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XListInputDevices(3X)





NAME

       XListInputDevices, XFreeDeviceList - list available input devices


SYNTAX

       XDeviceInfo *XListInputDevices(Display *display, int *ndevices_return);

       int XFreeDeviceList(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 cor-
       responds 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  XDevi-
       ceInfo  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 key-
       board.  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 valua-
       tors 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

X Version 11                      libXi 1.0.2          XListInputDevices(3X11)

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