This section discusses the immediate subclasses of
choice which can be used to build button panels. If you have a group of several buttons, you can use the appropriate
button-panel element to specify them all as a group, rather than using
push-button or check-button to specify each one separately. There are three such elements altogether: push-button-panel, check-button-panel and radio-button-panel. The specifics of each are discussed below.
The arrangement of a number of push buttons into one group can be done with a push-button-panel. Since this provides a panel of buttons which do not maintain a selection when the user clicks on them, push-button-panel is a choice that does not allow a selection. When a button is activated it causes a
:selection-callback, but the button does not maintain the selected state.
The layout of a button panel (for instance, whether items are listed vertically or horizontally) can be specified using the
:layout-class keyword. This can take two values:
'column-layout if you wish buttons to be listed vertically, and
'row-layout if you wish them to be listed horizontally. The default value is
'row-layout. If you define your own layout classes, you can also use these as values to
:layout-class. Layouts, which apply to many other CAPI objects, are discussed in detail in Laying Out CAPI Panes.
A group of radio buttons (a group of buttons of which only one at a time can be selected) is created with the radio-button-panel class. Here is an example of a radio button panel:
A group of check buttons can be created with the check-button-panel class. Any number of check buttons can be selected.
The panels inherit the callbacks functionality from callbacks, most importantly the selection-callback and retract-callback , which are used as the default callbacks for the buttons.
functionality of button panel is inherited from collection. Typically you just use the initarg
:items to specify the items, but in principle you can set the items dynamically. The other important functionality from collection is the
to define the strings that are displayed in the buttons.
Accessing the state of the buttons in check-button-panel and radio-button-panel is done by the selection functionality that is defined on choice. For example, making a check-button-panel with four buttons and the last is selected, and after two seconds selecting the first and the third:
All the button panel classes inherit from button-panel, which defines all the functionality of button panels. This includes a mechanism for specifying the layout of the buttons, images for the buttons, mnemonics, and also default and
button. It also has an initarg
:callbacks to define an individual selection callback for each item.
The function set-button-panel-enabled-items is used dynamically to enable/disable individual items in a panel.
For more control over individual buttons, some (or all) of the items in a panel may be buttons themselves (that is, instances of a subclass of button). The behavior on an item that is actually a button is controlled by accessing the button.
CAPI User Guide and Reference Manual (Macintosh version) - 3 Aug 2017