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timer: change the timer offset warning to a client bug

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This looks like a libinput bug (well, it does say "libinput bug" on the
package) but it hasn't been that for a long time. The cause is almost always
insufficient motivation to call libinput_dispatch() by the caller, or at least
not doing it with the celerity libinput demands (and deserves, if I may say
so).

Up-, down- or side-grade it to a client bug, so the outrage can be
directed elsewhere, preferably away from me. And add a section to the
documentation, just in case someone actually reads this stuff.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Olivier Fourdan <ofourdan@redhat.com>
This commit is contained in:
Peter Hutterer 2018-02-06 14:10:40 +10:00
parent d4b76be18b
commit 64c73d7ae6
2 changed files with 26 additions and 4 deletions
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22
doc/faqs.dox
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@ -198,4 +198,26 @@ href="https://www.freedesktop.org/software/systemd/man/hwdb.html">udev
hwdb</a> or patches that include a change to the hwdb. See @ref hwdb for
details on the hwdb and how to modify it locally.
@section faq_timer_offset What causes the "timer offset negative" warning?
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
and can trigger some timers to be set (e.g. palm detection, tap-to-click,
disable-while-typing, etc.). Internally, libinput's time offsets are always
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 +
180ms. When setting a timer, libinput checks the wall clock time to ensure
that this time T + offset is still in the future. If not, the warning is
logged.
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
time. In almost all cases this is an indication of the caller being
overloaded and not handling events as speedily as required.
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
detected as they should be).
*/

8
src/timer.c
View file

@ -86,10 +86,10 @@ libinput_timer_set_flags(struct libinput_timer *timer,
uint64_t now = libinput_now(timer->libinput);
if (expire < now) {
if ((flags & TIMER_FLAG_ALLOW_NEGATIVE) == 0)
log_bug_libinput(timer->libinput,
"timer %s: offset negative (-%dms)\n",
timer->timer_name,
us2ms(now - expire));
log_bug_client(timer->libinput,
"timer %s: offset negative (-%dms)\n",
timer->timer_name,
us2ms(now - expire));
} else if ((expire - now) > ms2us(5000)) {
log_bug_libinput(timer->libinput,
"timer %s: offset more than 5s, now %d expire %d\n",