This chapter discusses the FLTK event model and how to handle events in your program or widget. Every time a user moves the mouse pointer, clicks a button, or presses a key, an event is generated and sent to your application.
Events can also come from other programs like the window manager.
A mouse button has gone down with the mouse pointing at this widget. The mouse has moved with a button held down. The mouse has been moved to point at this widget. This can be used for highlighting feedback. The focus will change either because the window manager changed which window gets the focus, or because the user tried to navigate using tab, arrows, or other keys.