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- .. _timestamps:
- ==============================================================================
- Timestamps
- ==============================================================================
- .. _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:
- ::
- Time Touchpad Mouse
- ---------------------------------
- t1 finger down
- t2 finger up
- t3 movement
- t4 tap timeout
- For this event sequence, the first event to be sent to a caller is in
- response to the mouse movement: an event of type
- **LIBINPUT_EVENT_POINTER_MOTION** with the timestamp t3.
- Once the timeout expires at t4, libinput generates an event of
- **LIBINPUT_EVENT_POINTER_BUTTON** (press) with a timestamp t1 and an event
- **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.
- libinput timestamps use **CLOCK_MONOTONIC**.
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