widget-map-buttons
widget-map-buttons is a compiled Lisp function in `wid-edit.el
'.
(widget-map-buttons FUNCTION &optional BUFFER MAPARG)
Map FUNCTION over the buttons in BUFFER.
FUNCTION is called with the arguments WIDGET and MAPARG.
If FUNCTION returns non-nil, the walk is canceled.
The arguments MAPARG, and BUFFER default to nil and (current-buffer),
respectively.