Too much scrolling down may eventually trigger an overflow of the valuator.
If this happens, reset the valuator to 0 and skip this event for button
emulation. Clients will have to figure out a way to deal with this, but a
scroll event from (close to) INT_MAX to 0 is a hint of that it needs to be
ignored.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Chase Douglas <chase.douglas@canonical.com>
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