Re: [platform-swt-dev] Eclipse3.0 M1 on MacOS X Panther DP

[Andre Weinand <weinand@xxxxxxx>]

Steve,

> Andre, is the problem in SWT or Eclipse?  Is there something we need to do
> to run 1.3.1 on Panther?

No, the problem is neither SWT nor Eclipse, it's /usr/bin/java (and 
its bundle cousin "JavaApplicationStub";
the JavaApplicationStub extracts the arguments from the Info.plist 
file instead of from the command line).

/usr/bin/java (and JavaApplicationStub) starts the Java VM in the 
second thread because it runs an event loop in the first thread (the 
"Main" thread), and assumes that the Java code (in any thread) behind 
the scene communicates with the event loop in the Main thread.

But this assumption breaks with SWT because it uses code (Carbon and 
Cocoa natives) that normally runs in the main thread and knows 
nothing about the fact that another event loop is already running.

[BTW, I will file a Radar bug against this behavior of /usr/bin/java 
since it prevents running Java code in the "main" thread]

So the only fix for this is a replacement for /usr/bin/java (and the 
"JavaApplicationStub") that runs no additional event loop in the main 
thread but starts the Java VM there. This is java_swt.

OK, this was the theory. Some caveats:

- for Java 1.3.1 "JavaApplicationStub" contained some workarounds to avoid
  the deadlocks, so with it Eclipse would run without problems as long as
  started from the bundle (via JavaApplicationStub ) and not from 
/usr/bin/java.
  (that's the reason why the launcher always creates a bundle on the 
fly instead
  of using /usr/bin/java)

- after installing any version of 1.4.1, the "JavaApplicationStub" was
  replaced with a version without the workaround (for all VM versions 
including 1.3.1 !).
  As a consequence, I had to adapt Eclipse's MacOS X launcher
  (org.eclipse.jdt.launching.macosx) to continue using the old version
  of the "JavaApplicationStub" (by shipping a copy of it).

- this copy no longer seems to work under Panther. That's the reason 
why launching
  Eclipse under 1.3.1 on Panther fails. I haven't tried to find the 
cause of this,
  because Panther is scheduled for the end of this year, with 1.4.1 
as default VM,
  and Eclipse will switch to 1.4.1 in September. So there is probably 
not a great
  need for running Eclipse on 1.3.1 on Panther.

- my new Java VM launcher "java_swt" is only activated if a 1.4.1 VM 
is selected in
  the Info.plist file. Otherwise, the old 1.3.1 code is used.
  This is done because I didn't want to fix something (1.3.1) that 
wasn't broken in Jaguar.
  (However, in Panther it is broken...)

- I understand that it would make sense to run SWT applications
  (which don't require 1.4.1) on Panther and a 1.3.1 VM.
  I believe that my fix (the java_swt launcher) will work under 1.3.1 too.
  I just have to find the time to verify it.

--andre