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WebLaf is a Java Swing Look and Feel and extended components library for cross-platform applications

There is a newer version: 2.2.1

/*
 * This file is part of WebLookAndFeel library.
 *
 * WebLookAndFeel library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * WebLookAndFeel library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with WebLookAndFeel library.  If not, see .
 */

package com.alee.managers.drag;

import com.alee.utils.SwingUtils;

import javax.swing.*;
import java.awt.*;
import java.awt.dnd.DragSourceDragEvent;
import java.awt.dnd.DragSourceDropEvent;
import java.awt.image.BufferedImage;
import java.lang.ref.WeakReference;

/**
 * @author Mikle Garin
 */

public abstract class ComponentDragViewHandler implements DragViewHandler
{
    /**
     * Initial mouse location on dragged component.
     * Used to position component snapshot correctly under the mouse.
     */
    protected Point location;

    /**
     * Dragged object reference.
     */
    protected WeakReference reference;

    @Override
    public BufferedImage getView ( final T object, final DragSourceDragEvent event )
    {
        // Saving initial mouse location
        if ( reference == null || reference.get () != object )
        {
            final Point los = object.getLocationOnScreen ();
            final Point eloc = event.getLocation ();
            location = new Point ( los.x - eloc.x, los.y - eloc.y );
            reference = new WeakReference ( object );
        }

        // Returning component snapshot
        return SwingUtils.createComponentSnapshot ( object, getSnapshotOpacity () );
    }

    /**
     * Returns component snapshot opacity.
     * By default snapshot is semi-transparent for usability purposes.
     *
     * @return component snapshot opacity
     */
    public float getSnapshotOpacity ()
    {
        return 0.8f;
    }

    @Override
    public Point getViewRelativeLocation ( final T object, final DragSourceDragEvent event )
    {
        return location;
    }

    @Override
    public void dragEnded ( final T object, final DragSourceDropEvent event )
    {
        // Clearing initial mouse location
        location = null;
        reference = null;
    }
}