Invisible Interfaces

According to our definition of a visible user interface, a feature should be considered invisible if its existence and functionality are not obvious by simple inspection. There are many ways to fail these visibility requirements. Any user interface feature can be invisible if poorly done. Many invisible user interfaces include various kinds of inexplicable buttons, bitmaps, and icons that do not pass the visibility test even though they are in plain sight. While their existence is obvious, their functionality clearly isn't. Another example is a standard user interface element that is programmed to have a nonstandard behavior. Because the user will assume the standard behavior for the element, the element's functionality isn't visible.

As I discussed previously, the user's experience is also a factor. Most of this chapter assumes that the user is familiar with Windows. Any program designed for all users, such as a kiosk, a point-of-sale display, or a museum exhibit, cannot assume that the user knows anything about graphical user interfaces. For this type of user, interface elements such as menus, toolbars, status bars, splitter windows, and cursor hinting should not be considered visible. In fact, for this type of user, pretty much everything should be considered invisible except for text, graphics, command buttons, simple list boxes, edit boxes for which all input is either valid or well understood (such as a password), and possibly check boxes and radio buttons. For this type of user, all the controls used should be simple and have affordance.

For users with at least some graphical user interface experience, the following features are invisible and therefore should never be the sole means of performing a task.

Invisible Existence

• Keyboard shortcuts, especially Alt and Ctrl key sequences and function keys
• Double-clicking
• Nonstandard mouse interactions, such as triple-clicking or chord-clicking
• Context menus

Invisible Functionality

• Buttons with incomprehensible text.
• Incomprehensible icons and bitmaps. The old saying that a picture is worth a thousand words doesn't apply to such graphics.
• Toolbars without tooltips.
• Edit boxes that require a specific format or special values.

Perhaps the ultimate in invisible user interfaces is the MS-DOS prompt box. All that is visible is the command line with the default drive and path and a blinking cursor. If you don't know what to do with it, you will never figure it out just by looking at it.