The next features I’ll cover are very cool. Lion has changed the way the OS and apps deal with documents. In supported apps, there is no save button anymore. Instead, there’s a new feature called Autosave that continuously save your document as you’re editing it. You may ask: “What if I screw up and want to load a previous version?”. Simple, there’s a new feature called Versions that’s like a Time Machine for each of your document. Just go there and restore the one you want. You can also manually create a version if you wish (that’s what command+S does now). The software developers will find this familiar, as it is pure version control, but done automatically and with a fancy GUI.
App developers don’t need to worry a lot about getting these into their apps, as the Cocoa document framework provides APIs to access the necessary features and will deal with most of the data management automagically.
Since we have Autosave, we also have Automatic Process Termination, which in practice means it’s fine for the OS to quit an app. Then if you switch back to that app, it will use the document restore feature to get you back where you were. The system may want to do this in order to reclaim resources (let’s say, memory, for instance). And it will only do it if: the app isn’t active, has no visible windows and supports Automatic Termination. iOS users will recall this behavior from their iPhone and iPad apps, but this might sound strange for Mac veterans. I particularly like it because it makes sense for most apps, and for those it doesn’t, it’s an optional feature.
Another interesting feature in this line is Resume. Plain and simple: you shutdown the computer and when you turn it back on, it’s exactly how you left it, same apps open and all. However, there are a few bugs, in particular some visual glitches when you resume the system with a lot of full screen apps open. But it works overall.
These are the main OS features most users will notice. The rest is about changes in the apps: Mail, System Information and FileVault are the most relevant. Mail has a great new search and the UI is hugely improved, System Information make it easier for the users to get the info they need to get proper tech support, and File Vault now encrypts the entire disk, is transparent to apps, and doesn’t have the fundamental flaw of destroying all of your data if a cosmic ray changes one bit in your disk.
Overall, I liked the system upgrade. It’s a much better feel than what I got from “Slow Leopard” when it was released. Good set of usability features, some performance improvements and cool new usability paradigms make it an interesting OS. I recommend it to all users who have a multitouch touchpad and 4GB of RAM or more.
The next part is more technical, so if you aren’t a developer, you’ll probably not be interested in it, so feel free to skip it.