xref: /xsrc/external/mit/libXi/dist/man/XGetDeviceMotionEvents.txt

XGETDEVICEMOTIONEVENTS(libmansuffix)
====================================

NAME
----

   XGetDeviceMotionEvents, XDeviceTimeCoord - get device motion
   history

SYNOPSIS
--------

   #include <X11/extensions/XInput.h>

   XDeviceTimeCoord *XGetDeviceMotionEvents( Display *display,
                                             XDevice *device,
                                             Time start,
                                             Time stop,
                                             int *nevents_return,
                                             int *mode_return,
                                             int *axis_count_return);

   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 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.