Recognizing the need to write reactor-based GUI applications, the ACE community has created several reactor extensions for use with X Window System. Each of these extends the ACE_Select_Reactor to work with a specific toolkit. By using these reactors, your GUI application can remain single threaded yet still respond to both GUI events, such as button presses, any your own application events. . The ACE_FoxReactor integrates with the FOX toolkit.