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package javax.swing;

import java.awt.Dimension;
import java.awt.Rectangle;



An interface that provides information to a scrolling container
like JScrollPane.  A complex component that's likely to be used
as a viewing a JScrollPane viewport (or other scrolling container)
should implement this interface.

Author:Hans Muller
See Also:
/**
 * An interface that provides information to a scrolling container
 * like JScrollPane.  A complex component that's likely to be used
 * as a viewing a JScrollPane viewport (or other scrolling container)
 * should implement this interface.
 *
 * @see JViewport
 * @see JScrollPane
 * @see JScrollBar
 * @author Hans Muller
 */
public interface Scrollable
{
    
Returns the preferred size of the viewport for a view component.
For example, the preferred size of a JList component
is the size required to accommodate all of the cells in its list.
However, the value of preferredScrollableViewportSize
is the size required for JList.getVisibleRowCount rows.
A component without any properties that would affect the viewport
size should just return getPreferredSize here.

See Also:
Returns:the preferredSize of a JViewport whose view
   is this Scrollable
/**
     * Returns the preferred size of the viewport for a view component.
     * For example, the preferred size of a <code>JList</code> component
     * is the size required to accommodate all of the cells in its list.
     * However, the value of <code>preferredScrollableViewportSize</code>
     * is the size required for <code>JList.getVisibleRowCount</code> rows.
     * A component without any properties that would affect the viewport
     * size should just return <code>getPreferredSize</code> here.
     *
     * @return the preferredSize of a <code>JViewport</code> whose view
     *    is this <code>Scrollable</code>
     * @see JViewport#getPreferredSize
     */
    Dimension getPreferredScrollableViewportSize();


    
Components that display logical rows or columns should compute
the scroll increment that will completely expose one new row
or column, depending on the value of orientation.  Ideally,
components should handle a partially exposed row or column by
returning the distance required to completely expose the item.


Scrolling containers, like JScrollPane, will use this method
each time the user requests a unit scroll.

Params:
  • visibleRect – The view area visible within the viewport
  • orientation – Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.
  • direction – Less than zero to scroll up/left, greater than zero for down/right.
See Also:
Returns:The "unit" increment for scrolling in the specified direction.
        This value should always be positive.
/**
     * Components that display logical rows or columns should compute
     * the scroll increment that will completely expose one new row
     * or column, depending on the value of orientation.  Ideally,
     * components should handle a partially exposed row or column by
     * returning the distance required to completely expose the item.
     * <p>
     * Scrolling containers, like JScrollPane, will use this method
     * each time the user requests a unit scroll.
     *
     * @param visibleRect The view area visible within the viewport
     * @param orientation Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.
     * @param direction Less than zero to scroll up/left, greater than zero for down/right.
     * @return The "unit" increment for scrolling in the specified direction.
     *         This value should always be positive.
     * @see JScrollBar#setUnitIncrement
     */
    int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction);


    
Components that display logical rows or columns should compute
the scroll increment that will completely expose one block
of rows or columns, depending on the value of orientation.


Scrolling containers, like JScrollPane, will use this method
each time the user requests a block scroll.

Params:
  • visibleRect – The view area visible within the viewport
  • orientation – Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.
  • direction – Less than zero to scroll up/left, greater than zero for down/right.
See Also:
Returns:The "block" increment for scrolling in the specified direction.
        This value should always be positive.
/**
     * Components that display logical rows or columns should compute
     * the scroll increment that will completely expose one block
     * of rows or columns, depending on the value of orientation.
     * <p>
     * Scrolling containers, like JScrollPane, will use this method
     * each time the user requests a block scroll.
     *
     * @param visibleRect The view area visible within the viewport
     * @param orientation Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.
     * @param direction Less than zero to scroll up/left, greater than zero for down/right.
     * @return The "block" increment for scrolling in the specified direction.
     *         This value should always be positive.
     * @see JScrollBar#setBlockIncrement
     */
    int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction);


    
Return true if a viewport should always force the width of this
Scrollable to match the width of the viewport.
For example a normal
text view that supported line wrapping would return true here, since it
would be undesirable for wrapped lines to disappear beyond the right
edge of the viewport.  Note that returning true for a Scrollable
whose ancestor is a JScrollPane effectively disables horizontal
scrolling.


Scrolling containers, like JViewport, will use this method each
time they are validated.

Returns:True if a viewport should force the Scrollables width to match its own.
/**
     * Return true if a viewport should always force the width of this
     * <code>Scrollable</code> to match the width of the viewport.
     * For example a normal
     * text view that supported line wrapping would return true here, since it
     * would be undesirable for wrapped lines to disappear beyond the right
     * edge of the viewport.  Note that returning true for a Scrollable
     * whose ancestor is a JScrollPane effectively disables horizontal
     * scrolling.
     * <p>
     * Scrolling containers, like JViewport, will use this method each
     * time they are validated.
     *
     * @return True if a viewport should force the Scrollables width to match its own.
     */
    boolean getScrollableTracksViewportWidth();

    
Return true if a viewport should always force the height of this
Scrollable to match the height of the viewport.  For example a
columnar text view that flowed text in left to right columns
could effectively disable vertical scrolling by returning
true here.


Scrolling containers, like JViewport, will use this method each
time they are validated.

Returns:True if a viewport should force the Scrollables height to match its own.
/**
     * Return true if a viewport should always force the height of this
     * Scrollable to match the height of the viewport.  For example a
     * columnar text view that flowed text in left to right columns
     * could effectively disable vertical scrolling by returning
     * true here.
     * <p>
     * Scrolling containers, like JViewport, will use this method each
     * time they are validated.
     *
     * @return True if a viewport should force the Scrollables height to match its own.
     */
    boolean getScrollableTracksViewportHeight();
}