RadioButton

Wire name radiobutton

One of a set of mutually exclusive choices. Selecting one clears the others in its group.

p=new panel layout=vbox children={
	new radiobutton caption="Left"   group=justify checked
	new radiobutton caption="Center" group=justify
	new radiobutton caption="Right"  group=justify
}

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Properties

Property	Type	Default	Meaning
caption	string	—	Radio button label text.
checked	flag	false	Whether this button is selected.
group	word	—	Radio group membership.
wrap	flag	false	Word-wrap the label.

Plus the common properties.

Events

toggle — The selected state changed. Selecting one button in a group unsets its siblings, so a group change raises this on more than one button.

Field	Type	Meaning
trinket	uint	The radio button's object ID.
checked	flag	The new state.

One user action raises this more than once. Selecting a button clears its previously selected sibling, and that sibling reports its own change — so a group of three produces a toggle with checked unset, and one with it set. Handle the set one and ignore the rest, or track the group by which button last reported checked.

Groups are a name, not a container

group= is a plain word. Buttons that share it on the same connection exclude one another — no wrapper trinket, no reliance on being siblings:

new radiobutton caption="Left"  group=justify
new panel children={
	new radiobutton caption="Right" group=justify    # different parent, same group
}

The groups live in the connection, which has two consequences worth knowing:

• Scope is the connection. Two applications, or two connections from one application, cannot collide on a group name.
• Position does not matter. Grouping is not inferred from layout, so moving a button between panels does not silently change what it excludes.

A button with no group= belongs to no group and excludes nothing — it behaves like a checkbox that cannot be unchecked by clicking. That is almost never what is wanted; if a radio button appears not to exclude its neighbours, a missing or misspelled group= is the first thing to check.

Keys and mouse

The same as Button: Space and Return select, a click selects, and it takes focus by Tab and by click.

Behavior

No action=. Unlike Button and CheckBox, a radio button has no action= property and never raises command. A choice among options is a state to read when something else is invoked, not a command in itself.

Wrapping. wrap word-wraps the label.

Accessibility. Role RadioButton, with the selected state reported.

See also

CheckBox · Button · ComboBox — the same choice as a list · Common Properties