On Saturday 14 June 2014 17:47:27, Alexander E. Patrakov <[email protected]> wrote: > 13.06.2014 15:22, Gabriele Mazzotta wrote: > > It appears that 71652fe ("Ignore motion the first X ms after a > > clickpad click") is not enough to prevent unwanted cursor jumps when > > two different fingers are used to respectively move the cursor and > > click. The jumps are due to the small delay between the actual click and > > the moment the finger is placed on the clickpad. Because of this delay, > > the two events are sometimes seen as independent from each other and > > since the finger detection happens first, the motion is not ignored. > > > Add a constraint on the distance covered to prevent jumps. > > The difference between two detections along the x axis has to be > > smaller than 1/4 of the clickpad width and smaller than 1/4 of the > > height along the y axis. > > See also https://bugs.freedesktop.org/show_bug.cgi?id=76722 for a > similar bug in libinput. In that case, though, I was able to trace it to > a touchpad firmware bug.
What I understood from your bug report is that you have jumps even when both the fingers are on the touchpad, is that correct? If I do that with my laptop, a scrolling event is sometimes generated, but no jumps. I have jumps only if the touchpad is touched only by one finger. I can reproduce this problem even without clicking, I just need to touch very quickly two different areas in sequence. I hence guess that my problem is due to the fact that the touchpad look for fingers every X milliseconds and if I'm faster than it, it doesn't notice that I removed one finger and started to use another. The final result is the same though, the click happens in a wrong position. > > Signed-off-by: Gabriele Mazzotta <[email protected]> > > --- > > This patch was tested on a Dell XPS13 9333. I don't know if 1/4 of the > > width and 1/4 of the height are good constraints, on my laptop I couldn't > > notice any side effect even with stricter constraints. > > In my patch for libinput (see the attachment to > http://lists.freedesktop.org/archives/wayland-devel/2014-March/013935.html) > I used 1/8 of the diagonal. I chose 1/4 of the width and height instead of the diagonal for simplicity and it seemed to be enough to prevent jumps. I must say that I stopped using two fingers because of this bug, so maybe something more restricting is required, I just did several tests which don't necessarily reflect the normal use case. _______________________________________________ [email protected]: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel
