touchpad: revamp thumb detection

Instead of a simple yes/no/maybe for thumbs, have a more extensive state
machine that keeps track of the thumb. Since we only support one thumb anyway,
the tracking moves to the tp_dispatch struct.

Test case changes:
touchpad_clickfinger_3fg_tool_position:
  with better thumb detection we can now handle this properly and expect a
  right button (2fg) press for the test case
touchpad_thumb_no_doublethumb_with_timeout:
  two thumbs are now always two fingers, so let's switch to axis events here

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

src/evdev-mt-touchpad-gestures.c

@@ -549,10 +549,16 @@ tp_gesture_handle_state_unknown(struct tp_dispatch *tp, uint64_t time)
 			return GESTURE_STATE_SCROLL;
 		}
 
-		/* If we get here, either both fingers have passed the inner
-		 * threshold (handled below), or >2 fingers are involved
-		 * (handled in a future event when both have moved enough).
+		/* If more than 2 fingers are involved, and the thumb moves
+		 * while the fingers stay still, assume a pinch if eligible.
 		 */
+		if (finger_mm < inner &&
+		    tp->gesture.finger_count > 2 &&
+		    tp->gesture.enabled &&
+		    tp->thumb.pinch_eligible) {
+			tp_gesture_init_pinch(tp);
+			return GESTURE_STATE_PINCH;
+		}
 	}
 
 	/* If either touch is still inside the inner threshold, we can't
@@ -711,8 +717,8 @@ tp_gesture_post_events(struct tp_dispatch *tp, uint64_t time)
 	if (tp->gesture.finger_count == 0)
 		return;
 
-	/* When tap-and-dragging, or a clickpad is clicked force 1fg mode */
-	if (tp_tap_dragging(tp) || (tp->buttons.is_clickpad && tp->buttons.state)) {
+	/* When tap-and-dragging, force 1fg mode. */
+	if (tp_tap_dragging(tp)) {
 		tp_gesture_cancel(tp, time);
 		tp->gesture.finger_count = 1;
 		tp->gesture.finger_count_pending = 0;

src/evdev-mt-touchpad-tap.c

@@ -1015,7 +1015,7 @@ tp_tap_handle_state(struct tp_dispatch *tp, uint64_t time)
 			/* The simple version: if a touch is a thumb on
 			 * begin we ignore it. All other thumb touches
 			 * follow the normal tap state for now */
-			if (tp_thumb_ignored(tp, t)) {
+			if (tp_thumb_ignored_for_tap(tp, t)) {
 				t->tap.is_thumb = true;
 				continue;
 			}