The library library(help_message) 
provides support for displaying
balloons. After loading this library, a loc_still 
event causes the system to look for a graphical 
implementing the <-help_message method. If <-help_message: 
tag yields a string, the library shows a little window with the message. 
Moving the pointer out of the area of the graphical or pressing a button 
causes the feedback window to disappear.
This tenchnique is commonly used in modern interfaces to provide feedback on the functions behind icons. See also section 11.3.2.
In addition to registering the global event-handler, the library 
defines ->help_message to the classes visual, graphical 
and menu.
tag (balloon) or extensive 
help message (summary) for the receiving object. At the 
moment
summary is not used.->help_message. User-defined classes may consider 
redefining this method to generate the help-message on-the-fly.
Here is a typical usage for this library.
:- use_module(library(help_message)).
resource(print, image, image('16x16/print.xpm')).
        ...
        send(X, append, new(B, button(print))),
        send(B, label, image(resource(print))),
        send(B, help_message, tag, 'Print document'),