XOPENDEVICE(3)

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,
    DeviceButtonRelease, 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.