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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * accompanied this code).
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package com.sun.javafx.event;

import javafx.event.Event;
import javafx.event.EventDispatchChain;
import javafx.event.EventDispatcher;

Event dispatcher which introduces event dispatch phase specific methods - dispatchCapturingEvent and dispatchBubblingEvent. These are used in the BasicEventDispatcher.dispatchEvent implementation, but because they are public they can be called directly as well. Their default implementation does nothing and is expected to be overridden in subclasses. The BasicEventDispatcher also adds possibility to chain event dispatchers. This is used together with the direct access to the phase specific dispatch methods to implement CompositeEventDispatcher. 
 An event dispatcher derived from BasicEventDispatcher can act as a standalone event dispatcher or can be used to form a dispatch chain in CompositeEventDispatcher. /**
 * Event dispatcher which introduces event dispatch phase specific methods -
 * {@code dispatchCapturingEvent} and {@code dispatchBubblingEvent}. These
 * are used in the {@code BasicEventDispatcher.dispatchEvent} implementation,
 * but because they are public they can be called directly as well. Their
 * default implementation does nothing and is expected to be overridden in
 * subclasses. The {@code BasicEventDispatcher} also adds possibility to chain
 * event dispatchers. This is used together with the direct access to the phase
 * specific dispatch methods to implement {@code CompositeEventDispatcher}.
 * <p>
 * An event dispatcher derived from {@code BasicEventDispatcher} can act as
 * a standalone event dispatcher or can be used to form a dispatch chain in
 * {@code CompositeEventDispatcher}.
 */
public abstract class BasicEventDispatcher implements EventDispatcher {
    private BasicEventDispatcher previousDispatcher;
    private BasicEventDispatcher nextDispatcher;

    @Override
    public Event dispatchEvent(Event event, final EventDispatchChain tail) {
        event = dispatchCapturingEvent(event);
        if (event.isConsumed()) {
            return null;
        }
        event = tail.dispatchEvent(event);
        if (event != null) {
            event = dispatchBubblingEvent(event);
            if (event.isConsumed()) {
                return null;
            }
        }

        return event;
    }

    public Event dispatchCapturingEvent(Event event) {
        return event;
    }

    public Event dispatchBubblingEvent(Event event) {
        return event;
    }

    public final BasicEventDispatcher getPreviousDispatcher() {
        return previousDispatcher;
    }

    public final BasicEventDispatcher getNextDispatcher() {
        return nextDispatcher;
    }

    public final void insertNextDispatcher(
            final BasicEventDispatcher newDispatcher) {
        if (nextDispatcher != null) {
            nextDispatcher.previousDispatcher = newDispatcher;
        }
        newDispatcher.nextDispatcher = nextDispatcher;
        newDispatcher.previousDispatcher = this;
        nextDispatcher = newDispatcher;
    }
}