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The ANTLR 4 grammar compiler.
/*
* [The "BSD license"]
* Copyright (c) 2012 Terence Parr
* Copyright (c) 2012 Sam Harwell
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.antlr.v4.gui;
import org.abego.treelayout.NodeExtentProvider;
import org.abego.treelayout.TreeForTreeLayout;
import org.abego.treelayout.TreeLayout;
import org.abego.treelayout.util.DefaultConfiguration;
import org.antlr.v4.runtime.ParserRuleContext;
import org.antlr.v4.runtime.misc.NotNull;
import org.antlr.v4.runtime.misc.Nullable;
import org.antlr.v4.runtime.misc.Utils;
import org.antlr.v4.runtime.tree.ErrorNode;
import org.antlr.v4.runtime.tree.Tree;
import org.antlr.v4.runtime.tree.Trees;
import javax.imageio.ImageIO;
import javax.print.PrintException;
import javax.swing.BorderFactory;
import javax.swing.Icon;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JDialog;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSlider;
import javax.swing.JSplitPane;
import javax.swing.JTree;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.filechooser.FileFilter;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;
import javax.swing.tree.TreeSelectionModel;
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Desktop;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.awt.geom.CubicCurve2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.prefs.Preferences;
@SuppressWarnings("serial")
public class TreeViewer extends JComponent {
public static final Color LIGHT_RED = new Color(244, 213, 211);
public static class DefaultTreeTextProvider implements TreeTextProvider {
private final List ruleNames;
public DefaultTreeTextProvider(@Nullable List ruleNames) {
this.ruleNames = ruleNames;
}
@Override
public String getText(Tree node) {
return String.valueOf(Trees.getNodeText(node, ruleNames));
}
}
public static class VariableExtentProvide implements NodeExtentProvider {
TreeViewer viewer;
public VariableExtentProvide(TreeViewer viewer) {
this.viewer = viewer;
}
@Override
public double getWidth(Tree tree) {
FontMetrics fontMetrics = viewer.getFontMetrics(viewer.font);
String s = viewer.getText(tree);
int w = fontMetrics.stringWidth(s) + viewer.nodeWidthPadding*2;
return w;
}
@Override
public double getHeight(Tree tree) {
FontMetrics fontMetrics = viewer.getFontMetrics(viewer.font);
int h = fontMetrics.getHeight() + viewer.nodeHeightPadding*2;
String s = viewer.getText(tree);
String[] lines = s.split("\n");
return h * lines.length;
}
}
protected TreeTextProvider treeTextProvider;
protected TreeLayout treeLayout;
protected java.util.List highlightedNodes;
protected String fontName = "Helvetica"; //Font.SANS_SERIF;
protected int fontStyle = Font.PLAIN;
protected int fontSize = 11;
protected Font font = new Font(fontName, fontStyle, fontSize);
protected double gapBetweenLevels = 17;
protected double gapBetweenNodes = 7;
protected int nodeWidthPadding = 2; // added to left/right
protected int nodeHeightPadding = 0; // added above/below
protected int arcSize = 0; // make an arc in node outline?
protected double scale = 1.0;
protected Color boxColor = null; // set to a color to make it draw background
protected Color highlightedBoxColor = Color.lightGray;
protected Color borderColor = null;
protected Color textColor = Color.black;
public TreeViewer(@Nullable List ruleNames, Tree tree) {
setRuleNames(ruleNames);
if ( tree!=null ) {
setTree(tree);
}
setFont(font);
}
private void updatePreferredSize() {
setPreferredSize(getScaledTreeSize());
invalidate();
if (getParent() != null) {
getParent().validate();
}
repaint();
}
// ---------------- PAINT -----------------------------------------------
private boolean useCurvedEdges = false;
public boolean getUseCurvedEdges() {
return useCurvedEdges;
}
public void setUseCurvedEdges(boolean useCurvedEdges) {
this.useCurvedEdges = useCurvedEdges;
}
protected void paintEdges(Graphics g, Tree parent) {
if (!getTree().isLeaf(parent)) {
BasicStroke stroke = new BasicStroke(1.0f, BasicStroke.CAP_ROUND,
BasicStroke.JOIN_ROUND);
((Graphics2D)g).setStroke(stroke);
Rectangle2D.Double parentBounds = getBoundsOfNode(parent);
double x1 = parentBounds.getCenterX();
double y1 = parentBounds.getMaxY();
for (Tree child : getTree().getChildren(parent)) {
Rectangle2D.Double childBounds = getBoundsOfNode(child);
double x2 = childBounds.getCenterX();
double y2 = childBounds.getMinY();
if (getUseCurvedEdges()) {
CubicCurve2D c = new CubicCurve2D.Double();
double ctrlx1 = x1;
double ctrly1 = (y1+y2)/2;
double ctrlx2 = x2;
double ctrly2 = y1;
c.setCurve(x1, y1, ctrlx1, ctrly1, ctrlx2, ctrly2, x2, y2);
((Graphics2D) g).draw(c);
} else {
g.drawLine((int) x1, (int) y1,
(int) x2, (int) y2);
}
paintEdges(g, child);
}
}
}
protected void paintBox(Graphics g, Tree tree) {
Rectangle2D.Double box = getBoundsOfNode(tree);
// draw the box in the background
boolean ruleFailedAndMatchedNothing = false;
if ( tree instanceof ParserRuleContext ) {
ParserRuleContext ctx = (ParserRuleContext) tree;
ruleFailedAndMatchedNothing = ctx.exception != null &&
ctx.stop != null && ctx.stop.getTokenIndex() < ctx.start.getTokenIndex();
}
if ( isHighlighted(tree) || boxColor!=null ||
tree instanceof ErrorNode ||
ruleFailedAndMatchedNothing)
{
if ( isHighlighted(tree) ) g.setColor(highlightedBoxColor);
else if ( tree instanceof ErrorNode || ruleFailedAndMatchedNothing ) g.setColor(LIGHT_RED);
else g.setColor(boxColor);
g.fillRoundRect((int) box.x, (int) box.y, (int) box.width - 1,
(int) box.height - 1, arcSize, arcSize);
}
if ( borderColor!=null ) {
g.setColor(borderColor);
g.drawRoundRect((int) box.x, (int) box.y, (int) box.width - 1,
(int) box.height - 1, arcSize, arcSize);
}
// draw the text on top of the box (possibly multiple lines)
g.setColor(textColor);
String s = getText(tree);
String[] lines = s.split("\n");
FontMetrics m = getFontMetrics(font);
int x = (int) box.x + arcSize / 2 + nodeWidthPadding;
int y = (int) box.y + m.getAscent() + m.getLeading() + 1 + nodeHeightPadding;
for (int i = 0; i < lines.length; i++) {
text(g, lines[i], x, y);
y += m.getHeight();
}
}
public void text(Graphics g, String s, int x, int y) {
// System.out.println("drawing '"+s+"' @ "+x+","+y);
s = Utils.escapeWhitespace(s, true);
g.drawString(s, x, y);
}
@Override
public void paint(Graphics g) {
super.paint(g);
if ( treeLayout==null ) {
return;
}
Graphics2D g2 = (Graphics2D)g;
// anti-alias the lines
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
// Anti-alias the text
g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
// AffineTransform at = g2.getTransform();
// g2.scale(
// (double) this.getWidth() / 400,
// (double) this.getHeight() / 400);
//
// g2.setTransform(at);
paintEdges(g, getTree().getRoot());
// paint the boxes
for (Tree Tree : treeLayout.getNodeBounds().keySet()) {
paintBox(g, Tree);
}
}
@Override
protected Graphics getComponentGraphics(Graphics g) {
Graphics2D g2d=(Graphics2D)g;
g2d.scale(scale, scale);
return super.getComponentGraphics(g2d);
}
// ----------------------------------------------------------------------
private static final String DIALOG_WIDTH_PREFS_KEY = "dialog_width";
private static final String DIALOG_HEIGHT_PREFS_KEY = "dialog_height";
private static final String DIALOG_X_PREFS_KEY = "dialog_x";
private static final String DIALOG_Y_PREFS_KEY = "dialog_y";
private static final String DIALOG_DIVIDER_LOC_PREFS_KEY = "dialog_divider_location";
private static final String DIALOG_VIEWER_SCALE_PREFS_KEY = "dialog_viewer_scale";
@NotNull
protected static JDialog showInDialog(final TreeViewer viewer) {
final JDialog dialog = new JDialog();
dialog.setTitle("Parse Tree Inspector");
final Preferences prefs = Preferences.userNodeForPackage(TreeViewer.class);
// Make new content panes
final Container mainPane = new JPanel(new BorderLayout(5,5));
final Container contentPane = new JPanel(new BorderLayout(0,0));
contentPane.setBackground(Color.white);
// Wrap viewer in scroll pane
JScrollPane scrollPane = new JScrollPane(viewer);
// Make the scrollpane (containing the viewer) the center component
contentPane.add(scrollPane, BorderLayout.CENTER);
JPanel wrapper = new JPanel(new FlowLayout());
// Add button to bottom
JPanel bottomPanel = new JPanel(new BorderLayout(0,0));
contentPane.add(bottomPanel, BorderLayout.SOUTH);
JButton ok = new JButton("OK");
ok.addActionListener(
new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
dialog.dispatchEvent(new WindowEvent(dialog, WindowEvent.WINDOW_CLOSING));
}
}
);
wrapper.add(ok);
// Add an export-to-png button right of the "OK" button
JButton png = new JButton("Export as PNG");
png.addActionListener(
new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
generatePNGFile(viewer, dialog);
}
}
);
wrapper.add(png);
bottomPanel.add(wrapper, BorderLayout.SOUTH);
// Add scale slider
double lastKnownViewerScale = prefs.getDouble(DIALOG_VIEWER_SCALE_PREFS_KEY, viewer.getScale());
viewer.setScale(lastKnownViewerScale);
int sliderValue = (int) ((lastKnownViewerScale - 1.0) * 1000);
final JSlider scaleSlider = new JSlider(JSlider.HORIZONTAL, -999, 1000, sliderValue);
scaleSlider.addChangeListener(
new ChangeListener() {
@Override
public void stateChanged(ChangeEvent e) {
int v = scaleSlider.getValue();
viewer.setScale(v / 1000.0 + 1.0);
}
}
);
bottomPanel.add(scaleSlider, BorderLayout.CENTER);
// Add a JTree representing the parser tree of the input.
JPanel treePanel = new JPanel(new BorderLayout(5, 5));
// An "empty" icon that will be used for the JTree's nodes.
Icon empty = new EmptyIcon();
UIManager.put("Tree.closedIcon", empty);
UIManager.put("Tree.openIcon", empty);
UIManager.put("Tree.leafIcon", empty);
Tree parseTreeRoot = viewer.getTree().getRoot();
TreeNodeWrapper nodeRoot = new TreeNodeWrapper(parseTreeRoot, viewer);
fillTree(nodeRoot, parseTreeRoot, viewer);
final JTree tree = new JTree(nodeRoot);
tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
tree.addTreeSelectionListener(new TreeSelectionListener() {
@Override
public void valueChanged(TreeSelectionEvent e) {
JTree selectedTree = (JTree) e.getSource();
TreePath path = selectedTree.getSelectionPath();
if (path!=null) {
TreeNodeWrapper treeNode = (TreeNodeWrapper) path.getLastPathComponent();
// Set the clicked AST.
viewer.setTree((Tree) treeNode.getUserObject());
}
}
});
treePanel.add(new JScrollPane(tree));
// Create the pane for both the JTree and the AST
final JSplitPane splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,
treePanel, contentPane);
mainPane.add(splitPane, BorderLayout.CENTER);
dialog.setContentPane(mainPane);
// make viz
WindowListener exitListener = new WindowAdapter() {
public void windowClosing(WindowEvent e) {
prefs.putInt(DIALOG_WIDTH_PREFS_KEY, (int) dialog.getSize().getWidth());
prefs.putInt(DIALOG_HEIGHT_PREFS_KEY, (int) dialog.getSize().getHeight());
prefs.putDouble(DIALOG_X_PREFS_KEY, dialog.getLocationOnScreen().getX());
prefs.putDouble(DIALOG_Y_PREFS_KEY, dialog.getLocationOnScreen().getY());
prefs.putInt(DIALOG_DIVIDER_LOC_PREFS_KEY, splitPane.getDividerLocation());
prefs.putDouble(DIALOG_VIEWER_SCALE_PREFS_KEY, viewer.getScale());
dialog.setVisible(false);
dialog.dispose();
}
};
dialog.addWindowListener(exitListener);
dialog.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
int width = prefs.getInt(DIALOG_WIDTH_PREFS_KEY, 600);
int height = prefs.getInt(DIALOG_HEIGHT_PREFS_KEY, 500);
dialog.setPreferredSize(new Dimension(width, height));
dialog.pack();
// After pack(): set the divider at 1/3 (200/600) of the frame.
int dividerLocation = prefs.getInt(DIALOG_DIVIDER_LOC_PREFS_KEY, 200);
splitPane.setDividerLocation(dividerLocation);
if (prefs.getDouble(DIALOG_X_PREFS_KEY, -1) != -1) {
dialog.setLocation(
(int)prefs.getDouble(DIALOG_X_PREFS_KEY, 100),
(int)prefs.getDouble(DIALOG_Y_PREFS_KEY, 100)
);
}
else {
dialog.setLocationRelativeTo(null);
}
dialog.setVisible(true);
return dialog;
}
private static void generatePNGFile(TreeViewer viewer, JDialog dialog) {
BufferedImage bi = new BufferedImage(viewer.getSize().width,
viewer.getSize().height,
BufferedImage.TYPE_INT_ARGB);
Graphics g = bi.createGraphics();
viewer.paint(g);
g.dispose();
try {
File suggestedFile = generateNonExistingPngFile();
JFileChooser fileChooser = new JFileChooserConfirmOverwrite();
fileChooser.setCurrentDirectory(suggestedFile.getParentFile());
fileChooser.setSelectedFile(suggestedFile);
FileFilter pngFilter = new FileFilter() {
@Override
public boolean accept(File pathname) {
if (pathname.isFile()) {
return pathname.getName().toLowerCase().endsWith(".png");
}
return true;
}
@Override
public String getDescription() {
return "PNG Files (*.png)";
}
};
fileChooser.addChoosableFileFilter(pngFilter);
fileChooser.setFileFilter(pngFilter);
int returnValue = fileChooser.showSaveDialog(dialog);
if (returnValue == JFileChooser.APPROVE_OPTION) {
File pngFile = fileChooser.getSelectedFile();
ImageIO.write(bi, "png", pngFile);
try {
// Try to open the parent folder using the OS' native file manager.
Desktop.getDesktop().open(pngFile.getParentFile());
}
catch (Exception ex) {
// We could not launch the file manager: just show a popup that we
// succeeded in saving the PNG file.
JOptionPane.showMessageDialog(dialog, "Saved PNG to: " +
pngFile.getAbsolutePath());
ex.printStackTrace();
}
}
}
catch (Exception ex) {
JOptionPane.showMessageDialog(dialog,
"Could not export to PNG: " + ex.getMessage(),
"Error",
JOptionPane.ERROR_MESSAGE);
ex.printStackTrace();
}
}
private static File generateNonExistingPngFile() {
final String parent = ".";
final String name = "antlr4_parse_tree";
final String extension = ".png";
File pngFile = new File(parent, name + extension);
int counter = 1;
// Keep looping until we create a File that does not yet exist.
while (pngFile.exists()) {
pngFile = new File(parent, name + "_"+ counter + extension);
counter++;
}
return pngFile;
}
private static void fillTree(TreeNodeWrapper node, Tree tree, TreeViewer viewer) {
if (tree == null) {
return;
}
for (int i = 0; i < tree.getChildCount(); i++) {
Tree childTree = tree.getChild(i);
TreeNodeWrapper childNode = new TreeNodeWrapper(childTree, viewer);
node.add(childNode);
fillTree(childNode, childTree, viewer);
}
}
private Dimension getScaledTreeSize() {
Dimension scaledTreeSize =
treeLayout.getBounds().getBounds().getSize();
scaledTreeSize = new Dimension((int)(scaledTreeSize.width*scale),
(int)(scaledTreeSize.height*scale));
return scaledTreeSize;
}
@NotNull
public Future open() {
final TreeViewer viewer = this;
viewer.setScale(1.5);
Callable callable = new Callable() {
JDialog result;
@Override
public JDialog call() throws Exception {
SwingUtilities.invokeAndWait(new Runnable() {
@Override
public void run() {
result = showInDialog(viewer);
}
});
return result;
}
};
ExecutorService executor = Executors.newSingleThreadExecutor();
try {
return executor.submit(callable);
}
finally {
executor.shutdown();
}
}
public void save(String fileName) throws IOException, PrintException {
JDialog dialog = new JDialog();
Container contentPane = dialog.getContentPane();
((JComponent) contentPane).setBorder(BorderFactory.createEmptyBorder(
10, 10, 10, 10));
contentPane.add(this);
contentPane.setBackground(Color.white);
dialog.pack();
dialog.setLocationRelativeTo(null);
dialog.dispose();
GraphicsSupport.saveImage(this, fileName);
}
// ---------------------------------------------------
protected Rectangle2D.Double getBoundsOfNode(Tree node) {
return treeLayout.getNodeBounds().get(node);
}
protected String getText(Tree tree) {
String s = treeTextProvider.getText(tree);
s = Utils.escapeWhitespace(s, true);
return s;
}
public TreeTextProvider getTreeTextProvider() {
return treeTextProvider;
}
public void setTreeTextProvider(TreeTextProvider treeTextProvider) {
this.treeTextProvider = treeTextProvider;
}
public void setFontSize(int sz) {
fontSize = sz;
font = new Font(fontName, fontStyle, fontSize);
}
public void setFontName(String name) {
fontName = name;
font = new Font(fontName, fontStyle, fontSize);
}
/** Slow for big lists of highlighted nodes */
public void addHighlightedNodes(Collection nodes) {
highlightedNodes = new ArrayList();
highlightedNodes.addAll(nodes);
}
public void removeHighlightedNodes(Collection nodes) {
if ( highlightedNodes!=null ) {
// only remove exact objects defined by ==, not equals()
for (Tree t : nodes) {
int i = getHighlightedNodeIndex(t);
if ( i>=0 ) highlightedNodes.remove(i);
}
}
}
protected boolean isHighlighted(Tree node) {
return getHighlightedNodeIndex(node) >= 0;
}
protected int getHighlightedNodeIndex(Tree node) {
if ( highlightedNodes==null ) return -1;
for (int i = 0; i < highlightedNodes.size(); i++) {
Tree t = highlightedNodes.get(i);
if ( t == node ) return i;
}
return -1;
}
@Override
public Font getFont() {
return font;
}
@Override
public void setFont(Font font) {
this.font = font;
}
public int getArcSize() {
return arcSize;
}
public void setArcSize(int arcSize) {
this.arcSize = arcSize;
}
public Color getBoxColor() {
return boxColor;
}
public void setBoxColor(Color boxColor) {
this.boxColor = boxColor;
}
public Color getHighlightedBoxColor() {
return highlightedBoxColor;
}
public void setHighlightedBoxColor(Color highlightedBoxColor) {
this.highlightedBoxColor = highlightedBoxColor;
}
public Color getBorderColor() {
return borderColor;
}
public void setBorderColor(Color borderColor) {
this.borderColor = borderColor;
}
public Color getTextColor() {
return textColor;
}
public void setTextColor(Color textColor) {
this.textColor = textColor;
}
protected TreeForTreeLayout getTree() {
return treeLayout.getTree();
}
public void setTree(Tree root) {
if ( root!=null ) {
boolean useIdentity = true; // compare node identity
this.treeLayout =
new TreeLayout(getTreeLayoutAdaptor(root),
new TreeViewer.VariableExtentProvide(this),
new DefaultConfiguration(gapBetweenLevels,
gapBetweenNodes),
useIdentity);
// Let the UI display this new AST.
updatePreferredSize();
}
else {
this.treeLayout = null;
repaint();
}
}
/** Get an adaptor for root that indicates how to walk ANTLR trees.
* Override to change the adapter from the default of {@link TreeLayoutAdaptor} */
public TreeForTreeLayout getTreeLayoutAdaptor(Tree root) {
return new TreeLayoutAdaptor(root);
}
public double getScale() {
return scale;
}
public void setScale(double scale) {
if(scale <= 0) {
scale = 1;
}
this.scale = scale;
updatePreferredSize();
}
public void setRuleNames(List ruleNames) {
setTreeTextProvider(new DefaultTreeTextProvider(ruleNames));
}
private static class TreeNodeWrapper extends DefaultMutableTreeNode {
final TreeViewer viewer;
TreeNodeWrapper(Tree tree, TreeViewer viewer) {
super(tree);
this.viewer = viewer;
}
@Override
public String toString() {
return viewer.getText((Tree) this.getUserObject());
}
}
private static class EmptyIcon implements Icon {
@Override
public int getIconWidth() {
return 0;
}
@Override
public int getIconHeight() {
return 0;
}
@Override
public void paintIcon(Component c, Graphics g, int x, int y) {
/* Do nothing. */
}
}
}