Unknown reference to GWT widget prevents clearing of detached DOM tree - dom

Question

I've got a GWT 2.4 app where I'm "swapping views" by switching out one Composite widget on the RootPanel for another, using the usual RootPanel.get().clear() and RootPanel.get().add(newWidget) to remove and add, respectively.
The first composite widget contains a PasswordTextBox. It listens for the Enter keypress, which triggers the swap. Nothing too fancy:
getDisplay().getPasswordBoxForKeyPresses().addKeyPressHandler(new KeyPressHandler() {
public void onKeyPress(KeyPressEvent event) {
if (event.getNativeEvent().getKeyCode() == KeyCodes.KEY_ENTER) {
swapWidgets(); // clear RootPanel and add new widget
}
}
});
The problem is that there is a DOM memory leak: after RootPanel.get().clear() is called, the old composite widget is stuck in the detached DOM tree because the HTMLInputElement for the PasswordTextBox has some strange reference to it which I cannot identify.
Update:
I took the helpful advice below, compiled at style=detailed and started trying to drive down the tree to look a reference to the element in JS. I'm pretty new with GWT, so it still isn't obvious to me what's going on. So starting with the second line in the retaining tree, I can see that lastEvent in _2 contains the nativeKeyTarget listed at the top of tree. But where do I go from there?

Answer 1

I tracked the reference down to SmartGWT. It tracks the last click event within ISC_Core.js. Further questions are
How will this behavior further affect memory usage in my app?
Can this behavior be bypassed if need be?
But those questions are for another post!

Answer 2

Looks like you may not be tracking the handler registrations which will cause memory leaks, prevent objects from being recovered, and cause phantom event captures.
In pure GWT, it looks like this
// class member
HandlerRegistration reg;
// save for recovery
reg = getDisplay().getPasswordBoxForKeyPresses().addKeyPressHandler(...);
public void onDetatch() {
// recover memory
reg.removeHandler();
reg = null;
}
GXT has a nice grouping feature to prevent registration sprawl, it looks like this
// class member
GroupingHandlerRegistration regs = new GroupingHandlerRegistration();
// save for later recovery
regs.add( getDisplay().getPasswordBoxForKeyPresses().addKeyPressHandler(...) );
// recover memory
regs.removeHandler();
Source code for GroupingHandlerRegistration