Re: Followup to JDK-8187957 Tab Size does not work correctly in JTextArea

[Volodin, Vladislav]

Hi David,

I was able to get the result by running your example on a freshly build JDK. 
The fix that you suggested should be applied to this line: 
https://github.com/openjdk/jdk/blob/master/src/java.desktop/share/classes/javax/swing/text/WrappedPlainView.java#L469
 (#469).
You can contribute to JDK if you want, but I know that it takes some time to 
build it from sources, prepare the test and the patch.

I think I can create the patch for you, and ask my colleague to create the bug 
report. But there is a usual difficulty is to cover this issue with a test 
file. Your example is not bad, no, but how to automate it? 😊
I can try to invest some time to it after I come from vacation and find a spare 
time. I guess you have about 3-4 weeks to practice with the JDK building and 
tests writing (jtreg).

Kind regards,
Vlad

From: swing-dev <swing-dev-boun...@openjdk.java.net> On Behalf Of David Polock
Sent: Freitag, 14. Februar 2020 14:47
To: swing-dev@openjdk.java.net
Subject: <Swing Dev> Followup to JDK-8187957 Tab Size does not work correctly 
in JTextArea

Hello,

this is my first post on the mailing list – please point me tot he right 
places, if i’m off topic.

I have an issue with tab stops in a JTextArea. The behaviour is very similar to 
the bug JDK-8187957, which was fixed for JDK10. I’m using JDK11 and see the 
same (wrong) behaviour in my code.
After some tests i could confirm, that the bug was fixed for a JTextArea 
without line wrapping. But calling JTextArea::setLineWrap(true) leads again to 
the false behaviour.

So in a next step I cloned the git Source repository and examined the patch for 
the Bug. Besides adding a testcase (TestTabSize.java) the fix is changing some 
float calculation to int:

================================================
commit 0da4c70d2d542d8ff37ee34e4878829af696b694
Author: Prasanta Sadhukhan 
<psadhuk...@openjdk.org<mailto:psadhuk...@openjdk.org>>
Date:   Tue Nov 14 10:32:31 2017 +0530

    8187957: Tab Size does not work correctly in JTextArea

    Reviewed-by: ssadetsky, serb

diff --git a/src/java.desktop/share/classes/javax/swing/text/PlainView.java 
b/src/java.desktop/share/classes/javax/swing/text/PlainView.java
index 9d1b4fc..6aabc24 100644
--- a/src/java.desktop/share/classes/javax/swing/text/PlainView.java
+++ b/src/java.desktop/share/classes/javax/swing/text/PlainView.java
@@ -646,7 +646,7 @@ public class PlainView extends View implements TabExpander {
         if (tabSize == 0) {
             return x;
         }
-        float ntabs = (x - tabBase) / tabSize;
+        int ntabs = (int) ((x - tabBase) / tabSize);
         return tabBase + ((ntabs + 1) * tabSize);
     }
================================================

So in PlainView.java one line was changed. I can see in the source code, that 
the same (false) line exists in the class WrappedPlainView – which is used as 
the rendering class, when setLineWrap(true) was called.

I think the same fix should be applied to the WrappedPlainView. I could not 
confirm this fix, because i’m not able to easily build / change the 
java.desktop module.

The issue is reproducible with the following code (adopted from the mentioned 
bug):

------------- BEGIN CODE ------------------
public class TabTestJFrame extends javax.swing.JFrame {
  private javax.swing.JScrollPane jScrollPane1;
  private javax.swing.JTextArea jTextArea1;

  public TabTestJFrame() {
    initComponents();
    jTextArea1.setTabSize( 8 );
  }

  private void initComponents() {

    jScrollPane1 = new javax.swing.JScrollPane();
    jTextArea1 = new javax.swing.JTextArea();

    setDefaultCloseOperation( javax.swing.WindowConstants.EXIT_ON_CLOSE );

    jTextArea1.setFont( new java.awt.Font( "Monospaced", 0, 10 ) );
    jTextArea1.setLineWrap( true ); // use WrappedPlainView as renderer
    jTextArea1.setText(
        "#################################################\n# Some 
Text\t\t\t\t\t#\n# Some Other Much Longer 
Text\t\t\t#\n#################################################" );
    jScrollPane1.setViewportView( jTextArea1 );

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout( 
getContentPane() );
    getContentPane().setLayout( layout );
    layout.setHorizontalGroup( layout.createParallelGroup( 
javax.swing.GroupLayout.Alignment.LEADING ).addGroup( 
layout.createSequentialGroup()
        .addContainerGap().addComponent( jScrollPane1, 
javax.swing.GroupLayout.DEFAULT_SIZE, 446, Short.MAX_VALUE ).addContainerGap() 
) );
    layout.setVerticalGroup( layout.createParallelGroup( 
javax.swing.GroupLayout.Alignment.LEADING )
        .addGroup( 
layout.createSequentialGroup().addContainerGap().addComponent( jScrollPane1 
).addContainerGap() ) );

    pack();
  }

  public static void main( String args[] ) {
    System.out.println( "Java Version: " + System.getProperty( 
"java.specification.version" ) );
    java.awt.EventQueue.invokeLater( () -> {
      new TabTestJFrame().setVisible( true );
    } );
  }
}
------------- END CODE ------------------

So my question: Can somebody easily confirm the problem? And if the answer is 
yes, what are the next steps (creating a bug report – but who and how ;-) ?)

Best regards,

  David