gcc/libjava/classpath/javax/swing/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
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WITHOUT ANY WARRANTY; without even the implied warranty of
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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
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terms of your choice, provided that you also meet, for each linked
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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();
  }
}