org.jcsp.awt
Class ActiveMenu

java.lang.Object
  java.awt.MenuComponent
      java.awt.MenuItem
          java.awt.Menu
              org.jcsp.awt.ActiveMenu

All Implemented Interfaces:

MenuContainer, Serializable, Accessible, CSProcess

public class ActiveMenu
extends Menu
implements CSProcess

java.awt.Menu with a channel interface.

Process Diagram

Description

ActiveMenu is a process extension of java.awt.Menu with channels for run-time configuration and event notification. The event channel should be connected to an application-specific server process (instead of registering a passive object as a Listener to this component).

The configure and event channels are settable from a constructor. The event channel delivers the command string associated with this ActiveMenu whenever it is selected. Messages can be sent down the configure channel at any time to configure the component. See the table below for details.

All channels are managed by independent internal handler processes. It is, therefore, safe for a serial application process both to service the event channel and configure the component -- no deadlock can occur.

IMPORTANT: it is essential that a (non-null) event channel from this process is always serviced -- otherwise the Java Event Thread will be blocked and the GUI will stop responding. A simple way to guarantee this is to use channels configured with overwriting buffers. For example:

   final One2OneChannel myMenuEvent = Channel.one2one (new OverWriteOldestBuffer (n));
 
   final ActiveMenu myMenu =
     new ActiveMenu (null, myMenuEvent.out (), "Look at this");
 

This will ensure that the Java Event Thread will never be blocked. Slow or inattentive readers may miss rapidly generated events, but the n most recent events will always be available.

Channel Protocols

Input Channels
configure	String	Change the label on the ActiveMenu to the value of the String
	java.awt.MenuShortcut	Sets the MenuShortcut for the ActiveMenu
	Integer	Inserts a separator at the specified position.
	Boolean	If this is the Boolean.TRUE object, the menu is made active If this is the Boolean.FALSE object, the menu is made inactive Other Boolean objects are ignored
	ActiveMenu.Configure	Invoke the user-defined Configure.configure method on the activeMenu.
Output Channels
event	String	The command for the ActiveMenu (when the menu is selected)

Example

 import java.awt.*;
 import java.awt.event.*;
 import org.jcsp.lang.*;
 import org.jcsp.util.*;
 import org.jcsp.awt.*;
 
 public class ActiveMenuExample {
 
   public static void main (String argv[]) {
 
     final ActiveClosingFrame activeClosingFrame =
       new ActiveClosingFrame ("ActiveCheckboxMenuItem Example");
 
     final ActiveFrame frame = activeClosingFrame.getActiveFrame ();
 
     final MenuBar menuBar = new MenuBar ();
     frame.setMenuBar (menuBar);
 
     final Menu fileMenu = new Menu ("File");
     menuBar.add (fileMenu);
 
     final String[] fileOptions = {"Hello World", "Rocket Science", "CSP",
                                   "Monitors", "Ignore Me", "Goodbye World"};
 
     final Any2OneChannel event[] = Channel.any2oneArray (2, new OverWriteOldestBuffer (10));
 
     final ActiveMenuItem[] fileMenuItem =
       new ActiveMenuItem[fileOptions.length];
     for (int i = 0; i < fileOptions.length; i++) {
       fileMenuItem[i] = new ActiveMenuItem (null, event[0].out (), fileOptions[i]);
       fileMenu.add (fileMenuItem[i]);
     }
 
     fileMenu.addSeparator ();
 
     final Any2OneChannel langConfigure = Channel.any2one ();
     final ActiveMenu langMenu = new ActiveMenu (langConfigure.in (), null, "Language");
     fileMenu.add (langMenu);  // set up the active langMenu as a sub-menu
 
     final String[] langOptions = {"occam-pi", "Java", "Smalltalk", "Algol-60",
                                   "Pascal", "Haskell", "SML", "Lisp"};
 
     final ActiveCheckboxMenuItem[] langCheckboxMenuItem =
       new ActiveCheckboxMenuItem[langOptions.length];
     for (int i = 0; i < langOptions.length; i++) {
       langCheckboxMenuItem[i] =
         new ActiveCheckboxMenuItem (null, event[1].out (), langOptions[i]);
       langMenu.add (langCheckboxMenuItem[i]);
     }
 
     frame.setSize (700, 350);
     frame.setBackground (Color.green);
     frame.setVisible (true);
 
     new Parallel (
       new CSProcess[] {     // don't forget to include all active processes
         langMenu,
         activeClosingFrame,
         new Parallel (fileMenuItem),
         new Parallel (langCheckboxMenuItem),
         new CSProcess () {
           public void run () {
             boolean running = true;
             while (running) {
               final String s = (String) event[0].in ().read ();
               System.out.println ("File ==> `" + s + "' selected ...");
               if (s == fileOptions[0]) {
                 langConfigure.out ().write (Boolean.TRUE);
                 System.out.println ("`Language' enabled ...");
               }
               running = (s != fileOptions[fileOptions.length - 1]);
             }
             frame.setVisible (false);
             System.exit (0);
           }
         },
         new CSProcess () {
           public void run () {
             while (true) {
               final ItemEvent e = (ItemEvent) event[1].in ().read ();
               final String item = (String) e.getItem ();
               System.out.print ("Language ==> `" + item);
               if (e.getStateChange () == ItemEvent.SELECTED) {
                 System.out.println ("' selected ...");
                 if (item == langOptions[0]) {
                   langConfigure.out ().write (Boolean.FALSE);
                   System.out.println ("`Language' disabled ...");
                 }
               } else {
                 System.out.println ("' deselected ...");
               }
             }
           }
         }
       }
     ).run ();
 
   }
 
 }
 

Author:

P.D. Austin and P.H. Welch

See Also:

Menu, ItemEvent, ComponentEvent, FocusEvent, KeyEvent, MouseEvent, OverWriteOldestBuffer, Serialized Form

Nested Class Summary

static interface

ActiveMenu.Configure This enables general configuration of this component.

Nested classes/interfaces inherited from class java.awt.Menu

Menu.AccessibleAWTMenu

Nested classes/interfaces inherited from class java.awt.MenuItem

MenuItem.AccessibleAWTMenuItem

Nested classes/interfaces inherited from class java.awt.MenuComponent

MenuComponent.AccessibleAWTMenuComponent

Constructor Summary

ActiveMenu()
Constructs an ActiveMenu with no initial label and no configuration or event channels.

ActiveMenu(ChannelInput configure, ChannelOutput event)
Constructs an ActiveMenu with configuration and event channels, but with no initial label.

ActiveMenu(ChannelInput configure, ChannelOutput event, String label)
Constructs an ActiveMenu with configuration and event channels and an initial label.

ActiveMenu(ChannelInput configure, ChannelOutput event, String label, boolean tearOff)
Constructs an ActiveMenu with configuration and event channels, an initial label and a tear-off option.

ActiveMenu(String label)
Constructs an ActiveMenu with an initial label, but with no configuration or event channels.

ActiveMenu(String label, boolean tearOff)
Constructs an ActiveMenu with an initial label and a tear-off option, but with no configuration or event channels.

Method Summary

void	run() The main body of this process.
void	setConfigureChannel(ChannelInput configure) Sets the configuration channel for this ActiveMenu.

Methods inherited from class java.awt.Menu

add, add, addNotify, addSeparator, countItems, getAccessibleContext, getItem, getItemCount, insert, insert, insertSeparator, isTearOff, paramString, remove, remove, removeAll, removeNotify

Methods inherited from class java.awt.MenuItem

addActionListener, deleteShortcut, disable, disableEvents, enable, enable, enableEvents, getActionCommand, getActionListeners, getLabel, getListeners, getShortcut, isEnabled, processActionEvent, processEvent, removeActionListener, setActionCommand, setEnabled, setLabel, setShortcut

Methods inherited from class java.awt.MenuComponent

dispatchEvent, getFont, getName, getParent, getPeer, getTreeLock, postEvent, setFont, setName, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.awt.MenuContainer

getFont, postEvent

Constructor Detail

ActiveMenu

public ActiveMenu()

Constructs an ActiveMenu with no initial label and no configuration or event channels.

ActiveMenu

public ActiveMenu(String label)

Constructs an ActiveMenu with an initial label, but with no configuration or event channels.

Parameters:

label - the label on the menu.

ActiveMenu

public ActiveMenu(String label,
                  boolean tearOff)

Constructs an ActiveMenu with an initial label and a tear-off option, but with no configuration or event channels.

Parameters:

label - the label on the menu.

tearOff - if true, this is a tear-off menu.

ActiveMenu

public ActiveMenu(ChannelInput configure,
                  ChannelOutput event)

Constructs an ActiveMenu with configuration and event channels, but with no initial label.

Parameters:

configure - the channel for configuration events -- can be null if no configuration is required.

ActiveMenu

public ActiveMenu(ChannelInput configure,
                  ChannelOutput event,
                  String label)

Constructs an ActiveMenu with configuration and event channels and an initial label.

Parameters:

configure - the channel for configuration events -- can be null if no configuration is required.

label - the label on the menu.

ActiveMenu

public ActiveMenu(ChannelInput configure,
                  ChannelOutput event,
                  String label,
                  boolean tearOff)

Constructs an ActiveMenu with configuration and event channels, an initial label and a tear-off option.

Parameters:

configure - the channel for configuration events -- can be null if no configuration is required.

label - the label on the menu.

tearOff - if true, this is a tear-off menu.

Method Detail

setConfigureChannel

public void setConfigureChannel(ChannelInput configure)

Sets the configuration channel for this ActiveMenu. This method overwrites any configuration channel set in the constructor.

Parameters:

configure - the channel for configuration events -- can be null if no configuration is required.

run

public void run()

The main body of this process.

Specified by:

run in interface CSProcess