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Java™ Binding for the OpenGL® API (Android)
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/**
 * 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
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * 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
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * 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 com.jogamp.opengl;

import com.jogamp.opengl.GLRendererQuirks;

/**
 * Adds capabilities to set a shared {@link GLContext} directly or via an {@link GLAutoDrawable}.
 * 
 * Sharing of server-side OpenGL objects such as buffer objects, e.g. VBOs,
 * and textures among OpenGL contexts is supported with this interface.
 * 
 * 
 * A master {@link GLContext} is the {@link GLContext} which is created first.
 * Subsequent shared {@link GLContext} w/ the master are referred as slave {@link GLContext}.
 * 
 * 
 * Implementations of this interface control the slave's {@link GLContext} and {@link GLAutoDrawable} realization,
 * i.e. the slave {@link GLAutoDrawable} will not be realized before their associated master.
 * 
 * 
 * Using the nearest or same {@link GLCapabilitiesImmutable#getVisualID(com.jogamp.nativewindow.VisualIDHolder.VIDType) visual ID}
 * or {@link GLCapabilitiesImmutable caps} across the shared {@link GLDrawable}s will yield best compatibility.
 * 
 * Lifecycle Considerations
 * 
 * After shared objects are created on the master, the OpenGL pipeline
 * might need to be synchronized w/ the slaves, e.g. via {@link GL#glFinish()}.
 * At least this has been experienced w/ OSX 10.9.
 * 
 * 
 * In general, destroying a master {@link GLContext} before their shared slaves
 * 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 com.jogamp.opengl.test.junit.jogl.acore.TestSharedContextVBOES2NEWT3 and similar.
 * 
 * 
 * However, to avoid scenarios with buggy drivers, users may not destroy the
 * master {@link GLContext} before its shared slave {@link GLContext} instances
 * as long as they are using them.

 * Otherwise the OpenGL driver may crash w/ SIGSEGV, due to using already destroyed shared resources,
 * if not handling the pending destruction of the latter!

 * Either proper lifecycle synchronization is implemented, e.g. by notifying the slaves about the loss of the shared resources,
 * or the slaves validate whether the resources are still valid.
 * 
 * 
 * To simplify above lifecycle issues, one may use a {@link GLDrawableFactory#createDummyDrawable(com.jogamp.nativewindow.AbstractGraphicsDevice, boolean, GLCapabilitiesImmutable, GLCapabilitiesChooser) dummy}
 * {@link GLDrawable} and it's {@link GLContext} as the master of all shared slave {@link GLContext}.
 * Since this dummy instance does not depend on any native windowing system, it can be controlled easily w/o being in sight.

 * Below code creates a {@link GLAutoDrawable} based on a dummy GLDrawable:
 * 
        // 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 ..
 * 
 * 
 * GL Object Synchronization
 * 
 * Usually synchronization of shared GL objects should not be required, if the shared GL objects
 * are created and immutable before concurrent usage.
 * 
 * 
 * However, using drivers exposing {@link GLRendererQuirks#NeedSharedObjectSync} always
 * require the user to synchronize access of shared GL objects.
 * 
 * 
 * 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.
 * 
 * 
 * Known Driver Issues
 * Intel's Mesa >= 9.1.2 Backend for [Sandybridge/Ivybridge] on GNU/Linux
 * 
 * 
 * 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
 * 
 * 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.
 * 
 * Hisilicon's Immersion.16 on Android
 * 
 * We failed to create a shared ES2 context on another thread.
 * 
 */
public interface GLSharedContextSetter extends GLAutoDrawable {
    /**
     * Specifies an {@link GLContext OpenGL context}, which shall be shared by this {@link GLAutoDrawable}'s {@link GLContext}.
     * 
     * 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.
     * 
     * 
     * A set sharedContext will block context creation, i.e. {@link GLAutoDrawable#initialization GLAutoDrawable initialization},
     * as long it is not {@link GLContext#isCreated() created natively}.
     * 
     * 
     * The preferred method of assigning a shared context is
     * to {@link #setSharedAutoDrawable(GLAutoDrawable) set the shared GLAutoDrawable},
     * since this method also takes the {@link GLEventListener}
     * {@link GLAutoDrawable#areAllGLEventListenerInitialized() initialization into account}.
     * 
     * 
     * See Lifecycle Considerations.
     * 
     *
     * @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}.
     * 
     * 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.
     * 
     * 
     * A set sharedAutoDrawable will block context creation, i.e. initialization
     * as long it's
     * 

     *   {@link GLContext} is null, or
     *   {@link GLContext} has not been {@link GLContext#isCreated() created natively}, or
     *   {@link GLEventListener} are not {@link GLAutoDrawable#areAllGLEventListenerInitialized() completely initialized}
     * 
     * 
     * 
     * See Lifecycle Considerations.
     * 
     *
     * @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;
}