ubuntu-x-swat team mailing list archive

[Maxime Gamboni <tendays-kde@xxxxxxxxxxx>]

Jim Rorie: It's not the same bug. Note the keywords "jump erratically
all over the screen *constantly* " and "not the same as known bug where
cursor jumps to place on release of finger".

This bug is triggered by having and keeping two (or more) fingers
pressed - the mouse pointer jumps around even though I'm not moving or
releasing or pressing my fingers. It looks like a protocol mismatch, the
touchpad sending information about both finger positions, and the driver
expecting data about a single finger, and returning garbage to X.

That bug number 21614 you linked, as well as the one you described in
comment #12, is triggered by *releasing* one finger and keeping another
one pressed. The cause of that other bug is obvious - The driver reports
the finger position as the average of physical finger positions, so when
two fingers touch the pad it reports a single but heavy finger in the
middle, and when you release one finger it reports the position of the
remaining finger, so to X it looks like the finger has moved and it
moves the pointer accordingly.

OTOH 308191 may be related, as xinput incorrectly reports the touchpad
not supporting multi-touch, so it's possible that fixing that one will
fix this one.

-- 
erratic cursor movement with multi touch
https://bugs.launchpad.net/bugs/503944
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