[PATCH libinput 6/6] touchpad: pretend the jumpy semi-mt touchpad is a single-touch touchpad

[Peter Hutterer]

The first finger is accurate, it's just the second finger that is imprecise,
so we can't handle it as a true touch. Instead, revert the device back to
being a single-touch touchpad and use the fake touch bits for second finger
handling.

Two-finger scrolling thus becomes usable though we will lose out on
other features like thumb detection. Useful scrolling trumps that though.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/evdev-mt-touchpad.c | 19 ++++++++++++++-----
 test/touchpad-tap.c     |  3 +++
 test/touchpad.c         |  9 +++------
 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
index af1cd47..54ea819 100644
--- a/src/evdev-mt-touchpad.c
+++ b/src/evdev-mt-touchpad.c
@@ -1465,6 +1465,19 @@ tp_init_slots(struct tp_dispatch *tp,
 
 	tp->semi_mt = libevdev_has_property(device->evdev, INPUT_PROP_SEMI_MT);
 
+	/* This device has a terrible 2fg resolution, but only for the
+	 * second finger, causing scroll jumps when we use the touch points
+	 * properly. The first finger resolution is accurate though, so
+	 * we simply pretend it's a single touch touchpad with the BTN_TOOL
+	 * bits.
+	 */
+	if (tp->semi_mt &&
+	    (device->model_flags & EVDEV_MODEL_JUMPING_SEMI_MT)) {
+		tp->num_slots = 1;
+		tp->slot = 0;
+		tp->has_mt = false;
+	}
+
 	ARRAY_FOR_EACH(max_touches, m) {
 		if (libevdev_has_event_code(device->evdev,
 					    EV_KEY,
@@ -1526,11 +1539,7 @@ tp_scroll_get_methods(struct tp_dispatch *tp)
 {
 	uint32_t methods = LIBINPUT_CONFIG_SCROLL_EDGE;
 
-	/* some Synaptics semi-mt touchpads have a terrible 2fg resolution,
-	 * causing scroll jumps. For all other 2fg touchpads, we enable 2fg
-	 * scrolling */
-	if (tp->ntouches >= 2 &&
-	    (tp->device->model_flags & EVDEV_MODEL_JUMPING_SEMI_MT) == 0)
+	if (tp->ntouches >= 2)
 		methods |= LIBINPUT_CONFIG_SCROLL_2FG;
 
 	return methods;
diff --git a/test/touchpad-tap.c b/test/touchpad-tap.c
index 00afcdb..62c7a5c 100644
--- a/test/touchpad-tap.c
+++ b/test/touchpad-tap.c
@@ -241,6 +241,9 @@ START_TEST(touchpad_1fg_multitap_n_drag_2fg)
 	int range = _i,
 	    ntaps;
 
+	if (litest_is_synaptics_semi_mt(dev))
+		return;
+
 	litest_enable_tap(dev->libinput_device);
 
 	litest_drain_events(li);
diff --git a/test/touchpad.c b/test/touchpad.c
index a6989e7..77c1d2d 100644
--- a/test/touchpad.c
+++ b/test/touchpad.c
@@ -402,14 +402,12 @@ START_TEST(touchpad_scroll_defaults)
 
 	method = libinput_device_config_scroll_get_methods(device);
 	ck_assert(method & LIBINPUT_CONFIG_SCROLL_EDGE);
-	if (libevdev_get_num_slots(evdev) > 1 &&
-	    !litest_is_synaptics_semi_mt(dev))
+	if (libevdev_get_num_slots(evdev) > 1)
 		ck_assert(method & LIBINPUT_CONFIG_SCROLL_2FG);
 	else
 		ck_assert((method & LIBINPUT_CONFIG_SCROLL_2FG) == 0);
 
-	if (libevdev_get_num_slots(evdev) > 1 &&
-	    !litest_is_synaptics_semi_mt(dev))
+	if (libevdev_get_num_slots(evdev) > 1)
 		expected = LIBINPUT_CONFIG_SCROLL_2FG;
 	else
 		expected = LIBINPUT_CONFIG_SCROLL_EDGE;
@@ -425,8 +423,7 @@ START_TEST(touchpad_scroll_defaults)
 	status = libinput_device_config_scroll_set_method(device,
 					  LIBINPUT_CONFIG_SCROLL_2FG);
 
-	if (libevdev_get_num_slots(evdev) > 1 &&
-	    !litest_is_synaptics_semi_mt(dev))
+	if (libevdev_get_num_slots(evdev) > 1)
 		ck_assert_int_eq(status, LIBINPUT_CONFIG_STATUS_SUCCESS);
 	else
 		ck_assert_int_eq(status, LIBINPUT_CONFIG_STATUS_UNSUPPORTED);
-- 
2.4.3