XOpenDevice

XOpenDevice(3X11)		 X FUNCTIONS		    XOpenDevice(3X11)



NAME
       XOpenDevice, XCloseDevice - open or close an extension input device

SYNTAX
       XDevice *XOpenDevice(Display *display, XID device_id);

       XCloseDevice(Display *display, XDevice *device);


ARGUMENTS
       display	   Specifies the connection to the X server.

       device_id   Specifies the id of the device to be opened

       device	   Specifies the device to be closed

DESCRIPTION
       The  XOpenDevice	 request makes an input device accessible to a client
       through input extension protocol requests.  If successful, it  returns
       a pointer to an XDevice structure.

       The  XCloseDevice  request  makes  an  input  device inaccessible to a
       client through input extension protocol requests.  Before terminating,
       and  client  that has opened input devices through the input extension
       should close them via CloseDevice.

       When a client makes an XCloseDevice request, any active grabs that the
       client  has on the device are released.	Any event selections that the
       client has are deleted, as well as any passive grabs.  If the request-
       ing  client  is	the  last client accessing the device, the server may
       disable all access by X to the device.

       XOpenDevice and XCloseDevice can generate a BadDevice error.

STRUCTURES
       The XDevice structure returned by XOpenDevice contains:
       typedef struct {
	    XID device_id;
	    int num_classes;
	    XInputClassInfo *classes;
       } XDevice;

       The classes field is a pointer to an array of  XInputClassInfo  struc-
       tures.	Each  element of this array contains an event type base for a
       class of input supported by the	specified  device.   The  num_classes
       field indicates the number of elements in the classes array.

       The XInputClassInfo structure contains:

       typedef struct {
	    unsigned char input_class;
	    unsigned char event_type_base;
       } XInputClassInfo;

       The  input_class	 field identifies one class of input supported by the
       device.	Defined types include KeyClass,	 ButtonClass,  ValuatorClass,
       ProximityClass,	 FeedbackClass,	  FocusClass,  and  OtherClass.	  The
       event_type_base identifies the event type of the first event  in	 that
       class.

       The  information contained in the XInputClassInfo structure is used by
       macros to  obtain  the  event  classes  that  clients  use  in  making
       XSelectExtensionEvent  requests.	  Currently  defined  macros  include
       DeviceKeyPress, DeviceKeyRelease,  DeviceButtonPress,  DeviceButtonRe-
       lese,  DeviceMotionNotify, DeviceFocusIn, DeviceFocusOut, ProximityIn,
       ProximityOut, DeviceStateNotify, DeviceMappiingNotify, ChangeDeviceNo-
       tify,	DevicePointerMotionHint,    DeviceButton1Motion,   DeviceBut-
       ton2Motion,   DeviceButton3Motion,   DeviceButton4Motion,   DeviceBut-
       ton5Motion,  DeviceButtonMotion,	 DeviceOwnerGrabButton, DeviceButton-
       PressGrab, and NoExtensionEvent.

       To obtain the proper event class for a particular device, one  of  the
       above  macros  is invoked using the XDevice structure for that device.
       For example,

       DeviceKeyPress (*device, type, eventclass);

       returns	the  DeviceKeyPress  event  type  and  the   eventclass	  for
       DeviceKeyPress events from the specified device.

       This  eventclass	 can then be used in an XSelectExtensionEvent request
       to ask the server to send  DeviceKeyPress  events  from	this  device.
       When a selected event is received via XNextEvent, the type can be used
       for comparison with the type in the event.

DIAGNOSTICS
       BadDevice   An invalid device was  specified.   The  specified  device
		   does	 not  exist, or is the X keyboard or X pointer.	 This
		   error may also occur if some other client has  caused  the
		   specified  device  to  become  the X keyboard or X pointer
		   device via the XChangeKeyboardDevice or  XChangePointerDe-
		   vice requests.

SEE ALSO
       Programming with Xlib



							    XOpenDevice(3X11)