Bug 539069

Description Sebastian Habenicht 2018-09-14 07:21:27 EDT

Removing the same client listener more than once from a widget within the same render request leads to a client side error:

Error: Error: Operation "call" on target "w3" of type "rwt.widgets.Text" failed:
rwt.qx.Target: removeEventListener(keypress): 'undefined' is not a function!

Example:

public class HelloWorld extends AbstractEntryPoint {
    @Override
    protected void createContents(final Composite parent) {
        
		//create test widgets
		final Text text1 = new Text(parent, SWT.BORDER);
        final Text text2 = new Text(parent, SWT.BORDER);
		
		//add client listener to first text
        final ClientListener clientListener = new ClientListener(
                "function handleEvent(event) { console.log('key down'); }");
        text1.addListener(SWT.KeyDown, clientListener);
		
		//remove client listener when first text looses focus and also when second text gains focus
        text1.addFocusListener(new FocusAdapter() {
            @Override
            public void focusLost(final FocusEvent event) {
                text1.removeFocusListener(this);
                text1.removeListener(SWT.KeyDown, clientListener);
            }
        });
        text2.addFocusListener(new FocusAdapter() {
            @Override
            public void focusGained(final FocusEvent event) {
                text2.removeFocusListener(this);
                text1.removeListener(SWT.KeyDown, clientListener);
            }
        });
    }
}

No such error occurs when trying the same with a server side listener, so it might be good to adjust the behavior for both types of listeners. 

Maybe in ClientListenerUtil, a new RemoveListener operation should only added to the widget's list of ClientListenerOperations if that list does not already contain a RemoveListener operation for the same listener.