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XOpenDevice(3) X FUNCTIONS XOpenDevice(3)
NAME
XOpenDevice, XCloseDevice - open or close an extension input device
SYNTAX
XDevice *XOpenDevice(Display *display, XID device_id);
XCloseDevice(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 pro-tocol protocol
tocol 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, Device-FocusIn, DeviceFocusIn,
FocusIn, DeviceFocusOut, ProximityIn, ProximityOut, DeviceStateNotify, DeviceMappiingNotify,
ChangeDeviceNotify, DevicePointerMotionHint, DeviceButton1Motion, DeviceButton2Motion, DeviceBut-ton3Motion, DeviceButton3Motion,
ton3Motion, 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 key-board keyboard
board or X pointer. This error may also occur if some other client has caused the speci-fied specified
fied device to become the X keyboard or X pointer device via the XChangeKeyboardDevice or
XChangePointerDevice requests.
SEE ALSO
Programming with Xlib
X Version 11 libXi 1.2.1 XOpenDevice(3)
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