/**

@page timestamps Timestamps

@section event_timestamps Event timestamps

Most libinput events provide a timestamp in millisecond and/or microsecond
resolution. These timestamp usually increase monotonically, but libinput
does not guarantee that this always the case. In other words, it is possible
to receive an event with a timestamp earlier than the previous event. 

For example, if a touchpad has @ref tapping enabled, a button event may have a
lower timestamp than an event from a different device. Tapping requires the
use of timeouts to detect multi-finger taps and/or @ref tapndrag.

Consider the following event sequences from a touchpad and a mouse:

<pre>
Time      Touchpad      Mouse
---------------------------------
t1       finger down
t2        finger up
t3                     movement
t4       tap timeout
</pre>

For this event sequence, the first event to be sent to a caller is in
response to the mouse movement: an event of type @ref
LIBINPUT_EVENT_POINTER_MOTION with the timestamp t3.
Once the timeout expires at t4, libinput generates an event of 
@ref LIBINPUT_EVENT_POINTER_BUTTON (press) with a timestamp t1 and an event
@ref LIBINPUT_EVENT_POINTER_BUTTON (release) with a timestamp t2.

Thus, the caller gets events with timestamps in the order t3, t1, t2,
despite t3 > t2 > t1.
*/
