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The Evolution of Scrolling: Reinventing the Wheel

[Interesting Thing of the Day (ITotD) is an ongoing series of articles about any topic I find interesting, including surprising discoveries in food, geography, science, language, history, philosophy, and even - from time to time - technology. Because I write for a general audience, the following article, which appeared on the site in early October 2004, contains some information that may seem like old news to technically savvy TidBITS readers. But I hope you'll find it useful and enjoy this taste of ITotD.]


When I'm not writing about interesting things, I spend my time writing computer books and doing the odd consulting job here and there - projects that hark back to the nine years I spent managing software development for high-tech companies. I spent five of those years working for Kensington Technology Group, a company best known for its mice and trackballs. You may not think of mice as the most cutting-edge computer peripheral, but it's hard to imagine where we'd be without them. And I was privileged during the time I was at Kensington to be involved in the development of some extremely cool input-device technologies. This is probably going to sound like a thinly veiled Kensington commercial, but I make no apologies: even though I don't work there anymore, I'm still a huge fan of their products.


Getting to the Point -- All modern computer operating systems are based on some form of graphical user interface (GUI) that assumes the presence of a mouse (or comparable pointing device) to move a pointer around on the screen. Most of us have become so accustomed to using a mouse that we don't even think about it anymore. Although it's possible to use most GUI programs with a keyboard alone, it's much more cumbersome - and the whole point of modern interfaces was to be less cumbersome than their keyboard-only predecessors.

When it comes to scrolling, however, most GUIs don't make it easy for ordinary mice. The usual way to move the contents of a window up and down (or left and right) is to position your mouse pointer over the tiny arrows at the corners of the window and click a button. The problem with this approach is one of target acquisition: if your pointer doesn't happen to be near those arrows (and it usually isn't) you have to move it into position, and it can be difficult to reach a relatively small clickable area on the screen both quickly and accurately. You must either move the pointer slowly or back up after overshooting. Although you may have become so used to doing this that you don't notice it, this method of scrolling is error-prone and time-consuming; it also results in your pointer being far away from the controls you're likely to need next (menus or toolbars, say).

One solution, certainly, is to use the Page Up/Page Down keys on your keyboard to scroll. But that requires moving your hand back and forth between your pointing device and your keyboard, which can also be tedious. Another approach, which has been an option in Kensington's MouseWorks software for years, is called "Scroll With Mouse" (formerly known by the unwieldy term "Scroll When You Move The Mouse"). The feature gave users the option of holding down a key or mouse button to turn the entire mouse (or trackball) into a virtual scroll control.

Wheel of Fortune -- The first widely successful attempt to address this problem in hardware was the scroll wheel. The idea was to combine a special wheel on a mouse with software that turned the wheel's movement into window-scrolling instructions. Although the scroll wheel was invented by Mouse Systems (now owned by KYE) in the early 1990s, its popularity skyrocketed in 1996 when Microsoft made it part of their IntelliMouse. Unlike other mouse manufacturers, Microsoft was in the unique position to adapt both their operating systems and applications to include "hooks" that tightly integrated the hardware with scrolling behavior in the software. All of a sudden, scrolling was no longer cumbersome; without moving your hand from the mouse or even having any idea where your pointer was, you could scroll up or down with a flick of the finger. This mechanism was almost immediately embraced by consumers, so that within about two years scroll wheels were the norm on almost all mice - except, incomprehensibly, for those made by Apple, on the grounds that anything more than a single button makes mice seem too complicated.

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The near-universal acceptance of the scroll wheel could have been the happy ending of the story, were it not for two niggling issues. First was the problem of horizontal scrolling. When documents are wider than a window - often the case with spreadsheets and graphics, for example - a single-axis scrolling mechanism only solves half of the problem. Numerous solutions emerged, with varying levels of acceptance. In some cases, holding down the Shift key or another modifier while moving a scroll wheel changes scrolling from vertical to horizontal. A few manufacturers chose to put two wheels on their mice, one for each axis. IBM's TrackPoint device, that miniature joystick that looks like an eraser head, found its way onto some mice in place of a wheel. And more recently, Microsoft began selling mice with "tilt wheel technology," in which the wheel assembly is mounted on a gimbal so that it can tilt to either side, thus scrolling left or right.

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One Ring to Rule Them All -- The other issue was that given the design of some input devices - notably trackballs - there simply isn't a good place to put a wheel so that it is as easily reachable as it would be on a mouse. During my time at Kensington, we spent long hours puzzling over this issue. The solution we arrived at was to replace the vertically oriented scroll wheel with a horizontal ring encircling the trackball. The shape of the ring enables it to be moved easily by the fingertips; users can choose to have clockwise turns scroll down and counterclockwise turns scroll up, or vice-versa. (You wouldn't believe how long and earnestly we argued over which of those two directions should be the default.) The Scroll Ring first appeared on Kensington's TurboRing trackball in 2000, which for a variety of reasons didn't sell especially well. But the company still felt the basic idea was a good one, and in 2003, they released version 7 of their flagship trackball, Expert Mouse - this time with both an optical sensor and a new, improved scroll ring. I have one on my desk right now, and all I can say is that having used Kensington trackballs for over 10 years, my fingers have never been happier.


No discussion of innovative scrolling mechanisms would be complete without mentioning a design that's near to my heart: the no-moving-parts, touch-sensitive, flat scroll sensor. My first encounter with touch-sensitive scrolling came during the development of Kensington's ill-fated WebRacer input device in the late 1990s. Pointer movement was controlled by a touchpad, and the right and bottom edges of the pad behaved just like the scroll bars in windows: slide your finger up or down on the right edge, for example, and the window scrolls at the same speed. Although WebRacer was not a commercial success, flat scrolling reappeared a few years later when the company was trying to design a sleek mouse with no aesthetically jarring protrusions. After many months of effort, they came up with the touch-sensitive pad on StudioMouse. It works just like a scroll wheel, with the added benefit that you can scroll up or down continuously by holding your finger at either end of the sensor.


Then there's a design that combines the touch-sensitivity of a flat scroll sensor with the shape of the scroll ring: the Apple Click Wheel used on all current models of the iPod. The first iPods had scroll wheels that physically moved, and were thus sensitive to dirt, moisture, and other contaminants. Besides providing touch-sensitive scrolling, the cardinal points of the click wheel can be depressed slightly to activate buttons beneath, making for an elegant all-purpose input control.


More Flatter-y -- Notwithstanding Apple's outstanding click wheel design, input devices on Macintosh computers remain behind the times. My current laptop, an Apple PowerBook G4, has a trackpad with no built-in scrolling capabilities (and, frustratingly, just one button). Fortunately I was able to find a wonderful $15 piece of software called SideTrack, which turns the edges of the trackpad into a highly configurable scrolling device much like the WebRacer touchpad - and many Windows-based laptops. This is a great enhancement, because target acquisition is even more difficult with a trackpad than with a mouse.


Having a scrolling mechanism (of whatever kind) on my input device has become a necessity for me. Like cell phones, it seems like a luxury until you get used to it; then you can't do without. So when I see someone laboriously scrolling the old-fashioned way by clicking on arrows, I just cringe. They might as well be using a rotary phone. Hmmm... a ring-shaped input device. Interesting. I guess it's true: what goes around, comes around.

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