touchpad: don't feed 0/0 deltas into the accel filters

[platform/upstream/libinput.git] / src / filter.c

diff --git a/src/filter.c b/src/filter.c
index 6fbd4d9..5b0b877 100644 (file)
--- a/src/filter.c
+++ b/src/filter.c
@@ -51,22 +51,21 @@ filter_destroy(struct motion_filter *filter)
  * Default parameters for pointer acceleration profiles.
  */
 
-#define DEFAULT_CONSTANT_ACCELERATION 10.0
-#define DEFAULT_THRESHOLD 4.0
-#define DEFAULT_ACCELERATION 2.0
+#define DEFAULT_THRESHOLD 0.4                  /* in units/ms */
+#define DEFAULT_ACCELERATION 2.0               /* unitless factor */
 
 /*
  * Pointer acceleration filter constants
  */
 
-#define MAX_VELOCITY_DIFF      1.0
+#define MAX_VELOCITY_DIFF      1.0 /* units/ms */
 #define MOTION_TIMEOUT         300 /* (ms) */
 #define NUM_POINTER_TRACKERS   16
 
 struct pointer_tracker {
-       double dx;
-       double dy;
-       uint64_t time;
+       double dx;      /* delta to most recent event, in device units */
+       double dy;      /* delta to most recent event, in device units */
+       uint64_t time;  /* ms */
        int dir;
 };
 
@@ -76,10 +75,10 @@ struct pointer_accelerator {
 
        accel_profile_func_t profile;
 
-       double velocity;
-       double last_velocity;
-       int last_dx;
-       int last_dy;
+       double velocity;        /* units/ms */
+       double last_velocity;   /* units/ms */
+       int last_dx;            /* device units */
+       int last_dy;            /* device units */
 
        struct pointer_tracker *trackers;
        int cur_tracker;
@@ -183,7 +182,7 @@ calculate_tracker_velocity(struct pointer_tracker *tracker, uint64_t time)
        dx = tracker->dx;
        dy = tracker->dy;
        distance = sqrt(dx*dx + dy*dy);
-       return distance / (double)(time - tracker->time);
+       return distance / (double)(time - tracker->time); /* units/ms */
 }
 
 static double
@@ -227,7 +226,7 @@ calculate_velocity(struct pointer_accelerator *accel, uint64_t time)
                }
        }
 
-       return result;
+       return result; /* units/ms */
 }
 
 static double
@@ -254,7 +253,7 @@ calculate_acceleration(struct pointer_accelerator *accel,
 
        factor = factor / 6.0;
 
-       return factor;
+       return factor; /* unitless factor */
 }
 
 static void
@@ -264,8 +263,8 @@ accelerator_filter(struct motion_filter *filter,
 {
        struct pointer_accelerator *accel =
                (struct pointer_accelerator *) filter;
-       double velocity;
-       double accel_value;
+       double velocity; /* units/ms */
+       double accel_value; /* unitless factor */
 
        feed_trackers(accel, motion->dx, motion->dy, time);
        velocity = calculate_velocity(accel, time);
@@ -329,19 +328,19 @@ calc_penumbral_gradient(double x)
 double
 pointer_accel_profile_smooth_simple(struct motion_filter *filter,
                                    void *data,
-                                   double velocity,
+                                   double velocity, /* units/ms */
                                    uint64_t time)
 {
-       double threshold = DEFAULT_THRESHOLD;
-       double accel = DEFAULT_ACCELERATION;
-       double smooth_accel_coefficient;
+       double threshold = DEFAULT_THRESHOLD; /* units/ms */
+       double accel = DEFAULT_ACCELERATION; /* unitless factor */
+       double smooth_accel_coefficient; /* unitless factor */
+       double factor; /* unitless factor */
 
-       if (threshold < 1.0)
-               threshold = 1.0;
+       if (threshold < 0.1)
+               threshold = 0.1;
        if (accel < 1.0)
                accel = 1.0;
 
-       velocity *= DEFAULT_CONSTANT_ACCELERATION;
 
        if (velocity < (threshold / 2.0))
                return calc_penumbral_gradient(0.5 + velocity / threshold) * 2.0 - 1.0;
@@ -349,12 +348,12 @@ pointer_accel_profile_smooth_simple(struct motion_filter *filter,
        if (velocity <= threshold)
                return 1.0;
 
-       velocity /= threshold;
-       if (velocity >= accel)
+       factor = velocity/threshold;
+       if (factor >= accel)
                return accel;
 
-       /* Velocity is between 1.0 and accel, scale this to 0.0 - 1.0 */
-       velocity = (velocity - 1.0) / (accel - 1.0);
-       smooth_accel_coefficient = calc_penumbral_gradient(velocity);
+       /* factor is between 1.0 and accel, scale this to 0.0 - 1.0 */
+       factor = (factor - 1.0) / (accel - 1.0);
+       smooth_accel_coefficient = calc_penumbral_gradient(factor);
        return 1.0 + (smooth_accel_coefficient * (accel - 1.0));
 }