[PATCH v2 libinput 3/3] touchpad: change tap motion threshold to 3 mm

[Peter Hutterer]

On Fri, Mar 06, 2015 at 11:41:44AM +0100, Hans de Goede wrote:
> Hi,
> 
> On 06-03-15 06:42, Peter Hutterer wrote:
> >Previous code used a device coordinate threshold of 300 which won't work on
> >Elantech touchpads (1280 vs the ~4000 that synaptics has).
> >Convert to normalized DPI and reduce the threshold to 3mm.
> >
> >https://bugs.freedesktop.org/show_bug.cgi?id=89206
> >
> >[note that because of the MAGIC in the accel code this is currently
> >more than 3mm]
> >
> >Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> >---
> >Changes to v1:
> >- use the new macro instead
> 
> Looks good, but please use the new new TP_MM_TO_DPI_NORMALIZED macro instead,
> then you can drop the comment about the MAGIC stuff. You likely want to change the
> threshold to a different value then too, say 5 mm (3 / MAGIC = 7.5 but that seems
> a bit much).
> 
> With that changes this is:
> 
> Reviewed-by: Hans de Goede <hdegoede at redhat.com>

fixed as requested, but after a bit of experimenting I left the 3mm
threshold. The amount of sideways movement needed to trigger a >3mm movement
during a tap is quite extreme, so I think this is a good enough trigger. I
think 5mm would only delay movement without substantially helping  with the
tap recognition.

Cheers,
   Peter

> 
> >
> >  src/evdev-mt-touchpad-tap.c | 11 ++++++++---
> >  src/evdev-mt-touchpad.h     |  1 +
> >  2 files changed, 9 insertions(+), 3 deletions(-)
> >
> >diff --git a/src/evdev-mt-touchpad-tap.c b/src/evdev-mt-touchpad-tap.c
> >index 228eb84..d2728ee 100644
> >--- a/src/evdev-mt-touchpad-tap.c
> >+++ b/src/evdev-mt-touchpad-tap.c
> >@@ -37,7 +37,7 @@
> >  #define CASE_RETURN_STRING(a) case a: return #a;
> >
> >  #define DEFAULT_TAP_TIMEOUT_PERIOD 180
> >-#define DEFAULT_TAP_MOVE_THRESHOLD 30
> >+#define DEFAULT_TAP_MOVE_THRESHOLD MM_TO_DPI_NORMALIZED(3)
> >
> >  enum tap_event {
> >  	TAP_EVENT_TOUCH = 12,
> >@@ -527,12 +527,15 @@ tp_tap_handle_event(struct tp_dispatch *tp,
> >  }
> >
> >  static bool
> >-tp_tap_exceeds_motion_threshold(struct tp_dispatch *tp, struct tp_touch *t)
> >+tp_tap_exceeds_motion_threshold(struct tp_dispatch *tp,
> >+				struct tp_touch *t)
> >  {
> >  	int threshold = DEFAULT_TAP_MOVE_THRESHOLD;
> >  	double dx, dy;
> >
> >-	tp_get_delta(t, &dx, &dy);
> >+	dx = abs(t->tap.initial_x - t->x);
> >+	dy = abs(t->tap.initial_y - t->y);
> >+	tp_normalize_delta(tp, &dx, &dy);
> >
> >  	return dx * dx + dy * dy > threshold * threshold;
> >  }
> >@@ -568,6 +571,8 @@ tp_tap_handle_state(struct tp_dispatch *tp, uint64_t time)
> >
> >  		if (t->state == TOUCH_BEGIN) {
> >  			t->tap.state = TAP_TOUCH_STATE_TOUCH;
> >+			t->tap.initial_x = t->x;
> >+			t->tap.initial_y = t->y;
> >  			tp_tap_handle_event(tp, t, TAP_EVENT_TOUCH, time);
> >  		} else if (t->state == TOUCH_END) {
> >  			tp_tap_handle_event(tp, t, TAP_EVENT_RELEASE, time);
> >diff --git a/src/evdev-mt-touchpad.h b/src/evdev-mt-touchpad.h
> >index 1b8b560..65581ae 100644
> >--- a/src/evdev-mt-touchpad.h
> >+++ b/src/evdev-mt-touchpad.h
> >@@ -162,6 +162,7 @@ struct tp_touch {
> >
> >  	struct {
> >  		enum tp_tap_touch_state state;
> >+		int32_t initial_x, initial_y;
> >  	} tap;
> >
> >  	struct {
> >