lightdm does not respect tap to click from GNOME/libinput settings

[fcole90]

When using lightdm as display manager and GNOME Shell as DE, with libinput installed, lightdm doesn't respect the GNOME setting for tap to click.

This setting is correctly respected under gdm3.

This setting is also correctly respected when using lightdm without libinput installed.

The synaptic driver is installed as well, if it was of any interest.

Also, this seems to be fixed (or always enabled) in 17.10, as I could use tap to click in lightdm with the Daily ISO (with GNOME DE installed).

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: lightdm 1.18.3-0ubuntu1.1
ProcVersionSignature: Ubuntu 4.8.0-53.56~16.04.1-generic 4.8.17
Uname: Linux 4.8.0-53-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.6
Architecture: amd64
CurrentDesktop: GNOME
Date: Mon Jun 5 11:04:14 2017
InstallationDate: Installed on 2016-09-09 (268 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
JournalErrors:
 Error: command ['journalctl', '-b', '--priority=warning', '--lines=1000'] failed with exit code 1: Hint: You are currently not seeing messages from other users and the system.
       Users in the 'systemd-journal' group can see all messages. Pass -q to
       turn off this notice.
 No journal files were opened due to insufficient permissions.
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)