[PATCH libinput] touchpad: fix clickfinger behavior with a thumb being present

[Friedrich Schöller]

With a thumb on the touchpad, a two-finger click was incorrectly
treated as a middle-click. This patch takes the thumb into account and
treats the click as a right-click.
---
 src/evdev-mt-touchpad-buttons.c | 44 ++++++++++++++++++-----------------------
 1 file changed, 19 insertions(+), 25 deletions(-)

diff --git a/src/evdev-mt-touchpad-buttons.c b/src/evdev-mt-touchpad-buttons.c
index 895cf0e..ffb6a58 100644
--- a/src/evdev-mt-touchpad-buttons.c
+++ b/src/evdev-mt-touchpad-buttons.c
@@ -981,23 +981,24 @@ out:
 static uint32_t
 tp_clickfinger_set_button(struct tp_dispatch *tp)
 {
-	uint32_t button;
+	bool thumb_detected = false;
 	unsigned int nfingers = tp->nfingers_down;
 	struct tp_touch *t;
 	struct tp_touch *first = NULL,
 			*second = NULL;
 
-	if (nfingers != 2)
-		goto out;
+	if (nfingers < 2)
+		return BTN_LEFT;
 
-	/* two fingers down on the touchpad. Check for distance
-	 * between the fingers. */
 	tp_for_each_touch(tp, t) {
 		if (t->state != TOUCH_BEGIN && t->state != TOUCH_UPDATE)
 			continue;
 
-		if (t->thumb.state == THUMB_STATE_YES)
+		if (t->thumb.state == THUMB_STATE_YES) {
+			thumb_detected = true;
+			nfingers--;
 			continue;
+		}
 
 		if (!first)
 			first = t;
@@ -1005,27 +1006,20 @@ tp_clickfinger_set_button(struct tp_dispatch *tp)
 			second = t;
 	}
 
-	if (!first || !second) {
-		nfingers = 1;
-		goto out;
-	}
+	if (nfingers < 2)
+		return BTN_LEFT;
+	else if (nfingers > 2)
+		return BTN_MIDDLE;
 
-	if (tp_clickfinger_within_distance(tp, first, second))
-		nfingers = 2;
+	/* Two fingers (not counting thumbs) are on the touchpad. If no
+	 * additional thumb was detected, we check the distance between the
+	 * touches. Some touchpads can not report more than two finger positions
+	 * so we do not check the distance if an additional thumb was detected.
+	 */
+	if (thumb_detected || tp_clickfinger_within_distance(tp, first, second))
+		return BTN_RIGHT;
 	else
-		nfingers = 1;
-
-out:
-	switch (nfingers) {
-	case 0:
-	case 1: button = BTN_LEFT; break;
-	case 2: button = BTN_RIGHT; break;
-	default:
-		button = BTN_MIDDLE; break;
-		break;
-	}
-
-	return button;
+		return BTN_LEFT;
 }
 
 static int
-- 
2.9.4