Launching multiple instances of an OS.js app from another app with different args

[maryam4s26]

Hi @andersevenrud

When launching an OS.js application from another application using core.run('AppName', args), OS.js reuses the existing instance if the app is already running.

As a result:
• Any new arguments passed to the app are ignored.
• Multiple calls to launch the app do not create new independent instances.

Expected behavior:
• Each launch should be able to create a new process instance of the application with its own arguments.
• The called application’s code should remain unchanged.

[andersevenrud]

Hi,

I've looked through the code and when an app is registered, the callback should always recieve the latest args:

const register = (core, args, options, metadata) => {
  // ^ args should be clean
}
osjs.register("name", register);

I'm not at a computer where I can test this however. This happens for all apps ?

Can you make a reproducible example ?

[maryam4s26]

Hi, thanks for the reply @andersevenrud . I can provide a simple reproducible example:
• I have an application (let’s call it Launcher) which lists several hosts.
• When I click on a host, it launches the Terminal app with core.run("Xterm", { hostname }).

Observed behavior:
• On the first click, the Terminal app launches correctly with the arguments of the selected host.
• If the Terminal app is already open and I click another host, the new arguments are ignored. The Terminal app still uses the previous hostname, because osjs.register is not called again and no new instance is created.
• If I close all open Terminals and then click a host, the arguments are again passed correctly.

In short:
• At any given time, only one instance of the Terminal app can be created.
• Multiple calls to core.run("Xterm", { hostname }) do not create new instances with new arguments.

[andersevenrud]

I'll have to try this myself to confirm the issue. I'm a little bit busy today, but I'll try to do it when I finish work.

[maryam4s26]

I'll have to try this myself to confirm the issue. I'm a little bit busy today, but I'll try to do it when I finish work.

tnx

[andersevenrud]

I created a codesandbox for this here: https://codesandbox.io/p/devbox/os-js-example-boilerplate-forked-tpnwzv

You can press the button in the first app to launch another app and dump the arguments it got. It should start with count 0 and increment every time you press the button.

So I am not currently able to reproduce this 🤔

---

If it doesn't work on first try, use the refresh button inside codesandbox. It's a little bit weird sometimes... at least on my computer.

[maryam4s26]

Thanks for your reply. I was able to pinpoint the root cause: the application had "singleton": true in its metadata (for example, Xterm).

Because of this setting, OS.js only allows a single instance of the app. As a result, any new arguments passed via core.run are ignored if the app is already running.

After changing the metadata to "singleton": false, the behavior works as expected — each call to core.run creates a new independent instance with its own arguments.

[andersevenrud]

Because of this setting, OS.js only allows a single instance of the app. As a result, any new arguments passed via core.run are ignored if the app is already running.

Aha! In that case you can get the args with an event :)

  proc.on('attention', (args) => console.log("New arguments", args));

---

Documentation: https://manual.os-js.org/tutorial/application/#events

[maryam4s26]

Aha! In that case you can get the args with an event :)

proc.on('attention', (args) => console.log("New arguments", args));
Documentation: https://manual.os-js.org/tutorial/application/#events

Thank you so much for clarifying this! 🙏
The explanation about singleton and the attention event makes everything clear. Really appreciate your help!