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Don't use linear regression when calculating touchpad motion deltas

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The results depend on the data rate of the device. A device with a
higher data rate, and thus lower individual deltas, will behave
differently with the regression calculation.

This can be verified on Synaptics semi-mt clickpads. The data rate is
halved when two or more touches are on the device. When trying to press
a button and drag the cursor with another touch, the motion will feel
faster than dragging with only one touch on the device.

Signed-off-by: Chase Douglas <chase.douglas@canonical.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
This commit is contained in:
Chase Douglas
2012-02-09 16:22:35 -08:00
committed by Peter Hutterer
parent 7f5bd79b2e
commit defc1d008e
1 changed files with 3 additions and 4 deletions
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7
src/synaptics.c
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@@ -1972,9 +1972,8 @@ get_delta(SynapticsPrivate *priv, const struct SynapticsHwState *hw,
int x_edge_speed = 0;
int y_edge_speed = 0;
/* 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);
*dx = hw->x - HIST(0).x;
*dy = hw->y - HIST(0).y;
if ((priv->tap_state == TS_DRAG) || para->edge_motion_use_always)
get_edge_speed(priv, hw, edge, &x_edge_speed, &y_edge_speed);
@@ -2043,7 +2042,7 @@ ComputeDeltas(SynapticsPrivate *priv, const struct SynapticsHwState *hw,
* POLL_MS declaration. */
delay = MIN(delay, POLL_MS);
if (priv->count_packet_finger <= 3) /* min. 3 packets, see get_delta() */
if (priv->count_packet_finger <= 1)
goto out; /* skip the lot */
if (priv->moving_state == MS_TRACKSTICK)