The button up debouncing states mirror the button down states with the
addition of the spurious debouncing states. Rename the states to better
show this symmetry.
When exiting RELEASE_DELAYED state, do not transition into states to detect
the need for spurious mode (RELEASE_WAITING, MAYBE_SPURIOUS).
RELEASE_DELAYED is only entered when spurious mode is enabled, there is no
need to detect the need for spurious mode again.
A set of wireless devices that can scramble the timestamps, so we get
press/release within 8ms even though I doubt the user is capable of doing
this. Since they're generally good quality anyway, let's just disable
debouncing on those until someone complains and we need something more
sophisticated.
https://bugs.freedesktop.org/show_bug.cgi?id=104415
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Sequences to trigger:
- spurious debouncing is enabled
- release a button in IS_DOWN state -> RELEASE_DELAYED
- short timeout triggers RELEASE_WAITING
If a button press now comes before the long timeout expires, we transition to
MAYBE_SPURIOUS where the long timeout may expire. In that case we should
transition to pressed state again.
Reported-by: Vicente Bergas <vicencb@gmail.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
The current debouncing code monitors events and switches on when events are
too close together. From then on, any event can be delayed.
Vicente Bergas provided an algorithm that avoids most of these delays:
on a button state change we now forward the change without delay but start a
timer. If the button changes state during that timer, the changes are
ignored. On timer expiry, events are sent to match the hardware state
with the client's view of the device. This is only done if needed.
Thus, a press-release sequence of: PRP sends a single press event, a sequence of
PRPR sends press and then the release at the end of the timeout. The timeout
is short enough that the delay should not be noticeable.
This new mode is called the 'bounce' mode. The old mode is now referred to as
'spurious' mode and only covers the case of a button held down that loses
contact. It works as before, monitoring a button for these spurious contact
losses and switching on. When on, button release events are delayed as before.
The whole button debouncing moves to a state machine which makes debugging a
lot easier. See the accompanying SVG for the diagram.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
