[Bug 2082009] Re: Tabbing through fields in a Java application periodically hangs text cursor

[Ubuntu Foundations Team Bug Bot]

** Package changed: ubuntu => openjdk-21 (Ubuntu)

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Title:
  Tabbing through fields in a Java application periodically hangs text
  cursor

Status in openjdk-21 package in Ubuntu:
  New

Bug description:
  The issue is that when I tab through the text fields in a Java
  application, the text cursor periodically hangs. When this happens,
  the cursor changes from a blinking line to a non-blinking line, and
  the keyboard focus does not advance.

  If I then press the "shift" key, then the window updates and the focus
  advances to the next text field properly and the cursor starts
  blinking again.

  This issue started when we installed a new copy of Ubuntu 24.04.1 LTS,
  We previously ran Ubuntu 22.04.5 LTS and the issue did not occur
  there. The problem is occuring on multiple desktop systems.

  While this issue occurred while running Java, I do not think that is a bug with Java (perhaps X11?)
  I have tested with Oracle Java 17 and OpenJDK Java 21, and the problem occurs with both Java versions when running on Ubuntu 24.04.1 LTS, but not when running on Ubuntu 22.04.5 LTS.

  We are using KDE as our window manager, but have also tried the
  Cinnamon window manager and the problem still occurs when running
  Cinnamon.

  
  Sample Java code to reproduce the issue:

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

  //
  // This class is a simple program to demonstrate the issue. To run it:
  // 1. Compile the program: javac TabBug.java
  // 2. Run the program: java TabBug
  //
  public class TabBug extends JFrame {
      public static void main(String[] args) throws Exception {
          SwingUtilities.invokeLater(TabBug::new);
      }

      public TabBug() {
          super("Test Tabbing");
          setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          Container pane = getContentPane();
          pane.setLayout(new GridLayout(9, 9));
          for (int i = 0; i < 81; i++) {
              pane.add(new JTextField(String.valueOf(i), 3));
          }
          setSize(600, 600);
          setVisible(true);
      }
  }

  ProblemType: Bug
  DistroRelease: Ubuntu 24.04
  Package: openjdk-21-jre-headless 21.0.4+7-1ubuntu2~24.04
  ProcVersionSignature: Ubuntu 6.8.0-44.44-generic 6.8.12
  Uname: Linux 6.8.0-44-generic x86_64
  NonfreeKernelModules: nvidia_modeset nvidia
  ApportVersion: 2.28.1-0ubuntu3.1
  Architecture: amd64
  CasperMD5CheckResult: unknown
  CurrentDesktop: KDE
  Date: Wed Sep 25 13:23:02 2024
  ExecutablePath: /usr/lib/jvm/java-21-openjdk-amd64/bin/java
  InstallationDate: Installed on 2024-09-06 (19 days ago)
  InstallationMedia: Kubuntu 24.04.1 LTS "Noble Numbat" - Release amd64 (20240827)
  SourcePackage: openjdk-21
  UpgradeStatus: No upgrade log present (probably fresh install)

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