[PATCH 07/15] Replace the motion estimator

[Daniel Stone]

From: Derek Foreman <derek.foreman at collabora.co.uk>

Use a smarter motion estimator that attempts to draw a best-fit line
through the history where possible, including taking acceleration into
account.

Signed-off-by: Derek Foreman <derek.foreman at collabora.co.uk>
Reviewed-by: Daniel Stone <daniel at fooishbar.org>
---
 src/synaptics.c |   76 +++++++++++++++++++++++++++++++++++++++++++++++++------
 1 files changed, 68 insertions(+), 8 deletions(-)

diff --git a/src/synaptics.c b/src/synaptics.c
index 8a6d56e..fb37030 100644
--- a/src/synaptics.c
+++ b/src/synaptics.c
@@ -1689,6 +1689,8 @@ store_history(SynapticsPrivate *priv, int x, int y, unsigned int millis)
     priv->move_hist[idx].y = y;
     priv->move_hist[idx].millis = millis;
     priv->hist_index = idx;
+    if (priv->count_packet_finger < SYNAPTICS_MOVE_HISTORY)
+        priv->count_packet_finger++;
 }
 
 /*
@@ -1777,6 +1779,63 @@ get_edge_speed(SynapticsPrivate *priv, const struct SynapticsHwState *hw,
     }
 }
 
+/*
+ * Fit a line through the three most recent points in the motion
+ * history and return relative co-ordinates.
+ *
+ * Three forms of filtering are present:
+ *      Acceleration - pointer accelerating too fast
+ *      Jerk - too great a change in pointer acceleration
+ *      Error - hw state deviates too much from the predicted position
+ *
+ * Note - The current state is used for filtering, but only its time is used
+ *        in the delta calculation
+ */
+
+static void regress(SynapticsPrivate *priv, const struct SynapticsHwState *hw,
+                    double *dx, double *dy)
+{
+    const SynapticsParameters *pars = &priv->synpara;
+    int i, j;
+    double ym = 0, xm = 0, tm = 0;
+    double yb1n = 0, xb1n = 0, b1d = 0, xb1, yb1;
+    double dista, distb, distc, vela, velb, velc, acca, accb, jerk;
+
+    if (priv->count_packet_finger == 1) {
+        *dx = hw->x - HIST(0).x;
+        *dy = hw->y - HIST(0).y;
+        return;
+    }
+
+    /* Determine the best fit line through the 3 most recent history entries */
+    for (i = 0; i < MIN(priv->count_packet_finger, 3); i++) {
+	ym += HIST(i).y;
+	xm += HIST(i).x;
+	tm += HIST_DELTA(i, 0, millis);
+    }
+    ym /= priv->count_packet_finger;
+    tm /= priv->count_packet_finger;
+    xm /= priv->count_packet_finger;
+
+    for (i = 0; i < MIN(priv->count_packet_finger, 3); i++) {
+        double t = HIST_DELTA(i, 0, millis);
+        yb1n += (t - tm) * (HIST(i).y - ym);
+        xb1n += (t - tm) * (HIST(i).x - xm);
+        b1d += (t - tm) * (t - tm);
+    }
+    xb1 = xb1n/b1d;
+    yb1 = yb1n/b1d;
+
+    *dx = xb1 * (hw->millis - HIST(0).millis);
+    *dy = yb1 * (hw->millis - HIST(0).millis);
+    return;
+
+filtered:
+    *dx = 0;
+    *dy = 0;
+    priv->count_packet_finger = 0;
+}
+
 static void
 get_delta(SynapticsPrivate *priv, const struct SynapticsHwState *hw,
           edge_type edge, double *dx, double *dy)
@@ -1787,10 +1846,11 @@ get_delta(SynapticsPrivate *priv, const struct SynapticsHwState *hw,
     double tmpf;
     int x_edge_speed = 0;
     int y_edge_speed = 0;
+    Bool outlier = FALSE;
 
     /* HIST is full enough: priv->count_packet_finger > 3 */
-    *dx = estimate_delta(hw->x, HIST(0).x, HIST(1).x, HIST(2).x);
-    *dy = estimate_delta(hw->y, HIST(0).y, HIST(1).y, HIST(2).y);
+
+    regress(priv, hw, dx, dy);
 
     if ((priv->tap_state == TS_DRAG) || para->edge_motion_use_always)
         get_edge_speed(priv, hw, edge, &x_edge_speed, &y_edge_speed);
@@ -1847,19 +1907,19 @@ ComputeDeltas(SynapticsPrivate *priv, const struct SynapticsHwState *hw,
     }
 
     /* to create fluid edge motion, call back 'soon'
-     * even in the absence of new hardware events */
+     * even in the absence of new hardware events
+     * Note: This should be longer that the device report rate!
+     */
     delay = MIN(delay, POLL_MS);
 
-    if (priv->count_packet_finger <= 3) /* min. 3 packets, see get_delta() */
-        goto skip; /* skip the lot */
+    if (priv->count_packet_finger < 1) /* min. 1 packet, see regress() */
+        goto out; /* skip the lot */
 
     if (priv->moving_state == MS_TRACKSTICK)
         get_delta_for_trackstick(priv, hw, &dx, &dy);
     else if (moving_state == MS_TOUCHPAD_RELATIVE)
         get_delta(priv, hw, edge, &dx, &dy);
 
-skip:
-    priv->count_packet_finger++;
 out:
     priv->prevFingers = hw->numFingers;
 
@@ -2594,7 +2654,7 @@ HandleState(InputInfoPtr pInfo, struct SynapticsHwState *hw, CARD32 now,
     priv->lastButtons = buttons;
 
     /* generate a history of the absolute positions */
-    if (inside_active_area)
+    if (inside_active_area && actual)
 	store_history(priv, hw->x, hw->y, hw->millis);
 
     return delay;
-- 
1.7.5.3