quirks: Add tablet smoothing attribute.

https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/512 disables
input smoothing for AES devices. However, some AES devices produce
segmented/wobbly curves without smoothing. This change introduces an
`AttrTabletSmoothing` boolean property, which overrides the default smoothing
behavior.

See #632

Signed-off-by: Quytelda Kahja <quytelda@tamalin.org>
(cherry picked from commit e6c4b1d16ead9c40599dcea30c1598ecb9760b7d)

5 files changed, 48 insertions, 8 deletions

diff --git a/doc/user/device-quirks.rst b/doc/user/device-quirks.rst
index 32d299c6..3d4fe83b 100644
--- a/doc/user/device-quirks.rst
+++ b/doc/user/device-quirks.rst
@@ -190,3 +190,6 @@ AttrInputPropEnable=INPUT_PROP_BUTTONPAD;INPUT_PROP_POINTER;
 AttrPointingStickIntegration=internal|external
     Indicates the integration of the pointing stick. This is a string enum.
     Only needed for external pointing sticks. These are rare.
+AttrTabletSmoothing=1|0
+    Enables (1) or disables (0) input smoothing for tablet devices. Smoothing is enabled
+    by default, except on AES devices.
diff --git a/src/evdev-tablet.c b/src/evdev-tablet.c
index e3cf658b..3b77b47c 100644
--- a/src/evdev-tablet.c
+++ b/src/evdev-tablet.c
@@ -2344,18 +2344,17 @@ tablet_init_left_handed(struct evdev_device *device)
 				       tablet_change_to_left_handed);
 }
 
-static void
-tablet_init_smoothing(struct evdev_device *device,
-		      struct tablet_dispatch *tablet)
+static bool
+tablet_is_aes(struct evdev_device *device,
+	      struct tablet_dispatch *tablet)
 {
-	size_t history_size = ARRAY_LENGTH(tablet->history.samples);
+	bool is_aes = false;
 #if HAVE_LIBWACOM
 	const char *devnode;
 	WacomDeviceDatabase *db;
 	WacomDevice *libwacom_device = NULL;
 	const int *stylus_ids;
 	int nstyli;
-	bool is_aes = false;
 	int vid = evdev_device_get_id_vendor(device);
 
 	/* Wacom-specific check for whether smoothing is required:
@@ -2384,12 +2383,36 @@ tablet_init_smoothing(struct evdev_device *device,
 		}
 	}
 
-	if (is_aes)
-		history_size = 1;
-
 	libwacom_destroy(libwacom_device);
+
 out:
 #endif
+	return is_aes;
+}
+
+static void
+tablet_init_smoothing(struct evdev_device *device,
+		      struct tablet_dispatch *tablet)
+{
+	size_t history_size = ARRAY_LENGTH(tablet->history.samples);
+	struct quirks_context *quirks = NULL;
+	struct quirks *q = NULL;
+	bool use_smoothing = true;
+
+	quirks = evdev_libinput_context(device)->quirks;
+	q = quirks_fetch_for_device(quirks, device->udev_device);
+
+	/* By default, always enable smoothing except on AES devices.
+	 * AttrTabletSmoothing can override this, if necessary.
+	 */
+	if (!q || !quirks_get_bool(q, QUIRK_ATTR_TABLET_SMOOTHING, &use_smoothing))
+		use_smoothing = !tablet_is_aes(device, tablet);
+
+	/* Setting the history size to 1 means we never do any actual smoothing. */
+	if (!use_smoothing)
+		history_size = 1;
+
+	quirks_unref(q);
 	tablet->history.size = history_size;
 }
 
diff --git a/src/quirks.c b/src/quirks.c
index 5216e5b8..b556a9ab 100644
--- a/src/quirks.c
+++ b/src/quirks.c
@@ -280,6 +280,7 @@ quirk_get_name(enum quirk q)
 	case QUIRK_ATTR_TRACKPOINT_MULTIPLIER:		return "AttrTrackpointMultiplier";
 	case QUIRK_ATTR_THUMB_PRESSURE_THRESHOLD:	return "AttrThumbPressureThreshold";
 	case QUIRK_ATTR_USE_VELOCITY_AVERAGING:		return "AttrUseVelocityAveraging";
+	case QUIRK_ATTR_TABLET_SMOOTHING:               return "AttrTabletSmoothing";
 	case QUIRK_ATTR_THUMB_SIZE_THRESHOLD:		return "AttrThumbSizeThreshold";
 	case QUIRK_ATTR_MSC_TIMESTAMP:			return "AttrMscTimestamp";
 	case QUIRK_ATTR_EVENT_CODE_DISABLE:		return "AttrEventCodeDisable";
@@ -796,6 +797,17 @@ parse_attr(struct quirks_context *ctx,
 		p->type = PT_BOOL;
 		p->value.b = b;
 		rc = true;
+	} else if (streq(key, quirk_get_name(QUIRK_ATTR_TABLET_SMOOTHING))) {
+		p->id = QUIRK_ATTR_TABLET_SMOOTHING;
+		if (streq(value, "1"))
+			b = true;
+		else if (streq(value, "0"))
+			b = false;
+		else
+			goto out;
+		p->type = PT_BOOL;
+		p->value.b = b;
+		rc = true;
 	} else if (streq(key, quirk_get_name(QUIRK_ATTR_THUMB_PRESSURE_THRESHOLD))) {
 		p->id = QUIRK_ATTR_THUMB_PRESSURE_THRESHOLD;
 		if (!safe_atou(value, &v))
diff --git a/src/quirks.h b/src/quirks.h
index 9a11df67..4a970b90 100644
--- a/src/quirks.h
+++ b/src/quirks.h
@@ -103,6 +103,7 @@ enum quirk {
 	QUIRK_ATTR_TRACKPOINT_MULTIPLIER,
 	QUIRK_ATTR_THUMB_PRESSURE_THRESHOLD,
 	QUIRK_ATTR_USE_VELOCITY_AVERAGING,
+	QUIRK_ATTR_TABLET_SMOOTHING,
 	QUIRK_ATTR_THUMB_SIZE_THRESHOLD,
 	QUIRK_ATTR_MSC_TIMESTAMP,
 	QUIRK_ATTR_EVENT_CODE_DISABLE,
diff --git a/tools/shared.c b/tools/shared.c
index 65c1c7ce..096fcbed 100644
--- a/tools/shared.c
+++ b/tools/shared.c
@@ -732,6 +732,7 @@ tools_list_device_quirks(struct quirks_context *ctx,
 				callback(userdata, buf);
 				break;
 			case QUIRK_ATTR_USE_VELOCITY_AVERAGING:
+			case QUIRK_ATTR_TABLET_SMOOTHING:
 				snprintf(buf, sizeof(buf), "%s=1", name);
 				callback(userdata, buf);
 				break;