Possible NPE in SyntaxView.calculateLongestLine

[pskowronek]

Description Possible NPE in SyntaxView.calculateLongestLine.

Steps to Reproduce Not known yet.

Expected behavior No NPE thrown.

Actual behavior NPE is thrown

Additional context

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "java.awt.Component.getFont()" because "c" is null
        at org.fife.ui.rsyntaxtextarea.SyntaxView.calculateLongestLine(SyntaxView.java:103)
        at org.fife.ui.rsyntaxtextarea.SyntaxView.updateMetrics(SyntaxView.java:904)
        at org.fife.ui.rsyntaxtextarea.SyntaxView.setSize(SyntaxView.java:812)
        at java.desktop/javax.swing.plaf.basic.BasicTextUI$RootView.setSize(BasicTextUI.java:1823)
        at java.desktop/javax.swing.plaf.basic.BasicTextUI.getPreferredSize(BasicTextUI.java:948)
        at java.desktop/javax.swing.plaf.basic.BasicTextAreaUI.getPreferredSize(BasicTextAreaUI.java:121)
        at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1734)
        at java.desktop/javax.swing.JTextArea.getPreferredSize(JTextArea.java:623)
        at com.mucommander.viewer.text.TextLineNumbersPanel.lambda$documentChanged$0(TextLineNumbersPanel.java:314)
        at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:318)
        at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:773)
        at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:720)
        at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:714)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
        at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
        at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
        at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
        at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
        at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
        at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
        at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
        at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Reported in another project: https://github.com/mucommander/mucommander/issues/841 - of course something might be wrong in muC, but nevertheless SyntaxView.calculateLongestLine could check if c is not null, especially that View.getContainer() states that it may return null.

[bobbylight]

Interesting - even javax.swing.text.PlainView, which SyntaxView cribs off of, assumes getContainer() is never null. I think it should be the case that the conatiner is never null if that method is called, but perhaps that's not always the case for RSTA. Hopefully you can get more context here, e.g. does this occur before the component is realized or displayed? Thinking of "edge" cases here where things might not be fully initialized yet.

[bobbylight]

On second thought, do you have multiple threads doing initialization? I don't see how this exception is possible on the line indicated if all GUI work is done on the EDT:

• Before SyntaxView.java#904, we query for and use the result from getContainer(), so it must be non-null
• Thus in the next stack trace frame, SyntaxView#103, it should still be non-null

[pskowronek]

In muC we kinda reworked how we initiate RSyntaxTextArea (https://github.com/mucommander/mucommander/issues/841) - since then we cannot produce the problem.

[pskowronek]

cannot reproduce in muC, closing