[PATCH libinput 5/3] touchpad: accumulate the initial scroll edge delta

[Peter Hutterer]

The previous setting of 10 wasn't 10 mm, it was used against the deltas
normalized to a 1000DPI mouse, i.e. closer to 4mm. It was also also per-event,
so a slow movement or a high-frequency touchpad can struggle to meet the
threshold.

Change the trigger to be ~5 mm from the initial touch down, accumulated until
we either meet the threshold or the timeout expires.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/evdev-mt-touchpad-edge-scroll.c | 36 +++++++++++++++++++++++++++++++++---
 src/evdev-mt-touchpad.h             |  2 ++
 test/touchpad.c                     |  6 +++---
 3 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/src/evdev-mt-touchpad-edge-scroll.c b/src/evdev-mt-touchpad-edge-scroll.c
index 28f29c2..8e1997e 100644
--- a/src/evdev-mt-touchpad-edge-scroll.c
+++ b/src/evdev-mt-touchpad-edge-scroll.c
@@ -34,8 +34,7 @@
    avoid accidentally locking in scrolling mode when trying to use the entire
    touchpad to move the pointer. The user can wait for the timeout to trigger
    to do a small scroll. */
-/* In mm for touchpads with valid resolution, see tp_init_accel() */
-#define DEFAULT_SCROLL_THRESHOLD 10.0
+#define DEFAULT_SCROLL_THRESHOLD MM_TO_DPI_NORMALIZED(5)
 
 enum scroll_event {
 	SCROLL_EVENT_TOUCH,
@@ -78,6 +77,8 @@ tp_edge_scroll_set_state(struct tp_dispatch *tp,
 		break;
 	case EDGE_SCROLL_TOUCH_STATE_EDGE_NEW:
 		t->scroll.edge = tp_touch_get_edge(tp, t);
+		t->scroll.initial_x = t->x;
+		t->scroll.initial_y = t->y;
 		libinput_timer_set(&t->scroll.timer,
 				   t->millis + DEFAULT_SCROLL_LOCK_TIMEOUT);
 		break;
@@ -315,6 +316,7 @@ tp_edge_scroll_post_events(struct tp_dispatch *tp, uint64_t time)
 	struct tp_touch *t;
 	enum libinput_pointer_axis axis;
 	double dx, dy, *delta;
+	double initial_dx, initial_dy, *initial_delta;
 
 	if (tp->scroll.method != LIBINPUT_CONFIG_SCROLL_EDGE)
 		return 0;
@@ -338,10 +340,12 @@ tp_edge_scroll_post_events(struct tp_dispatch *tp, uint64_t time)
 			case EDGE_RIGHT:
 				axis = LIBINPUT_POINTER_AXIS_SCROLL_VERTICAL;
 				delta = &dy;
+				initial_delta = &initial_dy;
 				break;
 			case EDGE_BOTTOM:
 				axis = LIBINPUT_POINTER_AXIS_SCROLL_HORIZONTAL;
 				delta = &dx;
+				initial_delta = &initial_dx;
 				break;
 			default: /* EDGE_RIGHT | EDGE_BOTTOM */
 				continue; /* Don't know direction yet, skip */
@@ -350,7 +354,33 @@ tp_edge_scroll_post_events(struct tp_dispatch *tp, uint64_t time)
 		tp_get_delta(t, &dx, &dy);
 		tp_filter_motion(tp, &dx, &dy, NULL, NULL, time);
 
-		if (fabs(*delta) < t->scroll.threshold)
+		switch (t->scroll.edge_state) {
+		case EDGE_SCROLL_TOUCH_STATE_NONE:
+		case EDGE_SCROLL_TOUCH_STATE_AREA:
+			log_bug_libinput(device->seat->libinput,
+					 "unexpected scroll state %d\n",
+					 t->scroll.edge_state);
+			break;
+		case EDGE_SCROLL_TOUCH_STATE_EDGE_NEW:
+			initial_dx = t->x - t->scroll.initial_x;
+			initial_dy = t->y - t->scroll.initial_y;
+			tp_normalize_delta(tp,
+					   &initial_dx,
+					   &initial_dy);
+			if (fabs(*initial_delta) < t->scroll.threshold) {
+				*delta = 0.0;
+			} else {
+				dx = initial_dx;
+				dy = initial_dy;
+			}
+			break;
+		case EDGE_SCROLL_TOUCH_STATE_EDGE:
+			if (fabs(*delta) < t->scroll.threshold)
+				*delta = 0.0;
+			break;
+		}
+
+		if (*delta == 0.0)
 			continue;
 
 		pointer_notify_axis(device, time,
diff --git a/src/evdev-mt-touchpad.h b/src/evdev-mt-touchpad.h
index 8ea7d84..500eb59 100644
--- a/src/evdev-mt-touchpad.h
+++ b/src/evdev-mt-touchpad.h
@@ -171,6 +171,8 @@ struct tp_touch {
 		int direction;
 		double threshold;
 		struct libinput_timer timer;
+		int32_t initial_x;		/* in device coordinates */
+		int32_t initial_y;		/* in device coordinates */
 	} scroll;
 
 	struct {
diff --git a/test/touchpad.c b/test/touchpad.c
index 5c8f579..d589d64 100644
--- a/test/touchpad.c
+++ b/test/touchpad.c
@@ -2105,10 +2105,10 @@ START_TEST(touchpad_edge_scroll_no_motion)
 
 	litest_drain_events(li);
 
-	litest_touch_down(dev, 0, 99, 20);
-	litest_touch_move_to(dev, 0, 99, 20, 99, 60, 10, 0);
+	litest_touch_down(dev, 0, 99, 10);
+	litest_touch_move_to(dev, 0, 99, 10, 99, 70, 10, 0);
 	/* moving outside -> no motion event */
-	litest_touch_move_to(dev, 0, 99, 60, 20, 80, 10, 0);
+	litest_touch_move_to(dev, 0, 99, 70, 20, 80, 10, 0);
 	/* moving down outside edge once scrolling had started -> scroll */
 	litest_touch_move_to(dev, 0, 20, 80, 40, 99, 10, 0);
 	litest_touch_up(dev, 0);
-- 
2.1.0