Choose the Proper Screen-Based Controls 467

Step 7: Choose the Proper Screen-Based Controls 467

— Text boxes for variable-length data must be large enough to contain the majority of the entries. — Where entries may be larger than the entry field, scrolling must be provided to permit keying into, or viewing, the entire field. — Employ word wrapping for continuous text in multiple-line text boxes.

Highlighting: — Call attention to text box data through a highlighting technique.

• Higher intensity. • If color is used, choose one that both complements the screen background and

contrasts well with it.

Unavailable fields: — Gray-out temporarily unavailable text boxes.

Fonts: — To support multiple fonts, use a rich-text box.

Structure.

A text box should attract attention, but not detract from the legibility of

the data contained within it, be capable of allowing an indication of the structure of the data contained within it, and indicate the appropriate number of characters to be keyed into it. An early study found that, in meeting these objectives, a bro- ken underscore and an outlined box were the best delimiters for screen entry fields. The older text-based screens traditionally have used the underscore as the delimiter; graphical screens, the outlined box. Interestingly, both resemble the coding areas most frequently found on paper forms. To visually indicate that it is an enterable field, present the box in a recessed manner, as is done by Microsoft Windows.

Present display/read-only text boxes on the window background. To make text boxes more readable, it is desirable to break them up into logical pieces. Slashes, dashes, and spaces should be inserted into the entry fields as illustrated.

Segment long text boxes by including slashes, dashes, or other common delimiters between their logical groups. For fixed-length data, provide multiple logical boxes using auto-skip to move between them.

Size. The size of a field must give an approximate indication of the data length. Text

boxes for fixed-length data must be long enough to contain the entry. Variable- length text boxes should be large enough to contain the majority of the entries. The size of a variable-length text box will be dependent on field alignment, space utilization, and aesthetics. If a text box is not large enough to key or view the entire entry, it must be scrollable. Scrolling, however, should be avoided when- ever possible.

Highlighting. Text box data (as opposed to captions) is the most important part

of a screen. Call attention to it through highlighting techniques. With mono- chrome screens, display it bright or in high intensity. With color, use the brightest colors. If a box is the delimiter, choose a background color that complements the screen body background and provides good contrast with the color chosen for the data.

468 Part 2: The User Interface Design Process

Temporarily unavailable. For fields temporarily unavailable for entry, gray-out the box and its associated label. This temporary graying out implies, however, that the user can perform some action that will again make the field enterable.

Rich-text boxes. Most text boxes typically support only the standard system font. A Microsoft Windows rich-text box is similar to a text box but provides, in addition, font properties, such as typeface, size, color, bold, and italics. It also supports character and paragraph alignment, tabs, indents, and numbering, as well as printing.