[PATCH libinput 4/5] touchpad: don't feed 0/0 deltas into the accel filters

[Peter Hutterer]

The resolution-based scaling may result in deltas of 0. The accel code doesn't
handle 0 deltas too well. 0/0 deltas can't happen for EV_REL devices, so the
code just isn't designed for it.

Most notably, events with delta 0/0 have no direction. That messes up the
history-based velocity calculation which stops whenever the current vector's
direction changes from the one in the trackers.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/evdev-mt-touchpad.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
index 0b06810..cf97eae 100644
--- a/src/evdev-mt-touchpad.c
+++ b/src/evdev-mt-touchpad.c
@@ -63,7 +63,8 @@ tp_filter_motion(struct tp_dispatch *tp,
 	motion.dx = *dx * tp->accel.x_scale_coeff;
 	motion.dy = *dy * tp->accel.y_scale_coeff;
 
-	filter_dispatch(tp->filter, &motion, tp, time);
+	if (motion.dx != 0.0 || motion.dy != 0)
+		filter_dispatch(tp->filter, &motion, tp, time);
 
 	*dx = motion.dx;
 	*dy = motion.dy;
-- 
1.9.3