The previous setting of 10 wasn't 10 mm, it was used against the deltas
normalized to a 1000DPI mouse, i.e. closer to 4mm. It was also also per-event,
so a slow movement or a high-frequency touchpad can struggle to meet the
threshold.
Change the trigger to be ~5 mm from the initial touch down, accumulated until
we either meet the threshold or the timeout expires. The first scroll event
includes the delta since the touch down rather than the most recent delta.
This removes the delay otherwise seen in scrolling and makes the scroll motion
match the finger motion. This accumulated delta only applies when exceeding
the motion threshold, when the timeout triggers the switch to scrolling the
first delta posted is the current delta.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>