org.jvnet.lafwidget.tree.dnd.AutoScrollingTreeDropTarget Maven / Gradle / Ivy

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Laf-Widget provides support for common "feel" widgets in look-and-feel libraries
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/*
 * Copyright (c) 2005-2006 Laf-Widget Kirill Grouchnikov. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 *  o Redistributions of source code must retain the above copyright notice, 
 *    this list of conditions and the following disclaimer. 
 *     
 *  o Redistributions in binary form must reproduce the above copyright notice, 
 *    this list of conditions and the following disclaimer in the documentation 
 *    and/or other materials provided with the distribution. 
 *     
 *  o Neither the name of Laf-Widget Kirill Grouchnikov nor the names of 
 *    its contributors may be used to endorse or promote products derived 
 *    from this software without specific prior written permission. 
 *     
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */
package org.jvnet.lafwidget.tree.dnd;
import java.awt.Point;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetListener;
import javax.swing.JTree;
import javax.swing.JViewport;
import javax.swing.SwingUtilities;

class AutoScrollingTreeDropTarget extends DropTarget
{
  private JViewport viewport;
  private int scrollUnits;
  private JTree tree;
  
  AutoScrollingTreeDropTarget(JTree aTree, DropTargetListener listener )
  {
    super(aTree, DnDConstants.ACTION_COPY_OR_MOVE, listener );
    this.viewport = (JViewport) SwingUtilities.getAncestorOfClass( JViewport.class, aTree );
    this.scrollUnits = Math.max( aTree.getRowHeight(), 16 );
    this.tree = aTree;
  }
  
  private Point lastDragCursorLocn = new Point(0,0);
  
  protected void updateAutoscroll(Point dragCursorLocn)
  {
    if ( this.lastDragCursorLocn.equals( dragCursorLocn ) )
      return;
    else
      this.lastDragCursorLocn.setLocation( dragCursorLocn );
    this.doAutoscroll( dragCursorLocn );
  }
  
  protected void initializeAutoscrolling(Point p)
  {
    this.doAutoscroll( p );
  }
  
  protected void clearAutoscroll()
  {
  }
  
  private static final int AUTOSCROLL_MARGIN = 16;
  
  protected void doAutoscroll(Point aPoint)
  {
    if ( this.viewport == null )
      return;
    
    Point treePosition = this.viewport.getViewPosition();
    int vH = this.viewport.getExtentSize().height;
    int vW = this.viewport.getExtentSize().width;
    Point nextPoint = null;
    if ((aPoint.y - treePosition.y) < AutoScrollingTreeDropTarget.AUTOSCROLL_MARGIN)
    {
      nextPoint = new Point(treePosition.x, Math.max( treePosition.y - this.scrollUnits, 0 ) );
    }
    else if (treePosition.y + vH - aPoint.y < AutoScrollingTreeDropTarget.AUTOSCROLL_MARGIN)
    {
      nextPoint = new Point(treePosition.x, Math.min( aPoint.y + AutoScrollingTreeDropTarget.AUTOSCROLL_MARGIN, this.tree.getHeight()  - vH ) );
    }
    else if (aPoint.x - treePosition.x < AutoScrollingTreeDropTarget.AUTOSCROLL_MARGIN)
    {
      nextPoint = new Point(Math.max( treePosition.x - AutoScrollingTreeDropTarget.AUTOSCROLL_MARGIN, 0 ), treePosition.y);
    }
    else if (treePosition.x + vW - aPoint.x < AutoScrollingTreeDropTarget.AUTOSCROLL_MARGIN)
    {
      nextPoint = new Point(Math.min( treePosition.x + AutoScrollingTreeDropTarget.AUTOSCROLL_MARGIN,
        this.tree.getWidth()  - vW ), treePosition.y);
    }
    if( nextPoint != null )
      this.viewport.setViewPosition( nextPoint );
  }
}