filter: always init a delta smoothener for 10/10ms on trackpoints

If the trackpoint gives us deltas with less than 10ms intervals, something is
wrong. Could be bad hardware, a glitch in the matrix or a discontinuity in
the otherwise appropriately named time-space continuum. Usually it's the
first.

Let's always set up trackpoint delta smoothening for 10ms to improve the
pointer speed calculation and avoid jerky behaviors. i.e. if a trackpoint
delta comes in below 10ms, pretend it came in with a 10ms interval for
calculating the speed.

Fixes https://gitlab.freedesktop.org/libinput/libinput/issues/104

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

src/filter-trackpoint.c

@@ -185,6 +185,7 @@ struct motion_filter *
 create_pointer_accelerator_filter_trackpoint(double multiplier)
 {
 	struct trackpoint_accelerator *filter;
+	struct pointer_delta_smoothener *smoothener;
 
 	assert(multiplier > 0.0);
 
@@ -210,5 +211,10 @@ create_pointer_accelerator_filter_trackpoint(double multiplier)
 
 	filter->base.interface = &accelerator_interface_trackpoint;
 
+	smoothener = zalloc(sizeof(*smoothener));
+	smoothener->threshold = ms2us(10);
+	smoothener->value = ms2us(10);
+	filter->trackers.smoothener = smoothener;
+
 	return &filter->base;
 }