[PATCH libinput] touchpad: if the second finger is within 20x5mm, bias towards 2fg scrolling

[Peter Hutterer]

Scrolling is much more common than a 2fg spread gesture, so if the finger
position indicates that the fingers are next to each other, switch to
scrolling immediately.

https://bugs.freedesktop.org/show_bug.cgi?id=93504

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/evdev-mt-touchpad-gestures.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/evdev-mt-touchpad-gestures.c b/src/evdev-mt-touchpad-gestures.c
index dc8d606..a9d7fa1 100644
--- a/src/evdev-mt-touchpad-gestures.c
+++ b/src/evdev-mt-touchpad-gestures.c
@@ -325,8 +325,9 @@ tp_gesture_handle_state_unknown(struct tp_dispatch *tp, uint64_t time)
 	struct tp_touch *first = tp->gesture.touches[0],
 			*second = tp->gesture.touches[1];
 	int dir1, dir2;
-	int yres = tp->device->abs.absinfo_y->resolution;
-	int vert_distance;
+	int yres = tp->device->abs.absinfo_y->resolution,
+	    xres = tp->device->abs.absinfo_x->resolution;
+	int vert_distance, horiz_distance;
 
 	/* for two-finger gestures, if the fingers stay unmoving for a
 	 * while, assume (slow) scroll */
@@ -338,10 +339,16 @@ tp_gesture_handle_state_unknown(struct tp_dispatch *tp, uint64_t time)
 
 	/* Else check if one finger is > 20mm below the others */
 	vert_distance = abs(first->point.y - second->point.y);
+	horiz_distance = abs(first->point.x - second->point.x);
 	if (vert_distance > 20 * yres &&
 	    tp->gesture.enabled) {
 		tp_gesture_init_pinch(tp);
 		return GESTURE_STATE_PINCH;
+	/* Else if the fingers are within 20x5mm of each other */
+	} else if (vert_distance < 5 * yres &&
+		   horiz_distance < 20 * xres) {
+		tp_gesture_set_scroll_buildup(tp);
+		return GESTURE_STATE_SCROLL;
 	}
 
 	/* Else wait for both fingers to have moved */
-- 
2.5.0