Appearance vs. Behavior

The character of a program is determined primarily by its appearance—its "look"—and its behavior—its "feel." The focus of user interface style guidelines should be on the appearance of the program. While the guidelines can address the program's behavior, much of the standard Microsoft Windows behavior is already covered in Designing for the User Experience. But note that Designing for the User Experience doesn't specify all user interface behaviors. For example, should a command button respond to a double click? The book doesn't say, but such behavior would be a bad idea simply because users don't expect command buttons to respond to double clicks. (In fact, for the standard Windows buttons, only owner-draw and radio buttons receive a BN_DOUBLECLICKED notification code via the WM_COMMAND message. Radio buttons receive double clicks because they can be considered equivalent to a single-selection list, which also receives double clicks. However, a custom command button could respond to double clicks.) For another example, should a list box have a horizontal scroll bar? Again, the standards don't say, but it is generally accepted that horizontal scrolling should be avoided because it makes the list text difficult to read.