XGetDeviceMotionEvents(3X11) X FUNCTIONS 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 buf‐
fer.
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 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 val‐
ues 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 XOpen‐
InputDevice. 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
X Version 11 Release 6 XGetDeviceMotionEvents(3X11)
