Why Glass Pane becomes visible when resizing JInternalFrame?

Question

This qustion has been asked _*here*_ but got no response.
Hello,
I've created a JFrame with JDesktop and one JInternalFrame on it. I've also added a glasspane (which draws a black circle only) to JFrame - it's invisible by default but when I resize JInternalFrame it shows up.. is this correct behavior? Why it is visible only when I resize and diappears when I release mouse button after resize? How I can make it invisible when resizing JInternalFrame? (Is removing JFrame's glasspane only solution?)import java.awt.Graphics;
import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.JPanel;
public class RunMe extends JFrame {
     public RunMe() {
          this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          this.setBounds(10, 10, 800, 600);
          JDesktopPane desktop = new JDesktopPane();
          JInternalFrame testJIF = new JInternalFrame("test", true, true, true, true);
          testJIF.setBounds(10, 10, 100, 100);
          desktop.add(testJIF);
          testJIF.setVisible(true);
          this.add(desktop);
          this.setGlassPane(new MyGlassPane());
          this.setVisible(true);
     private class MyGlassPane extends JPanel {
          public MyGlassPane() {
               this.setOpaque(false);
          @Override
          protected void paintComponent(Graphics g) {
               g.fillOval(0, 0, 100, 100);
               super.paintComponent(g);
     public static void main(String[] args) {
          new RunMe();
}

Answer 1

First of all, thank you for being upfront about cross posting.
Whether this is "correct" behavior or not may be debatable, but it's certainly expected behavior. From the source of javax.swing.plaf.basic.BasicInternalFrameUI.BorderListener.mousePressed (towards the end of the method)Container c = frame.getTopLevelAncestor();
if (c instanceof RootPaneContainer) {
   Component glassPane = ((RootPaneContainer)c).getGlassPane();
   glassPane.setVisible(true);
   glassPane.setCursor(s);
}The glass pane is made visible to show the resize cursor.
It's set back to visible(false) in finishMouseReleased() which is invoked from mouseRelease and elsewhere (e;g; from cancelResize which is invoked from windowLostFocus)
Looks like you can't use the glass pane for whatever you had planned, the Swing designers have already used it for something else. Or this could be a workaround, depending on exactly what it is you're trying to do.@Override
protected void paintComponent(Graphics g) {
   super.paintComponent(g);
   if (this.isOpaque()) {
      g.fillOval(0, 0, 100, 100);
}You could also declare and use a boolean flag, rather than using isOpaque (which may happen to be set/reset somewhere else in the Swing code ;-)
db