NAME

       joy - Global array of joystick state information. Allegro game programming 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 configuration 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  directional  control  has  two, but the Flightstick Pro throttle is only a single 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  analogue  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 directional 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(3alleg4),  poll_joystick(3alleg4),  num_joysticks(3alleg4), calibrate_joystick(3alleg4),
       calibrate_joystick_name(3alleg4), exjoy(3alleg4)