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Among those who have tried OS X Lion (s aapl) for the first time, there is near universal dismay at the “reverse scrolling” behavior in the Apple-provided applications. It feels strange to push your fingers up on the trackpad to see content that is further down in the document, when we have had years of practice moving our fingers down instead.
The difference is best understood as a change in the user’s point of view. Instead of pulling the scrollbar down, you push the content up. The change signals a huge shift not just in scroll direction, but in user interface design where gestures are used to manipulate content instead of on-screen interface controls like scrollbars and sliders.
Scrollbar, We Hardly Knew Ye
The venerable scrollbar has been with us for ages. It was probably invented at Xerox PARC in the 70s, well before the graphic user interface (GUI) Macintosh was released in 1984. Back in those days, if you wanted to control something in the GUI, you had to be able to point at a control and click on it. The scrollbar was an obvious visual control to manipulate an application’s viewport, the section of content visible in the current window. It was versatile as well. The scroller not only provided the means to move the viewport, but its position also indicated where you were in the document.
One of the first steps away from direct manipulation of visual controls was the scroll wheel mouse, introduced in 1995 as a different way to move the scrollbar. Apple’s touch-sensitive trackpad and Mighty Mouse later used two-finger gestures for scrolling. However, the controls were still present on the screen to provide visual feedback on the scroller position.
The downside of the GUI was that every control needed to take up some real estate on the screen. Pretty soon we had apps with toolbars that were bigger than the content area.
After over 25 years of scrollbars in Mac OS X, Apple was willing to rethink the UI for the touchscreen when the iPhone was introduced. Gestures provide a way around the need for an on-screen control for every GUI interaction and devote more space to the content itself (quite important on a small screen). Scrollbars were no longer controls, and remained only as a visual indicator of where you were. Instead, you moved content in the viewport by direct manipulation – you pushed the content itself up or down by making a gesture with your finger. This direct manipulation of the content itself is so intuitive on a touchscreen that even toddlers quickly grasp its use.
Different Strokes for Different Folks
On the touchscreen we have grown accustomed to using gestures to manipulate content directly. Unfortunately, when applied to the desktop this approach creates some cognitive dissonance for longtime Mac users as we try to use two-finger scrolling or mouse gestures they way we were taught, to move scrollbars indirectly.
What If You Don’t Know About Gestures?
Because the scrollbar fades out of view until moved, the scrollbars are not easily discovered and there is no visual indication of how to move content in the viewport. We rely on our memory of when we used to see scrollbars. In some applications like Safari, it is not clear where we are in the viewport because there is no scroller or thumb to tell us. Not only is it nigh impossible to discover how to scroll the content for someone unfamiliar with gestures, there is no indication (beyond cut off graphics and text) that you *need* to scroll down the page to see anything below the current viewport.
As it stands, the Lion UI is also a bit inconsistent now. Mail, Address Book, iCal, Safari, etc. all sport the new fading scroll indicators. However, iTunes still uses a scrollbar. Of course, gestures work the iOS way, and the scrollbar works the Mac way. Confusing. I have to think that other controls on desktop apps that could be replaced with gestures, like the zoom slider in iPhoto, might also disappear eventually.
Frankly, Apple’s human interface guidelines and enforcement of those guidelines in the App Store become even more important once you widely adopt gestures. They just need to be consistent. If you can’t see a control on-screen, you are going to try standard gestures. Developers must adhere to those expected behaviors if users are to have any chance of figuring out how to scroll. Can you imagine an app with no scrollbar on-screen that requires you to use four-finger swipes to scroll? How would you figure that out? Would you bother before deleting the app in frustration? Could you imagine a future with mandatory 3-minute introductory videos to explain all the non-standard gestures?
It’s Not All Bad
The scrollbar in OS X Lion does have an advantage in that it doesn’t take up as much space and visual weight in the interface. Gestures provide enough flexibility in control schemes that we don’t have to rely on a mouse click on the scrollbar control to move the viewport and a mouse click on the content to move the cursor. We have multiple ways to interact directly with the content. Content is highlighted before UI controls. What remains to be seen is if the change will prove as comfortable in practice as the theory might suggest.