JPanel.java

/* JPanel.java --
   Copyright (C) 2002, 2004, 2006, Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath 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, or (at your option)
any later version.

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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.

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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
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package javax.swing;

import java.awt.FlowLayout;
import java.awt.LayoutManager;

import javax.accessibility.Accessible;
import javax.accessibility.AccessibleContext;
import javax.accessibility.AccessibleRole;
import javax.swing.plaf.PanelUI;

/**
 * An instance of JPanel can be added to a panel, frame etc
 *
 * @author Ronald Veldema (rveldema@cs.vu.nl)
 */
public class JPanel extends JComponent implements Accessible
{
  /**
   * Provides accessibility support for <code>JPanel</code>.
   *
   * @author Roman Kennke (roman@kennke.org)
   */
  protected class AccessibleJPanel extends AccessibleJComponent
  {
    /**
     * Creates a new instance of <code>AccessibleJPanel</code>.
     */
    protected AccessibleJPanel()
    {
      // Nothing to do here.
    }

    /**
     * Returns the accessible role for <code>JPanel</code>, which is
     * {@link AccessibleRole#PANEL}.
     *
     * @return the accessible role for <code>JPanel</code>
     */
    public AccessibleRole getAccessibleRole()
    {
      return AccessibleRole.PANEL;
    }
  }

  /**
   * Creates a new panel with a new instance of {@link FlowLayout} as the
   * layout manager and double-buffering enabled.
   */
  public JPanel()
  {
    this(new FlowLayout(), true);
  }

  /**
   * Creates a new panel with double-buffering enabled or disabled as
   * specified.  The default layout manager is an instance of 
   * {@link FlowLayout}.
   * 
   * @param isDoubleBuffered  a flag that controls whether or not 
   *     double-buffering is enabled.
   */
  public JPanel(boolean isDoubleBuffered)
  {
    this(new FlowLayout(), isDoubleBuffered);
  }

  /**
   * Creates a new panel with the specified layout manager.  Double-buffering
   * is enabled by default.
   * 
   * @param layout  the layout manager (<code>null</code> permitted).
   */
  public JPanel(LayoutManager layout)
  {
    this(layout, true);
  }

  /**
   * Creates a new panel with the specified layout manager and 
   * double-buffering.
   * 
   * @param layout  the layout manager (<code>null</code> permitted).
   * @param isDoubleBuffered  a flag that controls whether or not 
   *     double-buffering is enabled.
   */
  public JPanel(LayoutManager layout, boolean isDoubleBuffered)
  {
    setLayout(layout); 
    setOpaque(true);
    setDoubleBuffered(isDoubleBuffered);
    updateUI();	
  } 

  /**
   * Returns the suffix (<code>"PanelUI"</code> in this case) used to 
   * determine the class name for a UI delegate that can provide the look and 
   * feel for a <code>JPanel</code>.
   *
   * @return <code>"PanelUI"</code>.
   */
  public String getUIClassID()
  {
    return "PanelUI";
  }

  /**
   * Sets the UI delegate for the <code>JPanel</code> component.
   * 
   * @param ui  the UI delegate.
   * 
   * @since 1.4
   * @see #getUI()
   */
  public void setUI(PanelUI ui)
  {
    super.setUI(ui);
  }

  /**
   * Returns the UI delegate for the <code>JPanel</code> component.
   * 
   * @return The UI delegate.
   * 
   * @since 1.4
   * @see #setUI(PanelUI)
   */
  public PanelUI getUI()
  {
    return (PanelUI) ui;
  }

  /**
   * Sets this panel's UI delegate to the default (obtained from the
   * {@link UIManager}) for the current look and feel.
   */
  public void updateUI()
  {
    setUI((PanelUI) UIManager.getUI(this));
  }

  /**
   * Returns the object that provides accessibility features for this
   * <code>JPanel</code> component.
   *
   * @return The accessible context (an instance of {@link AccessibleJPanel}).
   */
  public AccessibleContext getAccessibleContext()
  {
    if (accessibleContext == null)
      accessibleContext = new AccessibleJPanel();
    return accessibleContext;
  }
    
  /**
   * Returns an implementation-dependent string describing the attributes of
   * this <code>JPanel</code>.
   *
   * @return A string describing the attributes of this <code>JPanel</code>
   *         (never <code>null</code>).
   */
  protected String paramString()
  {
	return super.paramString();
  }
}