From 40c5b64f82174eb701068bad77a7087cb6d73ffb Mon Sep 17 00:00:00 2001
From: Peter Hutterer <peter.hutterer@who-t.net>
Date: Tue, 10 Apr 2018 16:20:45 +1000
Subject: [PATCH] filter: make the simpsons accel calculation available through
 the header

This is the standard approach for mice and touchpads to calculate the
acceleration based on the last two deltas, let's make that code shareable.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
---
 src/filter-private.h |  8 +++++++
 src/filter.c         | 52 +++++++++++++++-----------------------------
 2 files changed, 26 insertions(+), 34 deletions(-)

diff --git a/src/filter-private.h b/src/filter-private.h
index 4779e8f2..554b7f64 100644
--- a/src/filter-private.h
+++ b/src/filter-private.h
@@ -106,6 +106,14 @@ tracker_by_offset(struct pointer_trackers *trackers, unsigned int offset);
 double
 calculate_velocity(struct pointer_trackers *trackers, uint64_t time);
 
+double
+calculate_acceleration_simpsons(struct motion_filter *filter,
+				accel_profile_func_t profile,
+				void *data,
+				double velocity,
+				double last_velocity,
+				uint64_t time);
+
 /* Convert speed/velocity from units/us to units/ms */
 static inline double
 v_us2ms(double units_per_us)
diff --git a/src/filter.c b/src/filter.c
index 5a593e17..291013a1 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -295,23 +295,6 @@ calculate_velocity(struct pointer_trackers *trackers, uint64_t time)
 	return result; /* units/us */
 }
 
-/**
- * Apply the acceleration profile to the given velocity.
- *
- * @param accel The acceleration filter
- * @param data Caller-specific data
- * @param velocity Velocity in device-units per µs
- * @param time Current time in µs
- *
- * @return A unitless acceleration factor, to be applied to the delta
- */
-static double
-acceleration_profile(struct pointer_accelerator *accel,
-		     void *data, double velocity, uint64_t time)
-{
-	return accel->profile(&accel->base, data, velocity, time);
-}
-
 /**
  * Calculate the acceleration factor for our current velocity, averaging
  * between our current and the most recent velocity to smoothen out changes.
@@ -324,23 +307,23 @@ acceleration_profile(struct pointer_accelerator *accel,
  *
  * @return A unitless acceleration factor, to be applied to the delta
  */
-static double
-calculate_acceleration(struct pointer_accelerator *accel,
-		       void *data,
-		       double velocity,
-		       double last_velocity,
-		       uint64_t time)
+double
+calculate_acceleration_simpsons(struct motion_filter *filter,
+				accel_profile_func_t profile,
+				void *data,
+				double velocity,
+				double last_velocity,
+				uint64_t time)
 {
 	double factor;
 
 	/* Use Simpson's rule to calculate the avarage acceleration between
 	 * the previous motion and the most recent. */
-	factor = acceleration_profile(accel, data, velocity, time);
-	factor += acceleration_profile(accel, data, last_velocity, time);
-	factor += 4.0 *
-		acceleration_profile(accel, data,
-				     (last_velocity + velocity) / 2,
-				     time);
+	factor = profile(filter, data, velocity, time);
+	factor += profile(filter, data, last_velocity, time);
+	factor += 4.0 * profile(filter, data,
+				(last_velocity + velocity) / 2,
+				time);
 
 	factor = factor / 6.0;
 
@@ -368,11 +351,12 @@ calculate_acceleration_factor(struct pointer_accelerator *accel,
 
 	feed_trackers(&accel->trackers, unaccelerated, time);
 	velocity = calculate_velocity(&accel->trackers, time);
-	accel_factor = calculate_acceleration(accel,
-					      data,
-					      velocity,
-					      accel->last_velocity,
-					      time);
+	accel_factor = calculate_acceleration_simpsons(&accel->base,
+						       accel->profile,
+						       data,
+						       velocity,
+						       accel->last_velocity,
+						       time);
 	accel->last_velocity = velocity;
 
 	return accel_factor;