XOpenDevice(3X11) X FUNCTIONS XOpenDevice(3X11)
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 suc-
cessful, 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 CloseDev-
ice.
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 XInputClas-
sInfo structures. Each element of this array contains an
event type base for a class of input supported by the speci-
fied device. The num_classes field indicates the number of
elements in the classes array.
XFree86 Version 4.5.0 1
XOpenDevice(3X11) X FUNCTIONS XOpenDevice(3X11)
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 sup-
ported by the device. Defined types include KeyClass, But-
tonClass, 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, DeviceMappiingNotify, ChangeDeviceNotify,
DevicePointerMotionHint, DeviceButton1Motion,
DeviceButton2Motion, DeviceButton3Motion,
DeviceButton4Motion, DeviceButton5Motion, DeviceButtonMo-
tion, DeviceOwnerGrabButton, DeviceButtonPressGrab, and
NoExtensionEvent.
To obtain the proper event class for a particular device,
one of the above macros is invoked using the XDevice struc-
ture 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 XNex-
tEvent, 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 XChangePointerDev-
ice requests.
SEE ALSO
Programming with Xlib
XFree86 Version 4.5.0 2