Investigating with the F-Script tool for Cocoa, I see that this part of Xcode's UI is implemented by an instance of an NSMatrix
with the following key observations:
- Its cells are custom classes derived from
NSButtonCell
, presumably for custom drawing and some eventing. - The
mode
property of theNSMatrix
instance is set toNSRadioModeMatrix
, to make sure that only one cell gets selected.