1 /*
2  * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4  *
5  * This code is free software; you can redistribute it and/or modify it
6  * under the terms of the GNU General Public License version 2 only, as
7  * published by the Free Software Foundation.
8  *
9  * This code is distributed in the hope that it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12  * version 2 for more details (a copy is included in the LICENSE file that
13  * accompanied this code).
14  *
15  * You should have received a copy of the GNU General Public License version
16  * 2 along with this work; if not, write to the Free Software Foundation,
17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18  *
19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20  * or visit www.oracle.com if you need additional information or have any
21  * questions.
22  */
23 
24 import javax.swing.*;
25 import java.awt.*;
26 import java.awt.dnd.Autoscroll;
27 
28 public class JListWithScroll<E> extends JList<E> implements Autoscroll {
29     private Insets scrollInsets;
30 
JListWithScroll(E[] listData)31     public JListWithScroll(E[] listData) {
32         super(listData);
33         scrollInsets = new Insets(50, 50, 50, 50);
34     }
35 
36     @Override
getAutoscrollInsets()37     public Insets getAutoscrollInsets() {
38         return scrollInsets;
39     }
40 
41     @Override
autoscroll(Point cursorLoc)42     public void autoscroll(Point cursorLoc) {
43         JViewport viewport = getViewport();
44 
45         if (viewport == null) {
46             return;
47         }
48 
49         Point viewPos = viewport.getViewPosition();
50         int viewHeight = viewport.getExtentSize().height;
51         int viewWidth = viewport.getExtentSize().width;
52 
53         if ((cursorLoc.y - viewPos.y) < scrollInsets.top) {
54             viewport.setViewPosition(new Point(viewPos.x, Math.max(viewPos.y - scrollInsets.top, 0)));
55         } else if (((viewPos.y + viewHeight) - cursorLoc.y) < scrollInsets.bottom) {
56             viewport.setViewPosition(
57                     new Point(viewPos.x, Math.min(viewPos.y + scrollInsets.bottom, this.getHeight() - viewHeight))
58             );
59         } else if ((cursorLoc.x - viewPos.x) < scrollInsets.left) {
60             viewport.setViewPosition(new Point(Math.max(viewPos.x - scrollInsets.left, 0), viewPos.y));
61         } else if (((viewPos.x + viewWidth) - cursorLoc.x) < scrollInsets.right) {
62             viewport.setViewPosition(
63                     new Point(Math.min(viewPos.x + scrollInsets.right, this.getWidth() - viewWidth), viewPos.y)
64             );
65         }
66 
67     }
68 
getViewport()69     public JViewport getViewport() {
70         Component curComp = this;
71 
72         while (!(curComp instanceof JViewport) && (curComp != null)) {
73             curComp = curComp.getParent();
74         }
75         if(curComp instanceof JViewport) {
76             return (JViewport) curComp;
77         } else {
78             return null;
79         }
80     }
81 }
82