XListInputDevices(3X11)
NAME
XListInputDevices, XFreeDeviceList - list available input
devices
SYNTAX
XDeviceInfo *XListInputDevices(display, ndevices_return)
Display *display;
int *ndevices_return;
XFreeDeviceList(list)
XDeviceInfo *list;
ARGUMENTS
display Specifies the connection to the X server.
ndevices_return
Specifies a pointer to a variable where the
number of available devices can be returned.
list Specifies the list of devices to free. The
XFreeDeviceList function frees the list of
available extension input devices.
DESCRIPTION
The XListInputDevices request lists the available exten-
sion input devices. This list includes the X pointer and
X keyboard, any other input devices that are currently
accessible through the X server, and any input devices
that are not currently accessible through the X server but
could be accessed if requested.
Some server implementations may make all input devices
available at the time the server is initialized. Others
may wait until requested by a client to access an input
device. In the latter case, it is possible that an input
device will be listed as available at one time but not at
another.
For each input device available to the server, the
XListInputDevices request returns an XDeviceInfo struc-
ture. That structure contains a pointer to a list of
structures, each of which contains information about one
class of input supported by the device.
The XDeviceInfo structure is defined as follows:
typedef struct _XDeviceInfo
{
XID id;
Atom type;
char *name;
int num_classes;
int use;
XAnyClassPtr inputclassinfo;
} XDeviceInfo;
The id is a number in the range 0-128 that uniquely iden-
tifies the device. It is assigned to the device when it
is initialized by the server.
The type field is of type Atom and indicates the nature of
the device.
The name field contains a pointer to a null-terminated
string that corresponds to one of the defined device
types. The name will correspond to one of the following
strings (defined in the header file XI.h:
XI_MOUSE XI_TABLET XI_KEYBOARD XI_TOUCHSCREEN XI_TOUCHPAD
XI_BUTTONBOX XI_BARCODE XI_TRACKBALL XI_QUADRATURE
XI_ID_MODULE XI_ONE_KNOB XI_NINE_KNOB XI_KNOB_BOX
XI_SPACEBALL XI_DATAGLOVE XI_EYETRACKER XI_CURSORKEYS
XI_FOOTMOUSE
These names may be directly compared with the name field
of the XDeviceInfo structure, or used in an XInternAtom
request to return an atom that can be compared with the
type field of the XDeviceInfo structure.
The num_classes field is a number in the range 0-255 that
specifies the number of input classes supported by the
device for which information is returned by ListInputDe-
vices. Some input classes, such as class Focus and class
Proximity do not have any information to be returned by
ListInputDevices.
The use field specifies how the device is currently being
used. If the value is IsXKeyboard, the device is cur-
rently being used as the X keyboard. If the value is IsX-
Pointer, the device is currently being used as the X
pointer. If the value is IsXExtensionDevice, the device
is available for use as an extension device.
The inputclassinfo field contains a pointer to the first
input-class specific data. The first two fields are com-
mon to all classes.
The class field is a number in the range 0-255. It
uniquely identifies the class of input for which informa-
tion is returned. Currently defined classes are KeyClass,
ButtonClass, and ValuatorClass.
The length field is a number in the range 0- 255. It
specifies the number of bytes of data that are contained
in this input class. The length includes the class and
length fields.
The XKeyInfo structure describes the characteristics of
the keys on the device. It is defined as follows:
typedef struct _XKeyInfo {
XID class;
int length;
unsigned short min_keycode;
unsigned short max_keycode;
unsigned short num_keys;
} XKeyInfo;
min_keycode is of type KEYCODE. It specifies the minimum
keycode that the device will report. The minimum keycode
will not be smaller than 8.
max_keycode is of type KEYCODE. It specifies the maximum
keycode that the device will report. The maximum keycode
will not be larger than 255.
num_keys specifies the number of keys that the device has.
The XButtonInfo structure defines the characteristics of
the buttons on the device. It is defined as follows:
typedef struct _XButtonInfo {
XID class;
int length;
short num_buttons;
} XButtonInfo;
num_buttons specifies the number of buttons that the
device has.
The XValuatorInfo structure defines the characteristics of
the valuators on the device. It is defined as follows:
typedef struct _XValuatorInfo {
XID class;
int length;
unsigned char num_axes;
unsigned char mode;
unsigned long motion_buffer;
XAxisInfoPtr axes;
} XValuatorInfo;
num_axes contains the number of axes the device supports.
mode is a constant that has one of the following values:
Absolute or Relative. Some devices allow the mode to be
changed dynamically via the SetDeviceMode request.
motion_buffer_size is a cardinal number that specifies the
number of elements that can be contained in the motion
history buffer for the device.
The axes field contains a pointer to an XAxisInfo
structure.
The XAxisInfo structure is defined as follows:
typedef struct _XAxisInfo {
int resolution;
int min_value;
int max_value;
} XAxisInfo;
The resolution contains a number in counts/meter.
The min_val field contains a number that specifies the
minimum value the device reports for this axis. For
devices whose mode is Relative, the min_val field will
contain 0.
The max_val field contains a number that specifies the
maximum value the device reports for this axis. For
devices whose mode is Relative, the max_val field will
contain 0.
To free the XDeviceInfo array created by XListInputDe-
vices, use XFreeDeviceList.
DIAGNOSTICS
none.
SEE ALSO
Programming with Xlib