#+title: Plymouth
#+setupfile: ../headers

* Plymouth
Plymouth is a utility which shows an animation at startup or when
powering off a device, instead of showing only terminal things. My
Plymouth settings are set in the =nixos.plymouth= module.

#+begin_src nix :tangle yes
{
  flake.modules.nixos.plymouth = {pkgs, ...}: {
    boot = {
      <<plymouth>>
      <<kernel-parameters>>
      <<quiet-console>>
      <<no-menu>>
    };
  };
}
#+end_src

** Quieting Down the Console
First, I need to set a few kernel parameters to make displaying
Plymouth possible:
#+name: kernel-parameters-list
- =quiet= :: silences the logs in the terminal
- =splash= :: show the splash screen (in our case, Plymouth)
- =boot.shell_on_fail= :: sets =allowShell=1=, which permits the =fail()=
  handler to drop an interactive rescue shell if stage-1 boot fails
- =udev.log_level=3= :: sets udev’s log level to =err=
- =rd.systemd.show_status=auto= :: suppress systemd status messages in
  initrd unless boot is significantly delayed

#+name: kernel-params
#+begin_src emacs-lisp :var params=kernel-parameters-list :cache yes
(mapconcat (lambda (param)
             (format "\"%s\""
                     (s-chop-suffix "=" (s-chop-prefix "=" (car (s-split " ::" param))))))
           params
           "\n")
#+end_src

#+RESULTS[7a824c095f2934792b4a3749e56091a8603aaacf]: kernel-params
: "quiet"
: "splash"
: "boot.shell_on_fail"
: "udev.log_level=3"
: "rd.systemd.show_status=auto"

This translates into:
#+name: kernel-parameters
#+begin_src nix :noweb yes
kernelParams = [
  <<kernel-params()>>
];
#+end_src

To further decrease the verbosity of the booting screen, we can
deactivate initrd’s verbosity and lower the console’s log level to
=err=.
#+name: quiet-console
#+begin_src nix
consoleLogLevel = 3;
initrd.verbose = false;
#+end_src

And we’ll show Plymouth immediately, skipping the bootloader’s menu.
We can hold a key to force displaying the menu, though.
#+name: no-menu
#+begin_src nix
loader.timeout = 0;
#+end_src


** Configuring Plymouth
Now, we can configure Plymouth proper.
#+name: plymouth
#+begin_src nix
plymouth = {
  enable = true;
  <<plymouth-theme>>
};
#+end_src

The only significant configuration I want to change in Plymouth is the
animation. I really like how it looks. You can find a preview of it in
[[https://github.com/adi1090x/plymouth-themes#previews][adi1090x's repository]], under the first pack. For this, I need to set
a theme package and the theme name.
#+name: plymouth-theme
#+begin_src nix
theme = "circle_hud";
themePackages = with pkgs; [
  (adi1090x-plymouth-themes.override {
    selected_themes = ["circle_hud"];
  })
];
#+end_src

And we’re done!