[PATCH synaptics] Fix coasting speed trigger

[Peter Hutterer]

CoastingSpeed is defined as scrolls/s. The previous code just used
delta/seconds which depended on the device coordinate range and exceeded the
default CoastingSpeed at almost any scroll event.

Divide the estimated delta by the scroll distance to get the accurate
scrolls/s number. Since that now changes the contents of what's in
coast_speed_y, change the users of that too.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
This changes the coasting behaviour to finish a lot quicker with the default
options. Which, iirc, was the behaviour in 1.4 or 1.5 anyway. 1.6 coasts a
bit too long though no idea what exact set of commits introduced that
regression to begin with.

 src/synaptics.c    |   16 +++++++---------
 src/synapticsstr.h |    6 +++---
 2 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/src/synaptics.c b/src/synaptics.c
index e47d8ff..e95c0fc 100644
--- a/src/synaptics.c
+++ b/src/synaptics.c
@@ -2109,7 +2109,7 @@ start_coasting(SynapticsPrivate * priv, struct SynapticsHwState *hw,
             double dy =
                 estimate_delta(HIST(0).y, HIST(1).y, HIST(2).y, HIST(3).y);
             if (pkt_time > 0) {
-                double scrolls_per_sec = dy / pkt_time;
+                double scrolls_per_sec = (dy / abs(para->scroll_dist_vert)) / pkt_time;
 
                 if (fabs(scrolls_per_sec) >= para->coasting_speed) {
                     priv->scroll.coast_speed_y = scrolls_per_sec;
@@ -2121,7 +2121,7 @@ start_coasting(SynapticsPrivate * priv, struct SynapticsHwState *hw,
             double dx =
                 estimate_delta(HIST(0).x, HIST(1).x, HIST(2).x, HIST(3).x);
             if (pkt_time > 0) {
-                double scrolls_per_sec = dx / pkt_time;
+                double scrolls_per_sec = (dx / abs(para->scroll_dist_vert)) / pkt_time;
 
                 if (fabs(scrolls_per_sec) >= para->coasting_speed) {
                     priv->scroll.coast_speed_x = scrolls_per_sec;
@@ -2133,7 +2133,7 @@ start_coasting(SynapticsPrivate * priv, struct SynapticsHwState *hw,
             double da = estimate_delta_circ(priv);
 
             if (pkt_time > 0) {
-                double scrolls_per_sec = da / pkt_time;
+                double scrolls_per_sec = (da / para->scroll_dist_circ) / pkt_time;
 
                 if (fabs(scrolls_per_sec) >= para->coasting_speed) {
                     if (vert) {
@@ -2391,10 +2391,9 @@ HandleScrolling(SynapticsPrivate * priv, struct SynapticsHwState *hw,
 
     if (priv->scroll.coast_speed_y) {
         double dtime = (hw->millis - priv->scroll.last_millis) / 1000.0;
-        double ddy =
-            para->coasting_friction * dtime * abs(para->scroll_dist_vert);
+        double ddy = para->coasting_friction * dtime;
 
-        priv->scroll.delta_y += priv->scroll.coast_speed_y * dtime;
+        priv->scroll.delta_y += priv->scroll.coast_speed_y * dtime * para->scroll_dist_vert;
         delay = MIN(delay, POLL_MS);
         if (abs(priv->scroll.coast_speed_y) < ddy) {
             priv->scroll.coast_speed_y = 0;
@@ -2408,9 +2407,8 @@ HandleScrolling(SynapticsPrivate * priv, struct SynapticsHwState *hw,
 
     if (priv->scroll.coast_speed_x) {
         double dtime = (hw->millis - priv->scroll.last_millis) / 1000.0;
-        double ddx =
-            para->coasting_friction * dtime * abs(para->scroll_dist_horiz);
-        priv->scroll.delta_x += priv->scroll.coast_speed_x * dtime;
+        double ddx = para->coasting_friction * dtime;
+        priv->scroll.delta_x += priv->scroll.coast_speed_x * dtime * para->scroll_dist_vert;
         delay = MIN(delay, POLL_MS);
         if (abs(priv->scroll.coast_speed_x) < ddx) {
             priv->scroll.coast_speed_x = 0;
diff --git a/src/synapticsstr.h b/src/synapticsstr.h
index 4bc2ed5..5b0120a 100644
--- a/src/synapticsstr.h
+++ b/src/synapticsstr.h
@@ -169,7 +169,7 @@ typedef struct _SynapticsParameters {
     Bool palm_detect;           /* Enable Palm Detection */
     int palm_min_width;         /* Palm detection width */
     int palm_min_z;             /* Palm detection depth */
-    double coasting_speed;      /* Coasting threshold scrolling speed */
+    double coasting_speed;      /* Coasting threshold scrolling speed in scrolls/s */
     double coasting_friction;   /* Number of scrolls per second per second to change coasting speed */
     int press_motion_min_z;     /* finger pressure at which minimum pressure motion factor is applied */
     int press_motion_max_z;     /* finger pressure at which maximum pressure motion factor is applied */
@@ -213,8 +213,8 @@ struct _SynapticsPrivateRec {
         double delta_y;         /* accumulated vert scroll delta */
         double last_a;          /* last angle-scroll position */
         CARD32 last_millis;     /* time last scroll event posted */
-        double coast_speed_x;   /* Horizontal coasting speed */
-        double coast_speed_y;   /* Vertical coasting speed */
+        double coast_speed_x;   /* Horizontal coasting speed in scrolls/s */
+        double coast_speed_y;   /* Vertical coasting speed in scrolls/s */
         double coast_delta_x;   /* Accumulated horizontal coast delta */
         double coast_delta_y;   /* Accumulated vertical coast delta */
         int packets_this_scroll;        /* Events received for this scroll */
-- 
1.7.10.1