XOpenDevice(3X11) SDK X11 R4.11MU05 XOpenDevice(3X11)
NAME
XOpenDevice, XCloseDevice - open or close an extension input device
SYNTAX
XDevice *XOpenDevice(display, deviceid)
Display *display;
XID deviceid;
XCloseDevice(display, device)
Display *display;
XDevice *device;
ARGUMENTS
display Specifies the connection to the X server.
deviceid 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,
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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