Show a Windows program

A desktop presence reads the computer through the host object, which starts empty. Each permission in the manifest adds functions to it, and people see that list before they turn the presence on. This guide builds a presence for a game, one piece at a time. Create it from the “Desktop program” template of the Developer page, and keep the Test tab watching it as you go.

1. Ask for what you need#

To know whether a game is open, the presence needs the list of running programs:

"permissions": { "process": true }

Now host.process.list() exists. Without the permission, calling it fails and the Developer page shows the error.

2. Find the program#

const PROGRAM = "game.exe";

function read(context) {
  const running = host.process.list().some((name) => name.toLowerCase() === PROGRAM);
  if (!running) return null;
  return { playing: true };
}

Program names can come in any case, so the script compares them in lower case. Returning null when the game is closed is what makes the presence go away. To see a program’s exact name, open the Details tab in Task Manager.

3. Count the time#

Discord draws the counter from start, so the script has to remember when the game opened. A variable outside the functions survives between calls.

let since = 0;

function read(context) {
  const running = host.process.list().some((name) => name.toLowerCase() === PROGRAM);
  if (!running) {
    since = 0;
    return null;
  }
  if (since === 0) since = context.now;
  return { since };
}

4. Show it#

function activity(game) {
  return {
    details: "My Game",
    state: t("playing"),
    kind: "playing",
    start: game.since,
    large_image: "logo",
  };
}

function meta() {
  return { application: PROGRAM };
}

"logo" is the name of an image uploaded to your Discord application. meta gives the program’s name so people can exclude it in Privacy.

5. Know when it is in front#

Ask for the window permission too, and the game can rank above other presences while you are playing it:

"permissions": { "process": true, "window": true }

function read(context) {
  // ...the code above...
  const window = host.window.foreground();
  return { since, focused: Boolean(window) && window.process.toLowerCase() === PROGRAM };
}

function meta(game) {
  return { application: PROGRAM, foreground: game.focused };
}

foreground also gives the window’s title, which often holds a file or project name. If the program’s name is enough, leave the title alone.

6. Read more about the game#

Log files often say what is happening inside a program. This reads the end of the newest log:

"permissions": { "process": true, "files": ["%LOCALAPPDATA%/MyGame/logs"] }

function read(context) {
  // ...the code above...
  const log = host.files.latest(host.files.roots[0], ".log");
  const lines = host.files.tail(log, 50);
  const level = lines.map((line) => /Entered level (.+)/.exec(line)).findLast(Boolean);
  return { since, level: level ? level[1] : null };
}

Then show it with state: game.level || t("playing") in activity.

Read the end of a file and not all of it, and keep the path of the log for a minute instead of searching on every call: a folder can hold hundreds of files.

Other permissions#

Programs can also be read through their command line, the media Windows is playing, web APIs and game servers. Host lists every permission and what it adds. Ask only for what the script uses: an update that adds a permission waits until the person accepts it.

The real thing#

presences/ready-or-not is steps 1 to 4 for a real game. presences/roblox goes further with a log file and a web API, and presences/creator-tools looks only at the program in front. All three are in the repository.

Without code#

To show a program with no code, open the Presences page and use “Add a program”. Pick it from the list, write the lines and the application makes the folder for you.

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