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    1   /*
    2    * Copyright (c) 1997, 2003, 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.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
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   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package javax.swing;
   27   
   28   import java.awt.Dimension;
   29   import java.awt.Rectangle;
   30   
   31   
   32   /**
   33    * An interface that provides information to a scrolling container
   34    * like JScrollPane.  A complex component that's likely to be used
   35    * as a viewing a JScrollPane viewport (or other scrolling container)
   36    * should implement this interface.
   37    *
   38    * @see JViewport
   39    * @see JScrollPane
   40    * @see JScrollBar
   41    * @author Hans Muller
   42    */
   43   public interface Scrollable
   44   {
   45       /**
   46        * Returns the preferred size of the viewport for a view component.
   47        * For example, the preferred size of a <code>JList</code> component
   48        * is the size required to accommodate all of the cells in its list.
   49        * However, the value of <code>preferredScrollableViewportSize</code>
   50        * is the size required for <code>JList.getVisibleRowCount</code> rows.
   51        * A component without any properties that would affect the viewport
   52        * size should just return <code>getPreferredSize</code> here.
   53        *
   54        * @return the preferredSize of a <code>JViewport</code> whose view
   55        *    is this <code>Scrollable</code>
   56        * @see JViewport#getPreferredSize
   57        */
   58       Dimension getPreferredScrollableViewportSize();
   59   
   60   
   61       /**
   62        * Components that display logical rows or columns should compute
   63        * the scroll increment that will completely expose one new row
   64        * or column, depending on the value of orientation.  Ideally,
   65        * components should handle a partially exposed row or column by
   66        * returning the distance required to completely expose the item.
   67        * <p>
   68        * Scrolling containers, like JScrollPane, will use this method
   69        * each time the user requests a unit scroll.
   70        *
   71        * @param visibleRect The view area visible within the viewport
   72        * @param orientation Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.
   73        * @param direction Less than zero to scroll up/left, greater than zero for down/right.
   74        * @return The "unit" increment for scrolling in the specified direction.
   75        *         This value should always be positive.
   76        * @see JScrollBar#setUnitIncrement
   77        */
   78       int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction);
   79   
   80   
   81       /**
   82        * Components that display logical rows or columns should compute
   83        * the scroll increment that will completely expose one block
   84        * of rows or columns, depending on the value of orientation.
   85        * <p>
   86        * Scrolling containers, like JScrollPane, will use this method
   87        * each time the user requests a block scroll.
   88        *
   89        * @param visibleRect The view area visible within the viewport
   90        * @param orientation Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.
   91        * @param direction Less than zero to scroll up/left, greater than zero for down/right.
   92        * @return The "block" increment for scrolling in the specified direction.
   93        *         This value should always be positive.
   94        * @see JScrollBar#setBlockIncrement
   95        */
   96       int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction);
   97   
   98   
   99       /**
  100        * Return true if a viewport should always force the width of this
  101        * <code>Scrollable</code> to match the width of the viewport.
  102        * For example a normal
  103        * text view that supported line wrapping would return true here, since it
  104        * would be undesirable for wrapped lines to disappear beyond the right
  105        * edge of the viewport.  Note that returning true for a Scrollable
  106        * whose ancestor is a JScrollPane effectively disables horizontal
  107        * scrolling.
  108        * <p>
  109        * Scrolling containers, like JViewport, will use this method each
  110        * time they are validated.
  111        *
  112        * @return True if a viewport should force the Scrollables width to match its own.
  113        */
  114       boolean getScrollableTracksViewportWidth();
  115   
  116       /**
  117        * Return true if a viewport should always force the height of this
  118        * Scrollable to match the height of the viewport.  For example a
  119        * columnar text view that flowed text in left to right columns
  120        * could effectively disable vertical scrolling by returning
  121        * true here.
  122        * <p>
  123        * Scrolling containers, like JViewport, will use this method each
  124        * time they are validated.
  125        *
  126        * @return True if a viewport should force the Scrollables height to match its own.
  127        */
  128       boolean getScrollableTracksViewportHeight();
  129   }

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