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XOpenDevice(3X11)


X11R6


NAME

  XOpenDevice, XCloseDevice - open or close an extension input device


SYNOPSIS

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

  XCloseDevice(display, device)
	  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 requesting
  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 structures.
  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, DeviceButtonRelese,
  DeviceMotionNotify, DeviceFocusIn, DeviceFocusOut, ProximityIn,
  ProximityOut, DeviceStateNotify, DeviceMappiingNotify, ChangeDeviceNotify,
  DevicePointerMotionHint, DeviceButton1Motion, DeviceButton2Motion,
  DeviceButton3Motion, DeviceButton4Motion, DeviceButton5Motion,
  DeviceButtonMotion, DeviceOwnerGrabButton, DeviceButtonPressGrab, 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 XChangePointerDevice requests.


SEE ALSO

  Programming with Xlib

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