CSP for Java (JCSP) 1.0-rc7 API Specification: Class ActiveFrame

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CSP for Java
(JCSP) 1.0-rc7

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jcsp.awt
Class ActiveFrame

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--java.awt.Window
                    |
                    +--java.awt.Frame
                          |
                          +--jcsp.awt.ActiveFrame

All Implemented Interfaces:: Accessible, CSProcess, ImageObserver, MenuContainer, Serializable

public class ActiveFrame
extends Frame
implements CSProcess

java.awt.Frame with a channel interface.

Process Diagram

                           _________________
                          |                 |
                          |                 | event
                          |                 |----->-----
                          |                 | (java.awt.event.WindowEvent)
                          |                 |
                          |                 | containerEvent
                          |                 |----->-----
                          |                 | (java.awt.event.ContainerEvent)
                          |                 |
                          |                 | componentEvent
                          |                 |----->-----
                          |                 | (java.awt.event.ComponentEvent)
                          |                 |
                configure |                 | focusEvent
               ----->-----|   ActiveFrame   |----->-----
      (java.lang.Boolean) |                 | (java.awt.event.FocusEvent)
  (ActiveFrame.Configure) |                 |
                          |                 | keyEvent
                          |                 |----->-----
                          |                 | (java.awt.event.KeyEvent)
                          |                 |
                          |                 | mouseEvent
                          |                 |----->-----
                          |                 | (java.awt.event.MouseEvent)
                          |                 |
                          |                 | mouseMotionEvent
                          |                 |----->-----
                          |                 | (java.awt.event.MouseEvent)
                          |_________________|

Description

ActiveFrame is a process extension of java.awt.Frame with channels for run-time configuration and event notification. The event channels should be connected to one or more application-specific server processes (instead of registering a passive object as a Listener to this component).

All channels are optional. The configure and event channels are settable from a constructor. The event channel delivers a WindowEvent whenever one is generated on the ActiveFrame. Other event channels can be added to notify the occurrence of any other events the component generates (by calling the appropriate addXXXEventChannel method before the process is run). 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 an event channel and configure the component -- no deadlock can occur.

IMPORTANT: it is essential that event channels from this process are 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 myWindowEvent =
     One2OneChannel.create (new OverWriteOldestBuffer (n));
   final One2OneChannel myMouseEvent =
     One2OneChannel.create (new OverWriteOldestBuffer (n));
 
   final ActiveFrame myFrame = new ActiveFrame (myWindowEvent);
   myFrame.addMouseEventChannel (myMouseEvent);

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	Boolean	If this is the `Boolean.TRUE` object, the frame is made visible If this is the `Boolean.FALSE` object, the frame is made invisible Other `Boolean` objects are ignored
configure	ActiveFrame.Configure	Invoke the user-defined `Configure.configure` method on the frame.
Output Channels
event	WindowEvent	The `WindowEvent` generated by the component
containerEvent	ContainerEvent	See the `addContainerEventChannel` method.
componentEvent	ComponentEvent	See the `addComponentEventChannel` method.
focusEvent	FocusEvent	See the `addFocusEventChannel` method.
keyEvent	KeyEvent	See the `addKeyEventChannel` method.
mouseEvent	MouseEvent	See the `addMouseEventChannel` method.
mouseMotionEvent	MouseEvent	See the `addMouseMotionEventChannel` method.

Example

 import java.awt.*;
 import java.awt.event.*;
 import jcsp.lang.*;
 import jcsp.util.*;
 import jcsp.awt.*;
 
 public class ActiveFrameButtonExample {
 
   public static void main (String argv[]) {
 
     final Any2OneChannel windowEvent =
       Any2OneChannel.create (new OverWriteOldestBuffer (10));
 
     final ActiveFrame frame =
       new ActiveFrame (null, windowEvent, "ActiveButton Example");
 
     final String[] label = {"Hello World", "Rocket Science", "CSP",
                             "Monitors", "Ignore Me", "Goodbye World"};
 
     final Any2OneChannel buttonEvent =
       Any2OneChannel.create (new OverWriteOldestBuffer (10));
 
     final ActiveButton[] button = new ActiveButton[label.length];
     for (int i = 0; i < label.length; i++) {
       button[i] = new ActiveButton (null, buttonEvent, label[i]);
     }
 
     frame.setSize (300, 200);
     frame.setLayout (new GridLayout (label.length/2, 2));
     for (int i = 0; i < label.length; i++) {
       frame.add (button[i]);
     }
     frame.setVisible (true);
 
     new Parallel (
       new CSProcess[] {
         new Parallel (button),
         new CSProcess () {                 // respond to window events
           public void run () {
             boolean running = true;
             while (running) {
               final WindowEvent w = (WindowEvent) windowEvent.read ();
               switch (w.getID ()) {
                 case WindowEvent.WINDOW_CLOSING:
                   System.out.println ("*** WINDOW_CLOSING ...");
                   running = false;
                 break;
                 default:
                   System.out.println (w);
                 break;
               }
             }
             frame.setVisible (false);
             System.exit (0);
           }
         },
         new CSProcess () {                 // respond to button events
           public void run () {
             boolean running = true;
             while (running) {
               final String s = (String) buttonEvent.read ();
               System.out.println ("Button `" + s + "' pressed ...");
               running = (s != label[label.length - 1]);
             }
             frame.setVisible (false);
             System.exit (0);
           }
         }
       }
     ).run ();
 
   }
 
 }

Author:: P.D.Austin and P.H.Welch
See Also:: ActiveClosingFrame, Frame, ContainerEvent, ComponentEvent, FocusEvent, KeyEvent, MouseEvent, OverWriteOldestBuffer, Serialized Form

Constructor Detail

ActiveFrame

public ActiveFrame()

Constructs a new ActiveFrame with no title and no configuration or event channels.

ActiveFrame

public ActiveFrame(String title)

Constructs a new ActiveFrame with a title but no configuration or event channels.

Parameters:: title - the title for the frame.

ActiveFrame

public ActiveFrame(ChannelInput configure,
                   ChannelOutput event)

Constructs a new ActiveFrame with configuration and event channels, but no title.

Parameters:: configure - the channel for configuration events -- can be null if no configuration is required.; event - a WindowEvent will be output whenever it occurs -- can be null if no notification is required.

ActiveFrame

public ActiveFrame(ChannelInput configure,
                   ChannelOutput event,
                   String title)

Constructs a new ActiveFrame with configuration and event channels and a title.

Parameters:: configure - the channel for configuration events -- can be null if no configuration is required.; event - a WindowEvent will be output whenever it occurs -- can be null if no notification is required.; title - the title for the frame.

Method Detail

setConfigureChannel

public void setConfigureChannel(ChannelInput configure)

Sets the configuration channel for this ActiveFrame. 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.

addContainerEventChannel

public void addContainerEventChannel(ChannelOutput containerEvent)

Add a new channel to this component that will be used to notify that a ContainerEvent has occurred. This should be used instead of registering a ContainerListener with the component. It is possible to add more than one Channel by calling this method multiple times If the channel passed is null, no action will be taken.