ImageJ hanging: EventQueue deadlock by PlugInFrame.setVisible(false)

Posted by Michael Schmid on Feb 02, 2011; 5:19pm
URL: http://imagej.273.s1.nabble.com/ImageJ-hanging-EventQueue-deadlock-by-PlugInFrame-setVisible-false-tp3685839.html

Hi everyone,

a strange and annoying problem:

I have written a PlugInFrame that displays a grid on an image as an  
overlay. It should close when the image is closed. It works well on  
Mac OS X 10.4 (Java 1.5.0_19), but on Mac OS X 10.5.8 (Java 1.5.0_26)  
quite often ImageJ becomes irresponsive on closing the image  
(sometimes, there was no problem, and in a rare cases it also  
happened that ImageJ did not hang after closing the PlugInFrame, it  
was hanging after closing another image later.)

Using debug messages to the console I found out that setVisible
(false) causes the EventQueue first to go to a waiting state with  
timeout, then it gets blocked forever (waiting for getting into a  
synchronized block somewhere).
ImageJ version 1.44n.

Here is the relevant code:

public class Grid_Measurement extends PlugInFrame implements  
ImageListener, ...
         (many more listeners for the GUI of the panel, with buttons,  
textfields, etc.)

     public void imageClosed(ImagePlus imp) {
         if (imp==this.imp) close();   //close PlugInFrame when image  
gets closed
     }

     public void close() {
         ImagePlus.removeImageListener(this);
         ... remove the other listeners referring to the ImageCanvas
         ... I don't remove the listeners for the buttons, textfields  
etc. (too many)
         imp.setOverlay(null);
             #debug message  (System.err.println) shows:
             # - the current thread is "Close", priority 4 (not the  
EventQueue)
             # - AWT-EventQueue-0 is in state RUNNABLE
         setVisible(false);
             #debug message shows now: AWT-EventQueue-0 is in state  
TIMED_WAITING
         IJ.wait(2000); //see whether we can get out after a while
             #debug message shows now: AWT-EventQueue-0 is in state  
BLOCKED
         dispose();
             #debug messages from here on don't display (dispose  
never gets finished).


Does anyone have experience with such a situation?
Any ideas what the EventQueue could be waiting for after setVisible
(false)?
Is there a way to debug it (maybe without too steep a learning curve  
for handling a debugger)?


Michael