[PATCH libinput] touchpad: require at least 3 events before enabling trackpoint palm detection

[Peter Hutterer]

Some trackpoints, notably the one on the Lenovo T460s have a tendency to send
the odd event even when they're not actually used. Trackpoint events trigger
palm detection (see 0210f1fee193) and thus effectively disable the touchpad,
causing the touchpad to appear nonresponsive.

Fix this by requiring at least 3 events from a trackpoint before palm
detection is enabled. For normal use it's hard enough to trigger a single
event anyway so this should not affect the normal use-case.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/evdev-mt-touchpad.c |  9 ++++++++-
 src/evdev-mt-touchpad.h |  1 +
 test/trackpoint.c       | 26 ++++++++++++++++++++++++++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
index 65b0abf..8f7dbf0 100644
--- a/src/evdev-mt-touchpad.c
+++ b/src/evdev-mt-touchpad.c
@@ -1302,6 +1302,7 @@ tp_trackpoint_timeout(uint64_t now, void *data)
 
 	tp_tap_resume(tp, now);
 	tp->palm.trackpoint_active = false;
+	tp->palm.trackpoint_event_count = 0;
 }
 
 static void
@@ -1314,6 +1315,13 @@ tp_trackpoint_event(uint64_t time, struct libinput_event *event, void *data)
 	if (event->type == LIBINPUT_EVENT_POINTER_BUTTON)
 		return;
 
+	tp->palm.trackpoint_last_event_time = time;
+	tp->palm.trackpoint_event_count++;
+
+	/* Require at least three events before enabling palm detection */
+	if (tp->palm.trackpoint_event_count < 3)
+		return;
+
 	if (!tp->palm.trackpoint_active) {
 		tp_edge_scroll_stop_events(tp, time);
 		tp_gesture_cancel(tp, time);
@@ -1321,7 +1329,6 @@ tp_trackpoint_event(uint64_t time, struct libinput_event *event, void *data)
 		tp->palm.trackpoint_active = true;
 	}
 
-	tp->palm.trackpoint_last_event_time = time;
 	libinput_timer_set(&tp->palm.trackpoint_timer,
 			   time + DEFAULT_TRACKPOINT_ACTIVITY_TIMEOUT);
 }
diff --git a/src/evdev-mt-touchpad.h b/src/evdev-mt-touchpad.h
index 8a8d2db..c2edb83 100644
--- a/src/evdev-mt-touchpad.h
+++ b/src/evdev-mt-touchpad.h
@@ -337,6 +337,7 @@ struct tp_dispatch {
 		struct libinput_event_listener trackpoint_listener;
 		struct libinput_timer trackpoint_timer;
 		uint64_t trackpoint_last_event_time;
+		uint32_t trackpoint_event_count;
 		bool monitor_trackpoint;
 	} palm;
 
diff --git a/test/trackpoint.c b/test/trackpoint.c
index b92b994..e9ba027 100644
--- a/test/trackpoint.c
+++ b/test/trackpoint.c
@@ -349,6 +349,31 @@ START_TEST(trackpoint_palmdetect_resume_touch)
 }
 END_TEST
 
+START_TEST(trackpoint_palmdetect_require_min_events)
+{
+	struct litest_device *trackpoint = litest_current_device();
+	struct litest_device *touchpad;
+	struct libinput *li = trackpoint->libinput;
+
+	touchpad = litest_add_device(li, LITEST_SYNAPTICS_I2C);
+	litest_drain_events(li);
+
+	/* A single event does not trigger palm detection */
+	litest_event(trackpoint, EV_REL, REL_X, 1);
+	litest_event(trackpoint, EV_REL, REL_Y, 1);
+	litest_event(trackpoint, EV_SYN, SYN_REPORT, 0);
+	libinput_dispatch(li);
+	litest_drain_events(li);
+
+	litest_touch_down(touchpad, 0, 30, 30);
+	litest_touch_move_to(touchpad, 0, 30, 30, 80, 80, 10, 1);
+	litest_touch_up(touchpad, 0);
+	litest_assert_only_typed_events(li, LIBINPUT_EVENT_POINTER_MOTION);
+
+	litest_delete_device(touchpad);
+}
+END_TEST
+
 void
 litest_setup_tests_trackpoint(void)
 {
@@ -362,4 +387,5 @@ litest_setup_tests_trackpoint(void)
 
 	litest_add("trackpoint:palmdetect", trackpoint_palmdetect, LITEST_POINTINGSTICK, LITEST_ANY);
 	litest_add("trackpoint:palmdetect", trackpoint_palmdetect_resume_touch, LITEST_POINTINGSTICK, LITEST_ANY);
+	litest_add("trackpoint:palmdetect", trackpoint_palmdetect_require_min_events, LITEST_POINTINGSTICK, LITEST_ANY);
 }
-- 
2.7.4