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57a2339779
Document that all timestamps are given in the CLOCK_MONOTONIC domain. Signed-off-by: Simon Ser <contact@emersion.fr>
46 lines
1.7 KiB
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46 lines
1.7 KiB
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.. _timestamps:
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==============================================================================
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Timestamps
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==============================================================================
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.. _event_timestamps:
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------------------------------------------------------------------------------
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Event timestamps
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------------------------------------------------------------------------------
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Most libinput events provide a timestamp in millisecond and/or microsecond
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resolution. These timestamp usually increase monotonically, but libinput
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does not guarantee that this always the case. In other words, it is possible
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to receive an event with a timestamp earlier than the previous event.
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For example, if a touchpad has :ref:`tapping` enabled, a button event may have a
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lower timestamp than an event from a different device. Tapping requires the
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use of timeouts to detect multi-finger taps and/or :ref:`tapndrag`.
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Consider the following event sequences from a touchpad and a mouse:
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::
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Time Touchpad Mouse
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---------------------------------
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t1 finger down
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t2 finger up
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t3 movement
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t4 tap timeout
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For this event sequence, the first event to be sent to a caller is in
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response to the mouse movement: an event of type
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**LIBINPUT_EVENT_POINTER_MOTION** with the timestamp t3.
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Once the timeout expires at t4, libinput generates an event of
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**LIBINPUT_EVENT_POINTER_BUTTON** (press) with a timestamp t1 and an event
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**LIBINPUT_EVENT_POINTER_BUTTON** (release) with a timestamp t2.
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Thus, the caller gets events with timestamps in the order t3, t1, t2,
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despite t3 > t2 > t1.
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libinput timestamps use **CLOCK_MONOTONIC**.
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