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.

                                            09/15/2021                             XOPENDEVICE(3)