How to set the size of a horizontal radio set.
Data type: LOGICAL
Access: Readable/Writeable
Applies to: RADIO-SET widget
This attribute applies to radio sets whose HORIZONTAL attribute are set to TRUE (for horizontal alignment).
If TRUE, the size for each button is equal to the width of the button with the longest label. If FALSE, the size for each button is set according to its label.
You can set this attribute only before the widget is realized.