VertialScrollablePanel.java

// BlogBridge -- RSS feed reader, manager, and web based service
// Copyright (C) 2002-2006 by R. Pito Salas
//
// This program is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free Software Foundation;
// either version 2 of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
// without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along with this program;
// if not, write to the Free Software Foundation, Inc., 59 Temple Place,
// Suite 330, Boston, MA 02111-1307 USA
//
// Contact: R. Pito Salas
// mailto:pitosalas@users.sourceforge.net
// More information: about BlogBridge
// http://www.blogbridge.com
// http://sourceforge.net/projects/blogbridge
//
// $Id: VertialScrollablePanel.java,v 1.3 2006/10/31 11:41:28 spyromus Exp $
//

package com.salas.bb.utils.uif;

import javax.swing.*;
import java.awt.*;

/**
 * A panel that tracks the width of the scroll panel.
 */
public class VertialScrollablePanel extends JPanel implements Scrollable
{
    /** Fixed scroll step size. */ 
    private static final int STEP_SIZE = 20;

    /**
     * Creates a new scrollable panel.
     */
    public VertialScrollablePanel()
    {
    }

    /**
     * Creates a new scrollable panel with layout manager.
     *
     * @param manager layout manager.
     */
    public VertialScrollablePanel(LayoutManager manager)
    {
        super(manager);
    }

    /**
     * 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.
     */
    public boolean getScrollableTracksViewportHeight()
    {
        return false;
    }

    /**
     * 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.
     */
    public boolean getScrollableTracksViewportWidth()
    {
        return true;
    }

    /**
     * Returns the preferred size of the viewport for a view component.
     * For example the preferredSize 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 effect the viewport size should just return
     * getPreferredSize() here.
     *
     * @return The preferredSize of a JViewport whose view is this Scrollable.
     *
     * @see javax.swing.JViewport#getPreferredSize
     */
    public Dimension getPreferredScrollableViewportSize()
    {
        return getPreferredSize();
    }

    /**
     * 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 javax.swing.JScrollBar#setBlockIncrement
     */
    public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction)
    {
        return visibleRect.height;
    }

    /**
     * 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 javax.swing.JScrollBar#setUnitIncrement
     */
    public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction)
    {
        return STEP_SIZE;
    }
}