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doc/user: update the timer offset warning for the new "too slow" message

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Related #533

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
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Peter Hutterer 2020-10-22 15:10:38 +10:00
parent 5faa3b7ae9
commit 11d517f969
1 changed files with 14 additions and 14 deletions
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28
doc/user/faqs.rst
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@ -287,28 +287,28 @@ details on the hwdb and how to modify it locally.
.. _faq_timer_offset: .. _faq_timer_offset:
------------------------------------------------------------------------------ ------------------------------------------------------------------------------
What causes the "timer offset negative" warning? What causes the "your system is too slow" warning?
------------------------------------------------------------------------------ ------------------------------------------------------------------------------
libinput relies on the caller to call **libinput_dispatch()** whenever data is libinput relies on the caller to call **libinput_dispatch()** whenever data is
available on the epoll-fd. Doing so will process the state of all devices available. **libinput_dispatch()** will process the state of all devices,
and can trigger some timers to be set (e.g. palm detection, tap-to-click, including some time-sensitive features (e.g. palm detection, tap-to-click,
disable-while-typing, etc.). Internally, libinput's time offsets are always disable-while-typing, etc.).
based on the event time of the triggering event.
For example, a touch event with time T may trigger a timer for the time T + If the time between the event and the call to **libinput_dispatch()**
180ms. When setting a timer, libinput checks the wall clock time to ensure is excessive, those features may not work correctly. For example, a delay in
that this time T + offset is still in the future. If not, the warning is touch event processing may cause wrong or missing tap-to-click events or
logged. a palm may not be detected correctly.
When this warning appears, it simply means that too much time has passed When this warning appears, it simply means that too much time has passed
between the event occurring (and the epoll-fd triggering) and the current between the event occurring and the current time. In almost all cases this
time. In almost all cases this is an indication of the caller being is an indication of the caller being overloaded and not handling events as
overloaded and not handling events as speedily as required. speedily as required.
The warning has no immediate effect on libinput's behavior but some of the The warning has no immediate effect on libinput's behavior but some of the
functionality that relies on the timer may be impeded (e.g. palms are not functionality that relies on the timer may be impeded. This is not a bug in
detected as they should be). libinput. libinput does not control how quickly **libinput_dispatch()** is
called.
.. _faq_wayland: .. _faq_wayland: