File: XOpenDevice.txt

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XOPENDEVICE(libmansuffix)
=========================

NAME
----

   XOpenDevice, XCloseDevice - open or close an extension input
   device

SYNOPSIS
--------

   #include <X11/extensions/XInput.h>

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

   XCloseDevice( Display *display,
                 XDevice *device);

   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,
   DeviceMappingNotify, 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.