Java User Group Berlin Brandenburg

package sqlrunner.text;
 
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.Shape;
 
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;
import javax.swing.plaf.TextUI;
import javax.swing.text.BadLocationException;
import javax.swing.text.Element;
import javax.swing.text.Highlighter;
import javax.swing.text.JTextComponent;
import javax.swing.text.LayeredHighlighter;
import javax.swing.text.Position;
import javax.swing.text.Utilities;
import javax.swing.text.View;
 
public class HighlightCurrentLineCaretListener implements CaretListener {
 
    static final Color DEFAULT_COLOR = new Color(230, 230, 250);
 
    private Highlighter.HighlightPainter painter;
 
    private Object highlight;
 
    public HighlightCurrentLineCaretListener() {
 
        this(null);
    }
 
    public HighlightCurrentLineCaretListener(Color highlightColor) {
 
        Color c = highlightColor != null ? highlightColor : DEFAULT_COLOR;
        this.painter = new LineHighlightPainter(c);
    }
 
    public void caretUpdate(CaretEvent evt) {
 
        final JTextComponent comp = (JTextComponent) evt.getSource();
        if (comp != null && this.highlight != null) {
            comp.getHighlighter().removeHighlight(this.highlight);
            this.highlight = null;
        }
        int pos = comp.getCaretPosition();
        final Element elem = Utilities.getParagraphElement(comp, pos);
        int start = elem.getStartOffset();
        int end = elem.getEndOffset();
        try {
            this.highlight = comp.getHighlighter().addHighlight(start,
                                                                end,
                                                                this.painter);
            comp.repaint();
        } catch (BadLocationException ex) {
            ex.printStackTrace();
        }
    }
 
    /**
     * Simple highlight painter that fills a highlighted area with
     * a solid color.
     */
    public static class LineHighlightPainter extends
        LayeredHighlighter.LayerPainter {
 
        private Color color;
 
        /**
         * Constructs a new highlight painter. If <code>c</code> is null,
         * the JTextComponent will be queried for its selection color.
         *
         * @param c
         *            the color for the highlight
         */
        public LineHighlightPainter(Color c) {
 
            this.color = c;
        }
 
        /**
         * Returns the color of the highlight.
         *
         * @return the color
         */
        public Color getColor() {
 
            return this.color;
        }
 
        // --- HighlightPainter methods ---------------------------------------
        /**
         * Paints a highlight.
         *
         * @param g
         *            the graphics context
         * @param offs0
         *            the starting model offset &gt;= 0
         * @param offs1
         *            the ending model offset &gt;= offs1
         * @param bounds
         *            the bounding box for the highlight
         * @param c
         *            the editor
         */
        public void paint(Graphics g, int offs0, int offs1, Shape bounds,
                          JTextComponent c) {
 
            final Rectangle alloc = bounds.getBounds();
            try {
                // --- determine locations ---
                TextUI mapper = c.getUI();
                final Rectangle p0 = mapper.modelToView(c, offs0);
                final Rectangle p1 = mapper.modelToView(c, offs1);
 
                // --- render ---
                if (getColor() == null) {
                    g.setColor(c.getSelectionColor());
                } else {
                    g.setColor(getColor());
                }
                final Rectangle r = p0.union(p1);
                g.fillRect(r.x, r.y, r.width, r.height);
            } catch (BadLocationException e) {
                // can't render
            }
        }
 
        // --- LayerPainter methods ----------------------------
        /**
         * Paints a portion of a highlight.
         *
         * @param g
         *            the graphics context
         * @param offs0
         *            the starting model offset &gt;= 0
         * @param offs1
         *            the ending model offset &gt;= offs1
         * @param bounds
         *            the bounding box of the view, which is not
         *            necessarily the region to paint.
         * @param c
         *            the editor
         * @param view
         *            View painting for
         * @return region drawing occured in
         */
        @Override
        public Shape paintLayer(Graphics g, int offs0, int offs1, Shape bounds,
                                JTextComponent c, View view) {
 
            if (getColor() == null) {
                g.setColor(c.getSelectionColor());
            } else {
                g.setColor(getColor());
            }
            // Should only render part of View.
            try {
                // --- determine locations ---
                Shape shape = view.modelToView(
                                               offs0,
                                               Position.Bias.Forward,
                                               offs1,
                                               Position.Bias.Backward,
                                               bounds);
                Rectangle r = shape instanceof Rectangle ? (Rectangle) shape
                        : shape.getBounds();
                g.fillRect(r.x, r.y, c.getWidth(), r.height);
                return r;
            } catch (BadLocationException e) {
                // can't render
            }
            return null;
        }
    }
}

textComp.addCaretListener(new HighlightCurrentLineCaretListener());