swaylock: Add module (#3003)

modules/programs/swaylock.nix

@@ -0,0 +1,32 @@
+{ config, lib, ... }:
+
+let cfg = config.programs.swaylock;
+in {
+  meta.maintainers = [ lib.hm.maintainers.rcerc ];
+
+  options.programs.swaylock.settings = lib.mkOption {
+    type = with lib.types; attrsOf (oneOf [ bool float int str ]);
+    default = { };
+    description = ''
+      Default arguments to <command>swaylock</command>. An empty set
+      disables configuration generation.
+    '';
+    example = {
+      color = "808080";
+      font-size = 24;
+      indicator-idle-visible = false;
+      indicator-radius = 100;
+      line-color = "ffffff";
+      show-failed-attempts = true;
+    };
+  };
+
+  config.xdg.configFile."swaylock/config" = lib.mkIf (cfg.settings != { }) {
+    text = lib.concatStrings (lib.mapAttrsToList (n: v:
+      if v == false then
+        ""
+      else
+        (if v == true then n else n + "=" + builtins.toString v) + "\n")
+      cfg.settings);
+  };
+}