[PATCH libinput 1/2] touchpad: reduce the initial timeout for tapping after touch

[Peter Hutterer]

This is the timeout before we decide "this is just a finger down, not a tap".
Until this timeout is hit a finger's movement is filtered. To allow for a more
responsive touchpad, we want that timeout as short as possible.

Event analysis from several users showed that 95% of the touches are less than
100ms long. Reducing the threshold should have almost no impact on most
tapping users but improves the reaction time of the pointer for normal
movements.

For a more details see:
http://who-t.blogspot.com/2016/12/libinput-touchpad-tap-analysis.html

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/evdev-mt-touchpad-tap.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/evdev-mt-touchpad-tap.c b/src/evdev-mt-touchpad-tap.c
index cb4abf2..b65bac4 100644
--- a/src/evdev-mt-touchpad-tap.c
+++ b/src/evdev-mt-touchpad-tap.c
@@ -33,6 +33,7 @@
 
 #include "evdev-mt-touchpad.h"
 
+#define DEFAULT_TAP_INITIAL_TIMEOUT_PERIOD ms2us(100)
 #define DEFAULT_TAP_TIMEOUT_PERIOD ms2us(180)
 #define DEFAULT_DRAG_TIMEOUT_PERIOD ms2us(300)
 #define DEFAULT_TAP_MOVE_THRESHOLD TP_MM_TO_DPI_NORMALIZED(3)
@@ -127,6 +128,13 @@ tp_tap_notify(struct tp_dispatch *tp,
 }
 
 static void
+tp_tap_set_initial_timer(struct tp_dispatch *tp, uint64_t time)
+{
+	libinput_timer_set(&tp->tap.timer,
+			   time + DEFAULT_TAP_INITIAL_TIMEOUT_PERIOD);
+}
+
+static void
 tp_tap_set_timer(struct tp_dispatch *tp, uint64_t time)
 {
 	libinput_timer_set(&tp->tap.timer, time + DEFAULT_TAP_TIMEOUT_PERIOD);
@@ -155,7 +163,7 @@ tp_tap_idle_handle_event(struct tp_dispatch *tp,
 	case TAP_EVENT_TOUCH:
 		tp->tap.state = TAP_STATE_TOUCH;
 		tp->tap.first_press_time = time;
-		tp_tap_set_timer(tp, time);
+		tp_tap_set_initial_timer(tp, time);
 		break;
 	case TAP_EVENT_RELEASE:
 		break;
-- 
2.9.3