[PATCH libinput] touchpad: sync BTN_TOOL_FINGER state on init

[Peter Hutterer]

The Elantech touchpad on my Asus Vivobook doesn't release BTN_TOOL_FINGER on
up. If the touchpad was used before libinput initializes, the kernel filters
the event because its state is already set. We never receive it and keep
ignoring all events until the first switch to BTN_TOOL_DOUBLETAP and back.

On touchpad init sync the BTN_TOOL_FINGER state and set it accordingly. This
is the only event that can be legitimately down on init. We don't care about
BTN_TOUCH because ignoring an ongoing touch on init is generally a good idea
and we can ignore any multifinger gesture as well.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/evdev-mt-touchpad.c |  8 ++++++++
 test/touchpad.c         | 24 ++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
index 0a261a3..762f539 100644
--- a/src/evdev-mt-touchpad.c
+++ b/src/evdev-mt-touchpad.c
@@ -1804,6 +1804,14 @@ tp_init_slots(struct tp_dispatch *tp,
 	for (i = 1; i < tp->num_slots; i++)
 		tp_sync_touch(tp, device, &tp->touches[i], i);
 
+	/* Some touchpads don't reset BTN_TOOL_FINGER on touch up and only
+	 * change to/from it when BTN_TOOL_DOUBLETAP is set. This causes us
+	 * to ignore the first touches events until a two-finger gesture is
+	 * performed.
+	 */
+	if (libevdev_get_event_value(device->evdev, EV_KEY, BTN_TOOL_FINGER))
+		tp_fake_finger_set(tp, BTN_TOOL_FINGER, 1);
+
 	return true;
 }
 
diff --git a/test/touchpad.c b/test/touchpad.c
index cdc261b..5b6f0a4 100644
--- a/test/touchpad.c
+++ b/test/touchpad.c
@@ -4365,6 +4365,29 @@ START_TEST(touchpad_slot_swap)
 }
 END_TEST
 
+START_TEST(touchpad_finger_always_down)
+{
+	struct litest_device *dev = litest_current_device();
+	struct libinput *li;
+
+	/* Set BTN_TOOL_FINGER before a new context is initialized */
+	litest_event(dev, EV_KEY, BTN_TOOL_FINGER, 1);
+	litest_event(dev, EV_SYN, SYN_REPORT, 0);
+
+	li = litest_create_context();
+	libinput_path_add_device(li,
+				 libevdev_uinput_get_devnode(dev->uinput));
+	litest_drain_events(li);
+
+	litest_touch_down(dev, 0, 50, 50);
+	litest_touch_move_to(dev, 0, 50, 50, 70, 50, 10, 0);
+
+	litest_assert_only_typed_events(li, LIBINPUT_EVENT_POINTER_MOTION);
+
+	libinput_unref(li);
+}
+END_TEST
+
 START_TEST(touchpad_time_usec)
 {
 	struct litest_device *dev = litest_current_device();
@@ -4742,6 +4765,7 @@ litest_setup_tests_touchpad(void)
 
 	litest_add_for_device("touchpad:bugs", touchpad_tool_tripletap_touch_count, LITEST_SYNAPTICS_TOPBUTTONPAD);
 	litest_add_for_device("touchpad:bugs", touchpad_slot_swap, LITEST_SYNAPTICS_TOPBUTTONPAD);
+	litest_add_for_device("touchpad:bugs", touchpad_finger_always_down, LITEST_SYNAPTICS_TOPBUTTONPAD);
 
 	litest_add("touchpad:time", touchpad_time_usec, LITEST_TOUCHPAD, LITEST_ANY);
 
-- 
2.9.3