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 extension
          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 structure.
          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
          identifies 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
          ListInputDevices.  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 currently
          being used as the X keyboard.  If the value is IsXPointer,
          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 common
          to all classes.

          The class field is a number in the range 0-255.  It uniquely
          identifies the class of input for which information 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 XListInputDevices,
          use XFreeDeviceList.

     DIAGNOSTICS
          none.

     SEE ALSO
          Programming with Xlib