In case of NestedJTabbedPane with SCROLL_TAB_LAYOUT policy,
scroll buttons enable and disable wrongly on Linux(7.2).

How to reproduce:
1) Run the attached test case on linux on Hopper or Mantis
2) Scroll to Tab3 click on it.
3) Scroll to Tab4 click on it.
4) Again click on Tab3
5) You will see the Right ScrollBtn is disabled which is not a correct behaviour.

Attached is the test program:


import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

import java.util.*;


 
public class NestedJTabbedPaneTest {

// Class variables goes here
JButton testBtn;
String labelOfCurrentJBtn = null;

JPanel panel;
int noOfTabs;

JTabbedPane innerTabPane;
JTabbedPane outerTabPane;
    
        
    public static void main(String args[]) {
NestedJTabbedPaneTest ref = new NestedJTabbedPaneTest();
            ref.runTest();

    }
  
    public NestedJTabbedPaneTest() {
//Testing code goes here
panel = new JPanel();
panel.setLayout(null);
panel.setBackground(new Color(0,0,128));
outerTabPane = new JTabbedPane();
innerTabPane = constructTabbedPane(JTabbedPane.SCROLL_TAB_LAYOUT);

outerTabPane.addTab("Testing Tab0", innerTabPane);
outerTabPane.setSize(230, 140);
panel.add(outerTabPane);


    }
  
private JTabbedPane constructTabbedPane(int tabPlacement) {
JTabbedPane tabPane = new JTabbedPane(tabPlacement, JTabbedPane.SCROLL_TAB_LAYOUT);

tabPane.addTab("Testing Tab0", testBtn = new JButton("Test Button0"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.addTab("Testing Tab1", testBtn = new JButton("Test Button1"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.addTab("Testing Tab2", testBtn = new JButton("Test Button2"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.addTab("Testing Tab3", testBtn = new JButton("Test Button3"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.addTab("Testing Tab4", testBtn = new JButton("Test Button4"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.addTab("Testing Tab5", testBtn = new JButton("Test Button5"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.setSize(230,160);
noOfTabs = tabPane.getTabCount();
tabPane.setForeground(new Color(0,0,128));
return tabPane;
}



  
    public void runTest() {
JFrame frame = new JFrame("NestedJTabbedPaneTest");
        frame.getContentPane().add(panel);
        frame.setSize(500,500);
        frame.show();
      
   }

}

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

import java.util.*;


 
public class NestedJTabbedPaneTest {

// Class variables goes here
JButton testBtn;
String labelOfCurrentJBtn = null;

JPanel panel;
int noOfTabs;

JTabbedPane innerTabPane;
JTabbedPane outerTabPane;
    
        
    public static void main(String args[]) {
NestedJTabbedPaneTest ref = new NestedJTabbedPaneTest();
            ref.runTest();

    }
  
    public NestedJTabbedPaneTest() {
//Testing code goes here
panel = new JPanel();
panel.setLayout(null);
panel.setBackground(new Color(0,0,128));
outerTabPane = new JTabbedPane();
innerTabPane = constructTabbedPane(JTabbedPane.SCROLL_TAB_LAYOUT);
outerTabPane.addTab("Testing Tab0", innerTabPane);
outerTabPane.setSize(230, 140);
panel.add(outerTabPane);


    }
  
private JTabbedPane constructTabbedPane(int tabPlacement) {
JTabbedPane tabPane = new JTabbedPane(tabPlacement, JTabbedPane.SCROLL_TAB_LAYOUT);

tabPane.addTab("Testing Tab0", testBtn = new JButton("Test Button0"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.addTab("Testing Tab1", testBtn = new JButton("Test Button1"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.addTab("Testing Tab2", testBtn = new JButton("Test Button2"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.addTab("Testing Tab3", testBtn = new JButton("Test Button3"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.addTab("Testing Tab4", testBtn = new JButton("Test Button4"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.addTab("Testing Tab5", testBtn = new JButton("Test Button5"));
testBtn.setBackground(new Color(0,0,128));
testBtn.setForeground(Color.yellow);
testBtn.addComponentListener(new ComponentAdapter() {
public void componentShown(ComponentEvent ce) {
Object compShown = ce.getSource();
if( compShown instanceof JButton )
labelOfCurrentJBtn = ((JButton)compShown).getText();
}
});

tabPane.setSize(230,160);
noOfTabs = tabPane.getTabCount();
tabPane.setForeground(new Color(0,0,128));
return tabPane;
}


  
    public void runTest() {
JFrame frame = new JFrame("NestedJTabbedPaneTest");
        frame.getContentPane().add(panel);
        frame.setSize(500,500);
        frame.show();
      
   }

}