XGetDeviceMotionEvents(3X11)
X FUNCTIONS
XGetDeviceMotionEvents(3X11)
NAME
XGetDeviceMotionEvents, XDeviceTimeCoord - get device
motion history
SYNTAX
XDeviceTimeCoord *XGetDeviceMotionEvents(display, device,
start, stop,
neventsreturn, modereturn, axiscountreturn)
Display *display;
XDevice *device;
Time start, stop;
int *neventsreturn;
int *modereturn;
int *axiscountreturn;
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.
neventsreturn
Returns the number of events from the motion
history buffer.
modereturn Returns the mode of the device (Absolute or
Relative).
axiscountreturn
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 abso-
lute positional data (mode=Absolute) or relative motion
data (mode=Relative). Some devices allow their mode to be
changed via the XSetDeviceMode request. These constants
are defined in the file XI.h. The axiscount returns the
X Version 11 Release 5 1
XGetDeviceMotionEvents(3X11)
X FUNCTIONS
XGetDeviceMotionEvents(3X11)
number of axes or valuators being reported by the device.
XGetDeviceMotionEvents can generate a BadDevice, or Bad-
Match 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 gener-
ated by the device. These may be scaled by client pro-
grams using the maximum values that the device can gener-
ate. 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 speci-
fied 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 XGetDeviceMotion-
Events request is made specifying a device
that has no valuators and reports no axes of
motion.
SEE ALSO
Programming with Xlib
X Version 11 Release 5 2