humble opinion, the wiimote can be considered as a joystick and as mouse for the IR part at least.
At least having a hat, make your device a joystick, i think.

isn't it possible to add eventDevices including all of them and let the application choose what it needs to filter on ?
For example, for a game, i could have the need of only one axis to increase or decrease a value (speed for example).

what about an argument when initializing joysticks ?

struct joystickRequirements {
  // something which help to customize EV_IsJoystick() behavior
  // hasAxisX, hasAxisY, hasHATX, hasHATY, hasButton = true/false
  // minimum list of required button = A 1 TRIGGER
};

defaultJoystickRequirements { // default value when initializing joystick
 // something which define the default behavior
};
Comment 3 Gabriel Jacobo 2013-11-05 23:49:17 UTC 
My two cents, with UDEV hotplugging in place, I think the IsJoystick test can be relaxed completely (if the device addition comes from UDEV).
Comment 4 Sam Lantinga 2013-11-06 05:34:32 UTC 
Agreed, as long as udev actually identifies it as a joystick device. Gabriel, do you want to make that change?
Comment 5 Gabriel Jacobo 2013-11-06 12:49:33 UTC 
Hopefully this fixes it: http://hg.libsdl.org/SDL/rev/4434ab25abf3