/*
 * Copyright (c) 2003 Sun Microsystems, Inc. All Rights Reserved.
 * Copyright (c) 2010 JogAmp Community. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 * - Redistribution of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * 
 * - Redistribution in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * 
 * Neither the name of Sun Microsystems, Inc. or the names of
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
 * INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN
 * MICROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR
 * ITS LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR
 * DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE
 * DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY,
 * ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, EVEN IF
 * SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 * 
 * You acknowledge that this software is not designed or intended for use
 * in the design, construction, operation or maintenance of any nuclear
 * facility.
 * 
 * Sun gratefully acknowledges that this software was originally authored
 * and developed by Kenneth Bradley Russell and Christopher John Kline.
 */

package javax.media.opengl.awt;

import javax.media.opengl.*;
import javax.media.nativewindow.*;

import java.awt.*;
import java.awt.geom.*;
import java.awt.image.*;
import java.beans.*;
import java.nio.*;
import java.security.*;
import javax.swing.JPanel;
import com.jogamp.opengl.util.FBObject;
import com.jogamp.opengl.impl.*;
import com.jogamp.opengl.impl.awt.*;

// FIXME: Subclasses need to call resetGLFunctionAvailability() on their
// context whenever the displayChanged() function is called on their
// GLEventListeners

/** A lightweight Swing component which provides OpenGL rendering
    support. Provided for compatibility with Swing user interfaces
    when adding a heavyweight doesn't work either because of
    Z-ordering or LayoutManager problems.
    <P>
    The GLJPanel can be made transparent by creating it with a
    GLCapabilities object with alpha bits specified and calling {@link
    #setOpaque}(false). Pixels with resulting OpenGL alpha values less
    than 1.0 will be overlaid on any underlying Swing rendering. </P>
    <P>
    Notes specific to the Reference Implementation: This component 
    attempts to use hardware-accelerated rendering via pbuffers and 
    falls back on to software rendering if problems occur. 
    Note that because this component attempts to use pbuffers for
    rendering, and because pbuffers can not be resized, somewhat
    surprising behavior may occur during resize operations; the {@link
    GLEventListener#init} method may be called multiple times as the
    pbuffer is resized to be able to cover the size of the GLJPanel.
    This behavior is correct, as the textures and display lists for
    the GLJPanel will have been lost during the resize operation. The
    application should attempt to make its GLEventListener.init()
    methods as side-effect-free as possible. </P>
    <P>
 *  Please read <A HREF="GLCanvas.html#java2dgl">Java2D OpenGL Remarks</A>.
 *  </P>
*/

public class GLJPanel extends JPanel implements AWTGLAutoDrawable {
  private static final boolean DEBUG = Debug.debug("GLJPanel");
  private static final boolean VERBOSE = Debug.verbose();

  private GLDrawableHelper drawableHelper = new GLDrawableHelper();
  private volatile boolean isInitialized;

  // Data used for either pbuffers or pixmap-based offscreen surfaces
  private GLCapabilitiesImmutable offscreenCaps;
  private GLProfile             glProfile;
  private GLDrawableFactoryImpl factory;
  private GLCapabilitiesChooser chooser;
  private GLContext             shareWith;
  // Width of the actual GLJPanel
  private int panelWidth   = 0;
  private int panelHeight  = 0;
  // Lazy reshape notification
  private boolean handleReshape = false;
  private boolean sendReshape = true;

  // The backend in use
  private Backend backend;

  // Used by all backends either directly or indirectly to hook up callbacks
  private Updater updater = new Updater();

  private static final AccessControlContext localACC = AccessController.getContext();

  // Turns off the pbuffer-based backend (used by default, unless the
  // Java 2D / OpenGL pipeline is in use)
  private static boolean hardwareAccelerationDisabled =
    Debug.isPropertyDefined("jogl.gljpanel.nohw", true, localACC);

  // Turns off the fallback to software-based rendering from
  // pbuffer-based rendering
  private static boolean softwareRenderingDisabled =
    Debug.isPropertyDefined("jogl.gljpanel.nosw", true, localACC);

  // Indicates whether the Java 2D OpenGL pipeline is enabled
  private boolean oglPipelineEnabled =
    Java2D.isOGLPipelineActive() &&
    !Debug.isPropertyDefined("jogl.gljpanel.noogl", true, localACC);

  // For handling reshape events lazily
  private int reshapeX;
  private int reshapeY;
  private int reshapeWidth;
  private int reshapeHeight;

  // These are always set to (0, 0) except when the Java2D / OpenGL
  // pipeline is active
  private int viewportX;
  private int viewportY;

  static {
    // Force eager initialization of part of the Java2D class since
    // otherwise it's likely it will try to be initialized while on
    // the Queue Flusher Thread, which is not allowed
    if (Java2D.isOGLPipelineActive() && Java2D.isFBOEnabled()) {
      Java2D.getShareContext(GraphicsEnvironment.
                             getLocalGraphicsEnvironment().
                             getDefaultScreenDevice());
    }
  }

  /** Creates a new GLJPanel component with a default set of OpenGL
      capabilities and using the default OpenGL capabilities selection
      mechanism. */
  public GLJPanel() {
    this(null);
  }

  /** Creates a new GLJPanel component with the requested set of
      OpenGL capabilities, using the default OpenGL capabilities
      selection mechanism. */
  public GLJPanel(GLCapabilitiesImmutable userCapsRequest) {
    this(userCapsRequest, null, null);
  }

  /** Creates a new GLJPanel component. The passed GLCapabilities
      specifies the OpenGL capabilities for the component; if null, a
      default set of capabilities is used. The GLCapabilitiesChooser
      specifies the algorithm for selecting one of the available
      GLCapabilities for the component; a DefaultGLCapabilitesChooser
      is used if null is passed for this argument. The passed
      GLContext specifies an OpenGL context with which to share
      textures, display lists and other OpenGL state, and may be null
      if sharing is not desired. See the note in the overview documentation on
      <a href="../../../overview-summary.html#SHARING">context sharing</a>.
      <P>
      Note: Sharing cannot be enabled using J2D OpenGL FBO sharing,
      since J2D GL Context must be shared and we can only share one context.
  */
  public GLJPanel(GLCapabilitiesImmutable userCapsRequest, GLCapabilitiesChooser chooser, GLContext shareWith) {
    super();

    // Works around problems on many vendors' cards; we don't need a
    // back buffer for the offscreen surface anyway
    {
        GLCapabilities caps;
        if (userCapsRequest != null) {
            caps = (GLCapabilities) userCapsRequest.cloneMutable();
        } else {
            caps = new GLCapabilities(null);
        }
        caps.setDoubleBuffered(false);
        offscreenCaps = caps;
    }
    this.glProfile = offscreenCaps.getGLProfile();
    this.factory = GLDrawableFactoryImpl.getFactoryImpl(glProfile);
    this.chooser = ((chooser != null) ? chooser : new DefaultGLCapabilitiesChooser());
    this.shareWith = shareWith;
  }

  public void display() {
    if (EventQueue.isDispatchThread()) {
      // Want display() to be synchronous, so call paintImmediately()
      paintImmediately(0, 0, getWidth(), getHeight());
    } else {
      // Multithreaded redrawing of Swing components is not allowed,
      // so do everything on the event dispatch thread
      try {
        EventQueue.invokeAndWait(paintImmediatelyAction);
      } catch (Exception e) {
        throw new GLException(e);
      }
    }
  }

  protected void dispose(boolean regenerate) {
    if(DEBUG) {
        Exception ex1 = new Exception("Info: dispose("+regenerate+") - start");
        ex1.printStackTrace();
    }

    if (backend != null) {
      boolean animatorPaused = false;
      GLAnimatorControl animator =  getAnimator();
      if(null!=animator) {
        if(regenerate) {
            animatorPaused = animator.pause();
        } else {
            animator.remove(this);
        }
      }

      disposeRegenerate=regenerate;
      disposeContext=backend.getContext();
      disposeDrawable=backend.getDrawable();

      if (Threading.isSingleThreaded() &&
          !Threading.isOpenGLThread()) {
          // Workaround for termination issues with applets --
          // sun.applet.AppletPanel should probably be performing the
          // remove() call on the EDT rather than on its own thread
          if (ThreadingImpl.isAWTMode() &&
              Thread.holdsLock(getTreeLock())) {
            // The user really should not be invoking remove() from this
            // thread -- but since he/she is, we can not go over to the
            // EDT at this point. Try to destroy the context from here.
            if(disposeContext.isCreated()) {
                drawableHelper.invokeGL(disposeDrawable, disposeContext, disposeAction, null);
            }
          } else if(disposeContext.isCreated()) {
            Threading.invokeOnOpenGLThread(disposeOnEventDispatchThreadAction);
          }
      } else if(disposeContext.isCreated()) {
          drawableHelper.invokeGL(disposeDrawable, disposeContext, disposeAction, null);
      }

      backend.setContext(disposeContext);
      if(null==disposeContext) {
        isInitialized = false;
      }

      if(animatorPaused) {
        animator.resume();
      }
    }

    if(DEBUG) {
        System.err.println("dispose("+regenerate+") - stop");
    }
  }

  /**
   * Just an alias for removeNotify
   */
  public void destroy() {
      removeNotify();
  }

  /** Overridden to cause OpenGL rendering to be performed during
      repaint cycles. Subclasses which override this method must call
      super.paintComponent() in their paintComponent() method in order
      to function properly. <P>

      <B>Overrides:</B>
      <DL><DD><CODE>paintComponent</CODE> in class <CODE>javax.swing.JComponent</CODE></DD></DL> */
  protected void paintComponent(final Graphics g) {
    if (Beans.isDesignTime()) {
      // Make GLJPanel behave better in NetBeans GUI builder
      g.setColor(Color.BLACK);
      g.fillRect(0, 0, getWidth(), getHeight());
      FontMetrics fm = g.getFontMetrics();
      String name = getName();
      if (name == null) {
        name = getClass().getName();
        int idx = name.lastIndexOf('.');
        if (idx >= 0) {
          name = name.substring(idx + 1);
        }
      }
      Rectangle2D bounds = fm.getStringBounds(name, g);
      g.setColor(Color.WHITE);
      g.drawString(name,
                   (int) ((getWidth()  - bounds.getWidth())  / 2),
                   (int) ((getHeight() + bounds.getHeight()) / 2));
      return;
    }

    if (backend == null || !isInitialized) {
      createAndInitializeBackend();
    }

    if (!isInitialized) {
      return;
    }

    // NOTE: must do this when the context is not current as it may
    // involve destroying the pbuffer (current context) and
    // re-creating it -- tricky to do properly while the context is
    // current
    if (handleReshape) {
      handleReshape();
    }

    updater.setGraphics(g);
    backend.doPaintComponent(g);
  }

  /** Overridden to track when this component is added to a container.
      Subclasses which override this method must call
      super.addNotify() in their addNotify() method in order to
      function properly. <P>

      <B>Overrides:</B>
      <DL><DD><CODE>addNotify</CODE> in class <CODE>java.awt.Component</CODE></DD></DL> */
  public void addNotify() {
    super.addNotify();
    if (DEBUG) {
      System.err.println("GLJPanel.addNotify()");
    }
  }

  /** Overridden to track when this component is removed from a
      container. Subclasses which override this method must call
      super.removeNotify() in their removeNotify() method in order to
      function properly. <P>

      <B>Overrides:</B>
      <DL><DD><CODE>removeNotify</CODE> in class <CODE>java.awt.Component</CODE></DD></DL> */
  public void removeNotify() {
    if(DEBUG) {
        Exception ex1 = new Exception("Info: removeNotify - start");
        ex1.printStackTrace();
    }
    dispose(false);
    if (backend != null) {
      backend.destroy();
      backend = null;
    }
    isInitialized = false;
    super.removeNotify();
    if(DEBUG) {
        System.err.println("Info: removeNotify - end");
    }
  }

  /** Overridden to cause {@link GLDrawableHelper#reshape} to be
      called on all registered {@link GLEventListener}s. Subclasses
      which override this method must call super.reshape() in
      their reshape() method in order to function properly. <P>

      <B>Overrides:</B>
      <DL><DD><CODE>reshape</CODE> in class <CODE>java.awt.Component</CODE></DD></DL> */
  public void reshape(int x, int y, int width, int height) {
    super.reshape(x, y, width, height);

    reshapeX = x;
    reshapeY = y;
    reshapeWidth = width;
    reshapeHeight = height;
    handleReshape = true;
  }

  public void setOpaque(boolean opaque) {
    if (backend != null) {
      backend.setOpaque(opaque);
    }
    super.setOpaque(opaque);
  }

  public void addGLEventListener(GLEventListener listener) {
    drawableHelper.addGLEventListener(listener);
  }

  public void addGLEventListener(int index, GLEventListener listener) {
    drawableHelper.addGLEventListener(index, listener);
  }

  public void removeGLEventListener(GLEventListener listener) {
    drawableHelper.removeGLEventListener(listener);
  }

  public void setAnimator(GLAnimatorControl animatorControl) {
    drawableHelper.setAnimator(animatorControl);
  }

  public GLAnimatorControl getAnimator() {
    return drawableHelper.getAnimator();
  }

  public void invoke(boolean wait, GLRunnable glRunnable) {
    drawableHelper.invoke(this, wait, glRunnable);
  }

  public GLContext createContext(GLContext shareWith) {
    return backend.createContext(shareWith);
  }

  public void setRealized(boolean realized) {
  }

  public boolean isRealized() {
      return isInitialized;
  }

  public void setContext(GLContext ctx) {
    if (backend == null) {
      return;
    }
    backend.setContext(ctx);
  }

  public GLContext getContext() {
    if (backend == null) {
      return null;
    }
    return backend.getContext();
  }

  public GL getGL() {
    if (Beans.isDesignTime()) {
      return null;
    }
    GLContext context = getContext();
    return (context == null) ? null : context.getGL();
  }

  public GL setGL(GL gl) {
    GLContext context = getContext();
    if (context != null) {
      context.setGL(gl);
      return gl;
    }
    return null;
  }

  public void setAutoSwapBufferMode(boolean onOrOff) {
    // In the current implementation this is a no-op. Both the pbuffer
    // and pixmap based rendering paths use a single-buffered surface
    // so swapping the buffers doesn't do anything. We also don't
    // currently have the provision to skip copying the data to the
    // Swing portion of the GLJPanel in any of the rendering paths.
  }

  public boolean getAutoSwapBufferMode() {
    // In the current implementation this is a no-op. Both the pbuffer
    // and pixmap based rendering paths use a single-buffered surface
    // so swapping the buffers doesn't do anything. We also don't
    // currently have the provision to skip copying the data to the
    // Swing portion of the GLJPanel in any of the rendering paths.
    return true;
  }

  public void swapBuffers() {
    // In the current implementation this is a no-op. Both the pbuffer
    // and pixmap based rendering paths use a single-buffered surface
    // so swapping the buffers doesn't do anything. We also don't
    // currently have the provision to skip copying the data to the
    // Swing portion of the GLJPanel in any of the rendering paths.
  }

  /** For a translucent GLJPanel (one for which {@link #setOpaque
      setOpaque}(false) has been called), indicates whether the
      application should preserve the OpenGL color buffer
      (GL_COLOR_BUFFER_BIT) for correct rendering of the GLJPanel and
      underlying widgets which may show through portions of the
      GLJPanel with alpha values less than 1.  Most Swing
      implementations currently expect the GLJPanel to be completely
      cleared (e.g., by <code>glClear(GL_COLOR_BUFFER_BIT |
      GL_DEPTH_BUFFER_BIT)</code>), but for certain optimized Swing
      implementations which use OpenGL internally, it may be possible
      to perform OpenGL rendering using the GLJPanel into the same
      OpenGL drawable as the Swing implementation uses. */
  public boolean shouldPreserveColorBufferIfTranslucent() {
    return oglPipelineEnabled;
  }

  public GLCapabilitiesImmutable getChosenGLCapabilities() {
    return backend.getChosenGLCapabilities();
  }

  public final GLProfile getGLProfile() {
    return glProfile;
  }

  public NativeSurface getNativeSurface() {
    throw new GLException("FIXME");
  }

  public long getHandle() {
    throw new GLException("FIXME");
  }

  public final GLDrawableFactory getFactory() {
    return factory;
  }

  //----------------------------------------------------------------------
  // Internals only below this point
  //

  private void createAndInitializeBackend() {
    if (panelWidth == 0 ||
        panelHeight == 0) {
      // See whether we have a non-zero size yet and can go ahead with
      // initialization
      if (reshapeWidth == 0 ||
          reshapeHeight == 0) {
        return;
      }

      // Pull down reshapeWidth and reshapeHeight into panelWidth and
      // panelHeight eagerly in order to complete initialization, and
      // force a reshape later
      panelWidth = reshapeWidth;
      panelHeight = reshapeHeight;
    }

    do {
      if (backend == null) {
        if (oglPipelineEnabled) {
          backend = new J2DOGLBackend();
        } else {
          if (!hardwareAccelerationDisabled &&
              factory.canCreateGLPbuffer(null)) {
            backend = new PbufferBackend();
          } else {
            if (softwareRenderingDisabled) {
              throw new GLException("Fallback to software rendering disabled by user");
            }
            backend = new SoftwareBackend();
          }
        }
      }

      if (!isInitialized) {
        backend.initialize();
      }
      // The backend might set itself to null, indicating it punted to
      // a different implementation -- try again
    } while (backend == null);

    if(null==closingListener) {
      synchronized(closingListenerLock) {
        if(null==closingListener) {
            closingListener=GLCanvas.addClosingListener(this, new GLCanvas.DestroyMethod() {
                        public void destroyMethod() { destroy(); } });
        }
      }
    }
  }
  private Object closingListener = null;
  private Object closingListenerLock = new Object();

  private void handleReshape() {
    panelWidth  = reshapeWidth;
    panelHeight = reshapeHeight;

    if (DEBUG) {
      System.err.println("GLJPanel.handleReshape: (w,h) = (" +
                         panelWidth + "," + panelHeight + ")");
    }

    sendReshape = true;
    backend.handleReshape();
    handleReshape = false;
  }

  // This is used as the GLEventListener for the pbuffer-based backend
  // as well as the callback mechanism for the other backends
  class Updater implements GLEventListener {
    private Graphics g;

    public void setGraphics(Graphics g) {
      this.g = g;
    }

    public void init(GLAutoDrawable drawable) {
      if (!backend.preGL(g)) {
        return;
      }
      drawableHelper.init(GLJPanel.this);
      backend.postGL(g, false);
    }

    public void dispose(GLAutoDrawable drawable) {
      drawableHelper.dispose(GLJPanel.this);
    }

    public void display(GLAutoDrawable drawable) {
      if (!backend.preGL(g)) {
        return;
      }
      if (sendReshape) {
        if (DEBUG||VERBOSE) {
          System.err.println("display: reshape(" + viewportX + "," + viewportY + " " + panelWidth + "x" + panelHeight + ")");
        }
        drawableHelper.reshape(GLJPanel.this, viewportX, viewportY, panelWidth, panelHeight);
        sendReshape = false;
      }

      drawableHelper.display(GLJPanel.this);
      backend.postGL(g, true);
    }

    public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height) {
      // This is handled above and dispatched directly to the appropriate context
    }

    public void displayChanged(GLAutoDrawable drawable, boolean modeChanged, boolean deviceChanged) {
    }
  }

  public String toString() {
    return "AWT-GLJPanel[ "+((null!=backend)?backend.getDrawable().getClass().getName():"null-drawable")+"]";
  }

  private boolean disposeRegenerate;
  private GLContext disposeContext;
  private GLDrawable disposeDrawable;
  private DisposeAction disposeAction = new DisposeAction();

  class DisposeAction implements Runnable {
      public void run() {
          updater.dispose(GLJPanel.this);

          if (null != disposeContext) {
              disposeContext.destroy();
              disposeContext = null;
          }
          if (null != disposeDrawable) {
              disposeDrawable.setRealized(false);
          }
          if (null != disposeDrawable) {
              if (disposeRegenerate) {
                  disposeDrawable.setRealized(true);
                  disposeContext = (GLContextImpl) disposeDrawable.createContext(shareWith);
                  disposeContext.setSynchronized(true);
              } else {
                  AbstractGraphicsDevice adevice = disposeDrawable.getNativeSurface().getGraphicsConfiguration().getNativeGraphicsConfiguration().getScreen().getDevice();
                  String adeviceMsg=null;
                  if(DEBUG) {
                    adeviceMsg = adevice.toString();
                  }
                  boolean closed = adevice.close();
                  if (DEBUG) {
                      System.err.println("GLJPanel.dispose(false): closed GraphicsDevice: " + adeviceMsg + ", result: " + closed);
                  }
              }
          }
      }
  }

  private DisposeOnEventDispatchThreadAction disposeOnEventDispatchThreadAction =
    new DisposeOnEventDispatchThreadAction();

  class DisposeOnEventDispatchThreadAction implements Runnable {
    public void run() {
      drawableHelper.invokeGL(disposeDrawable, disposeContext, disposeAction, null);
    }
  }


  class InitAction implements Runnable {
    public void run() {
      updater.init(GLJPanel.this);
    }
  }
  private InitAction initAction = new InitAction();

  class DisplayAction implements Runnable {
    public void run() {
      updater.display(GLJPanel.this);
    }
  }
  private DisplayAction displayAction = new DisplayAction();

  class PaintImmediatelyAction implements Runnable {
    public void run() {
      paintImmediately(0, 0, getWidth(), getHeight());
    }
  }
  private PaintImmediatelyAction paintImmediatelyAction = new PaintImmediatelyAction();

  private int getNextPowerOf2(int number) {
    // Workaround for problems where 0 width or height are transiently
    // seen during layout
    if (number == 0) {
      return 2;
    }

    if (((number-1) & number) == 0) {
      //ex: 8 -> 0b1000; 8-1=7 -> 0b0111; 0b1000&0b0111 == 0
      return number;
    }
    int power = 0;
    while (number > 0) {
      number = number>>1;
      power++;
    }
    return (1<<power);
  }

  private int getGLInteger(GL gl, int which) {
    int[] tmp = new int[1];
    gl.glGetIntegerv(which, tmp, 0);
    return tmp[0];
  }

  //----------------------------------------------------------------------
  // Implementations of the various backends
  //

  // Abstraction of the different rendering backends: i.e., pure
  // software / pixmap rendering, pbuffer-based acceleration, Java 2D
  // / JOGL bridge
  static interface Backend {
    // Called each time the backend needs to initialize itself
    public void initialize();

    // Called when the backend should clean up its resources
    public void destroy();

    // Called when the opacity of the GLJPanel is changed
    public void setOpaque(boolean opaque);

    // Called to manually create an additional OpenGL context against
    // this GLJPanel
    public GLContext createContext(GLContext shareWith);

    // Called to set the current backend's GLContext
    public void setContext(GLContext ctx);

    // Called to get the current backend's GLContext
    public GLContext getContext();

    // Called to get the current backend's GLDrawable
    public GLDrawable getDrawable();

    // Called to fetch the "real" GLCapabilities for the backend
    public GLCapabilitiesImmutable getChosenGLCapabilities();

    // Called to fetch the "real" GLProfile for the backend
    public GLProfile getGLProfile();

    // Called to handle a reshape event. When this is called, the
    // OpenGL context associated with the backend is not current, to
    // make it easier to destroy and re-create pbuffers if necessary.
    public void handleReshape();

    // Called before the OpenGL work is done in init() and display().
    // If false is returned, this render is aborted.
    public boolean preGL(Graphics g);

    // Called after the OpenGL work is done in init() and display().
    // The isDisplay argument indicates whether this was called on
    // behalf of a call to display() rather than init().
    public void postGL(Graphics g, boolean isDisplay);

    // Called from within paintComponent() to initiate the render
    public void doPaintComponent(Graphics g);
  }

  // Base class used by both the software (pixmap) and pbuffer
  // backends, both of which rely on reading back the OpenGL frame
  // buffer and drawing it with a BufferedImage
  abstract class AbstractReadbackBackend implements Backend {
    // This image is exactly the correct size to render into the panel
    protected BufferedImage         offscreenImage;
    // One of these is used to store the read back pixels before storing
    // in the BufferedImage
    protected ByteBuffer            readBackBytes;
    protected IntBuffer             readBackInts;
    protected int                   readBackWidthInPixels;
    protected int                   readBackHeightInPixels;

    private int awtFormat;
    private int glFormat;
    private int glType;

    // For saving/restoring of OpenGL state during ReadPixels
    private int[] swapbytes    = new int[1];
    private int[] rowlength    = new int[1];
    private int[] skiprows     = new int[1];
    private int[] skippixels   = new int[1];
    private int[] alignment    = new int[1];

    public void setOpaque(boolean opaque) {
      if (opaque != isOpaque()) {
        if (offscreenImage != null) {
          offscreenImage.flush();
          offscreenImage = null;
        }
      }
    }

    public boolean preGL(Graphics g) {
      // Empty in this implementation
      return true;
    }

    public void postGL(Graphics g, boolean isDisplay) {
      if (isDisplay) {
        // Must now copy pixels from offscreen context into surface
        if (offscreenImage == null) {
          if (panelWidth > 0 && panelHeight > 0) {
            // It looks like NVidia's drivers (at least the ones on my
            // notebook) are buggy and don't allow a sub-rectangle to be
            // read from a pbuffer...this doesn't really matter because
            // it's the Graphics.drawImage() calls that are the
            // bottleneck

            int awtFormat = 0;

            // Should be more flexible in these BufferedImage formats;
            // perhaps see what the preferred image types are on the
            // given platform
            if (isOpaque()) {
              awtFormat = BufferedImage.TYPE_INT_RGB;
            } else {
              awtFormat = BufferedImage.TYPE_INT_ARGB;
            }

            offscreenImage = new BufferedImage(panelWidth,
                                               panelHeight,
                                               awtFormat);
            switch (awtFormat) {
            case BufferedImage.TYPE_3BYTE_BGR:
              glFormat = GL2.GL_BGR;
              glType   = GL2.GL_UNSIGNED_BYTE;
              readBackBytes = ByteBuffer.allocate(readBackWidthInPixels * readBackHeightInPixels * 3);
              break;

            case BufferedImage.TYPE_INT_RGB:
            case BufferedImage.TYPE_INT_ARGB:
              glFormat = GL2.GL_BGRA;
              glType   = getGLPixelType();
              readBackInts = IntBuffer.allocate(readBackWidthInPixels * readBackHeightInPixels);
              break;

            default:
              // FIXME: Support more off-screen image types (current
              // offscreen context implementations don't use others, and
              // some of the OpenGL formats aren't supported in the 1.1
              // headers, which we're currently using)
              throw new GLException("Unsupported offscreen image type " + awtFormat);
            }
          }
        }

        if (offscreenImage != null) {
          GL2 gl = getGL().getGL2();
          // Save current modes
          gl.glGetIntegerv(GL2.GL_PACK_SWAP_BYTES,    swapbytes, 0);
          gl.glGetIntegerv(GL2.GL_PACK_ROW_LENGTH,    rowlength, 0);
          gl.glGetIntegerv(GL2.GL_PACK_SKIP_ROWS,     skiprows, 0);
          gl.glGetIntegerv(GL2.GL_PACK_SKIP_PIXELS,   skippixels, 0);
          gl.glGetIntegerv(GL2.GL_PACK_ALIGNMENT,     alignment, 0);

          gl.glPixelStorei(GL2.GL_PACK_SWAP_BYTES,    GL.GL_FALSE);
          gl.glPixelStorei(GL2.GL_PACK_ROW_LENGTH,    readBackWidthInPixels);
          gl.glPixelStorei(GL2.GL_PACK_SKIP_ROWS,     0);
          gl.glPixelStorei(GL2.GL_PACK_SKIP_PIXELS,   0);
          gl.glPixelStorei(GL2.GL_PACK_ALIGNMENT,     1);

          // Actually read the pixels.
          gl.glReadBuffer(GL2.GL_FRONT);
          if (readBackBytes != null) {
            gl.glReadPixels(0, 0, readBackWidthInPixels, readBackHeightInPixels, glFormat, glType, readBackBytes);
          } else if (readBackInts != null) {
            gl.glReadPixels(0, 0, readBackWidthInPixels, readBackHeightInPixels, glFormat, glType, readBackInts);
          }

          // Restore saved modes.
          gl.glPixelStorei(GL2.GL_PACK_SWAP_BYTES,  swapbytes[0]);
          gl.glPixelStorei(GL2.GL_PACK_ROW_LENGTH,  rowlength[0]);
          gl.glPixelStorei(GL2.GL_PACK_SKIP_ROWS,   skiprows[0]);
          gl.glPixelStorei(GL2.GL_PACK_SKIP_PIXELS, skippixels[0]);
          gl.glPixelStorei(GL2.GL_PACK_ALIGNMENT,   alignment[0]);

          if (readBackBytes != null || readBackInts != null) {
            // Copy temporary data into raster of BufferedImage for faster
            // blitting Note that we could avoid this copy in the cases
            // where !offscreenContext.offscreenImageNeedsVerticalFlip(),
            // but that's the software rendering path which is very slow
            // anyway
            Object src  = null;
            Object dest = null;
            int    srcIncr  = 0;
            int    destIncr = 0;

            if (readBackBytes != null) {
              src = readBackBytes.array();
              dest = ((DataBufferByte) offscreenImage.getRaster().getDataBuffer()).getData();
              srcIncr = readBackWidthInPixels * 3;
              destIncr = offscreenImage.getWidth() * 3;
            } else {
              src = readBackInts.array();
              dest = ((DataBufferInt) offscreenImage.getRaster().getDataBuffer()).getData();
              srcIncr = readBackWidthInPixels;
              destIncr = offscreenImage.getWidth();
            }

            if (flipVertically()) {
              int srcPos = 0;
              int destPos = (offscreenImage.getHeight() - 1) * destIncr;
              for (; destPos >= 0; srcPos += srcIncr, destPos -= destIncr) {
                System.arraycopy(src, srcPos, dest, destPos, destIncr);
              }
            } else {
              int srcPos = 0;
              int destEnd = destIncr * offscreenImage.getHeight();
              for (int destPos = 0; destPos < destEnd; srcPos += srcIncr, destPos += destIncr) {
                System.arraycopy(src, srcPos, dest, destPos, destIncr);
              }
            }

            // Note: image will be drawn back in paintComponent() for
            // correctness on all platforms
          }
        }
      }
    }

    public void doPaintComponent(Graphics g) {
      doPaintComponentImpl();
      if (offscreenImage != null) {
        // Draw resulting image in one shot
        g.drawImage(offscreenImage, 0, 0,
                    offscreenImage.getWidth(),
                    offscreenImage.getHeight(),
                    GLJPanel.this);
      }
    }

    protected abstract void    doPaintComponentImpl();
    protected abstract int     getGLPixelType();
    protected abstract boolean flipVertically();
  }

  class SoftwareBackend extends AbstractReadbackBackend {
    // Implementation using software rendering
    private GLDrawableImpl offscreenDrawable;
    private GLContextImpl offscreenContext;

    public void initialize() {
      // Fall-through path: create an offscreen context instead
      offscreenDrawable = (GLDrawableImpl) factory.createOffscreenDrawable(
                                                null /* default platform device */,
                                                offscreenCaps,
                                                chooser,
                                                Math.max(1, panelWidth),
                                                Math.max(1, panelHeight));
      offscreenContext = (GLContextImpl) offscreenDrawable.createContext(shareWith);
      offscreenContext.setSynchronized(true);
      isInitialized = true;
    }

    public void destroy() {
      if (offscreenContext != null) {
        offscreenContext.destroy();
        offscreenContext = null;
      }
      if (offscreenDrawable != null) {
        offscreenDrawable.destroy();
        offscreenDrawable = null;
      }
    }

    public GLContext createContext(GLContext shareWith) {
      return offscreenDrawable.createContext(shareWith);
    }

    public void setContext(GLContext ctx) {
      offscreenContext=(GLContextImpl)ctx;
    }

    public GLContext getContext() {
      return offscreenContext;
    }

    public GLDrawable getDrawable() {
        return offscreenDrawable;
    }

    public GLCapabilitiesImmutable getChosenGLCapabilities() {
      if (offscreenDrawable == null) {
        return null;
      }
      return offscreenDrawable.getChosenGLCapabilities();
    }

    public GLProfile getGLProfile() {
      if (offscreenDrawable == null) {
        return null;
      }
      return offscreenDrawable.getGLProfile();
    }

    public void handleReshape() {
      destroy();
      initialize();
      readBackWidthInPixels  = Math.max(1, panelWidth);
      readBackHeightInPixels = Math.max(1, panelHeight);

      if (offscreenImage != null) {
        offscreenImage.flush();
        offscreenImage = null;
      }
    }

    protected void doPaintComponentImpl() {
      drawableHelper.invokeGL(offscreenDrawable, offscreenContext, displayAction, initAction);
    }

    protected int getGLPixelType() {
      return offscreenContext.getOffscreenContextPixelDataType();
    }

    protected boolean flipVertically() {
      return offscreenContext.offscreenImageNeedsVerticalFlip();
    }
  }

  class PbufferBackend extends AbstractReadbackBackend {
    private GLPbuffer pbuffer;
    private int       pbufferWidth  = 256;
    private int       pbufferHeight = 256;

    public void initialize() {
      if (pbuffer != null) {
        throw new InternalError("Creating pbuffer twice without destroying it (memory leak / correctness bug)");
      }
      try {
        pbuffer = factory.createGLPbuffer(null /* default platform device */,
                                          offscreenCaps,
                                          null,
                                          pbufferWidth,
                                          pbufferHeight,
                                          shareWith);
        pbuffer.addGLEventListener(updater);
        isInitialized = true;
      } catch (GLException e) {
        if (DEBUG) {
          e.printStackTrace();
          System.err.println("Info: GLJPanel: Falling back on software rendering because of problems creating pbuffer");
        }
        hardwareAccelerationDisabled = true;
        backend = null;
        isInitialized = false;
        createAndInitializeBackend();
      }
    }

    public void destroy() {
      if (pbuffer != null) {
        pbuffer.destroy();
        pbuffer = null;
      }
    }

    public GLContext createContext(GLContext shareWith) {
      return pbuffer.createContext(shareWith);
    }

    public void setContext(GLContext ctx) {
      if (pbuffer == null && Beans.isDesignTime()) {
        return;
      }
      pbuffer.setContext(ctx);
    }

    public GLContext getContext() {
      // Workaround for crashes in NetBeans GUI builder
      if (pbuffer == null && Beans.isDesignTime()) {
        return null;
      }
      return pbuffer.getContext();
    }

    public GLDrawable getDrawable() {
        return pbuffer;
    }

    public GLCapabilitiesImmutable getChosenGLCapabilities() {
      if (pbuffer == null) {
        return null;
      }
      return pbuffer.getChosenGLCapabilities();
    }
    
    public GLProfile getGLProfile() {
      if (pbuffer == null) {
        return null;
      }
      return pbuffer.getGLProfile();
    }
    
    public void handleReshape() {
      // Use factor larger than 2 during shrinks for some hysteresis
      float shrinkFactor = 2.5f;
      if ((panelWidth > pbufferWidth)                  || (panelHeight > pbufferHeight) ||
          (panelWidth < (pbufferWidth / shrinkFactor)) || (panelHeight < (pbufferHeight / shrinkFactor))) {
        if (DEBUG) {
          System.err.println("Resizing pbuffer from (" + pbufferWidth + ", " + pbufferHeight + ") " +
                             " to fit (" + panelWidth + ", " + panelHeight + ")");
        }
        // Must destroy and recreate pbuffer to fit
        if (pbuffer != null) {
          // Watch for errors during pbuffer destruction (due to
          // buggy / bad OpenGL drivers, in particular SiS) and fall
          // back to software rendering
          try {
            pbuffer.destroy();
          } catch (GLException e) {
            hardwareAccelerationDisabled = true;
            backend = null;
            isInitialized = false;
            // Just disabled hardware acceleration during this resize operation; do a fixup
            readBackWidthInPixels  = Math.max(1, panelWidth);
            readBackHeightInPixels = Math.max(1, panelHeight);
            if (DEBUG) {
              System.err.println("Warning: falling back to software rendering due to bugs in OpenGL drivers");
              e.printStackTrace();
            }
            createAndInitializeBackend();
            return;
          }
        }
        pbuffer = null;
        isInitialized = false;
        pbufferWidth = getNextPowerOf2(panelWidth);
        pbufferHeight = getNextPowerOf2(panelHeight);
        if (DEBUG && !hardwareAccelerationDisabled) {
          System.err.println("New pbuffer size is (" + pbufferWidth + ", " + pbufferHeight + ")");
        }
        initialize();
      }

      // It looks like NVidia's drivers (at least the ones on my
      // notebook) are buggy and don't allow a rectangle of less than
      // the pbuffer's width to be read...this doesn't really matter
      // because it's the Graphics.drawImage() calls that are the
      // bottleneck. Should probably make the size of the offscreen
      // image be the exact size of the pbuffer to save some work on
      // resize operations...
      readBackWidthInPixels  = pbufferWidth;
      readBackHeightInPixels = panelHeight;

      if (offscreenImage != null) {
        offscreenImage.flush();
        offscreenImage = null;
      }
    }

    protected void doPaintComponentImpl() {
      pbuffer.display();
    }

    protected int getGLPixelType() {
      // This seems to be a good choice on all platforms
      return GL2.GL_UNSIGNED_INT_8_8_8_8_REV;
    }

    protected boolean flipVertically() {
      return true;
    }
  }

  class J2DOGLBackend implements Backend {
    // Opaque Object identifier representing the Java2D surface we are
    // drawing to; used to determine when to destroy and recreate JOGL
    // context
    private Object j2dSurface;
    // Graphics object being used during Java2D update action
    // (absolutely essential to cache this)
    private Graphics cached2DGraphics;
    // No-op context representing the Java2D OpenGL context
    private GLContext j2dContext;
    // Context associated with no-op drawable representing the JOGL
    // OpenGL context
    private GLDrawable joglDrawable;
    // The real OpenGL context JOGL uses to render
    private GLContext  joglContext;
    // State captured from Java2D OpenGL context necessary in order to
    // properly render into Java2D back buffer
    private int[] drawBuffer   = new int[1];
    private int[] readBuffer   = new int[1];
    // This is required when the FBO option of the Java2D / OpenGL
    // pipeline is active
    private int[] frameBuffer  = new int[1];
    // Current (as of this writing) NVidia drivers have a couple of bugs
    // relating to the sharing of framebuffer and renderbuffer objects
    // between contexts. It appears we have to (a) reattach the color
    // attachment and (b) actually create new depth buffer storage and
    // attach it in order for the FBO to behave properly in our context.
    private boolean checkedForFBObjectWorkarounds;
    private boolean fbObjectWorkarounds;
    private int[] frameBufferDepthBuffer;
    private int[] frameBufferTexture;
    private boolean createNewDepthBuffer;
    // Current (as of this writing) ATI drivers have problems when the
    // same FBO is bound in two different contexts. Here we check for
    // this case and explicitly release the FBO from Java2D's context
    // before switching to ours. Java2D will re-bind the FBO when it
    // makes its context current the next time. Interestingly, if we run
    // this code path on NVidia hardware, it breaks the rendering
    // results -- no output is generated. This doesn't appear to be an
    // interaction with the abovementioned NVidia-specific workarounds,
    // as even if we disable that code the FBO is still reported as
    // incomplete in our context.
    private boolean checkedGLVendor;
    private boolean vendorIsATI;

    // Holding on to this GraphicsConfiguration is a workaround for a
    // problem in the Java 2D / JOGL bridge when FBOs are enabled; see
    // comment related to Issue 274 below
    private GraphicsConfiguration workaroundConfig;

    public void initialize() {
      // No-op in this implementation; everything is done lazily
      isInitialized = true;
    }

    public void destroy() {
      Java2D.invokeWithOGLContextCurrent(null, new Runnable() {
          public void run() {
            if (joglContext != null) {
              joglContext.destroy();
              joglContext = null;
            }
            joglDrawable = null;
            if (j2dContext != null) {
              j2dContext.destroy();
              j2dContext = null;
            }
          }
        });
    }

    public void setOpaque(boolean opaque) {
      // Empty in this implementation
    }

    public GLContext createContext(GLContext shareWith) {
      // FIXME: should implement this, but it was not properly
      // implemented before the refactoring anyway
      throw new GLException("Not yet implemented");
    }

    public void setContext(GLContext ctx) {
        joglContext=ctx;
    }

    public GLContext getContext() {
      return joglContext;
    }

    public GLDrawable getDrawable() {
        return joglDrawable;
    }

    public GLCapabilitiesImmutable getChosenGLCapabilities() {
      // FIXME: should do better than this; is it possible to using only platform-independent code?
      return new GLCapabilities(null);
    }

    public GLProfile getGLProfile() {
      // FIXME: should do better than this; is it possible to using only platform-independent code?
      return GLProfile.getDefault(GLProfile.getDefaultDesktopDevice());
    }

    public void handleReshape() {
      // Empty in this implementation
    }

    public boolean preGL(Graphics g) {
      GL2 gl = joglContext.getGL().getGL2();
      // Set up needed state in JOGL context from Java2D context
      gl.glEnable(GL2.GL_SCISSOR_TEST);
      Rectangle r = Java2D.getOGLScissorBox(g);

      if (r == null) {
        if (DEBUG && VERBOSE) {
          System.err.println("Java2D.getOGLScissorBox() returned null");
        }
        return false;
      }
      if (DEBUG && VERBOSE) {
        System.err.println("GLJPanel: gl.glScissor(" + r.x + ", " + r.y + ", " + r.width + ", " + r.height + ")");
      }

      gl.glScissor(r.x, r.y, r.width, r.height);
      Rectangle oglViewport = Java2D.getOGLViewport(g, panelWidth, panelHeight);
      // If the viewport X or Y changes, in addition to the panel's
      // width or height, we need to send a reshape operation to the
      // client
      if ((viewportX != oglViewport.x) ||
          (viewportY != oglViewport.y)) {
        sendReshape = true;
        if (DEBUG) {
          System.err.println("Sending reshape because viewport changed");
          System.err.println("  viewportX (" + viewportX + ") ?= oglViewport.x (" + oglViewport.x + ")");
          System.err.println("  viewportY (" + viewportY + ") ?= oglViewport.y (" + oglViewport.y + ")");
        }
      }
      viewportX = oglViewport.x;
      viewportY = oglViewport.y;

      // If the FBO option is active, bind to the FBO from the Java2D
      // context.
      // Note that all of the plumbing in the context sharing stuff will
      // allow us to bind to this object since it's in our namespace.
      if (Java2D.isFBOEnabled() &&
          Java2D.getOGLSurfaceType(g) == Java2D.FBOBJECT) {

        // The texture target for Java2D's OpenGL pipeline when using FBOs
        // -- either GL_TEXTURE_2D or GL_TEXTURE_RECTANGLE_ARB
        int fboTextureTarget = Java2D.getOGLTextureType(g);

        if (!checkedForFBObjectWorkarounds) {
          checkedForFBObjectWorkarounds = true;
          gl.glBindTexture(fboTextureTarget, 0);
          gl.glBindFramebuffer(GL2.GL_FRAMEBUFFER, frameBuffer[0]);
          int status = gl.glCheckFramebufferStatus(GL.GL_FRAMEBUFFER);
          if (status != GL.GL_FRAMEBUFFER_COMPLETE) {
              // Need to do workarounds
              fbObjectWorkarounds = true;
              createNewDepthBuffer = true;
              if (DEBUG || VERBOSE) {
                  System.err.println("GLJPanel: ERR GL_FRAMEBUFFER_BINDING: Discovered Invalid J2D FBO("+frameBuffer[0]+"): "+FBObject.getStatusString(status) +
                                     ", frame_buffer_object workarounds to be necessary");
              }
          } else {
            // Don't need the frameBufferTexture temporary any more
            frameBufferTexture = null;
            if (DEBUG || VERBOSE) {
              System.err.println("GLJPanel: OK GL_FRAMEBUFFER_BINDING: "+frameBuffer[0]);
            }
          }
        }

        if (fbObjectWorkarounds && createNewDepthBuffer) {
          if (frameBufferDepthBuffer == null)
            frameBufferDepthBuffer = new int[1];

          // Create our own depth renderbuffer and associated storage
          // If we have an old one, delete it
          if (frameBufferDepthBuffer[0] != 0) {
            gl.glDeleteRenderbuffers(1, frameBufferDepthBuffer, 0);
            frameBufferDepthBuffer[0] = 0;
          }

          gl.glBindTexture(fboTextureTarget, frameBufferTexture[0]);
          int[] width = new int[1];
          int[] height = new int[1];
          gl.glGetTexLevelParameteriv(fboTextureTarget, 0, GL2.GL_TEXTURE_WIDTH, width, 0);
          gl.glGetTexLevelParameteriv(fboTextureTarget, 0, GL2.GL_TEXTURE_HEIGHT, height, 0);
                    
          gl.glGenRenderbuffers(1, frameBufferDepthBuffer, 0);
          if (DEBUG) {
            System.err.println("GLJPanel: Generated frameBufferDepthBuffer " + frameBufferDepthBuffer[0] +
                               " with width " + width[0] + ", height " + height[0]);
          }
                    
          gl.glBindRenderbuffer(GL.GL_RENDERBUFFER, frameBufferDepthBuffer[0]);
          // FIXME: may need a loop here like in Java2D
          gl.glRenderbufferStorage(GL.GL_RENDERBUFFER, GL2GL3.GL_DEPTH_COMPONENT24, width[0], height[0]);

          gl.glBindRenderbuffer(GL2.GL_RENDERBUFFER, 0);
          createNewDepthBuffer = false;
        }

        gl.glBindTexture(fboTextureTarget, 0);
        gl.glBindFramebuffer(GL.GL_FRAMEBUFFER, frameBuffer[0]);

        if (fbObjectWorkarounds) {
          // Hook up the color and depth buffer attachment points for this framebuffer
          gl.glFramebufferTexture2D(GL.GL_FRAMEBUFFER,
                                    GL.GL_COLOR_ATTACHMENT0,
                                    fboTextureTarget,
                                    frameBufferTexture[0],
                                    0);
          if (DEBUG && VERBOSE) {
            System.err.println("GLJPanel: frameBufferDepthBuffer: " + frameBufferDepthBuffer[0]);
          }
          gl.glFramebufferRenderbuffer(GL.GL_FRAMEBUFFER,
                                       GL.GL_DEPTH_ATTACHMENT,
                                       GL.GL_RENDERBUFFER,
                                       frameBufferDepthBuffer[0]);
        }

        if (DEBUG) {
          int status = gl.glCheckFramebufferStatus(GL.GL_FRAMEBUFFER);
          if (status != GL.GL_FRAMEBUFFER_COMPLETE) {
            throw new GLException("Error: framebuffer was incomplete: status = 0x" +
                                  Integer.toHexString(status));
          }
        }
      } else {
        if (DEBUG && VERBOSE) {
          System.err.println("GLJPanel: Setting up drawBuffer " + drawBuffer[0] +
                             " and readBuffer " + readBuffer[0]);
        }

        gl.glDrawBuffer(drawBuffer[0]);
        gl.glReadBuffer(readBuffer[0]);
      }

      return true;
    }

    public void postGL(Graphics g, boolean isDisplay) {
      // Cause OpenGL pipeline to flush its results because
      // otherwise it's possible we will buffer up multiple frames'
      // rendering results, resulting in apparent mouse lag
      GL gl = getGL();
      gl.glFinish();

      if (Java2D.isFBOEnabled() &&
          Java2D.getOGLSurfaceType(g) == Java2D.FBOBJECT) {
        // Unbind the framebuffer from our context to work around
        // apparent driver bugs or at least unspecified behavior causing
        // OpenGL to run out of memory with certain cards and drivers
        gl.glBindFramebuffer(GL.GL_FRAMEBUFFER, 0);
      }
    }

    public void doPaintComponent(final Graphics g) {
      // This is a workaround for an issue in the Java 2D / JOGL
      // bridge (reported by an end user as JOGL Issue 274) where Java
      // 2D can occasionally leave its internal OpenGL context current
      // to the on-screen window rather than its internal "scratch"
      // pbuffer surface to which the FBO is attached. JOGL expects to
      // find a stable OpenGL drawable (on Windows, an HDC) upon which
      // it can create another OpenGL context. It turns out that, on
      // Windows, when Java 2D makes its internal OpenGL context
      // current against the window in order to put pixels on the
      // screen, it gets the device context for the window, makes its
      // context current, and releases the device context. This means
      // that when JOGL's Runnable gets to run below, the HDC is
      // already invalid. The workaround for this is to force Java 2D
      // to make its context current to the scratch surface, which we
      // can do by executing an empty Runnable with the "shared"
      // context current. This will be fixed in a Java SE 6 update
      // release, hopefully 6u2.
      if (Java2D.isFBOEnabled()) {
        if (workaroundConfig == null) {
          workaroundConfig = GraphicsEnvironment.
            getLocalGraphicsEnvironment().
            getDefaultScreenDevice().
            getDefaultConfiguration();
        }
        Java2D.invokeWithOGLSharedContextCurrent(workaroundConfig, new Runnable() { public void run() {}});
      }

      Java2D.invokeWithOGLContextCurrent(g, new Runnable() {
          public void run() {
            if (DEBUG && VERBOSE) {
              System.err.println("-- In invokeWithOGLContextCurrent");
            }

            // Create no-op context representing Java2D context
            if (j2dContext == null) {
              j2dContext = factory.createExternalGLContext();
              if (DEBUG||VERBOSE) {
                System.err.println("-- Created External Context: "+j2dContext);
              }
              if (DEBUG) {
//                j2dContext.setGL(new DebugGL2(j2dContext.getGL().getGL2()));
              }

              // Check to see whether we can support the requested
              // capabilities or need to fall back to a pbuffer
              // FIXME: add more checks?

              j2dContext.makeCurrent();
              GL gl = j2dContext.getGL();
              if ((getGLInteger(gl, GL.GL_RED_BITS)         < offscreenCaps.getRedBits())        ||
                  (getGLInteger(gl, GL.GL_GREEN_BITS)       < offscreenCaps.getGreenBits())      ||
                  (getGLInteger(gl, GL.GL_BLUE_BITS)        < offscreenCaps.getBlueBits())       ||
                  //                  (getGLInteger(gl, GL.GL_ALPHA_BITS)       < offscreenCaps.getAlphaBits())      ||
                  (getGLInteger(gl, GL2.GL_ACCUM_RED_BITS)   < offscreenCaps.getAccumRedBits())   ||
                  (getGLInteger(gl, GL2.GL_ACCUM_GREEN_BITS) < offscreenCaps.getAccumGreenBits()) ||
                  (getGLInteger(gl, GL2.GL_ACCUM_BLUE_BITS)  < offscreenCaps.getAccumBlueBits())  ||
                  (getGLInteger(gl, GL2.GL_ACCUM_ALPHA_BITS) < offscreenCaps.getAccumAlphaBits()) ||
                  //          (getGLInteger(gl, GL2.GL_DEPTH_BITS)       < offscreenCaps.getDepthBits())      ||
                  (getGLInteger(gl, GL.GL_STENCIL_BITS)     < offscreenCaps.getStencilBits())) {
                if (DEBUG) {
                  System.err.println("GLJPanel: Falling back to pbuffer-based support because Java2D context insufficient");
                  System.err.println("                    Available              Required");
                  System.err.println("GL_RED_BITS         " + getGLInteger(gl, GL.GL_RED_BITS)         + "              " + offscreenCaps.getRedBits());
                  System.err.println("GL_GREEN_BITS       " + getGLInteger(gl, GL.GL_GREEN_BITS)       + "              " + offscreenCaps.getGreenBits());
                  System.err.println("GL_BLUE_BITS        " + getGLInteger(gl, GL.GL_BLUE_BITS)        + "              " + offscreenCaps.getBlueBits());
                  System.err.println("GL_ALPHA_BITS       " + getGLInteger(gl, GL.GL_ALPHA_BITS)       + "              " + offscreenCaps.getAlphaBits());
                  System.err.println("GL_ACCUM_RED_BITS   " + getGLInteger(gl, GL2.GL_ACCUM_RED_BITS)   + "              " + offscreenCaps.getAccumRedBits());
                  System.err.println("GL_ACCUM_GREEN_BITS " + getGLInteger(gl, GL2.GL_ACCUM_GREEN_BITS) + "              " + offscreenCaps.getAccumGreenBits());
                  System.err.println("GL_ACCUM_BLUE_BITS  " + getGLInteger(gl, GL2.GL_ACCUM_BLUE_BITS)  + "              " + offscreenCaps.getAccumBlueBits());
                  System.err.println("GL_ACCUM_ALPHA_BITS " + getGLInteger(gl, GL2.GL_ACCUM_ALPHA_BITS) + "              " + offscreenCaps.getAccumAlphaBits());
                  System.err.println("GL_DEPTH_BITS       " + getGLInteger(gl, GL.GL_DEPTH_BITS)       + "              " + offscreenCaps.getDepthBits());
                  System.err.println("GL_STENCIL_BITS     " + getGLInteger(gl, GL.GL_STENCIL_BITS)     + "              " + offscreenCaps.getStencilBits());
                }
                isInitialized = false;
                backend = null;
                oglPipelineEnabled = false;
                handleReshape = true;
                j2dContext.release();
                j2dContext.destroy();
                j2dContext = null;
                return;
              }
              j2dContext.release();
            }

            j2dContext.makeCurrent();
            try {
              captureJ2DState(j2dContext.getGL(), g);
              Object curSurface = Java2D.getOGLSurfaceIdentifier(g);
              if (curSurface != null) {
                if (j2dSurface != curSurface) {
                  if (joglContext != null) {
                    joglContext.destroy();
                    joglContext = null;
                    joglDrawable = null;
                    sendReshape = true;
                    if (DEBUG||VERBOSE) {
                      System.err.println("Sending reshape because surface changed");
                      System.err.println("New surface = " + curSurface);
                    }
                  }
                  j2dSurface = curSurface;
                  if (DEBUG || VERBOSE) {
                      System.err.print("-- Surface type: ");
                      int surfaceType = Java2D.getOGLSurfaceType(g);
                      if (surfaceType == Java2D.UNDEFINED) {
                        System.err.println("UNDEFINED");
                      } else if (surfaceType == Java2D.WINDOW) {
                        System.err.println("WINDOW");
                      } else if (surfaceType == Java2D.PBUFFER) {
                        System.err.println("PBUFFER");
                      } else if (surfaceType == Java2D.TEXTURE) {
                        System.err.println("TEXTURE");
                      } else if (surfaceType == Java2D.FLIP_BACKBUFFER) {
                        System.err.println("FLIP_BACKBUFFER");
                      } else if (surfaceType == Java2D.FBOBJECT) {
                        System.err.println("FBOBJECT");
                      } else {
                        System.err.println("(Unknown surface type " + surfaceType + ")");
                      }
                  }
                }
                if (joglContext == null) {
                  AbstractGraphicsDevice device = j2dContext.getGLDrawable().getNativeSurface().getGraphicsConfiguration().getNativeGraphicsConfiguration().getScreen().getDevice();
                  if (factory.canCreateExternalGLDrawable(device)) {
                    joglDrawable = factory.createExternalGLDrawable();
                    // FIXME: Need to share with j2d context, due to FBO resource .. 
                    // - ORIG: joglContext = joglDrawable.createContext(shareWith);
                    joglContext = joglDrawable.createContext(j2dContext);
                    if (DEBUG||VERBOSE) {
                        System.err.println("-- Created External Drawable: "+joglDrawable);
                        System.err.println("-- Created Context: "+joglContext);
                    }
                  } else if (factory.canCreateContextOnJava2DSurface(device)) {
                    // Mac OS X code path
                    // FIXME: Need to share with j2d context, due to FBO resource .. 
                    // - ORIG: joglContext = factory.createContextOnJava2DSurface(g, shareWith);
                    joglContext = factory.createContextOnJava2DSurface(g, j2dContext);
                    if (DEBUG||VERBOSE) {
                        System.err.println("-- Created Context: "+joglContext);
                    }
                  }
                  /*if (DEBUG) {
                    joglContext.setGL(new DebugGL2(joglContext.getGL().getGL2()));
                  }*/

                  if (Java2D.isFBOEnabled() &&
                      Java2D.getOGLSurfaceType(g) == Java2D.FBOBJECT &&
                      fbObjectWorkarounds) {
                    createNewDepthBuffer = true;
                  }
                }
                if (joglContext instanceof Java2DGLContext) {
                  // Mac OS X code path
                  ((Java2DGLContext) joglContext).setGraphics(g);
                }

                drawableHelper.invokeGL(joglDrawable, joglContext, displayAction, initAction);
              }
            } finally {
              j2dContext.release();
            }
          }
        });
    }

    private void captureJ2DState(GL gl, Graphics g) {
      gl.glGetIntegerv(GL2.GL_DRAW_BUFFER, drawBuffer, 0);
      gl.glGetIntegerv(GL2.GL_READ_BUFFER, readBuffer, 0);
      if (Java2D.isFBOEnabled() &&
          Java2D.getOGLSurfaceType(g) == Java2D.FBOBJECT) {
        gl.glGetIntegerv(GL.GL_FRAMEBUFFER_BINDING, frameBuffer, 0);
        if(!gl.glIsFramebuffer(frameBuffer[0])) {
          checkedForFBObjectWorkarounds=true;
          fbObjectWorkarounds = true;
          createNewDepthBuffer = true;
          if (DEBUG || VERBOSE) {
              System.err.println("GLJPanel: Fetched ERR GL_FRAMEBUFFER_BINDING: "+frameBuffer[0]+" - NOT A FBO"+
                                 ", frame_buffer_object workarounds to be necessary");
          }
        } else if (DEBUG) {
          System.err.println("GLJPanel: Fetched OK GL_FRAMEBUFFER_BINDING: "+frameBuffer[0]);
        }

        if(fbObjectWorkarounds || !checkedForFBObjectWorkarounds) {
            // See above for description of what we are doing here
            if (frameBufferTexture == null)
                frameBufferTexture = new int[1];

            // Query the framebuffer for its color buffer so we can hook
            // it back up in our context (should not be necessary)
            gl.glGetFramebufferAttachmentParameteriv(GL.GL_FRAMEBUFFER,
                                                     GL.GL_COLOR_ATTACHMENT0,
                                                     GL.GL_FRAMEBUFFER_ATTACHMENT_OBJECT_NAME,
                                                     frameBufferTexture, 0);
            if (DEBUG && VERBOSE) {
                System.err.println("GLJPanel: FBO COLOR_ATTACHMENT0: " + frameBufferTexture[0]);
            }
        }

        if (!checkedGLVendor) {
          checkedGLVendor = true;
          String vendor = gl.glGetString(GL.GL_VENDOR);

          if ((vendor != null) &&
              vendor.startsWith("ATI")) {
            vendorIsATI = true;
          }
        }

        if (vendorIsATI) {
          // Unbind the FBO from Java2D's context as it appears that
          // driver bugs on ATI's side are causing problems if the FBO is
          // simultaneously bound to more than one context. Java2D will
          // re-bind the FBO during the next validation of its context.
          // Note: this breaks rendering at least on NVidia hardware
          gl.glBindFramebuffer(GL.GL_FRAMEBUFFER, 0);
        }
      }
    }
  }
}