LinePainter.java

/**
 * 
 */
package apu.scratch.converter;

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.
 */
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() + 20, 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);

					// 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) {
	}
}