JPanel child zoom

Question

I am trying to get a JPanel to paint its child JPanel according to a certain scale factor which the user selects from a JComboBox that is also in the JPanel, the parent one. The problem is that it's painting funny and not scaling the child JPanel. Please take a look at my code. Thanks.
import javax.swing.*;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.event.*;
public class ZoomPanel extends JPanel
     private double zoom_factor = 1.0;
     private JComboBox zoom_combo;
     private JPanel widget_panel, child_panel;
     public ZoomPanel( JPanel child )
          super( new BorderLayout() );
          zoom_combo =
               new JComboBox(
                    new Double[]
                         new Double( 0.10 ), new Double( 0.25 ), new Double( 0.33 ),
                         new Double( 0.50 ), new Double( 0.75 ), new Double( 1.00 ),
                         new Double( 1.25 ), new Double( 1.50 ), new Double( 2.00 ),
                         new Double( 3.00 ), new Double( 4.00 ), new Double( 5.00 ),
          zoom_combo.setEditable( true );
          zoom_combo.setSelectedIndex( 5 );
          zoom_combo.addActionListener(
               new ActionListener()
                    public void actionPerformed( ActionEvent ae )
                         zoom_factor = ((Double) zoom_combo.getSelectedItem()).doubleValue();
          widget_panel = new JPanel();
          widget_panel.add( zoom_combo );
          add( widget_panel, BorderLayout.NORTH );
          child_panel = child;
          add( child_panel, BorderLayout.CENTER );
     public JPanel getChild()
          return child_panel;
     * Returns the zoom factor.
     public double getZoom()
          return zoom_factor;
     * Changes zoom factor.
     public void setZoom( final double d )
          zoom_factor = d;
          repaint();
     public void paintChildren( Graphics g )
          widget_panel.repaint();
          ((Graphics2D) child_panel.getGraphics()).setTransform(
               AffineTransform.getScaleInstance(
                    zoom_factor,
                    zoom_factor ) );
          child_panel.repaint();
} // ZoomPanel.java

Answer 1

Ok, I did the following changes to your class : import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.geom.AffineTransform;
import java.awt.event.*;
public class ZoomPanel extends JPanel {
     private JComboBox zoom_combo;
     private JPanel widget_panel;
     private ZoomedPanel child_panel;
     public ZoomPanel(ZoomedPanel child) {
          super(new BorderLayout());
          zoom_combo = new JComboBox(new Double[]{new Double(0.10), new Double(0.25), new Double(0.33), new Double(0.50), new Double(0.75), new Double(1.00), new Double(1.25), new Double(1.50), new Double(2.00), new Double(3.00), new Double(4.00), new Double(5.00), });
          zoom_combo.setEditable(true);
          zoom_combo.setSelectedIndex(5);
          zoom_combo.addActionListener(new ActionListener() {
               public void actionPerformed(ActionEvent ae) {
                    child_panel.setZoomFactor(((Double)zoom_combo.getSelectedItem()).doubleValue());
                    revalidate();
                    repaint();
          widget_panel = new JPanel();
          widget_panel.add(zoom_combo);
          add(widget_panel, BorderLayout.NORTH);
          child_panel = child;
          JPanel pan1 = new JPanel(new BorderLayout());
          JPanel pan2 = new JPanel(new BorderLayout());
          pan1.add(pan2, BorderLayout.NORTH);
          pan2.add(child_panel, BorderLayout.WEST);
          add(pan1, BorderLayout.CENTER);
     public JPanel getChild() {
          return child_panel;
     private static class ZoomedPanel extends JPanel {
          private double zoomFactor;
          public ZoomedPanel() {
               this(true);
          public ZoomedPanel(boolean isDoubleBuffered) {
               this(new FlowLayout(), isDoubleBuffered);
          public ZoomedPanel(LayoutManager layout) {
               this(layout, true);
          public ZoomedPanel(LayoutManager layout, boolean isDoubleBuffered) {
               super(layout, isDoubleBuffered);
               zoomFactor = 1.0;
          public void setZoomFactor(double aZoomFactor) {
               zoomFactor = aZoomFactor;
          public void paint(Graphics g) {
               int w = getWidth();
               int h = getHeight();
               BufferedImage bi = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
               Graphics2D g2D = (Graphics2D)bi.getGraphics();
               super.paint(g2D);
               Rectangle clipBounds = g.getClipBounds();
               g.setClip(clipBounds.x, clipBounds.y,
                           (int)(clipBounds.width * zoomFactor),
                           (int)(clipBounds.height * zoomFactor));
               ((Graphics2D)g).drawImage(bi, AffineTransform.getScaleInstance(zoomFactor, zoomFactor), null);
     public static void main(String[] args) {
          final JFrame frame = new JFrame("TestZoomPanel");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          ZoomedPanel insidePanel = new ZoomedPanel(new GridLayout(2, 2));
          insidePanel.add(new JButton("totot"));
          insidePanel.add(new JLabel("tutututu"));
          insidePanel.add(new JTextArea("qmsdfkqsdmlfkqsd\nqsdfqsdfqsdfkqsdf\nqsdfqsdfqsdf\nqsdfqsdfqsdfqsdf"));
          insidePanel.add(new JTextField("sdqsdfqsdf"));
          ZoomPanel zoomPanel = new ZoomPanel(insidePanel);
          frame.setContentPane(zoomPanel);
          SwingUtilities.invokeLater(new Runnable() {
               public void run() {
                    frame.pack();
                    frame.setVisible(true);
} // ZoomPanel.javaThis is only to show you how it can be achieved following the approach you were using (that is, override a paint type method).
However, you have to realize that in no way are the subcomponents scaled according to the zoom value. You should think of a more elaborate solution that would effectively change the size of the subcomponents. They could implement a Scalable interface with a scale(double zoomFactor) method used to modify the size of their font, their preferredSize...