XGetDeviceMotionEvents(3X11)

NAME
XGetDeviceMotionEvents, XDeviceTimeCoord - get device motion history

SYNTAX

XDeviceTimeCoord *XGetDeviceMotionEvents(Display *display, XDevice *device, Time start, Time 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 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