Touchpad randomly fires incorrect events when scrolling

[Sandro Mani]

Using up-to-date karmic as of 15.08.2009

Problem:
When using the "virtual scroll" on the touchpad (i.e. only moving the finger on the right side of the pad, not pressing any button!), occasionally (apparently randomly) incorrect events are generated. It also occurs with tap-to-click disabled.
I can easily reproduce the issue by placing to fingers on the right side of the tab, i.e.
     _____________
     | finger ->|
     | |
     | finger ->|
     |____________|

and tapping and slightly dragging with both fingers at a fast rate. Looking at the output from xev while doing this, between the events 4 and 5, occasionally some events of type 2 (center click) and 3 (rightclick) appear.

This also happens when using the touchpad "normally", i.e. browsing in firefox: quite often when scrolling through pages actions get perfomed that are either triggered by the center click or by a funciton of the contextmenu (which apparently hides again so quickly that one does not see it). To be noted is that this issue is NOT specific to any progam.

I started noticing the problem since the last xserver-xorg-input-synaptics update, possibly related to the issues created with the patch that was introduced there, such as bug #405943.

Hardware is a lenovo T400.

[Alberto Milone (albertomilone)]

Are you sure this bug is not a duplicate of bug 386017 ?

[Sandro Mani (sandromani)]

Uhm I never experienced the issue described there, the issue here is more general, i.e. the touchpad driver misreports events and then the program executes actions as if the reported button was pressed.

[Alberto Milone (albertomilone)]

The top right corner and the bottom right corner of your touchpad trigger events 2 and 3 respectively. This is called corner tapping and (technically) it's not a bug. It's exactly what causes bug #386017

[Sandro Mani (sandromani)]

Indeed, now that you pointed it is exactely what I am experiencing. Marking as duplicate, thanks.