/**
 * Copyright 2013 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:
 *
 *    1. Redistributions of source code must retain the above copyright notice, this list of
 *       conditions and the following disclaimer.
 *
 *    2. Redistributions 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.
 *
 * THIS SOFTWARE IS PROVIDED BY JogAmp Community ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JogAmp Community OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and documentation are those of the
 * authors and should not be interpreted as representing official policies, either expressed
 * or implied, of JogAmp Community.
 */

package javax.media.opengl;

import com.jogamp.opengl.GLRendererQuirks;

/**
 * Adds capabilities to set a shared {@link GLContext} directly or via an {@link GLAutoDrawable}.
 * <p>
 * Sharing of server-side OpenGL objects such as buffer objects, e.g. VBOs,
 * and textures among OpenGL contexts is supported with this interface.
 * </p>
 * <p>
 * A <i>master</i> {@link GLContext} is the {@link GLContext} which is created first.
 * Subsequent shared {@link GLContext} w/ the <i>master</i> are referred as <i>slave</i> {@link GLContext}.
 * </p>
 * <p>
 * Implementations of this interface control the <i>slave's</i> {@link GLContext} and {@link GLAutoDrawable} realization,
 * i.e. the <i>slave</i> {@link GLAutoDrawable} will not be realized before their associated <i>master</i>.
 * </p>
 * <p>
 * Using the nearest or same {@link GLCapabilitiesImmutable#getVisualID(javax.media.nativewindow.VisualIDHolder.VIDType) visual ID}
 * or {@link GLCapabilitiesImmutable caps} across the shared {@link GLDrawable}s will yield best compatibility.
 * </p>
 * <h5><a name="lifecycle">Lifecycle Considerations</a></h5>
 * <p>
 * After shared objects are created on the <i>master</i>, the OpenGL pipeline
 * might need to be synchronized w/ the <i>slaves</i>, e.g. via {@link GL#glFinish()}.
 * At least this has been experienced w/ OSX 10.9.
 * </p>
 * <p>
 * In general, destroying a <i>master</i> {@link GLContext} before their shared <i>slaves</i>
 * shall be permissible, i.e. the OpenGL driver needs to handle pending destruction of shared resources.
 * This is confirmed to work properly on most platform/driver combinations,
 * see unit test <code>com.jogamp.opengl.test.junit.jogl.acore.TestSharedContextVBOES2NEWT3</code> and similar.
 * </p>
 * <p>
 * However, to avoid scenarios with buggy drivers, users <i>may not</i> destroy the
 * <i>master</i> {@link GLContext} before its shared <i>slave</i> {@link GLContext} instances
 * <i>as long as they are using them</i>.<br>
 * Otherwise the OpenGL driver may crash w/ SIGSEGV, due to using already destroyed shared resources,
 * if not handling the pending destruction of the latter!<br>
 * Either proper lifecycle synchronization is implemented, e.g. by notifying the <i>slaves</i> about the loss of the shared resources,
 * <i>or</i> the <i>slaves</i> validate whether the resources are still valid.
 * </p>
 * <p>
 * To simplify above lifecycle issues, one may use a {@link GLDrawableFactory#createDummyDrawable(javax.media.nativewindow.AbstractGraphicsDevice, boolean, GLCapabilitiesImmutable, GLCapabilitiesChooser) dummy}
 * {@link GLDrawable} and it's {@link GLContext} as the <i>master</i> of all shared <i>slave</i> {@link GLContext}.
 * Since this <i>dummy instance</i> does not depend on any native windowing system, it can be controlled easily w/o being <i>in sight</i>.<br>
 * Below code creates a {@link GLAutoDrawable} based on a <i>dummy GLDrawable</i>:
 * <pre>
        // GLProfile and GLCapabilities should be equal across all shared GL drawable/context.
        final GLCapabilitiesImmutable caps = ... ;
        final GLProfile glp = caps.getGLProfile();
        ..
        final boolean createNewDevice = true; // use 'own' display device!
        final GLAutoDrawable sharedDrawable = GLDrawableFactory.getFactory(glp).createDummyAutoDrawable(null, createNewDevice, caps, null);
        sharedDrawable.display(); // triggers GLContext object creation and native realization.
        ...
        // Later a shared 'slave' can be created e.g.:
        GLWindow glad = GLWindow.create(caps); // or any other GLAutoDrawable supporting GLSharedContextSetter
        glad.setSharedAutoDrawable(sharedDrawable);
        glad.addGLEventListener(..);
        glad.setVisible(true); // GLWindow creation ..
 * </pre>
 * </p>
 * <h5><a name="synchronization">GL Object Synchronization</a></h5>
 * <p>
 * Usually synchronization of shared GL objects should not be required, if the shared GL objects
 * are created and immutable before concurrent usage.
 * </p>
 * <p>
 * However, using drivers exposing {@link GLRendererQuirks#NeedSharedObjectSync} always
 * require the user to synchronize access of shared GL objects.
 * </p>
 * <p>
 * Synchronization can be avoided if accessing the shared GL objects
 * exclusively via a queue or {@link com.jogamp.common.util.Ringbuffer Ringbuffer}, see GLMediaPlayerImpl as an example.
 * </p>
 * </p>
 * <h5><a name="driverissues">Known Driver Issues</a></h5>
 * <h7><a name="intelmesa">Intel's Mesa >= 9.1.2 Backend for [Sandybridge/Ivybridge] on GNU/Linux</a></h7>
 * <p>
 * <pre>
 * Error: 'intel_do_flush_locked: No such file or directory'
 * JogAmp: https://jogamp.org/bugzilla/show_bug.cgi?id=873
 * freedesktop.org: https://bugs.freedesktop.org/show_bug.cgi?id=41736#c8
 * </pre>
 * Shared context seems not to be supported w/ lock-free bound X11 display connections
 * per OpenGL drawable/context. The error message above is thrown in this case.
 * Hence the driver bug renders shared context use w/ JOGL impossible.
 * </p>
 * <h7><a name="hisilicon">Hisilicon's Immersion.16 on Android</a></h7>
 * <p>
 * We failed to create a shared ES2 context on another thread.
 * </p>
 */
public interface GLSharedContextSetter extends GLAutoDrawable {
    /**
     * Specifies an {@link GLContext OpenGL context}, which shall be shared by this {@link GLAutoDrawable}'s {@link GLContext}.
     * <p>
     * Since the {@link GLDrawable drawable} and {@link GLContext context} is created
     * at {@link GLAutoDrawable#initialization GLAutoDrawable initialization}
     * this method shall be called beforehand to have any effect.
     * </p>
     * <p>
     * A set <i>sharedContext</i> will block context creation, i.e. {@link GLAutoDrawable#initialization GLAutoDrawable initialization},
     * as long it is not {@link GLContext#isCreated() created natively}.
     * </p>
     * <p>
     * The <i>preferred method</i> of assigning a <i>shared context</i> is
     * to {@link #setSharedAutoDrawable(GLAutoDrawable) set the shared GLAutoDrawable},
     * since this method also takes the {@link GLEventListener}
     * {@link GLAutoDrawable#areAllGLEventListenerInitialized() initialization into account}.
     * </p>
     * <p>
     * See <a href="#lifecycle">Lifecycle Considerations</a>.
     * </p>
     *
     * @param sharedContext The OpenGL context to be shared by this {@link GLAutoDrawable}'s {@link GLContext}.
     * @throws IllegalStateException if a {@link #setSharedContext(GLContext) shared GLContext}
     *                               or {@link #setSharedAutoDrawable(GLAutoDrawable) shared GLAutoDrawable} is already set,
     *                               the given sharedContext is null or equal to this {@link GLAutoDrawable}'s context.
     * @see #setSharedAutoDrawable(GLAutoDrawable)
     */
    void setSharedContext(GLContext sharedContext) throws IllegalStateException;

    /**
     * Specifies an {@link GLAutoDrawable}, which {@link GLContext OpenGL context} shall be shared by this {@link GLAutoDrawable}'s {@link GLContext}.
     * <p>
     * Since the {@link GLDrawable drawable} and {@link GLContext context} is created
     * at {@link GLAutoDrawable#initialization GLAutoDrawable initialization}
     * this method shall be called beforehand to have any effect.
     * </p>
     * <p>
     * A set <i>sharedAutoDrawable</i> will block context creation, i.e. <a href="GLAutoDrawable.html#initialization">initialization</a>
     * as long it's
     * <ul>
     *   <li>{@link GLContext} is <code>null</code>, or</li>
     *   <li>{@link GLContext} has not been {@link GLContext#isCreated() created natively}, or</li>
     *   <li>{@link GLEventListener} are <i>not</i> {@link GLAutoDrawable#areAllGLEventListenerInitialized() completely initialized}</li>
     * </ul>
     * </p>
     * <p>
     * See <a href="#lifecycle">Lifecycle Considerations</a>.
     * </p>
     *
     * @param sharedContext The GLAutoDrawable, which OpenGL context shall be shared by this {@link GLAutoDrawable}'s {@link GLContext}.
     * @throws IllegalStateException if a {@link #setSharedContext(GLContext) shared GLContext}
     *                               or {@link #setSharedAutoDrawable(GLAutoDrawable) shared GLAutoDrawable} is already set,
     *                               the given sharedAutoDrawable is null or equal to this GLAutoDrawable.
     * @see #setSharedContext(GLContext)
     */
    void setSharedAutoDrawable(GLAutoDrawable sharedAutoDrawable) throws IllegalStateException;
}
