Special Properties

BITMAP-NUMBER (numeric)

This property identifies a particular bitmap image to use with the radio button. If you explicitly name this property when creating a control, the BITMAP style is automatically applied by the compiler. Note that this does not occur if you use the PROPERTY phrase to specify this property (by giving its identifying number). See Paged List Boxes for more information.

BITMAP-HANDLE (handler)

This property identifies the bitmap image strip to use with the radio button. See Paged List Boxes for more information.

TERMINATION-VALUE (numeric)

This property works in a manner identical to the TERMINATION-VALUE push button property. This property is used only when the NOTIFY style is also used. The compiler applies the NOTIFY style automatically if you explicitly name this property when creating a control. Note that the NOTIFY style is not automatically applied if you use the PROPERTY phrase to specify this property (by giving its identifying number).

EXCEPTION-VALUE (numeric)

This property works in a manner identical to the push button property of the same name. This property is used only when the NOTIFY style is also used. The compiler applies the NOTIFY style automatically if you explicitly name this property when creating a control. Note that the NOTIFY style is not automatically applied if you use the PROPERTY phrase to specify this property (by giving its identifying number).

GROUP (numeric)

Radio buttons usually operate in groups of related buttons. Normally, only one button of the group may be selected. When a button is selected, all other buttons of the same group are unselected. The GROUP property describes which buttons belong together. In any one floating window, all radio buttons with the same non-zero GROUP property value are treated as a single group. The runtime will ensure that only one button in a group is selected at any one time.

The default GROUP value is 1. If all radio buttons on the same floating window retain the default value, they will be treated as a single group.

Radio buttons with a GROUP value of 0 do not perform any checks to ensure that only one button is selected. These buttons behave much like check boxes; each one may be independently selected.

GROUP-VALUE (numeric)

This property simplifies the process of managing a group of radio buttons. Normally, the program must determine which button in a group is selected by examining the value of each button. The button with a value of 1 is the selected button. The GROUP-VALUE property is used to turn the value checking process into a single operation. You assign each radio button in a group a distinct GROUP-VALUE number. This links each button with its corresponding GROUP-VALUE. In this way, you can determine which button is selected by assigning all of the buttons in the group the same VALUE data item. The data item will hold the GROUP-VALUE number of the selected radio button.

Technically, this works as follows. For any radio button with a non-zero GROUP-VALUE property, a selected button will update its VALUE data item only during an ACCEPT. A selected button will return its GROUP-VALUE property as its VALUE. During a DISPLAY, a radio button will be selected only if its VALUE matches its GROUP-VALUE. Any other VALUE will be treated as a VALUE of zero.

Use this by assigning distinct GROUP-VALUE numbers to each button in a group, and by assigning all the buttons to the same VALUE data item. Then you can select a button by moving the button's GROUP-VALUE number to the VALUE data item and updating all the buttons. On input, you can determine which button is currently selected by simply examining the VALUE data item. It will contain the GROUP-VALUE number of the selected button.

The default value for GROUP-VALUE is zero, which disables the GROUP-VALUE mechanism.