X Version 11 (Release 5) XGetDeviceMotionEvents(3X11)
NAME
XGetDeviceMotionEvents, XDeviceTimeCoord - get device motion
history
SYNTAX
XDeviceTimeCoord *XGetDeviceMotionEvents(display, device,
start, stop,
nevents_return, mode_return, axis_count_return)
Display *display;
XDevice *device;
Time start, stop;
int *nevents_return;
int *mode_return;
int *axis_count_return;
ARGUMENTS
display Specifies the connection to the X server.
device Specifies the device whose motion history is to
be queried.
start
stop Specify the time interval in which the events
are returned from the motion history buffer.
You can pass a timestamp or CurrentTime.
nevents_return
Returns the number of events from the motion
history buffer.
mode_return Returns the mode of the device (Absolute or
Relative).
axis_count_return
Returns the count of axes being reported.
DESCRIPTION
The server may retain the recent history of the device
motion and do so to a finer granularity than is reported by
DeviceMotionNotify events. The XGetDeviceMotionEvents
request makes this history available.
The XGetDeviceMotionEvents request returns all events in the
motion history buffer that fall between the specified start
and stop times, inclusive. If the start time is later than
the stop time or if the start time is in the future, no
events are returned. If the stop time is in the future, it
is equivalent to specifying CurrentTime.
The mode indicates whether the device is reporting absolute
positional data (mode=Absolute) or relative motion data
(mode=Relative). Some devices allow their mode to be
Licensed material--property of copyright holder(s) Page 1
X Version 11 (RelX
eG
ae
se
tD5
e)
viceMotionEvents(3X11)
changed via the XSetDeviceMode request. These constants are
defined in the file XI.h. The axis_count returns the number
of axes or valuators being reported by the device.
XGetDeviceMotionEvents can generate a BadDevice, or BadMatch
error.
STRUCTURES
The XDeviceTimeCoord structure contains:
typedef struct {
Time time;
int *data;
} XDeviceTimeCoord;
The time member is set to the time, in milliseconds. The
data member is a pointer to an array of integers. These
integers are set to the values of each valuator or axis
reported by the device. There is one element in the array
per axis of motion reported by the device. The value of the
array elements depends on the mode of the device. If the
mode is Absolute, the values are the raw values generated by
the device. These may be scaled by client programs using
the maximum values that the device can generate. The
maximum value for each axis of the device is reported in the
max_val field of the XAxisInfo returned by the
XListInputDevices request. If the mode is Relative, the
data values are the relative values generated by the device.
You should use XFreeDeviceMotionEvents to free the data
returned by this request.
Errors returned by this request: BadDevice, BadMatch.
DIAGNOSTICS
BadDevice An invalid device was specified. The specified
device does not exist or has not been opened by
this client via XOpenInputDevice. This error
may also occur if the specified device is the X
keyboard or X pointer device.
BadMatch This error may occur if an
XGetDeviceMotionEvents request is made
specifying a device that has no valuators and
reports no axes of motion.
SEE ALSO
Programming with Xlib
Licensed material--property of copyright holder(s) Page 2