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Table of Contents
XGetDeviceMotionEvents, XDeviceTimeCoord - get device
motion history
- 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.
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.
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.
- 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.
Programming with Xlib
Table of Contents
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