plymouth: set custom font

modules/plymouth/nixos.nix

@@ -2,6 +2,7 @@
 
 with lib;
 with config.lib.stylix.colors;
+with config.stylix.fonts;
 
 let
   cfg = config.stylix.targets.plymouth;
@@ -41,6 +42,25 @@ let
     " > $themeDir/stylix.plymouth
   '';
 
+  mkPlymouthFont =
+    font:
+    pkgs.runCommand "${font.package.name}.ttf"
+      { FONTCONFIG_FILE = pkgs.makeFontsConf { fontDirectories = [ font.package ]; }; }
+      ''
+        matchingFonts=$(${pkgs.fontconfig}/bin/fc-match -asf "%{family}|%{file}\n" "${font.name}" | grep "^${font.name}|" | cut -d'|' -f2)
+
+        if [[ -z "$matchingFonts" ]]; then
+          echo "No font named `$font` found."
+          exit 1
+        fi
+
+        if ttfFont=$(echo "$matchingFonts" | grep -m1 -E "\.ttf$"); then
+          cp "$ttfFont" "$out"
+        else
+          font=$(echo "$matchingFonts" | head -n1)
+          ${pkgs.fontforge}/bin/fontforge -lang=ff -c 'Open($1); Generate($2); Close()' "$font" "$out"
+        fi
+      '';
 in {
   options.stylix.targets.plymouth = {
     enable = config.lib.stylix.mkEnableTarget "the Plymouth boot screen" true;
@@ -88,5 +108,6 @@ in {
   config.boot.plymouth = mkIf cfg.enable {
     theme = "stylix";
     themePackages = [ theme ];
+    font = mkPlymouthFont sansSerif;
   };
 }