Use Simple Interactions

In addition to making sure your program has a simple appearance, you need to make sure that users can perform their tasks using simple interactions. While Windows uses many different types of interaction techniques, let's just consider two: dragging and dropping, and double-clicking.

Dragging and Dropping

As I discuss in Chapter 17, "Direct Manipulation Is Cool" I think dragging and dropping is one of the best features in Windows and I definitely want you to support it. However, it isn't always an especially easy feature to use. The first problem is that the drop target must be visible. And how do you make a drop target visible without accidentally dropping your selections at the wrong place? Try this: open a large document in Microsoft Word, select some text at the head of the document, and drag it to the bottom of the document. While Microsoft Word is nice enough to scroll automatically, the scrolling isn't easy to do. A thin region at the top and bottom of the window lets you scroll when you have a drop source, but it is especially difficult to control the scrolling when the document window is small. And if you accidentally drop the text on the desktop or the taskbar, you will be in for a real surprise. This action will create a scrap object—probably not what you had in mind.

The other problem with dragging and dropping is dragging across a long distance without scrolling. For example, try to drag an object from one corner of the screen to the opposite corner of the screen. It's difficult to move the mouse such a long distance without accidentally releasing the mouse button.

Double-Clicking

One trend in user interface design is to use single-clicking instead of double-clicking when possible. Windows 95 requires less double-clicking than Windows 3.1. For example, the Start menu and taskbar use single clicks where the File Manager and Program Manager use double clicks. Windows 98 gives the user the option to eliminate double-clicking almost entirely with the View As Web Page option. HTML pages have also helped promote single-clicking, since all hypertext links use single-clicking.

Is double-clicking really more difficult than single-clicking? Of course it is. How many times have you accidentally launched several instances of a program by double-clicking its icon on the desktop? This happens to me a lot. The problem is that when you double-click an item but don't get an immediate and obvious response, you think the double click didn't happen so you try again. If you don't perform the double click just right, Windows interprets it as two single clicks. (The wait cursor helps this problem but doesn't completely eliminate it.) On the other hand, how many times have you accidentally launched several instances of a program from the Quick Launch bar? I rarely make this mistake. This is because the single click is much easier to perform and I have confidence that I have successfully performed a single click, even if I don't get immediate feedback from the program.

Are you skeptical? Do you think these interaction techniques are really easy and I am overstating my case? If so, try testing your program with a trackball, an IBM TrackPoint or other similar pointing device, or a touch pad instead of a mouse. If you are like me, any interaction that is too complex becomes immediately obvious when you're using a trackball. In fact, everything seems more complex when using a trackball. Trackballs and touch pads are used on all laptop computers (except IBM notebook computers, which use TrackPoint), so users of these devices represent a significant portion of the market. I personally use a trackball because the Surgeon General has determined that using a mouse can be hazardous to my wrist.

TIP

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Test the program using a trackball. All interactions seem more complex when using a trackball.

When testing with a trackball, I find that some interactions are just too difficult. For example, constantly having to make a selection from a cascading context menu can be especially difficult. For commands that are used often, I find providing plenty of keyboard shortcuts to be helpful.

Keeping the interaction techniques used by your interface simple, and providing alternatives to those techniques, helps your laptop users and your physically impaired users. In fact, it helps everyone else as well.