editbus.java

开源的java 编辑器源代码

/*
 * EditBus.java - The EditBus
 * :tabSize=8:indentSize=8:noTabs=false:
 * :folding=explicit:collapseFolds=1:
 *
 * Copyright (C) 1999 Slava Pestov
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

package org.gjt.sp.jedit;

import java.util.*;
import org.gjt.sp.util.Log;

/**
 * jEdit's global event notification mechanism.<p>
 *
 * Plugins register with the EditBus to receive messages reflecting
 * changes in the application's state, including changes in buffers,
 * views and edit panes, changes in the set of properties maintained
 * by the application, and the closing of the application.<p>
 *
 * The EditBus maintains a list of objects that have requested to receive
 * messages. When a message is sent using this class, all registered
 * components receive it in turn. Classes for objects that subscribe to
 * the EditBus must implement the {@link EBComponent} interface, which
 * defines the single method {@link EBComponent#handleMessage(EBMessage)}.<p>
 *
 * A plugin core class that extends the
 * {@link EBPlugin} abstract class (and whose name ends with
 * <code>Plugin</code> for identification purposes) will automatically be
 * added to the EditBus during jEdit's startup routine.  Any other
 * class - for example, a dockable window that needs to receive
 * notification of buffer changes - must perform its own registration by calling
 * {@link #addToBus(EBComponent)} during its initialization.
 * A convenient place to register in a class derived from <code>JComponent</code>
 * would be in an implementation of the <code>JComponent</code> method
 * <code>addNotify()</code>.<p>
 *
 * Message types sent by jEdit can be found in the
 * {@link org.gjt.sp.jedit.msg} package.<p>
 *
 * Plugins can also send their own messages - any object can send a message to
 * the EditBus by calling the static method {@link #send(EBMessage)}.
 * Most plugins, however, only concern themselves with receiving, not
 * sending, messages.
 *
 * @see org.gjt.sp.jedit.EBComponent
 * @see org.gjt.sp.jedit.EBMessage
 *
 * @author Slava Pestov
 * @author John Gellene (API documentation)
 * @version $Id: EditBus.java,v 1.11 2003/05/01 02:21:26 spestov Exp $
 *
 * @since jEdit 2.2pre6
 */
public class EditBus
{
	//{{{ addToBus() method
	/**
	 * Adds a component to the bus. It will receive all messages sent
	 * on the bus.
	 *
	 * @param comp The component to add
	 */
	public static void addToBus(EBComponent comp)
	{
		synchronized(components)
		{
			components.add(comp);
			copyComponents = null;
		}
	} //}}}

	//{{{ removeFromBus() method
	/**
	 * Removes a component from the bus.
	 * @param comp The component to remove
	 */
	public static void removeFromBus(EBComponent comp)
	{
		synchronized(components)
		{
			components.remove(comp);
			copyComponents = null;
		}
	} //}}}

	//{{{ getComponents() method
	/**
	 * Returns an array of all components connected to the bus.
	 */
	public static EBComponent[] getComponents()
	{
		synchronized(components)
		{
			if (copyComponents == null)
			{
				copyComponents = (EBComponent[])components.toArray(
					new EBComponent[components.size()]);
			}
			return copyComponents;
		}
	} //}}}

	//{{{ send() method
	/**
	 * Sends a message to all components on the bus in turn.
	 * @param message The message
	 */
	public static void send(EBMessage message)
	{
		Log.log(Log.DEBUG,EditBus.class,message.toString());

		// To avoid any problems if components are added or removed
		// while the message is being sent
		EBComponent[] comps = getComponents();

		for(int i = 0; i < comps.length; i++)
		{
			try
			{
				EBComponent comp = comps[i];
				if(Debug.EB_TIMER)
				{
					long start = System.currentTimeMillis();
					comp.handleMessage(message);
					long time = (System.currentTimeMillis() - start);
					if(time != 0)
					{
						Log.log(Log.DEBUG,EditBus.class,comp + ": " + time + " ms");
					}
				}
				else
					comps[i].handleMessage(message);
			}
			catch(Throwable t)
			{
				Log.log(Log.ERROR,EditBus.class,"Exception"
					+ " while sending message on EditBus:");
				Log.log(Log.ERROR,EditBus.class,t);
			}
		}
	} //}}}

	//{{{ Private members
	private static ArrayList components = new ArrayList();
	private static EBComponent[] copyComponents;

	// can't create new instances
	private EditBus() {}
	//}}}
}