Slick-looking LightDM greeter

 Slick-Greeter is cross-distribution and should work pretty much
 anywhere.
 .
 All panel applets are embedded. No external indicators are launched or
 loaded by the greeter.
 .
 No settings daemon are launched or loaded by the greeter.
 .
 This greeter supports HiDPI.
 .
 Sessions are validated. If a default/chosen session isn't present on
 the system, the greeter scans for known sessions in
 /usr/share/xsessions and replaces the invalid session choice with a
 valid session.
 .
 You can take a screenshot by pressing PrintScrn. The screenshot is
 saved in /var/lib/lightdm/Screenshot.png.
 .
 Slick Greeter started as a fork of Unity Greeter 16.04.2, a greeter
 developed for Ubuntu by Canonical, which used indicators and
 unity-settings-daemon.