LightDM µGreeter

A minimalist LightDM greeter written in Go, powered by gotk3 and inspired by lightdm-mini-greeter.

Many thanks to Matt Fischer for his great blog post.

Example screenshot, unknown artist: please open an issue to credit him/her !

Features

• log in
• single-user or multi-user mode
• suited for HiDPI monitor
• triggers
  • poweroff (Ctrl+Shift+P)
  • reboot (Ctrl+Shift+R)
  • suspend (Ctrl+Shift+S)
  • hibernate (Ctrl+Shift+H)
• customization
  • wallpaper
    • autoscaling on your primary monitor
    • random selection from a directory
  • entry
    • width
    • colors (font, background and carret)
  • label
    • choose text for username and password mode

Installation

🚨 Any help to package µGreeter for your favorite distribution is greatly appreciated 🚨

Arch-based

It's not in the AUR yet, but there is a PKGBUILD available in pkg/AUR.

git clone https://github.com/nizil/lightdm-micro-greeter
cd lightdm-micro-greeter/pkg/AUR
makepkg --install

Manual

Requirements

You need to install lightdm and gtk3. Depending on your distro, you might have to install some -dev or -devel packages.
Obviously, you also need Go.

Get the binary

go install github.com/nizil/lightdm-micro-greeter@latest

or

git clone https://github.com/nizil/lightdm-micro-greeter
cd lightdm-micro-greeter
go build

Setup the greeter

Now, you have to tell LightDM to use this greeter, and this is done in two simples steps:

• Create a XDG desktop entry at /usr/share/xgreeters which execute lightdm-micro-greeter.
• Change the LightDM config to use the newly created .desktop, it could be done through the greeter-session parameter of /etc/lightdm/lightdm.conf.

If you have used go install and GOBIN is in your PATH, you could use the desktop and config files provided.

If you have used go build, you could just run the install.sh script as root, which put the built binary inside /usr/bin/, setup the desktop file and a default configuration, and even modify your LightDM configuration file (while doing a backup).

Configuration

All the configuration is handled within the /etc/lightdm/lightdm-micro-greeter/config.json file. If the file does not exist, this configuration will be used.

Parameters	Effect
Username	keep empty for multi-user mode, providing an username will switch to single-user.
Wallpaper	path to an image or a directory, /etc/lightdm/lightdm-micro-greeter/ will be prepended.
DPI	dpi used.
Entry.WidthChars	entry width in chars.
Entry.TextColor	entry text color (hexcode or rgba).
Entry.BackgroundColor	entry background color (hexcode or rgba).
Entry.CaretColor	entry caret color (hexcode or rgba).
Entry.TextAlignment	entry text alignement, float between 0 (left) and 1 (right).
Label.Margin	label margin in pixel.
Label.Color	label text color (hexcode or rgba).
Label.UsernameText	label text when waiting for username.
Label.PasswordText	label text when waiting for password.
Label.Color	label text color (hexcode or rgba).
Box.MarginTop	box margin top, in pixel.
Box.MarginBottom	box margin bottom, in pixel.
Box.MarginLeft	box margin left, in pixel.
Box.MarginRight	box margin right, in pixel.

If Wallpaper is a directory, it must only contain images, as the greeter will randomly chose a file from this directory.

Dev notes

I had to rely on C macro G_CALLBACK to bind the LightDM server callbacks, which is unfortunately not accessible through the import "C" statement.
To bind a go function to glib events, I've exported few go functions using //export statement and binded them with G_CALLBACK from C code greeter_signal_connect.c.
With this architecture, it has been pretty difficult to avoid the use of global vars to carry information from the UI to these callbacks. If you have any idea how to make a cleaner code here, open a ticket, I'll be more than happy to discuss about it :)