[java-gnome-hackers] WeakReferences going away

[Tom B. <Tom...@Su...>]

It appears that org.gnu.gtk is misusing the WeakReference class to store
its event listeners.  On my system, widgets that are initially
responsive to events quickly stop being responsive, even with simple
Java-GNOME example apps.  The problem is that the app's event listeners
are being GC'd even though the widgets they are listening to are still
live.

A WeakReference is supposed to be used for cases where it's okay for a
reference to go away, usually because it can be recreated.  The classic
example is with a cache; if a lookup is expensive, you cache the result
in a hashtable using a WeakReference (or just use WeakHashMap) -- if the
cache gets emptied by the garbage collector, it just means more
lookups.  The cache may have an entry disappear, but the caller never
knows this because the cache is a hidden implementation detail.

Event listeners need to remain permanently attached to their respective
widgets, however; they are not transitory in any way.  When I remove all
of the WeakReference use in GTK, the problem goes away as it should.  It
also simplies the event handling code quite a bit, and most likely
speeds it up as well.  I suspect there's a lot more potential for shared
code now, too.

Unless anyone objects soon, I want to check in this "WeakReference-free"
delta.

Tom