garbage collection of graphics objects

[ddyer0]

I've had a long running, occasional bug where a background that was drawn into an image
is damaged; basically incompletely drawn. I had an epiphany last night; that the underlying
cause is that the java-level pointer to system object is garbage collected while the drawing
is still in process. I found this:

protected void finalize() {
    if (nativeGraphics != null) {
        impl.disposeGraphics(nativeGraphics);
    }
}

A simple experiment to retain the objects returned by getGraphics() seems to have fixed the
problem. I have a pretty disciplined use strategy for getGraphics() so this is satisfactory for
me; but disposeGraphics ought to use some strategy to delay disposal until drawing is complete.

[Shai Almog]

If the finalizer is invoked it means there was a GC process that already collected the object. That is WAY WAY WAY too late.

I don't see any valid use case allowed by our API that would allow it.

[ddyer0]

my actual use case is i create a writable image, get a graphics, perform hundreds of graphics operations, and the move on, at which point the graphics becomes garage and collectable. later, i expect all the operations i've performed to be reflected in the image.

what is actually happening is if a Gc collects the graphics before the underlying operations have finished,
the image i am building is incomplete.

[Shai Almog]

The number of operations doesn't matter. If you can create a case where an object is reachable but still gets GCd that would be an interesting test case. Either way, this line isn't the bug.

[ddyer0]

the GC is legitimate, but the system level operations are still continuing, and the "destroy" operation
triggered by the finalize is terminating them before they complete.