two-finger scrolling produces spurious button 5 events

[Marius Gedminas]

Binary package hint: xserver-xorg-input-synaptics

I've a Lenovo T61 with a Synaptics touchpad with the following options in my xorg.conf:

        Option "HorizEdgeScroll" "0"
        Option "VertTwoFingerScroll" "true"

If I try to use two-finger scrolling, very often I get spurious scroll down events immediately after I lift my fingers off the touchpad. This makes two-finger scrolling feature absolutely unusable :(

This is on Hardy with xserver-xorg-input-synaptics 0.14.7~git20070706-1ubuntu4

Steps to reproduce:

1. Enable VertTwoFingerScroll
2. Start xev
3. Move the mouse into the xev window
4. Place two fingers on the touchpad, move them forward a bit and immediately lift them, without pausing.

Expected results:

* you see a few button 4 press & release events in the xev log

Actual results:

* you see a few button 4 press & release events, and following those about 120 button 5 press & release events.

(This might be related to bug 228311, although it refers to right-edge scrolling, which never caused big problems for me. I'd get a couple of scroll events in the wrong direction after lifting my finger, but I always thought it was my finger shifting position while I was lifting it up.)

[Nicolas Cavallari (batchman)]

i discovered, looked up and solved this problem on my Inspiron 1520 running Debian.

Only problem is that my fix currently breaks Trackstick emulation mode.

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=437254

[Marius Gedminas (mgedmin)]

That Debian bug also links to Ubuntu bug 133060.

I can confirm that if I look with synclient -m 10, and do the brief two-finger scroll up motion, I see a bunch of lines with events x=1, y=5855, 0<=z<=3 at the end.

Will try the workaround next.

I don't know what "Trackstick emulation mode" is.

[Marius Gedminas (mgedmin)]

The patch attached to bu 113060 (namely, http://launchpadlibrarian.net/14094880/Dell-Inspiron-6400-taps-fix.patch) fixes two-finger scrolling problems for me.

Thank you, Nicolas!

[William Grant (wgrant)]

That patch to ignore the (1, 5855) events fixes things for me too. Does it break anything for other people?

[Nicolas Cavallari (batchman)]

The hackish patch doesn't break anything, but that doesn't mean it's great.

[Michele (mikelito)]

Got bitten by this bug on Intrepid, running on a Thinkpad T60.
the patch mentioned above makes the thing more usable, but still a lot of garbage button 4-5 events are being generated. Any news from upstream?

[Michele (mikelito)]

just wanted to report that the patch at

http://bugs.debian.org/cgi-bin/bugreport.cgi?msg=30;filename=dell-touchpad.patch;att=1;bug=437254

works fine on my system. The author reports it to break 'trackstick emulation mode', but since I don't even know what it is, I am quite happy with it.
It also seems less hackish than the "ignore (1,5855)" patch.

[Nicolas Cavallari (batchman)]

It seems that trackstick emulation mode was fixed since last time i tried (which was a long time).

This patch is now making its way into the new upstream...

[Marius Gedminas (mgedmin)]

Nicolas: is this the upstream patch that fixes this bug?

http://cgit.freedesktop.org/xorg/driver/xf86-input-synaptics/commit/?id=13c93be34dfcd0e57b14f86688fd2ad4efda028c

[Nicolas Cavallari (batchman)]

Yes, it was commited overnight ;)

[ischoegl (ischoegl)]

Just ran into the same problem with random scrolls on Intrepid on my thinkpad T60. Will there be a fix in the standard ubuntu packages anytime soon?

[Mark Gross (mark97229)]

I'm getting almost this bug running Karmic alpha 6.
but its button 3 in this case.
MotionNotify event, serial 31, synthetic NO, window 0x3200001,
    root 0x100, subw 0x0, time 1357157, (116,133), root:(121,851),
    state 0x0, is_hint 0, same_screen YES

ButtonPress event, serial 31, synthetic NO, window 0x3200001,
    root 0x100, subw 0x0, time 1357305, (116,133), root:(121,851),
    state 0x0, button 3, same_screen YES

ButtonRelease event, serial 31, synthetic NO, window 0x3200001,
    root 0x100, subw 0x0, time 1357356, (116,133), root:(121,851),
    state 0x400, button 3, same_screen YES

ButtonPress event, serial 31, synthetic NO, window 0x3200001,
    root 0x100, subw 0x0, time 1357536, (116,133), root:(121,851),
    state 0x0, button 3, same_screen YES

ButtonRelease event, serial 31, synthetic NO, window 0x3200001,
    root 0x100, subw 0x0, time 1357536, (116,133), root:(121,851),
    state 0x400, button 3, same_screen YES

MotionNotify event, serial 31, synthetic NO, window 0x3200001,
    root 0x100, subw 0x0, time 1357672, (116,133), root:(121,851),
    state 0x0, is_hint 0, same_screen YES

[Bryce Harrington (bryce)]

Hi, the spurious click issue has been fixed in current Ubuntu. There was a subsequent issue but I patched it in natty yesterday.

Can you re-test on natty to see if this is still occurring for you?

[Marius Gedminas (mgedmin)]

I can't reproduce this on maverick.

I'm not sure I can find the time to test natty; I'll try.

What was the subsequent issue that you patched?

[Ahmed Shams (ashams)]

Hi, does this bug still affect any of the current Ubuntu releases?
Thanks.

[Mark Gross (mark97229)]

FWIW I have not seen this problem in a long time. But, also my hardware has changed since 2009 so that doesn't prove much.