All the widget types in this chapter are concerned with the need to deal with more information than will fit on the screen. This requires some of the information to be missing from the display. Typically this missing information can be reached by scrolling or by clicking on a button that brings up a temporary window.

Lists are often too long to display on the screen – scrollbars provide a way of letting users navigate through them.

Menus give users the power to initiate actions and change operating parameters but menus take up too much room to remain on the screen when they are not in use. You can think of a menubutton as a partially displayed menu that brings up the full display when the user clicks on it.

Tk's normal menubutton produces a menu that shows itself below the button. This is useful for menu bars at the top of a window. Tk has a cascade button for use within menus – this produces a menu on the side of the button.

Finally, Tk supports the kind of menu which appears above and below its button. These are called options menus and are implemented with a special library command, tk_optionMenu.

• Listboxes
• Scrollbars
• Menus and Menubuttons
• Option Menus
• Solutions to Exercises