Add non-steam app declaratively

[johnrobharrison]

I've retroarch installed via the nixos config along with Jovian. Is there a way for me to add it to the non-steam apps section of steam big picture decoratively via my config?

[Rumbiz]

It's possible, but i would say it's ...tricky.
I used the following method:

1. Declare the text version of .vdf file.
2. Locate the steam config folder
3. Use python with vdf library to encode your text file to .vdf format.
   Worked for me (i used it to add Retroarch and Sunshine streams). Sadly, at the moment i can't really provide source code of python script, but you can ask any AI for details.
   The basic syntax is something like :
   shortcuts = pkgs.writeText "shortcuts.vdf" ''
   shortcuts {
   0 {
   AppName "WHATEVER"
   Exe "WHATEVERYOUWANT"
   StartDir "YOUGETIT"
   LaunchOptions ""
   IsHidden 0
   AllowDesktopConfig 1
   AllowOverlay 1
   OpenVR 0
   Devkit 0
   DevkitGameID ""
   LastPlayTime 0
   }
   }
   '';

[johnrobharrison]

If anyone's interested, this is what I ended up with. It's a touch hacky, but does the job. It even adds flatpaks to the Steam shortcuts too.

{ config, pkgs, lib, ... }:

let
  pythonEnv = pkgs.python3.withPackages (ps: with ps; [ vdf ]);
  desktopEntries = config.xdg.desktopEntries;
  desktopEntryList = lib.attrValues desktopEntries;

  entriesFromHM = builtins.toJSON (map (entry: {
    name = entry.name;
    exec = entry.exec;
    icon = entry.icon;
  }) desktopEntryList);
in {
  home.packages = [ pythonEnv ];

  home.file.".local/bin/add-steam-shortcuts".text = ''
    #!/bin/sh
    export HOME_MANAGER_XDG_DESKTOP_ENTRIES=${lib.escapeShellArg entriesFromHM}
    exec ${pythonEnv}/bin/python3 ~/.local/share/add-steam-shortcuts.py
  '';
  home.file.".local/bin/add-steam-shortcuts".executable = true;

  home.file.".local/share/add-steam-shortcuts.py".text = ''
    #!/usr/bin/env python3

    import os
    import vdf
    import json
    import sys
    import zlib
    import configparser
    from glob import glob

    # Load entries passed from Home Manager
    entries_from_hm = []
    try:
        env_json = os.environ.get("HOME_MANAGER_XDG_DESKTOP_ENTRIES")
        if env_json:
            entries_from_hm = json.loads(env_json)
    except Exception as e:
        print("⚠️ Failed to load Home Manager desktop entries:", e)

    # Directories to scan for .desktop files
    XDG_DATA_DIRS = [
        os.path.expanduser("~/.local/share/applications"),
        os.path.expanduser("~/.local/share/flatpak/exports/share/applications"),
        "/var/lib/flatpak/exports/share/applications",
        "/usr/share/applications"
    ]

    def parse_desktop_file(path):
        filename = os.path.basename(path)
        if filename.startswith("steam-") or filename == "steam.desktop":
            return None

        config = configparser.ConfigParser(interpolation=None)
        try:
            config.read(path)
            entry = config["Desktop Entry"]

            if entry.get("NoDisplay", "false").lower() == "true":
                return None
            if "Exec" not in entry or "Name" not in entry:
                return None

            exec_line = entry["Exec"]
            if exec_line.strip().startswith("steam") or "steam://" in exec_line:
                return None

            return {
                "name": entry["Name"],
                "exec": exec_line.split()[0],
                "icon": entry.get("Icon", "")
            }
        except Exception as e:
            print(f"⚠️ Failed to parse {path}: {e}")
            return None

    desktop_entries = []
    seen = set()

    # Parse files from disk
    for dir in XDG_DATA_DIRS:
        if os.path.isdir(dir):
            for file in glob(os.path.join(dir, "*.desktop")):
                parsed = parse_desktop_file(file)
                if parsed:
                    key = (parsed["name"], parsed["exec"])
                    if key not in seen:
                        seen.add(key)
                        desktop_entries.append(parsed)

    # Merge in entries from Home Manager
    for entry in entries_from_hm:
        key = (entry["name"], entry["exec"])
        if key not in seen:
            seen.add(key)
            desktop_entries.append(entry)

    # Locate Steam userdata
    try:
        user_dirs = [
            d for d in os.listdir(os.path.expanduser("~/.steam/steam/userdata"))
            if d.isdigit()
        ]
        steam_user_id = user_dirs[0]
    except Exception:
        print("❌ Could not find Steam userdata directory.")
        sys.exit(1)

    steam_shortcut_file = os.path.expanduser(
        f"~/.steam/steam/userdata/{steam_user_id}/config/shortcuts.vdf"
    )

    def generate_appid(name, exe):
        base = f"{exe}{name}".encode("utf-8") + b"\\0"
        crc = zlib.crc32(base) & 0xFFFFFFFF
        val = crc | 0x80000000
        return val if val < 0x80000000 else val - 0x100000000

    if os.path.exists(steam_shortcut_file):
        with open(steam_shortcut_file, "rb") as f:
            try:
                existing = vdf.binary_loads(f.read())
            except Exception as e:
                print("⚠️ Failed to parse existing shortcuts.vdf:", e)
                existing = {"shortcuts": {}}
    else:
        existing = {"shortcuts": {}}

    existing["shortcuts"] = {}
    shortcuts = existing["shortcuts"]
    count = 0

    for entry in desktop_entries:
        name = entry["name"]
        exec_path = entry["exec"]
        icon_path = entry["icon"]

        shortcut = {
            "appid": generate_appid(name, exec_path),
            "appname": name,
            "exe": exec_path,
            "StartDir": os.path.expanduser("~"),
            "icon": icon_path,
            "ShortcutPath": "",
            "LaunchOptions": "gamemoderun %command%",
            "IsHidden": 0,
            "AllowDesktopConfig": 1,
            "AllowOverlay": 1,
            "OpenVR": 0,
            "Devkit": 0,
            "DevkitGameID": "",
            "LastPlayTime": 0,
            "tags": {
                "0": "Game"
            }
        }

        shortcuts[str(count)] = shortcut
        count += 1
        print(f"✅ Added: {name}")

    with open(steam_shortcut_file, "wb") as f:
        f.write(vdf.binary_dumps(existing))

    print("✅ All Steam shortcuts updated.")
  '';
  home.file.".local/share/add-steam-shortcuts.py".executable = true;

  home.activation.addSteamShortcuts =
    lib.hm.dag.entryAfter [ "reloadSystemd" ] ''
      echo "🔁 Scanning for XDG desktop entries..."
      ~/.local/bin/add-steam-shortcuts || true
    '';
}