InfoWorld review: Mac OS X Lion, more than multitouch

Full-screen is a Lion framework feature. A feature in this category works only in apps that are compiled for Lion (or later) and specifically configured to activate that feature. In some cases, it's as simple as opting in, but other features require substantial code changes and fresh App Store validation. Several of Lion's core bundled apps -- Safari, Preview, TextEdit, and Finder, among others -- are good showcases of the sort of framework features that future Lion apps will pick up.

The Lion framework also brings application and session-level resume to the Mac. When you exit an application, Lion memorizes your open documents, the position of your windows, the text you've selected, and the location of the cursor. When you relaunch the app, all of this state is restored so that you can pick up your work where you left off.

Session resume builds on this, kicking in when you log off, shut down, or reboot. When you log back in, all of your open apps are relaunched, desktops are arranged as you left them, and each app's state is restored as described above. You can easily opt out of this behavior if you'd like a fresh start instead.

Application resume -- and, therefore, session resume -- works best but not exclusively with Lion apps. Older apps will vary in their behavior at relaunch. Office 2011, for example, reopens documents and restores window positions but doesn't deal with the cursor or selected text.

Mac OS X Lion: Working with files
Lion implements file protection at two levels: system and framework. At the system level, Apple has added hourly local snapshots to protect users who either don't use Time Machine for backups or are disconnected from Time Machine for long stretches. Local snapshots can recover inadvertently deleted or altered files and folders. As with Time Machine, you can revisit the state of any folder as it existed at a particular point in time. But unlike Time Machine, snapshots don't protect you from disk failure.

A different kind of protection that's implemented at the system level is full-volume encryption. FileVault previously allowed individual users to encrypt their home folders, but did not guard data stored elsewhere in the system. Lion's FileVault has been accelerated to reduce processing overhead, and now any entire physical disk -- even your boot disk -- can be encrypted. To encrypt a disk other than the startup disk, you enable encryption when you format it; only the startup disk can be encrypted after it is formatted.

You can also use Lion's FileVault to encrypt a Time Machine backup so that none of your data is in the open. At your command, Lion's FileVault will destroy the encryption key on the disk, rendering it permanently unreadable to anyone.