evdev: always defuzz absolute touchscreens

If a touchscreen has a fuzz value use it for motion hysteresis similar to how
we do it for a touchpad. This stops pointer wobbles as seen in
https://bugs.freedesktop.org/show_bug.cgi?id=94918

It's up to the system to override or set the kernel's fuzz value correctly,
i.e. a udev hwdb entry is required where the kernel driver does not set it.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>

src/evdev.c

@@ -342,6 +342,30 @@ evdev_post_trackpoint_scroll(struct evdev_device *device,
 	return true;
 }
 
+static inline bool
+evdev_filter_defuzz_touch(struct evdev_device *device, struct mt_slot *slot)
+{
+	struct device_coords point;
+
+	if (!device->mt.want_hysteresis)
+		return false;
+
+	point.x = evdev_hysteresis(slot->point.x,
+				   slot->hysteresis_center.x,
+				   device->mt.hysteresis_margin.x);
+	point.y = evdev_hysteresis(slot->point.y,
+				   slot->hysteresis_center.y,
+				   device->mt.hysteresis_margin.y);
+
+	slot->hysteresis_center = slot->point;
+	if (point.x == slot->point.x && point.y == slot->point.y)
+		return true;
+
+	slot->point = point;
+
+	return false;
+}
+
 static void
 evdev_flush_pending_event(struct evdev_device *device, uint64_t time)
 {
@@ -414,6 +438,7 @@ evdev_flush_pending_event(struct evdev_device *device, uint64_t time)
 
 		seat->slot_map |= 1 << seat_slot;
 		point = slot->point;
+		slot->hysteresis_center = point;
 		evdev_transform_absolute(device, &point);
 
 		touch_notify_touch_down(base, time, slot_idx, seat_slot,
@@ -429,6 +454,9 @@ evdev_flush_pending_event(struct evdev_device *device, uint64_t time)
 		if (seat_slot == -1)
 			break;
 
+		if (evdev_filter_defuzz_touch(device, slot))
+			break;
+
 		evdev_transform_absolute(device, &point);
 		touch_notify_touch_motion(base, time, slot_idx, seat_slot,
 					  &point);
@@ -2015,6 +2043,12 @@ evdev_configure_mt_device(struct evdev_device *device)
 	device->mt.slots_len = num_slots;
 	device->mt.slot = active_slot;
 
+	if (device->abs.absinfo_x->fuzz || device->abs.absinfo_y->fuzz) {
+		device->mt.want_hysteresis = true;
+		device->mt.hysteresis_margin.x = device->abs.absinfo_x->fuzz/2;
+		device->mt.hysteresis_margin.y = device->abs.absinfo_y->fuzz/2;
+	}
+
 	return 0;
 }
 

src/evdev.h

@@ -120,6 +120,7 @@ enum evdev_device_model {
 struct mt_slot {
 	int32_t seat_slot;
 	struct device_coords point;
+	struct device_coords hysteresis_center;
 };
 
 struct evdev_device {
@@ -153,6 +154,8 @@ struct evdev_device {
 		int slot;
 		struct mt_slot *slots;
 		size_t slots_len;
+		bool want_hysteresis;
+		struct device_coords hysteresis_margin;
 	} mt;
 	struct mtdev *mtdev;
 

test/Makefile.am

@@ -44,6 +44,7 @@ liblitest_la_SOURCES = \
 	litest-device-synaptics-x1-carbon-3rd.c \
 	litest-device-trackpoint.c \
 	litest-device-touch-screen.c \
+	litest-device-touchscreen-fuzz.c \
 	litest-device-wacom-bamboo-tablet.c \
 	litest-device-wacom-cintiq-tablet.c \
 	litest-device-wacom-cintiq-24hd.c \

test/litest-device-touchscreen-fuzz.c

@@ -0,0 +1,96 @@
+/*
+ * Copyright © 2015 Canonical, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "litest.h"
+#include "litest-int.h"
+
+static void litest_fuzz_mt_setup(void)
+{
+	struct litest_device *d =
+		litest_create_device(LITEST_MULTITOUCH_FUZZ_SCREEN);
+	litest_set_current_device(d);
+}
+
+static struct input_event down[] = {
+	{ .type = EV_ABS, .code = ABS_MT_SLOT, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_TRACKING_ID, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_POSITION_X, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_POSITION_Y, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_PRESSURE, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_SYN, .code = SYN_REPORT, .value = 0 },
+	{ .type = -1, .code = -1 },
+};
+
+static struct input_event move[] = {
+	{ .type = EV_ABS, .code = ABS_MT_SLOT, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_POSITION_X, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_POSITION_Y, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_PRESSURE, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_SYN, .code = SYN_REPORT, .value = 0 },
+	{ .type = -1, .code = -1 },
+};
+
+static struct litest_device_interface interface = {
+	.touch_down_events = down,
+	.touch_move_events = move,
+};
+
+static struct input_absinfo absinfo[] = {
+	{ ABS_X, 0, 1500, 10, 0, 0 },
+	{ ABS_Y, 0, 2500, 10, 0, 0 },
+	{ ABS_MT_SLOT, 0, 9, 0, 0, 0 },
+	{ ABS_MT_POSITION_X, 0, 1500, 10, 0, 0 },
+	{ ABS_MT_POSITION_Y, 0, 2500, 10, 0, 0 },
+	{ ABS_MT_PRESSURE, 0, 255, 0, 0, 0 },
+	{ ABS_MT_TRACKING_ID, 0, 65535, 0, 0, 0 },
+	{ .value = -1 },
+};
+
+static struct input_id input_id = {
+	.bustype = 0x1,
+	.vendor = 0x0,
+	.product = 0x25,
+};
+
+static int events[] = {
+	EV_KEY, BTN_TOUCH,
+	INPUT_PROP_MAX, INPUT_PROP_DIRECT,
+	-1, -1
+};
+
+struct litest_test_device litest_multitouch_fuzz_screen_device = {
+	.type = LITEST_MULTITOUCH_FUZZ_SCREEN,
+	.features = LITEST_TOUCH,
+	.shortname = "touchscreen-fuzz",
+	.setup = litest_fuzz_mt_setup,
+	.interface = &interface,
+
+	.name = "touchscreen with fuzz",
+	.id = &input_id,
+	.events = events,
+	.absinfo = absinfo,
+};

test/litest.c

@@ -379,6 +379,7 @@ extern struct litest_test_device litest_cyborg_rat_device;
 extern struct litest_test_device litest_yubikey_device;
 extern struct litest_test_device litest_synaptics_i2c_device;
 extern struct litest_test_device litest_wacom_cintiq_24hd_device;
+extern struct litest_test_device litest_multitouch_fuzz_screen_device;
 
 struct litest_test_device* devices[] = {
 	&litest_synaptics_clickpad_device,
@@ -424,6 +425,7 @@ struct litest_test_device* devices[] = {
 	&litest_yubikey_device,
 	&litest_synaptics_i2c_device,
 	&litest_wacom_cintiq_24hd_device,
+	&litest_multitouch_fuzz_screen_device,
 	NULL,
 };
 

test/litest.h

@@ -196,6 +196,7 @@ enum litest_device_type {
 	LITEST_YUBIKEY = -42,
 	LITEST_SYNAPTICS_I2C = -43,
 	LITEST_WACOM_CINTIQ_24HD = -44,
+	LITEST_MULTITOUCH_FUZZ_SCREEN = -45,
 };
 
 enum litest_device_feature {

test/touch.c

@@ -675,6 +675,50 @@ START_TEST(touch_time_usec)
 }
 END_TEST
 
+START_TEST(touch_fuzz)
+{
+	struct litest_device *dev = litest_current_device();
+	struct libinput *li = dev->libinput;
+	struct libinput_event *event;
+	int i;
+	int x = 700, y = 300;
+
+	litest_drain_events(dev->libinput);
+
+	litest_event(dev, EV_ABS, ABS_MT_TRACKING_ID, 30);
+	litest_event(dev, EV_ABS, ABS_MT_SLOT, 0);
+	litest_event(dev, EV_ABS, ABS_MT_POSITION_X, x);
+	litest_event(dev, EV_ABS, ABS_MT_POSITION_Y, y);
+	litest_event(dev, EV_KEY, BTN_TOUCH, 1);
+	litest_event(dev, EV_SYN, SYN_REPORT, 0);
+	libinput_dispatch(li);
+
+	event = libinput_get_event(li);
+	litest_is_touch_event(event, LIBINPUT_EVENT_TOUCH_DOWN);
+	libinput_event_destroy(event);
+	event = libinput_get_event(li);
+	litest_is_touch_event(event, LIBINPUT_EVENT_TOUCH_FRAME);
+	libinput_event_destroy(event);
+
+	litest_drain_events(li);
+
+	for (i = 0; i < 50; i++) {
+		if (i % 2) {
+			x++;
+			y--;
+		} else {
+			x--;
+			y++;
+		}
+		litest_event(dev, EV_ABS, ABS_MT_POSITION_X, x);
+		litest_event(dev, EV_ABS, ABS_MT_POSITION_Y, y);
+		litest_event(dev, EV_SYN, SYN_REPORT, 0);
+		libinput_dispatch(li);
+		litest_assert_empty_queue(li);
+	}
+}
+END_TEST
+
 void
 litest_setup_tests(void)
 {
@@ -703,4 +747,6 @@ litest_setup_tests(void)
 	litest_add_ranged("touch:state", touch_initial_state, LITEST_TOUCH, LITEST_PROTOCOL_A, &axes);
 
 	litest_add("touch:time", touch_time_usec, LITEST_TOUCH, LITEST_TOUCHPAD);
+
+	litest_add_for_device("touch:fuzz", touch_fuzz, LITEST_MULTITOUCH_FUZZ_SCREEN);
 }