Semi-mt devices do not track touches. The locations of touches are unknown, we only have the bounding box of two of them. We the number of fingers changes, the bounding box coordinates may change as well, but the cumulative relative motion updates at that instant are invalid.
To work around this, ignore changes in cumulative relative motion if the touch count changes. Signed-off-by: Chase Douglas <chase.doug...@canonical.com> --- src/synaptics.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/src/synaptics.c b/src/synaptics.c index e80dff8..ff3c32e 100644 --- a/src/synaptics.c +++ b/src/synaptics.c @@ -1589,6 +1589,14 @@ ReadInput(InputInfoPtr pInfo) SynapticsResetTouchHwState(hw); while (SynapticsGetHwState(pInfo, priv, hw)) { + /* Semi-mt device touch slots do not track touches. When there is a + * change in the number of touches, we must disregard the temporary + * motion changes. */ + if (priv->has_semi_mt && hw->numFingers != priv->hwState->numFingers) { + hw->cumulative_dx = priv->hwState->cumulative_dx; + hw->cumulative_dy = priv->hwState->cumulative_dy; + } + SynapticsCopyHwState(priv->hwState, hw); delay = HandleState(pInfo, hw, hw->millis, FALSE); newDelay = TRUE; -- 1.7.9 _______________________________________________ xorg-devel@lists.x.org: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel