DoubleClickTrigger.java

/*******************************************************************************
 * Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.tools.workbench.framework.uitools;

// JDK
import java.awt.event.InputEvent;
import java.awt.event.MouseEvent;

/**
 * This class is used for detecting the occurence of a double-click. For the
 * purposes of this class, a "double-click" is the occurence of two
 * {@link MouseEvent}s corresponding to the mouse1 button without any modifier
 * keys being pressed.
 * <p>
 * The detection of double-click is mediated by the {@link #isDoubleClick(MouseEvent)}
 * method. All mouse events for a particular {@link java.awt.event.MouseListener
 * MouseListener} must be forwarded to {@link #isDoubleClick(MouseEvent)} for
 * processing in order for the proper sequence of clicks to be detected.
 * <p>
 * The implementation of {@link #isDoubleClick(MouseEvent)} is somewhat
 * unforgiving, since it will return <CODE>true</CODE> only when the click count
 * is a multiple of 2, so long as the last two clicks were mouse1 clicks without
 * modifier keys.
 *
 * @version 10.1.3
 * @author Pascal Filion
 */
final class DoubleClickTrigger
{
    /**
     * Keeps track of the last click and its state, whether it could be used as
     * the first of the double clicks.
     */
    private boolean lastClickOK;

    /**
     * The mask used to determine if any ...
     */
    private static final int CLICK_MASK = InputEvent.BUTTON1_MASK   |
                                                      InputEvent.ALT_MASK       |
                                                      InputEvent.ALT_GRAPH_MASK |
                                                      InputEvent.CTRL_MASK      |
                                                      InputEvent.META_MASK      |
                                                      InputEvent.SHIFT_MASK;

    /**
     * This method is intended to serve as a delegate for the
     * {@link MouseListener#mouseClicked(MouseEvent)} method.
     *
     * @return <code>true</code> if the specified {@link MouseEvent} is deemed to
     * be the second click of a double-click sequence; as an additional side
     * effect of returning <CODE>true</CODE>, the {@link MouseEvent} is also
     * consumed
     */
    public boolean isDoubleClick(MouseEvent e)
    {
        int clickCount = e.getClickCount();

        // Sanity check the click count
        if (clickCount <= 0)
        {
            lastClickOK = false;
            return false;
        }

        int modifiers = e.getModifiers();
        boolean currentClickOk = (modifiers & CLICK_MASK) == InputEvent.BUTTON1_MASK;

        if ((clickCount >= 2) && lastClickOK)
        {
            lastClickOK = false;

            if (currentClickOk)
                e.consume();

            return currentClickOk;
        }

        lastClickOK = currentClickOk;

        return false;
    }
}