XOpenDevice(3X11) X FUNCTIONS XOpenDevice(3X11)NAME
XOpenDevice, XCloseDevice - open or close an extension
input device
SYNTAX
XDevice *XOpenDevice(display, device_id)
Display *display;
XID device_id;
XCloseDevice(display, device)
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 inaccessi-
ble 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 XInputClass-
Info 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
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XOpenDevice(3X11) X FUNCTIONS XOpenDevice(3X11)
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 sup-
ported by the device. Defined types include KeyClass,
ButtonClass, ValuatorClass, ProximityClass, FeedbackClass,
FocusClass, and OtherClass. The event_type_base identi-
fies 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, ChangeDeviceNo-
tify, DevicePointerMotionHint, DeviceButton1Motion,
DeviceButton2Motion, DeviceButton3Motion, DeviceBut-
ton4Motion, DeviceButton5Motion, DeviceButtonMotion,
DeviceOwnerGrabButton, DeviceButtonPressGrab, and NoExten-
sionEvent.
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 XSelectExtension-
Event 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 compari-
son with the type in the event.
DIAGNOSTICS
BadDevice An invalid device was specified. The speci-
fied device does not exist, or is the X key-
board 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.
SEE ALSO
Programming with Xlib
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