Choose the Proper Screen-Based Controls 487

Step 7: Choose the Proper Screen-Based Controls 487

Defaults: — If a check box is displayed that contains a choice previously selected or default

choice, display the selected choice as set in the control.

Select/deselect all: — Do not use Select All and Deselect All check boxes.

Mixed-value state: — When a check box represents a value, and a multiple selection encompasses mul-

tiple value occurrences set in both the on and off state, display the check box in a mixed value state. • Fill the check box with another easily differentiable symbol or pattern.

Figure 7.54

— Toggle the check box as follows:

• Selection 1: Set the associated value for all elements. Fill the check box with an

“X” or “check.” • Selection 2: Unset the value for all associated elements. Blank-out the check

box. • Selection 3: Return all elements to their original state. Fill the check box with

the mixed value symbol or pattern.

Pointing. The selection target area should be as large as possible in order to make it

easy to move to. If a small check box is the selection indication method used, the target area should include the box and the choice description text. If the rectan- gular box selection method is used, the entire box should be the target. Highlight the selection choice in some visually distinctive way when the pointer is resting on it and the choice is available for selection. If a check box is the selection indi- cation method used, a distinctive reverse video, reverse color, or dotted or dashed box selection cursor or bar may be used to surround the selected choice description. This cursor should be as long as the longest description plus one space at each end. The cursor should not cover the check box.

Activation. When a choice is selected, distinguish it visually from the unselected

choices. A check box may be marked with an X or check or filled in. Other meth- ods include making the button look depressed or raised through appropriate use of drop shadows. A rectangular box can be highlighted in a manner different from when it is pointed at, or a bolder border can be drawn around it. The style chosen must be consistently applied throughout an application or system.

Defaults. If a selection field is displayed with a choice previously selected or a

default choice, display the currently active choice in the same manner as when it is selected.

Select/deselect all. Do not use Select All and Deselect All check boxes. If this option

488 Part 2: The User Interface Design Process Mixed-value state.

A check box can have three states.

Checked — the associated property or value is set.

Cleared — the associated value or property is not set.

Mixed value — the associated value is set for some, but not all elements of the selection.

An example of the mixed value state would be when a sentence is selected and the selected text is partly bold and partly normal. So, when a check box rep- resents a value, and a selection encompasses multiple value occurrences set in both the on and off state, display the check box in the mixed value state. Fill the check box with another easily differentiable symbol or pattern. Toggle the check box through clicking as described in the preceding guidelines.