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joy(3)				Allegro	manual				joy(3)

NAME
       joy - Global array of joystick state information. Allegro game program-
       ming library.

SYNOPSIS
       #include	<allegro.h>

       extern JOYSTICK_INFO joy[n];

DESCRIPTION
       Global array of joystick	state information, which  is  updated  by  the
       poll_joystick()	function.  Only	 the first num_joysticks elements will
       contain meaningful information. The JOYSTICK_INFO structure is  defined
       as:

	  typedef struct JOYSTICK_INFO
	  {
	     int flags;			      -	status flags for this
						joystick
	     int num_sticks;		      -	how many stick inputs?
	     int num_buttons;		      -	how many buttons?
	     JOYSTICK_STICK_INFO stick[n];    -	stick state information
	     JOYSTICK_BUTTON_INFO button[n];  -	button state information
	  } JOYSTICK_INFO;

       The button status is stored in the structure:

	  typedef struct JOYSTICK_BUTTON_INFO
	  {
	     int b;			      -	boolean	on/off flag
	     char *name;		      -	description of this
						button
	  } JOYSTICK_BUTTON_INFO;

       You may wish to display the button names	as part	of an input configura-
       tion screen to let the user choose what game function will be performed
       by  each	 button,  but in simpler situations you	can safely assume that
       the first two elements in the button array  will	 always	 be  the  main
       trigger controls.

       Each  joystick will provide one or more stick inputs, of	varying	types.
       These can be digital controls which snap	to specific positions  (eg.  a
       gamepad	controller,  the  coolie  hat  on a Flightstick	Pro or Wingman
       Extreme,	or a normal joystick which hasn't  yet	been  calibrated),  or
       they  can be full analogue inputs with a	smooth range of	motion.	Sticks
       may also	have different numbers of axes,	for example  a	normal	direc-
       tional control has two, but the Flightstick Pro throttle	is only	a sin-
       gle axis, and it	is possible that the system could be extended  in  the
       future  to  support  full 3d controllers. A stick input is described by
       the structure:

	  typedef struct JOYSTICK_STICK_INFO
	  {
	     int flags;			      -	status flags for this
						input
	     int num_axis;		      -	how many axes do we
						have? (note the	misspelling)
	     JOYSTICK_AXIS_INFO	axis[n];      -	axis state information
	     char *name;		      -	description of this
						input
	  } JOYSTICK_STICK_INFO;

       A single	joystick may provide several different stick inputs,  but  you
       can safely assume that the first	element	in the stick array will	always
       be the main directional controller.

       Information about each of the stick axis	is stored in the substructure:

	  typedef struct JOYSTICK_AXIS_INFO
	  {
	     int pos;			      -	analogue axis position
	     int d1, d2;		      -	digital	axis position
	     char *name;		      -	description of this axis
	  } JOYSTICK_AXIS_INFO;

       This  provides  both analogue input in the pos field (ranging from -128
       to 128 or from 0	to 255,	depending on the type  of  the	control),  and
       digital	values	in  the	d1 and d2 fields. For example, when describing
       the X-axis position, the	pos field will hold the	horizontal position of
       the joystick, d1	will be	set if it is moved left, and d2	will be	set if
       it is moved right. Allegro will fill in all these values	regardless  of
       whether	it  is using a digital or analogue joystick, emulating the pos
       field for digital inputs	by snapping it to the min, middle, and maximum
       positions,  and emulating the d1	and d2 values for an analogue stick by
       comparing the current position with the centre point.

       The joystick flags field	may contain any	combination of the bit flags:

       JOYFLAG_DIGITAL This control is currently providing digital input.

       JOYFLAG_ANALOGUE	This control is	currently providing analogue input.

       JOYFLAG_CALIB_DIGITAL This control will be capable of providing digital
       input once it has been calibrated, but is not doing this	at the moment.

       JOYFLAG_CALIB_ANALOGUE This control will	be capable of  providing  ana-
       logue  input  once it has been calibrated, but is not doing this	at the
       moment.

       JOYFLAG_CALIBRATE Indicates that	this control needs to  be  calibrated.
       Many devices require multiple calibration steps,	so you should call the
       calibrate_joystick() function from a loop until this flag is cleared.

       JOYFLAG_SIGNED Indicates	that the analogue axis position	is  in	signed
       format,	ranging	 from  -128 to 128. This is the	case for all 2d	direc-
       tional controls.

       JOYFLAG_UNSIGNED	Indicates  that	 the  analogue	axis  position	is  in
       unsigned	 format,  ranging  from	 0 to 255. This	is the case for	all 1d
       throttle	controls.

       Note for	people who spell funny:	in case	you don't like having to  type
       "analogue",  there  are some #define aliases in allegro/joystick.h that
       will allow you to write "analog"	instead.

SEE ALSO
       install_joystick(3), poll_joystick(3), num_joysticks(3),	calibrate_joy-
       stick(3), calibrate_joystick_name(3), exjoy(3)

Allegro				 version 4.4.2				joy(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO

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