XGetDeviceMotionEvents(3X11)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 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.
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XGetDeviceMotionEvents(3X11)X Version 11(Release 5)XGetDeviceMotionEvents(3X11)
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
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