NAME

       ButtonState, Button, TextButton, PushButton, RadioButton, CheckBox - interactive buttons

SYNOPSIS

       #include <InterViews/button.h>

DESCRIPTION

       Button  is  a class of interactors that can set the value of a piece of state.  ButtonState is a class of
       objects that contain a value and a list of buttons that can set its value.  A value is either an  integer
       or an arbitrary pointer.

       TextButton  is  a  subclass  of Button that has an associated text label to be displayed inside or to the
       right of the button.  PushButton, RadioButton, and CheckBox are subclasses  of  TextButton  that  provide
       particular  displays  for  buttons.   Each kind of button will display itself differently for each of the
       five possible cases: ``enabled'', when the button is listening to input, ``disabled'', when the button is
       not  listening, ``chosen'', when the button's value is equal to its button state's value, ``hit'', when a
       button that is not chosen first receives a DownEvent, and ``same-hit'', when  a  button  that  is  chosen
       receives a DownEvent.

       When  a button receives a DownEvent, it calls the virtual Refresh() to update its display.  It then reads
       input waiting for an UpEvent.  If the UpEvent coordinates are also within the button, then it  calls  the
       virtual Press().  The default Press operation sets the associated state's value to the button's value.

       A  button  can  have  a  list  of attached buttons.  When a button is not chosen its attached buttons are
       ``disabled'', meaning they ignore all input events.

BUTTONSTATE OPERATIONS

       ButtonState()
       ButtonState(int)
       ButtonState(void*)
              Define a button state optionally with an initial value.

       void Attach(Button*)
              Add a button to the list associated with a button state.  The button will  be  notified  when  the
              button state's value is modified.

       void Detach(Button*)
              Remove a button from the list associated with a button state.

       void GetValue(int&)
       void GetValue(void*&)
              Get the value of a button.

       void SetValue(int)
       void SetValue(void*)
              Set the value of a button state and notify all the buttons associated with the state.

       void operator=(ButtonState&)
              Copy  the value of one button state to another.  The button list associated with the source button
              state is not copied.

BUTTON OPERATIONS

       void PushButton(const char* text, ButtonState* s, int v)
       void PushButton(const char* text, ButtonState* s, void* v)
              Construct a button with text in the center and a polygon on the outside.  The polygon  is  like  a
              rectangle,  but with rounded corners.  When chosen, the entire button is drawn with foreground and
              background colors reversed.

       void RadioButton(const char* text, ButtonState* s, int v)
       void RadioButton(const char* text, ButtonState* s, void* v)
              Construct a button with a circle on the left and text on the right.  When hit, a second circle  is
              drawn inside the first.  When chosen, a filled circle is drawn inside the outer circle.

       void CheckBox(const char* text, ButtonState* s, int on, int off)
       void CheckBox(const char* text, ButtonState* s, void* on, void* off)
              Construct  a  button  with  a  rectangle  on  the  left and text on the right.  When hit, a second
              rectangle is drawn inside the first.  When chosen, two diagonal lines  are  drawn  connecting  the
              opposite corners of the rectangle.  When a checkbox is pressed the first time, it sets s to off if
              the value is on and sets s to on otherwise.  Subsequent presses swap the values  of  the  checkbox
              and s.

       void Attach(Button*)
              Add  to  this  button's  list of associated buttons.  These buttons are enabled when the button is
              chosen and disabled when it is not chosen.

       void Detach(Button*)
              Remove a button from this button's list of associated buttons.

       void Disable()
              Stop listening to input events.  Disabled buttons are typically ``grayed out'' by drawing a  half-
              filled rectangle in the background.

       void Enable()
              Start listening to input events.

       void Choose()
              Make the button as chosen, enabling any associated buttons.

       void Handle(Event&)
              If  the  event  type is DownEvent and the button is enabled, call Refresh and read events until an
              UpEvent occurs.  If the button is the target of the UpEvent, then call Press.

       virtual void Press()
              Take the appropriate action for the button being pressed.  The default is to  set  the  associated
              state to the button's value, which will trigger all related buttons to update their display.

       virtual void Refresh()
              Update the button display.

       void SetDimensions(int width, int height)
              Specify  the  natural size of the button.  The default size is a function of the size of the text.
              This routine is obsolete; use Interactor::Reshape instead.

       void UnChoose()
              Mark the button as not chosen, disabling any associated buttons.

SEE ALSO

       Event(3I), Interactor(3I)