conky: ship on sway

this probably causes double conky on sxmo, but i can fix in future patch

hosts/common/programs/conky/default.nix

@@ -0,0 +1,36 @@
+{ config, lib, pkgs, ... }:
+{
+  sane.programs.conky = {
+    fs.".config/conky/conky.conf".symlink.target =
+      let
+        battery_estimate = pkgs.static-nix-shell.mkBash {
+          pname = "battery_estimate";
+          src = ./.;
+        };
+      in pkgs.substituteAll {
+        src = ./conky.conf;
+        bat = "${battery_estimate}/bin/battery_estimate";
+        weather = "timeout 20 ${pkgs.sane-weather}/bin/sane-weather";
+      };
+  };
+
+  # TODO: give `sane.programs` native support for defining services
+  systemd.user.services.conky = lib.mkIf config.sane.programs.conky.enabled {
+    description = "conky dynamic desktop background";
+    wantedBy = [ "default.target" ];
+    # XXX: should be part of graphical-session.target, but whatever mix of greetd/sway
+    # i'm using means that target's never reached...
+    # wantedBy = [ "graphical-session.target" ];
+    # partOf = [ "graphical-session.target" ];
+    # TODO: might want `ConditionUser=!@system`
+
+    serviceConfig.ExecStart = "${pkgs.conky}/bin/conky";
+    serviceConfig.Type = "simple";
+    serviceConfig.Restart = "on-failure";
+    serviceConfig.RestartSec = "10s";
+    # serviceConfig.Slice = "session.slice";
+
+    # don't start conky until after sway
+    preStart = ''test -n "$SWAYSOCK"'';
+  };
+}

hosts/common/programs/default.nix

@@ -7,6 +7,7 @@
     ./assorted.nix
     ./cantata.nix
     ./chatty.nix
+    ./conky
     ./cozy.nix
     ./dino.nix
     ./element-desktop.nix

hosts/modules/gui/sway/default.nix

@@ -117,6 +117,7 @@ in
         package = null;
         suggestedPrograms = [
           "guiApps"
+          "conky"  # for a nice background
           "splatmoji"  # used by us, but 'enabling' it gets us persistence & cfg
           "swaylock"
           "swayidle"

hosts/modules/gui/sxmo/default.nix

@@ -339,16 +339,8 @@ in
         in
           lib.generators.toKeyValue { inherit mkKeyValue; } cfg.settings;
 
-        sane.user.fs.".config/sxmo/conky.conf".symlink.target = let
-          battery_estimate = pkgs.static-nix-shell.mkBash {
-            pname = "battery_estimate";
-            src = ./.;
-          };
-        in pkgs.substituteAll {
-          src = ./conky-config;
-          bat = "${battery_estimate}/bin/battery_estimate";
-          weather = "timeout 20 ${pkgs.sane-weather}/bin/sane-weather";
-        };
+        sane.user.fs.".config/sxmo/conky.conf".symlink.target
+          = "../conky/conky.conf";
       }
 
       (lib.mkIf (cfg.greeter == "lightdm-mobile") {