
This example has three button widgets one of which, the Dest button
has a tool tip.

When the Change button is selected, The tooltip message is changed and
a tooltip is added to the Quit button.

The addition of the tooltip to the quit button requires access to the
definition of the Tooltip class.  The code definition of the ToolTip
class was added to the GUI module because I had specified a tooltip
for the Change button. If I had not set up a tooltip in the GUI module I
would have had to add that code manually to the support module.