Question

I installed the VTK toolkit and I use the Java wrapper for VTK in Eclipse. I added the vtk.jar to my java project and set the environment variable to point to my VTK installation.
Basically, it is working. The vtk classes etc. are found and the program starts, at least until I come to the point where I show a/the window.

For instance following example program:
http://www.vtk.org/Wiki/VTK/Examples/Java/Imaging/ImageTest

If I run it, the following exception is thrown by OS-X (or Cocoa) stating some problems with the UndoManager:

I have no clue what I am doing wrong or what causes this problem, anyone any ideas?

2012-05-22 22:48:09.093 java[925:1a03] *** Assertion failure in +[NSUndoManager _endTopLevelGroupings], /SourceCache/Foundation/Foundation-833.25/Misc.subproj/NSUndoManager.m:324
2012-05-22 22:48:09.093 java[925:1a03] +[NSUndoManager(NSInternal) _endTopLevelGroupings] is only safe to invoke on the main thread.
2012-05-22 22:48:09.096 java[925:1a03] (
    0   CoreFoundation                      0x00007fff9363cf56 __exceptionPreprocess + 198
    1   libobjc.A.dylib                     0x00007fff8aa9fd5e objc_exception_throw + 43
    2   CoreFoundation                      0x00007fff9363cd8a +[NSException raise:format:arguments:] + 106
    3   Foundation                          0x00007fff910a371f -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 169
    4   Foundation                          0x00007fff9101295f +[NSUndoManager(NSPrivate) _endTopLevelGroupings] + 144
    5   AppKit                              0x00000001025680ef -[NSApplication run] + 596
    6   libvtkRendering.5.10.dylib          0x000000010ff8c2df -[vtkCocoaServer start] + 335
    7   libvtkRendering.5.10.dylib          0x000000010ff8cf87 _ZN30vtkCocoaRenderWindowInteractor5StartEv + 293
    8   libvtkRenderingJava.5.10.0.dylib    0x000000010f94f29e Java_vtk_vtkRenderWindowInteractor_Start_15 + 62
    9   ???                                 0x0000000103b70d6e 0x0 + 4357295470
    10  ???                                 0x0000000103b6585a 0x0 + 4357249114
)
2012-05-22 22:48:09.096 java[925:1a03] *** Assertion failure in +[NSUndoManager _endTopLevelGroupings], /SourceCache/Foundation/Foundation-833.25/Misc.subproj/NSUndoManager.m:324
2012-05-22 22:48:09.096 java[925:1a03] An uncaught exception was raised
2012-05-22 22:48:09.097 java[925:1a03] +[NSUndoManager(NSInternal) _endTopLevelGroupings] is only safe to invoke on the main thread.
2012-05-22 22:48:09.098 java[925:1a03] (
    0   CoreFoundation                      0x00007fff9363cf56 __exceptionPreprocess + 198
    1   libobjc.A.dylib                     0x00007fff8aa9fd5e objc_exception_throw + 43
    2   CoreFoundation                      0x00007fff9363cd8a +[NSException raise:format:arguments:] + 106
    3   Foundation                          0x00007fff910a371f -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 169
    4   Foundation                          0x00007fff9101295f +[NSUndoManager(NSPrivate) _endTopLevelGroupings] + 144
    5   AppKit                              0x000000010256819c -[NSApplication run] + 769
    6   libvtkRendering.5.10.dylib          0x000000010ff8c2df -[vtkCocoaServer start] + 335
    7   libvtkRendering.5.10.dylib          0x000000010ff8cf87 _ZN30vtkCocoaRenderWindowInteractor5StartEv + 293
    8   libvtkRenderingJava.5.10.0.dylib    0x000000010f94f29e Java_vtk_vtkRenderWindowInteractor_Start_15 + 62
    9   ???                                 0x0000000103b70d6e 0x0 + 4357295470
    10  ???                                 0x0000000103b6585a 0x0 + 4357249114
)
2012-05-22 22:48:09.098 java[925:1a03] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '+[NSUndoManager(NSInternal) _endTopLevelGroupings] is only safe to invoke on the main thread.'
*** First throw call stack:
(
    0   CoreFoundation                      0x00007fff9363cf56 __exceptionPreprocess + 198
    1   libobjc.A.dylib                     0x00007fff8aa9fd5e objc_exception_throw + 43
    2   CoreFoundation                      0x00007fff9363cd8a +[NSException raise:format:arguments:] + 106
    3   Foundation                          0x00007fff910a371f -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 169
    4   Foundation                          0x00007fff9101295f +[NSUndoManager(NSPrivate) _endTopLevelGroupings] + 144
    5   AppKit                              0x000000010256819c -[NSApplication run] + 769
    6   libvtkRendering.5.10.dylib          0x000000010ff8c2df -[vtkCocoaServer start] + 335
    7   libvtkRendering.5.10.dylib          0x000000010ff8cf87 _ZN30vtkCocoaRenderWindowInteractor5StartEv + 293
    8   libvtkRenderingJava.5.10.0.dylib    0x000000010f94f29e Java_vtk_vtkRenderWindowInteractor_Start_15 + 62
    9   ???                                 0x0000000103b70d6e 0x0 + 4357295470
    10  ???                                 0x0000000103b6585a 0x0 + 4357249114
)
terminate called throwing an exception

proposed VM parameter lead to this error:

2012-05-23 09:10:18.635 java[747:307] [Java CocoaComponent compatibility mode]: Enabled
2012-05-23 09:10:18.635 java[747:307] [Java CocoaComponent compatibility mode]: Setting timeout for SWT to 0.100000
2012-05-23 09:10:18.985 java[747:d303] *** -[NSConditionLock unlock]: lock (<NSConditionLock: 0x7fa108c64600> '(null)') unlocked when not locked
2012-05-23 09:10:18.985 java[747:d303] *** Break on _NSLockError() to debug.

Answer 1

This could be a problem related to the Cocoa restriction that some things can be run only on the first thread that the process runs. The same issue arises with the SWT event loop, for example. The problem is that main method is not executed on the first thread because it is reserved for AWT’s event loop — for the same reason. The workaround: use the JVM switch -XstartOnFirstThread.