constructor (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%)) = #f

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.