.. _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.