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XOpenDevice

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.