I need to show something similar to skype pop up saying "A came online" in my OS x app. When I researched on this I found that we can use Growl for achieving it. But for this, do every user who use my app needs to install Growl too?
Is there any way I can make a standalone app for showing notifications? Because we are not installing Growl or any other softwares when installing skype, but still they are showing the notification pop up.
I am really confused. Please help me out! Thanks in advance!
No, your users don't need to have Growl. That was true for older versions, but as of 1.3, to quote from A Note to Developers:
Growl itself is no longer required in order to display a notification. The 1.3 SDK allows for applications to generate Growl notifications without Growl installed. This is called "Mist" and is a new feature of the 1.3 SDK. Thus, Growl becomes the "pro" version of Growl when allowing you to customize the notifications, and the "free" version is the built-in notification.
You can see this working if you download one of the app plugins and install it, without installing Growl itself—Mail, iTunes, or whatever will still display notifications. You just don't have a handy tool to configure them (or see the history, or roll up notifications that happened while you were away). This is exactly how your app will work for users who don't have Growl.
The main Growl documentation still hasn't been completely updated, so it's a source of much confusion, and learning all of the details is a bit complicated.
But the simple version is simple: Just use the Growl framework display notifications, and it uses Growl if the user has it, or "Mist" if not.