This article is continued from ‘OSX Mountain Lion – 1‘ how we preview about new OSX upgrade.

Gatekeeper

When Apple introduced the Mac App Store, the rumblings started: Is the Mac headed for an iOS-like future, one in which only Apple-approved apps will be able to run on the Mac?

With Lion and now Mountain Lion, those fears haven’t come to reality. You can still run apps not bought in the App Store to your heart’s content. However, with Mountain Lion, Apple is introducing a new feature called Gatekeeper that allows users to choose for themselves the kinds of apps they can run on their Macs.

Right now, the first time an app launches, OS X checks it and displays a warning. It’s an attempt to prevent malware apps from launching when you never intended them to. Mountain Lion extends that feature and ties it into a new setting in the Security & Privacy pane of System Preferences.

By default, Mountain Lion lets only Mac App Store apps and apps from “identified developers” launch for the first time. To become an identified developer, a Mac developer has to register with Apple and get a personalized certificate, which the developer then uses to sign apps cryptographically. Apple doesn’t do any sort of background check on the developer, and it doesn’t see any of the software.

Apple says that although these apps aren’t as safe as those from the Mac App Store, they’re safer than many apps, for a couple of reasons. First, a signed app can’t be modified—to add spyware, for instance—without breaking the signature. By default, Mountain Lion refuses to launch an app with a broken signature. Second, if it turns out that an app from a particular developer is actually malware, Apple has the ability to revoke that developer’s license—at which point no future Mac users will be able to install software from that source.

Gatekeeper has an option to allow only Mac App Store software to run, as well as an option to allow any app to run. The latter option is what has been the case in all previous OS X versions.

Share Sheets

Mountain Lion introduces another interface element inspired by iOS, Share Sheets. This pop-up menu appears when you click on the Share icon in an app. Apple has implemented Share Sheets in several of its apps, including Safari, Preview, and Notes. Developers will be able to add Share Sheets to their apps as well.

A Share Sheet provides a quick way to share what you’re working on—a photo in iPhoto, a webpage in Safari—with other services. If you share a webpage from Safari, you can choose to insert it (or just its URL) in a new mail message, or insert a link in a new message in Messages, or even compose a tweet containing the URL. From Preview, you can choose to email the document you’re viewing, send it via Messages, tweet it via Twitter, upload it to Flickr, or transfer it locally via AirDrop.

Most of these aren’t really new functions, but Apple has centralized them and given developers access to the Share Sheets element, which presumably will result in a more consistent sharing interface in future Mac apps.

iCloud Integration

Apple developed Lion and iCloud in parallel. As a result, while the current version of Mac OS X supports Apple’s suite of online services, it doesn’t truly embrace it. One of Apple’s goals in Mountain Lion is apparently to truly integrate iCloud throughout the system.

The results of this effort are apparent at setup: In Setup Assistant, the system asks for your Apple ID and syncs your existing accounts, settings, and personal data. It might not be quite as thorough as restoring an iOS backup from iCloud, but the idea is that your iCloud account unlocks a whole bunch of Mac data so you don’t have to reenter it on every new system you use.

Mountain Lion also brings a new Documents in the Cloud view to the traditional Open and Save dialog boxes. Any apps that support Documents in the Cloud open to an iCloud view that displays the documents available via iCloud, with the most recent items first. You can organize this view by dragging one document on top of another to create a folder, iOS style.

Safari Tweaks

Apple isn’t making a big deal about changes to the Safari Web browser in Mountain Lion, but there are a few. There’s a Share Sheet in the toolbar, with options to add a page to Reading List, bookmark a page, email it, send it to Messages, or share it via a tweet. The now-larger Safari Reader button sits just to the right of the address bar, turning blue when a page is viewable with Reader.

The search box no longer appears next to the address bar. Instead, at long last, Apple has unified the address bar and the search box. Now, if you type “apple gtd” into that box, you’ll get a bunch of links about Tom Baker instead of an error message telling you that Safari can’t find the website http://apple%20gtd/. The address bar also now omits the http://prefix on URLs, and while the main part of the URL is displayed in black text, the rest of the URL appears in gray.