import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.util.Timer;
import java.util.TimerTask;

import javafx.application.Platform;
import javafx.embed.swing.JFXPanel;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
import javafx.stage.StageStyle;

import javax.swing.*;

/**
 * Steps to demonstrate the issue:
 * 1) Launch the application, observe the Swing window.
 * 2) Click the "GC" button to get a baseline memory reading.
 * 3) Click the "Open JavaFX Window", observing the JavaFX window that opens.
 * 4) Observe that the used memory reading has increased by about 5 megabytes, as expected.
 * 5) Close the JavaFX window.
 * 6) Click the "GC" button again, and observe that the memory does not go back to a 
 *    reasonable number (close to the baseline).  If you observe this object inside of a 
 *    memory profiler, you can see that the byte[] is still strong-reachable.
 * 7) If running with a memory profiler, open another JavaFX window, and observe that the 
 *    previous JavaFX window is now garbage collected.
 *
 * @author lperkins
 */
public class WindowMemoryLeak
{
   private static final double megabyte = (1024d * 1024d);

   private static void createAndShowFxGui()
   {
      // allocating 5 megabytes to simulate a large data model
      int byteCount = 5 * (int) megabyte;
      byte[] dataModel = new byte[byteCount];

      // attach the data model to the UI so it doesn't get garbage
      // collected until the UI does
      Label label = new Label("Dummy Window Data");
      label.setUserData(dataModel);

      // builders are getting removed in Java 8... /sadface
      BorderPane root = new BorderPane();
      root.setCenter(label);

      // open the JavaFX window
      Stage stage = new Stage(StageStyle.DECORATED);
      stage.setTitle("JavaFX Window (Sub App)");
      stage.setScene(new Scene(root, 150, 100));
      stage.centerOnScreen();
      stage.show();
   }

   private static void createAndShowSwingGui()
   {
      // construct the Swing UI
      JPanel contentPanel = new JPanel(new BorderLayout(0, 10));
      contentPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
      contentPanel.add(new JButton(new AbstractAction("Open JavaFX Window")
      {
         @Override
         public void actionPerformed(ActionEvent e)
         {
            Platform.runLater(new Runnable()
            {
               @Override
               public void run()
               {
                  createAndShowFxGui();
               }
            });
         }
      }), BorderLayout.NORTH);
      contentPanel.add(new SwingMemoryReadout(), BorderLayout.CENTER);

      // initializing the JavaFX toolkit
      contentPanel.putClientProperty("initializeFxToolkit", new JFXPanel());

      // open the Swing window
      JFrame frame = new JFrame("Swing Window (Main App)");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setContentPane(contentPanel);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args)
   {
      SwingUtilities.invokeLater(new Runnable()
      {
         @Override
         public void run()
         {
            createAndShowSwingGui();
         }
      });
   }

   private static class SwingMemoryReadout extends JPanel implements Runnable
   {
      private final JLabel currentLabel;

      private final JLabel maxLabel;

      private final Timer refreshTimer;

      public SwingMemoryReadout()
      {
         currentLabel = new JLabel();
         maxLabel = new JLabel();

         refreshTimer = new Timer("Refresh Memory Stats Timer");
         refreshTimer.schedule(new TimerTask()
         {
            @Override
            public void run()
            {
               triggerStatsRefresh();
            }
         }, 1000L, 1000L);

         setLayout(new BoxLayout(this, BoxLayout.X_AXIS));
         add(currentLabel);
         add(Box.createHorizontalStrut(10));
         add(maxLabel);
         add(Box.createHorizontalStrut(10));
         add(new JButton(new AbstractAction("GC")
         {
            @Override
            public void actionPerformed(ActionEvent e)
            {
               triggerGc();
            }
         }));

         run();
      }

      public void triggerGc()
      {
         System.gc();
         triggerStatsRefresh();
      }

      public void triggerStatsRefresh()
      {
         SwingUtilities.invokeLater(this);
      }

      @Override
      public void run()
      {
         Runtime runtime = Runtime.getRuntime();
         long maxMemory = runtime.maxMemory();
         long totalMemory = runtime.totalMemory();
         long freeMemory = runtime.freeMemory();
         long usedMemory = totalMemory - freeMemory;

         currentLabel.setText(String.format("Used: %.2f MB", Double.valueOf(usedMemory / megabyte)));
         maxLabel.setText(String.format("Max: %.2f MB", Double.valueOf(maxMemory / megabyte)));
      }
   } // end class SwingMemoryReadout

}