Start a GUI process in Mac OS X without dock icon

Question

I have an application that normally runs with a standard graphical interface. However, for certain long-running tasks, it spawns additional processes of the same application

Answer 1

Motivated from here, you can do:

[NSApp setActivationPolicy: NSApplicationActivationPolicyAccessory];

or

[NSApp setActivationPolicy: NSApplicationActivationPolicyProhibited];

This should hide the dock icon. See here for some documentation about NSApplicationActivationPolicy.

In Python, the code to hide the dock icon is:

# https://stackoverflow.com/a/9220857/133374
import AppKit
# https://developer.apple.com/library/mac/#documentation/AppKit/Reference/NSRunningApplication_Class/Reference/Reference.html
NSApplicationActivationPolicyRegular = 0
NSApplicationActivationPolicyAccessory = 1
NSApplicationActivationPolicyProhibited = 2
AppKit.NSApp.setActivationPolicy_(NSApplicationActivationPolicyProhibited)

See also the related question "How to hide the Dock icon".

---

If you want to avoid that the dock icon pops up at all right at the beginning, you can do that:

import AppKit
info = AppKit.NSBundle.mainBundle().infoDictionary()
info["LSBackgroundOnly"] = "1"

Answer 2

import AppKit
info = AppKit.NSBundle.mainBundle().infoDictionary()
info["LSBackgroundOnly"] = "1"

This code works for my Non-GUI background python script.