Laptop Lower-Left Click Button - unusual behavior

[J. McDonald]

I am using the Mint 18 Cinnamon LTS distribution on a Lenovo T530. After upgrading the kernel from 4.4.0-38 to 4.4.0-43, I noticed that the lower left touchpad button had unusual behavior assigned to it. Instead of being a left click, it appeared to behave as a middle-click or had other unexpected behavior. Clicking in the middle of a tab in Firefox would close the tab instead of selecting it. Clicking on a hyperlink in Firefox would open the link in a new tab instead of following the link. The upper left left button still had "normal" left-click behavior, as did a single tap-to-click in the touchpad. Going into the Cinnamon settings for "Mouse and Touchpad" and looking at both the "Mouse" and "Touchpad" tabs, I noticed that "Emulate middle click by clicking both left and right buttons" was "on" by default. I turned it off and "normal", or at least expected, touchpad button behavior returned. If I turn this back on, the odd lower-left touchpad button behavior returns.

Additional info:

$ egrep -i 'synap|alps|etps' /proc/bus/input/devices
N: Name="SynPS/2 Synaptics TouchPad"
P: Phys=synaptics-pt/serio0/input0

$ cat /etc/*-release
DISTRIB_ID=LinuxMint
DISTRIB_RELEASE=18
DISTRIB_CODENAME=sarah
DISTRIB_DESCRIPTION="Linux Mint 18 Sarah"
NAME="Ubuntu"
VERSION="16.04 LTS (Xenial Xerus)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 16.04 LTS"
VERSION_ID="16.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"
UBUNTU_CODENAME=xenial

$ cat /proc/version
Linux version 4.4.0-43-generic (buildd@lgw01-22) (gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.2) ) #63-Ubuntu SMP Wed Oct 12 13:48:03 UTC 2016

[J. McDonald (mcdonald-joseph)]

After renewing from a suspend, the weird behavior with the lower left touchpad button returned. Simply opening "Mouse and Touchpad" and changing any settings returned the behavior to normal. This is really odd.

[J. McDonald (mcdonald-joseph)]

I checked this with XEV. Instead of "normal" behavior that triggers "button 1", it instead triggers either button 2 (middle click) or button 1 followed by button 2. The behavior identified in XEV was intermittent and not consistent. I am not adept enough at configuring xinput to fix this. I ended up installing "Easystroke Gesture Recognition" from synaptic, recorded the button using "Add Action" and assigned the recorded action to "button 1". That appears to have solved the issue for me and testing with XEV registers the button as "button 1" consistently.