taverna-ui/src/main/java/org/apache/taverna/lang/ui/LinePainter.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.taverna.lang.ui;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;

/*
 *  Track the movement of the Caret by painting a background line at the
 *  current caret position.
 *  
 *  Copied from http://www.camick.com/java/source/LinePainter.java
 *  
 *  Written by Rob Camick
 */
public class LinePainter
	implements Highlighter.HighlightPainter, CaretListener, MouseListener, MouseMotionListener
{
	private JTextComponent component;

	private Color color;

	private Rectangle lastView;

	/*
	 *  The line color will be calculated automatically by attempting
	 *  to make the current selection lighter by a factor of 1.2.
	 *
	 *  @param component  text component that requires background line painting
	 */
	public LinePainter(JTextComponent component)
	{
		this(component, null);
		setLighter(component.getSelectionColor());
	}

	/*
	 *  Manually control the line color
	 *
	 *  @param component  text component that requires background line painting
	 *  @param color      the color of the background line
	 */
	public LinePainter(JTextComponent component, Color color)
	{
		this.component = component;
		setColor( color );

		//  Add listeners so we know when to change highlighting

		component.addCaretListener( this );
		component.addMouseListener( this );
		component.addMouseMotionListener( this );

		//  Turn highlighting on by adding a dummy highlight

		try
		{
			component.getHighlighter().addHighlight(0, 0, this);
		}
		catch(BadLocationException ble) {}
	}

	/*
	 *	You can reset the line color at any time
	 *
	 *  @param color  the color of the background line
	 */
	public void setColor(Color color)
	{
		this.color = color;
	}

	/*
	 *  Calculate the line color by making the selection color lighter
	 *
	 *  @return the color of the background line
	 */
	public void setLighter(Color color)
	{
		int red   = Math.min(255, (int)(color.getRed() * 1.2));
		int green = Math.min(255, (int)(color.getGreen() * 1.2));
		int blue  = Math.min(255, (int)(color.getBlue() * 1.2));
		setColor(new Color(red, green, blue));
	}

	//  Paint the background highlight

	public void paint(Graphics g, int p0, int p1, Shape bounds, JTextComponent c)
	{
		try
		{
			Rectangle r = c.modelToView(c.getCaretPosition());
			g.setColor( color );
			g.fillRect(0, r.y, c.getWidth(), r.height);

			if (lastView == null)
				lastView = r;
		}
		catch(BadLocationException ble) {System.out.println(ble);}
	}

	/*
	*   Caret position has changed, remove the highlight
	*/
	private void resetHighlight()
	{
		//  Use invokeLater to make sure updates to the Document are completed,
		//  otherwise Undo processing causes the modelToView method to loop.

		SwingUtilities.invokeLater(new Runnable()
		{
			public void run()
			{
				try
				{
					int offset =  component.getCaretPosition();
					Rectangle currentView = component.modelToView(offset);

					if (lastView == null) {
						lastView = currentView;
					} else {
						//  Remove the highlighting from the previously highlighted line
						if (lastView.y != currentView.y)
						{
							component.repaint(0, lastView.y, component.getWidth(), lastView.height);
							lastView = currentView;
						}
					}
				}
				catch(BadLocationException ble) {}
			}
		});
	}

	//  Implement CaretListener

	public void caretUpdate(CaretEvent e)
	{
		resetHighlight();
	}

	//  Implement MouseListener

	public void mousePressed(MouseEvent e)
	{
		resetHighlight();
	}

	public void mouseClicked(MouseEvent e) {}
	public void mouseEntered(MouseEvent e) {}
	public void mouseExited(MouseEvent e) {}
	public void mouseReleased(MouseEvent e) {}

	//  Implement MouseMotionListener

	public void mouseDragged(MouseEvent e)
	{
		resetHighlight();
	}

	public void mouseMoved(MouseEvent e) {}
}