XOpenDevice(3X11) X Version 11(Release 5) 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 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.
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XOpenDevice(3X11) X Version 11(Release 5) 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 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, DeviceMappiingNotify,
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.
SEE ALSO
Programming with Xlib
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