Tix (Tk Interface Extension), an add-on for the Tk widget set, is an extensive set of over 40 widgets. In general, Tix widgets are more complex and more capable than the widgets provided in Tk. Tix widgets include a ComboBox, a Motif-style FileSelectBox, an MS Windows-style FileSelectBox, a PanedWindow, a NoteBook, a hierarchical list, a directory tree and a file manager. Install the tix package if you want to try out more complicated widgets for Tk. You'll also need to have the tcl and tk packages installed.