Scrollable


1   /*
2    * @(#)Scrollable.java  1.12 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package javax.swing;
9   
10  import java.awt.Dimension  ;
11  import java.awt.Rectangle  ;
12  
13  
14  /** 
15   * An interface that provides information to a scrolling container
16   * like JScrollPane.  A complex component that's likely to be used 
17   * as a viewing a JScrollPane viewport (or other scrolling container) 
18   * should implement this interface.
19   * 
20   * @see JViewport
21   * @see JScrollPane
22   * @see JScrollBar
23   * @version 1.12 12/19/03
24   * @author Hans Muller
25   */
26  public interface Scrollable  
27  {
28      /**
29       * Returns the preferred size of the viewport for a view component.
30       * For example, the preferred size of a <code>JList</code> component
31       * is the size required to accommodate all of the cells in its list.
32       * However, the value of <code>preferredScrollableViewportSize</code>
33       * is the size required for <code>JList.getVisibleRowCount</code> rows.
34       * A component without any properties that would affect the viewport
35       * size should just return <code>getPreferredSize</code> here.
36       * 
37       * @return the preferredSize of a <code>JViewport</code> whose view
38       *    is this <code>Scrollable</code>
39       * @see JViewport#getPreferredSize
40       */
41      Dimension   getPreferredScrollableViewportSize();
42  
43  
44      /**
45       * Components that display logical rows or columns should compute
46       * the scroll increment that will completely expose one new row
47       * or column, depending on the value of orientation.  Ideally, 
48       * components should handle a partially exposed row or column by 
49       * returning the distance required to completely expose the item.
50       * <p>
51       * Scrolling containers, like JScrollPane, will use this method
52       * each time the user requests a unit scroll.
53       * 
54       * @param visibleRect The view area visible within the viewport
55       * @param orientation Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.
56       * @param direction Less than zero to scroll up/left, greater than zero for down/right.
57       * @return The "unit" increment for scrolling in the specified direction.
58       *         This value should always be positive.
59       * @see JScrollBar#setUnitIncrement
60       */
61      int getScrollableUnitIncrement(Rectangle   visibleRect, int orientation, int direction);
62  
63  
64      /**
65       * Components that display logical rows or columns should compute
66       * the scroll increment that will completely expose one block
67       * of rows or columns, depending on the value of orientation. 
68       * <p>
69       * Scrolling containers, like JScrollPane, will use this method
70       * each time the user requests a block scroll.
71       * 
72       * @param visibleRect The view area visible within the viewport
73       * @param orientation Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.
74       * @param direction Less than zero to scroll up/left, greater than zero for down/right.
75       * @return The "block" increment for scrolling in the specified direction.
76       *         This value should always be positive.
77       * @see JScrollBar#setBlockIncrement
78       */
79      int getScrollableBlockIncrement(Rectangle   visibleRect, int orientation, int direction);  
80      
81  
82      /**
83       * Return true if a viewport should always force the width of this 
84       * <code>Scrollable</code> to match the width of the viewport. 
85       * For example a normal 
86       * text view that supported line wrapping would return true here, since it
87       * would be undesirable for wrapped lines to disappear beyond the right
88       * edge of the viewport.  Note that returning true for a Scrollable
89       * whose ancestor is a JScrollPane effectively disables horizontal
90       * scrolling.
91       * <p>
92       * Scrolling containers, like JViewport, will use this method each 
93       * time they are validated.  
94       * 
95       * @return True if a viewport should force the Scrollables width to match its own.
96       */
97      boolean getScrollableTracksViewportWidth();
98  
99      /**
100      * Return true if a viewport should always force the height of this 
101      * Scrollable to match the height of the viewport.  For example a 
102      * columnar text view that flowed text in left to right columns 
103      * could effectively disable vertical scrolling by returning
104      * true here.
105      * <p>
106      * Scrolling containers, like JViewport, will use this method each 
107      * time they are validated.  
108      * 
109      * @return True if a viewport should force the Scrollables height to match its own.
110      */
111     boolean getScrollableTracksViewportHeight();
112 }
113
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