src/java.desktop/share/classes/java/awt/KeyEventPostProcessor.java

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package java.awt;

import java.awt.event.KeyEvent;


/**
 * A KeyEventPostProcessor cooperates with the current KeyboardFocusManager
 * in the final resolution of all unconsumed KeyEvents. KeyEventPostProcessors
 * registered with the current KeyboardFocusManager will receive KeyEvents
 * after the KeyEvents have been dispatched to and handled by their targets.
 * KeyEvents that would have been otherwise discarded because no Component in
 * the application currently owns the focus will also be forwarded to
 * registered KeyEventPostProcessors. This will allow applications to implement
 * features that require global KeyEvent post-handling, such as menu shortcuts.
 * <p>
 * Note that the KeyboardFocusManager itself implements KeyEventPostProcessor.
 * By default, the current KeyboardFocusManager will be the final
 * KeyEventPostProcessor in the chain. The current KeyboardFocusManager cannot
 * be completely deregistered as a KeyEventPostProcessor. However, if a
 * KeyEventPostProcessor reports that no further post-processing of the
 * KeyEvent should take place, the AWT will consider the event fully handled
 * and will take no additional action with regard to the event. (While it is
 * possible for client code to register the current KeyboardFocusManager as
 * a KeyEventPostProcessor one or more times, this is usually unnecessary and
 * not recommended.)
 *
 * @author David Mendenhall
 *
 * @see KeyboardFocusManager#addKeyEventPostProcessor
 * @see KeyboardFocusManager#removeKeyEventPostProcessor
 * @since 1.4
 */
@FunctionalInterface
public interface KeyEventPostProcessor {

    /**
     * This method is called by the current KeyboardFocusManager, requesting
     * that this KeyEventPostProcessor perform any necessary post-processing
     * which should be part of the KeyEvent's final resolution. At the time
     * this method is invoked, typically the KeyEvent has already been
     * dispatched to and handled by its target. However, if no Component in
     * the application currently owns the focus, then the KeyEvent has not
     * been dispatched to any Component. Typically, KeyEvent post-processing
     * will be used to implement features which require global KeyEvent
     * post-handling, such as menu shortcuts. Note that if a
     * KeyEventPostProcessor wishes to dispatch the KeyEvent, it must use
     * {@code redispatchEvent} to prevent the AWT from recursively
     * requesting that this KeyEventPostProcessor perform post-processing
     * of the event again.
     * <p>
     * If an implementation of this method returns {@code false}, then the
     * KeyEvent is passed to the next KeyEventPostProcessor in the chain,
     * ending with the current KeyboardFocusManager. If an implementation
     * returns {@code true}, the KeyEvent is assumed to have been fully
     * handled (although this need not be the case), and the AWT will take no
     * further action with regard to the KeyEvent. If an implementation
     * consumes the KeyEvent but returns {@code false}, the consumed
     * event will still be passed to the next KeyEventPostProcessor in the
     * chain. It is important for developers to check whether the KeyEvent has
     * been consumed before performing any post-processing of the KeyEvent. By
     * default, the current KeyboardFocusManager will perform no post-
     * processing in response to a consumed KeyEvent.
     *
     * @param e the KeyEvent to post-process
     * @return {@code true} if the AWT should take no further action with
     *         regard to the KeyEvent; {@code false} otherwise
     * @see KeyboardFocusManager#redispatchEvent
     */
    boolean postProcessKeyEvent(KeyEvent e);
}