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.
