XGetDeviceMotionEvents
Section: X FUNCTIONS (3X11)
Updated: Release 5
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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.
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
Index
- NAME
-
- SYNTAX
-
- ARGUMENTS
-
- DESCRIPTION
-
- STRUCTURES
-
- DIAGNOSTICS
-
- SEE ALSO
-
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