Varying size of JScrollPane

Question

Hi.
I hope you can help me figure out what's going on. I have a component that I've written that should display buttons vertically (it's a basis for an OutlookBar styled component).
The component is based on a JPanel that is put in a JScrollPane and the buttons are added to the JPanel. The JPanel has a VerticalFlowLayout (a custom layout class).
Now for the problem: Every time I adjust the size of the component so that a scroll bar should appear, the getPreferredSize() method of the JScrollPane returns a width that is lesser than it returns when the scroll bar is not visible! The weird thing is that the difference in the width is exactly the width of the scroll bar... but it doesn't make much sense since the width that is returned when the scroll bar is visible is less than the width that is returned when the scroll bar is not visible (it would make sense to have it the other way around!).
Since my component needs to keep a consistent width this behavior is extremely annoying! Below you can find the code for the panel (and the needed layout) if you'd like to try this out, any help will be greatly appreciated:
import javax.swing.*;
import javax.swing.plaf.ComponentUI;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
* A panel that contains a set of operations that are displayed under a common
* category name on a <code>OutlookBar</code>.
* @version Revision:$ Date:$
public class OutlookBarCategoryPanel extends JPanel
    protected JPanel m_contentPanel = new JPanel( new VerticalFlowLayout( 5 ) );
    private JScrollPane m_contentScrollPane = new JScrollPane( m_contentPanel,
                                                    JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                                                    JScrollPane.HORIZONTAL_SCROLLBAR_NEVER );
     * Constructs a new <tt>OutlookBarCategoryPanel</tt> that is initially empty.
    public OutlookBarCategoryPanel()
        super( new BorderLayout() );
        m_contentPanel.setBackground( SystemColor.control );
        super.add( m_contentScrollPane, BorderLayout.CENTER );
     * If the <code>preferredSize</code> has been set to a
     * non-<code>null</code> value just returns it.
     * If the UI delegate's <code>getPreferredSize</code>
     * method returns a non <code>null</code> value then return that;
     * otherwise defer to the component's layout manager.
     * @return the value of the <code>preferredSize</code> property
     * @see #setPreferredSize
     * @see ComponentUI
    public Dimension getPreferredSize()
        Dimension size = super.getPreferredSize();
        if( size.width < m_contentScrollPane.getPreferredSize().width )
            size.width = m_contentScrollPane.getPreferredSize().width;
        return size;
     * Appends the specified component to the end of this container.
     * This is a convenience method for {@link #addImpl}.
     * <p>
     * Note: If a component has been added to a container that
     * has been displayed, <code>validate</code> must be
     * called on that container to display the new component.
     * If multiple components are being added, you can improve
     * efficiency by calling <code>validate</code> only once,
     * after all the components have been added.
     * @param     comp   the component to be added
     * @see #addImpl
     * @see #validate
     * @see #revalidate
     * @return    the component argument
    public Component add( Component comp )
        return m_contentPanel.add( comp );
     * Adds the specified component to the end of this container.
     * Also notifies the layout manager to add the component to
     * this container's layout using the specified constraints object.
     * This is a convenience method for {@link #addImpl}.
     * <p>
     * Note: If a component has been added to a container that
     * has been displayed, <code>validate</code> must be
     * called on that container to display the new component.
     * If multiple components are being added, you can improve
     * efficiency by calling <code>validate</code> only once,
     * after all the components have been added.
     * @param     comp the component to be added
     * @param     constraints an object expressing
     *                  layout contraints for this component
     * @see #addImpl
     * @see #validate
     * @see #revalidate
     * @see       LayoutManager
     * @since     JDK1.1
    public void add( Component comp, Object constraints )
        m_contentPanel.add( comp );
     * Adds the specified component to this container with the specified
     * constraints at the specified index.  Also notifies the layout
     * manager to add the component to the this container's layout using
     * the specified constraints object.
     * This is a convenience method for {@link #addImpl}.
     * <p>
     * Note: If a component has been added to a container that
     * has been displayed, <code>validate</code> must be
     * called on that container to display the new component.
     * If multiple components are being added, you can improve
     * efficiency by calling <code>validate</code> only once,
     * after all the components have been added.
     * @param comp the component to be added
     * @param constraints an object expressing layout contraints for this
     * @param index the position in the container's list at which to insert
     * the component; <code>-1</code> means insert at the end
     * component
     * @see #addImpl
     * @see #validate
     * @see #revalidate
     * @see #remove
     * @see LayoutManager
    public void add( Component comp, Object constraints, int index )
        m_contentPanel.add( comp, index );
     * Adds the specified component to this container at the given
     * position.
     * This is a convenience method for {@link #addImpl}.
     * <p>
     * Note: If a component has been added to a container that
     * has been displayed, <code>validate</code> must be
     * called on that container to display the new component.
     * If multiple components are being added, you can improve
     * efficiency by calling <code>validate</code> only once,
     * after all the components have been added.
     * @param     comp   the component to be added
     * @param     index    the position at which to insert the component,
     *                   or <code>-1</code> to append the component to the end
     * @return    the component <code>comp</code>
     * @see #addImpl
     * @see #remove
     * @see #validate
     * @see #revalidate
    public Component add( Component comp, int index )
        return m_contentPanel.add( comp, index );
     * Adds the specified component to this container.
     * This is a convenience method for {@link #addImpl}.
     * <p>
     * This method is obsolete as of 1.1.  Please use the
     * method <code>add(Component, Object)</code> instead.
     * @see add(Component, Object)
    public Component add( String name, Component comp )
        return m_contentPanel.add( name, comp );
     * Removes the specified button from the panel.  The reference that is sent as
     * a parameter needs to point to the same instance as the button that should actually
     * be removed (in other words, this method will not perform an equal() comparison).
     * @param button    a reference to the button that should be removed.
    public void remove( OutlookBarOperationButton button )
        m_contentPanel.remove( button );
     * Removes all operations that have the specified caption.
     * @param caption   the caption of the operation(s) that should be removed.
    public void removeOperation( String caption )
        Component[] components = m_contentPanel.getComponents();
        for( int i=0; i<components.length; i++ )
            Component component = components;
if( component != null && component instanceof AbstractButton )
if( ((AbstractButton)component).getText().equals( caption ) )
m_contentPanel.remove( i );
public static void main( String[] args )
JFrame frame = new JFrame( "OutlookBarCategorButton" );
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
frame.getContentPane().setLayout( new BorderLayout() );
OutlookBarCategoryPanel obcp = new OutlookBarCategoryPanel();
obcp.add( new OutlookBarOperationButton( "foo", new ImageIcon( "images/History24.gif" ) ) );
obcp.add( new OutlookBarOperationButton( "bar", new ImageIcon( "images/Help24.gif" ) ) );
obcp.add( new OutlookBarOperationButton( "foobar", new ImageIcon( "images/Cut24.gif" ) ) );
obcp.add( new OutlookBarOperationButton( "index 2", new ImageIcon( "images/isl_faninn.png" ) ), 2 );
frame.getContentPane().add( obcp, BorderLayout.WEST );
frame.pack();
frame.show();
And here is the code for the VerticalFlowLayout class:
import java.awt.*;
* A layout manager that works like the default layout manager in swing
* (FlowLayout) except that it arranges its components vertically instead
* of horizontally.
* @version $Revision: 1.1 $ $Date: 2003/03/11 13:37:38 $
public class VerticalFlowLayout implements LayoutManager
    private int m_vgap;
     * Creates a new instance of the class with an initial vertical gap of 0
     * pixels.
    public VerticalFlowLayout()
        this( 0 );
     * Creates a new instance of the class with an initial vertical gap of
     * the specified number of pixels.
     * @param vgap  the number of pixels to use as a gap between
     *              components
    public VerticalFlowLayout( int vgap )
        m_vgap = vgap;
     * Lays out the container in the specified panel.
     * @param theParent the component which needs to be laid out
    public void layoutContainer( Container theParent )
        Insets insets = theParent.getInsets();
        int w = theParent.getSize().width - insets.left - insets.right;
        int numComponents = theParent.getComponentCount();
        if( numComponents == 0 )
            return;
        int y = insets.top;
        int x = insets.left;
        for( int i = 0; i < numComponents; ++i )
            Component c = theParent.getComponent(i);
            if( c.isVisible() )
                Dimension d = c.getPreferredSize();
                c.setBounds( x, y, w, d.height );
                y += d.height + m_vgap;
     * Calculates the minimum size dimensions for the specified
     * panel given the components in the specified parent container.
     * @param theParent the component to be laid out
     * @see #preferredLayoutSize
    public Dimension minimumLayoutSize( Container theParent )
        Insets insets = theParent.getInsets();
        int maxWidth = 0;
        int totalHeight = 0;
        int numComponents = theParent.getComponentCount();
        for( int i = 0; i < numComponents; ++i )
            Component c = theParent.getComponent( i );
            if( c.isVisible() )
                Dimension cd = c.getMinimumSize();
                maxWidth = Math.max( maxWidth, cd.width );
                totalHeight += cd.height;
        Dimension td = new Dimension( maxWidth + insets.left + insets.right,
                totalHeight + insets.top + insets.bottom + m_vgap * numComponents );
        return td;
     * If the layout manager uses a per-component string,
     * adds the component <code>comp</code> to the layout,
     * associating it
     * with the string specified by <code>name</code>.
     * @param name the string to be associated with the component
     * @param comp the component to be added
    public void addLayoutComponent( String name, Component comp )
     * Removes the specified component from the layout.
     * @param comp the component to be removed
    public void removeLayoutComponent( Component comp )
     * Calculates the preferred size dimensions for the specified
     * panel given the components in the specified parent container.
     * @param theParent the component to be laid out
     * @see #minimumLayoutSize
    public Dimension preferredLayoutSize( Container theParent )
        Insets insets = theParent.getInsets();
        int maxWidth = 0;
        int totalHeight = 0;
        int numComponents = theParent.getComponentCount();
        for( int i = 0; i < numComponents; ++i )
            Component c = theParent.getComponent( i );
            if( c.isVisible() )
                Dimension cd = c.getPreferredSize();
                maxWidth = Math.max( maxWidth, cd.width );
                totalHeight += cd.height;
        Dimension td = new Dimension( maxWidth + insets.left + insets.right,
                totalHeight + insets.top + insets.bottom + m_vgap * numComponents );
        return td;

Answer 1

You can use calligraphy/ art brush strokes, can you not? Some of them come with AI and you can find quite a few on ze interweb. You could even create your own, if need be.
Mylenium