(new close-icon%   [parent parent]      [ [callback callback]]       [bg-color bg-color]      [ [horizontal-pad horizontal-pad]       [vertical-pad vertical-pad]])

→ (is-a?/c close-icon%)

parent : (is-a? area-container<%>)

callback : (-> any) = void

bg-color : (or/c #f string (is-a?/c color%))

horizontal-pad : positive-integer? = 4

vertical-pad : positive-integer? = 4

The callback is called when the close icon is clicked.

If bg-color is specified, it is used as the background color of the icon.