/*
 * Copyright (c) 2003 Sun Microsystems, Inc. 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
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 * 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.
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 * Sun gratefully acknowledges that this software was originally authored
 * and developed by Kenneth Bradley Russell and Christopher John Kline.
 */

package javax.media.opengl;

/** Abstraction for an OpenGL rendering context. In order to perform
    OpenGL rendering, a context must be "made current" on the current
    thread. OpenGL rendering semantics specify that only one context
    may be current on the current thread at any given time, and also
    that a given context may be current on only one thread at any
    given time. Because components can be added to and removed from
    the component hierarchy at any time, it is possible that the
    underlying OpenGL context may need to be destroyed and recreated
    multiple times over the lifetime of a given component. This
    process is handled by the implementation, and the GLContext
    abstraction provides a stable object which clients can use to
    refer to a given context. */

public abstract class GLContext {
  /** Indicates that the context was not made current during the last call to {@link #makeCurrent makeCurrent}. */
  public static final int CONTEXT_NOT_CURRENT = 0;
  /** Indicates that the context was made current during the last call to {@link #makeCurrent makeCurrent}. */
  public static final int CONTEXT_CURRENT     = 1;
  /** Indicates that a newly-created context was made current during the last call to {@link #makeCurrent makeCurrent}. */
  public static final int CONTEXT_CURRENT_NEW = 2;

  private static ThreadLocal currentContext = new ThreadLocal();

  /**
   * Returns the GLDrawable to which this context may be used to
   * draw.
   */
  public abstract GLDrawable getGLDrawable();

  /**
   * Makes this GLContext current on the calling thread.
   *
   * There are two return values that indicate success and one that
   * indicates failure. A return value of CONTEXT_CURRENT_NEW
   * indicates that that context has been made current, and that
   * this is the first time this context has been made current, or
   * that the state of the underlying context or drawable may have
   * changed since the last time this context was made current. In
   * this case, the application may wish to initialize the state.  A
   * return value of CONTEXT_CURRENT indicates that the context has
   * been made currrent, with its previous state restored.
   * 
   * If the context could not be made current (for example, because
   * the underlying drawable has not ben realized on the display) ,
   * a value of CONTEXT_NOT_CURRENT is returned.
   *
   * If the context is in use by another thread at the time of the
   * call, then if isSynchronized() is true the call will
   * block. If isSynchronized() is false, an exception will be
   * thrown and the context will remain current on the other thread.
   *
   * @return CONTEXT_CURRENT if the context was successfully made current
   * @return CONTEXT_CURRENT_NEW if the context was successfully made
   * current, but need to be initialized.
   *
   * @return CONTEXT_NOT_CURRENT if the context could not be made current.
   *
   * @throws GLException if synchronization is disabled and the
   * context is current on another thread, or because the context
   * could not be created or made current due to non-recoverable,
   * window system-specific errors.
   */
  public abstract int makeCurrent() throws GLException;

  /**
   * Releases control of this GLContext from the current thread.
   *
   * @throws GLException if the context had not previously been made
   * current on the current thread
   */
  public abstract void release() throws GLException;

  /**
   * Returns the context which is current on the current thread. If no
   * context is current, returns null.
   *
   * @return the context current on this thread, or null if no context
   * is current.
   */
  public static GLContext getCurrent() {
    return (GLContext) currentContext.get();
  }

  /**
   * Sets the thread-local variable returned by {@link #getCurrent}
   * and has no other side-effects. For use by third parties adding
   * new GLContext implementations; not for use by end users.
   */
  protected static void setCurrent(GLContext cur) {
    currentContext.set(cur);
  }
  
  /**
   * Destroys this OpenGL context and frees its associated
   * resources. The context should have been released before this
   * method is called.
   */
  public abstract void destroy();

  /**
   * Returns true if 'makeCurrent' will exhibit synchronized behavior.
   */
  public abstract boolean isSynchronized();
    
  /** 
   * Determines whether 'makeCurrent' will exhibit synchronized behavior.
   */
  public abstract void setSynchronized(boolean isSynchronized);

  /**
   * Returns the GL pipeline object for this GLContext.
   */
  public abstract GL getGL();

  /**
   * Sets the GL pipeline object for this GLContext.
   */
  public abstract void setGL(GL gl);
}