[PATCH 07/15] Replace the motion estimator

[Simon Thum]

On 06/09/2011 09:57 PM, Daniel Stone wrote:
> 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>
Thanks git someone improved that pile'o'junk!

Reviewed-by: Simon Thum <simon.thum at gmx.de>

(I have a few comments though.)

> ---
>  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
At this stage, perhaps it's better to talk about fingers or touch
points. Pointer acceleration, I can assure, has no way of interfering here.

It's all the more ambiguous since synaptics actually interacts with the
server's 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);
I sounds good but seems to belong somewhere else.