path: root/org.eclipse.ui.workbench.texteditor/src/org/eclipse/ui/texteditor/EditorStatusLine.java

/**********************************************************************
Copyright (c) 2000, 2002 IBM Corp. and others.
All rights reserved. This program and the accompanying materials
are made available under the terms of the Common Public License v1.0
which accompanies this distribution, and is available at
http://www.eclipse.org/legal/cpl-v10.html

Contributors:
    IBM Corporation - Initial implementation
**********************************************************************/

package org.eclipse.ui.texteditor;

import org.eclipse.swt.graphics.Image;

import org.eclipse.jface.text.Assert;

import org.eclipse.jface.action.IStatusLineManager;
import org.eclipse.jface.viewers.ISelectionChangedListener;
import org.eclipse.jface.viewers.ISelectionProvider;
import org.eclipse.jface.viewers.SelectionChangedEvent;

/**
 * An editor status line.
 * The selection provider of the editor triggers the status line to be cleared.
 * @since 2.1
 */
class EditorStatusLine implements IEditorStatusLine {

	/**
	 * Clears the status line on selection changed.
	 */
	private class StatusLineClearer implements ISelectionChangedListener {
		public void selectionChanged(SelectionChangedEvent event) {
			fStatusLineManager.setErrorMessage(null);

			Assert.isTrue(this == fStatusLineClearer);
			uninstallStatusLineClearer();
		}
	};

	/** The status line manager. */
	private final IStatusLineManager fStatusLineManager;

	/** The selection provider. */
	private final ISelectionProvider fSelectionProvider;
	
	/** The status line clearer, <code>null</code> if not installed. */
	private StatusLineClearer fStatusLineClearer;

	/**
	 * Constructor for EditorStatusLine.
	 */
	public EditorStatusLine(IStatusLineManager statusLineManager, ISelectionProvider selectionProvider) {

		Assert.isNotNull(statusLineManager);
		Assert.isNotNull(selectionProvider);		

		fStatusLineManager= statusLineManager;		
		fSelectionProvider= selectionProvider;
	}
	
	/**
	 * Returns the status line manager.
	 */
	public IStatusLineManager getStatusLineManager() {
		return fStatusLineManager;	
	}

	/**
	 * Returns the selection provider.
	 */	
	public ISelectionProvider getSelectionProvider() {
		return fSelectionProvider;	
	}

	/*
	 * @see org.eclipse.ui.texteditor.IStatusLine#setMessage(boolean, String, Image)
	 */
	public void setMessage(boolean error, String message, Image image) {

		if (error)
			fStatusLineManager.setErrorMessage(image, message);
		else
			fStatusLineManager.setMessage(image, message);

		if (isMessageEmpty(message))
			uninstallStatusLineClearer();			
		else
			installStatusLineClearer();
	}

	private static boolean isMessageEmpty(String message) {
		return message == null || message.trim().length() == 0;
	}

	private void uninstallStatusLineClearer() {
		if (fStatusLineClearer == null)
			return;

		fSelectionProvider.removeSelectionChangedListener(fStatusLineClearer);
		fStatusLineClearer= null;
	}
	
	private void installStatusLineClearer() {
		if (fStatusLineClearer != null)
			return;
			
		StatusLineClearer statusLineClearer= new StatusLineClearer();
		fSelectionProvider.addSelectionChangedListener(statusLineClearer);
		fStatusLineClearer= statusLineClearer;		
	}
}