[PATCH libinput] filter: fix constant acceleration for the X230

[Peter Hutterer]

The x230 has a special acceleration method that relies on the touchpad magic
slowdown. This was missing from commit c8da19b50a30d8, making two-finger
scroll motions unusably fast

https://bugs.freedesktop.org/show_bug.cgi?id=91819

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/filter.c | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/src/filter.c b/src/filter.c
index 5df50d3..a646857 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -114,6 +114,8 @@ filter_get_speed(struct motion_filter *filter)
 #define X230_THRESHOLD v_ms2us(0.4)		/* in units/us */
 #define X230_ACCELERATION 2.0			/* unitless factor */
 #define X230_INCLINE 1.1			/* unitless factor */
+#define X230_MAGIC_SLOWDOWN 0.4			/* unitless */
+#define X230_TP_MAGIC_LOW_RES_FACTOR 4.0	/* unitless */
 
 /*
  * Pointer acceleration filter constants
@@ -421,6 +423,21 @@ accelerator_filter_x230(struct motion_filter *filter,
 }
 
 static struct normalized_coords
+accelerator_filter_constant_x230(struct motion_filter *filter,
+				 const struct normalized_coords *unaccelerated,
+				 void *data, uint64_t time)
+{
+	struct normalized_coords normalized;
+	const double factor =
+		X230_MAGIC_SLOWDOWN/X230_TP_MAGIC_LOW_RES_FACTOR;
+
+	normalized.x = factor * unaccelerated->x;
+	normalized.y = factor * unaccelerated->y;
+
+	return normalized;
+}
+
+static struct normalized_coords
 touchpad_constant_filter(struct motion_filter *filter,
 			 const struct normalized_coords *unaccelerated,
 			 void *data, uint64_t time)
@@ -631,26 +648,22 @@ touchpad_lenovo_x230_accel_profile(struct motion_filter *filter,
 				      double speed_in,
 				      uint64_t time)
 {
-	/* Keep the magic factor from touchpad_accel_profile_linear.  */
-	const double X230_MAGIC_SLOWDOWN = 0.4; /* unitless */
-
 	/* Those touchpads presents an actual lower resolution that what is
 	 * advertised. We see some jumps from the cursor due to the big steps
 	 * in X and Y when we are receiving data.
 	 * Apply a factor to minimize those jumps at low speed, and try
 	 * keeping the same feeling as regular touchpads at high speed.
 	 * It still feels slower but it is usable at least */
-	const double TP_MAGIC_LOW_RES_FACTOR = 4.0; /* unitless */
 	double factor; /* unitless */
 	struct pointer_accelerator *accel_filter =
 		(struct pointer_accelerator *)filter;
 
 	double f1, f2; /* unitless */
 	const double max_accel = accel_filter->accel *
-				  TP_MAGIC_LOW_RES_FACTOR; /* unitless factor */
+				  X230_TP_MAGIC_LOW_RES_FACTOR; /* unitless factor */
 	const double threshold = accel_filter->threshold /
-				  TP_MAGIC_LOW_RES_FACTOR; /* units/us */
-	const double incline = accel_filter->incline * TP_MAGIC_LOW_RES_FACTOR;
+				  X230_TP_MAGIC_LOW_RES_FACTOR; /* units/us */
+	const double incline = accel_filter->incline * X230_TP_MAGIC_LOW_RES_FACTOR;
 
 	/* Note: the magic values in this function are obtained by
 	 * trial-and-error. No other meaning should be interpreted.
@@ -658,14 +671,14 @@ touchpad_lenovo_x230_accel_profile(struct motion_filter *filter,
 	 * pointer_accel_profile_linear(), look at the git history of that
 	 * function for an explaination of what the min/max/etc. does.
 	 */
-	speed_in *= X230_MAGIC_SLOWDOWN / TP_MAGIC_LOW_RES_FACTOR;
+	speed_in *= X230_MAGIC_SLOWDOWN / X230_TP_MAGIC_LOW_RES_FACTOR;
 
 	f1 = min(1, v_us2ms(speed_in) * 5);
 	f2 = 1 + (v_us2ms(speed_in) - v_us2ms(threshold)) * incline;
 
 	factor = min(max_accel, f2 > 1 ? f2 : f1);
 
-	return factor * X230_MAGIC_SLOWDOWN / TP_MAGIC_LOW_RES_FACTOR;
+	return factor * X230_MAGIC_SLOWDOWN / X230_TP_MAGIC_LOW_RES_FACTOR;
 }
 
 double
@@ -795,7 +808,7 @@ create_pointer_accelerator_filter_touchpad(int dpi)
 
 struct motion_filter_interface accelerator_interface_x230 = {
 	.filter = accelerator_filter_x230,
-	.filter_constant = accelerator_filter_noop,
+	.filter_constant = accelerator_filter_constant_x230,
 	.restart = accelerator_restart,
 	.destroy = accelerator_destroy,
 	.set_speed = accelerator_set_speed,
-- 
2.4.3