
fltk:Fl_Button(x_position,y_position,width,height,"label")

The selection_color method can be used to change the color of
the "hot spot" of buttons. For round/radio and check buttons
it is the dot or check mark. For light buttons it is the light.
For all other buttons it is the whole button in its down state.
selection_color can be replaced with color2 or down_color to
achieve the same effect.

The box types shown in the boxtypes example can be applied to
buttons or (nearly?) any other FLTK widget. The box type for
the hot spot of the special buttons, such as the light button,
can be changed by applying these box types to the down_box.

Keyboard control:
Tab and Shift+Tab are used to navigate forward and backward through
visible widgets. If Fl:visible_focus() has not been set to 0, the
active widget is surrounded by dashed lines, representing focus.
Fl_Return_Button can be activated with the Return key, regardless
of whether or not it has focus. All others can be activated with
the spacebar when the button has focus. 
