/*
* Copyright (c) 2002-2011 LWJGL Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * 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.
*
* * Neither the name of 'LWJGL' nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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 THE COPYRIGHT OWNER 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.
*/
package org.lwjgl.opengles;
import org.lwjgl.LWJGLException;
import org.lwjgl.LWJGLUtil;
import org.lwjgl.Sys;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Map;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.WeakHashMap;
import static org.lwjgl.opengles.GLES20.*;
/**
* <p/>
* Manages GL contexts. Before any rendering is done by a LWJGL system, a call should be made to GLContext.useContext() with a
* context. This will ensure that GLContext has an accurate reflection of the current context's capabilities and function
* pointers.
* <p/>
* This class is thread-safe in the sense that multiple threads can safely call all public methods. The class is also
* thread-aware in the sense that it tracks a per-thread current context (including capabilities and function pointers).
* That way, multiple threads can have multiple contexts current and render to them concurrently.
*
* @author elias_naur <elias_naur@users.sourceforge.net>
* @version $Revision: 3279 $
* $Id: GLContext.java 3279 2010-03-11 21:06:49Z spasi $
*/
public final class GLContext {
/** Maps threads to their current context's ContextCapabilities, if any */
private static final ThreadLocal<ContextCapabilities> current_capabilities = new ThreadLocal<ContextCapabilities>();
/**
* The getCapabilities() method is a potential hot spot in any LWJGL application, since
* it is needed for context capability discovery (e.g. is OpenGL 2.0 supported?), and
* for the function pointers of gl functions. However, the 'current_capabilities' ThreadLocal
* is (relatively) expensive to look up, and since most OpenGL applications use are single threaded
* rendering, the following two is an optimization for this case.
* <p/>
* ThreadLocals can be thought of as a mapping between threads and values, so the idea
* is to use a lock-less cache of mappings between threads and the current ContextCapabilities. The cache
* could be any size, but in our case, we want a single sized cache for optimal performance
* in the single threaded case.
* <p/>
* 'fast_path_cache' is the most recent ContextCapabilities (potentially null) and its owner. By
* recent I mean the last thread setting the value in setCapabilities(). When getCapabilities()
* is called, a check to see if the current is the owner of the ContextCapabilities instance in
* fast_path_cache. If so, the instance is returned, if not, some thread has since taken ownership
* of the cache entry and the slower current_capabilities ThreadLocal is queried instead.
* <p/>
* No locks are needed in get/setCapabilities, because even though fast_path_cache can be accessed
* from multiple threads at once, we are guaranteed by the JVM spec that its value is always valid.
* Furthermore, if the ownership test in getCapabilities() succeeds, the cache entry can only contain
* the correct ContextCapabilites (that is, the one from getThreadLocalCapabilites()),
* since no other thread can set the owner to anyone else than itself.
*/
private static CapabilitiesCacheEntry fast_path_cache = new CapabilitiesCacheEntry();
/**
* Simple lock-free cache of CapabilitesEntryCache to avoid allocating more than one
* cache entry per thread
*/
private static final ThreadLocal<CapabilitiesCacheEntry> thread_cache_entries = new ThreadLocal<CapabilitiesCacheEntry>();
/**
* The weak mapping from context Object instances to ContextCapabilities. Used
* to avoid recreating a ContextCapabilities every time a context is made current.
*/
private static final Map<Object, ContextCapabilities> capability_cache = new WeakHashMap<Object, ContextCapabilities>();
/** Reference count of the native opengl implementation library */
private static int gl_ref_count;
private static boolean did_auto_load;
static {
Sys.initialize();
}
/**
* Get the current capabilities instance. It contains the flags used
* to test for support of a particular extension.
*
* @return The current capabilities instance.
*/
public static ContextCapabilities getCapabilities() {
CapabilitiesCacheEntry recent_cache_entry = fast_path_cache;
// Check owner of cache entry
if ( recent_cache_entry.owner == Thread.currentThread() ) {
/* The owner ship test succeeded, so the cache must contain the current ContextCapabilities instance
* assert recent_cache_entry.capabilities == getThreadLocalCapabilities();
*/
return recent_cache_entry.capabilities;
} else // Some other thread has written to the cache since, and we fall back to the slower path
return getThreadLocalCapabilities();
}
private static ContextCapabilities getThreadLocalCapabilities() {
return current_capabilities.get();
}
/**
* Set the current capabilities instance. It contains the flags used
* to test for support of a particular extension.
*
* @return The current capabilities instance.
*/
static void setCapabilities(ContextCapabilities capabilities) {
current_capabilities.set(capabilities);
CapabilitiesCacheEntry thread_cache_entry = thread_cache_entries.get();
if ( thread_cache_entry == null ) {
thread_cache_entry = new CapabilitiesCacheEntry();
thread_cache_entries.set(thread_cache_entry);
}
thread_cache_entry.owner = Thread.currentThread();
thread_cache_entry.capabilities = capabilities;
fast_path_cache = thread_cache_entry;
}
/**
* Determine which extensions are available and returns the context profile mask. Helper method to ContextCapabilities.
*
* @param supported_extensions the Set to fill with the available extension names
*
* @return the context profile mask, will be 0 for any version < 3.2
*/
static void getSupportedExtensions(final Set<String> supported_extensions) {
// Detect OpenGL version first
final String version = glGetString(GL_VERSION);
if ( version == null )
throw new IllegalStateException("glGetString(GL_VERSION) returned null - possibly caused by missing current context.");
final String VERSION_PREFIX = "OpenGL ES ";
final StringTokenizer version_tokenizer = new StringTokenizer(version.substring(VERSION_PREFIX.length()), ". ");
int majorVersion = 0;
int minorVersion = 0;
try {
majorVersion = Integer.parseInt(version_tokenizer.nextToken());
minorVersion = Integer.parseInt(version_tokenizer.nextToken());
} catch (NumberFormatException e) {
LWJGLUtil.log("The major and/or minor OpenGL version is malformed: " + e.getMessage());
}
// ----------------------[ 2.X ]----------------------
if ( 3 <= majorVersion )
supported_extensions.add("OpenGLES30");
if ( 2 <= majorVersion )
supported_extensions.add("OpenGLES20");
// Parse EXTENSIONS string
final String extensions_string = glGetString(GL_EXTENSIONS);
if ( extensions_string == null )
throw new IllegalStateException("glGetString(GL_EXTENSIONS) returned null - is there a context current?");
final StringTokenizer tokenizer = new StringTokenizer(extensions_string);
while ( tokenizer.hasMoreTokens() )
supported_extensions.add(tokenizer.nextToken());
}
/**
* Helper method to ContextCapabilities. It will try to initialize the native stubs,
* and remove the given extension name from the extension set if the initialization fails.
*/
static void initNativeStubs(final Class extension_class, Set<String> supported_extensions, String ext_name) {
//resetNativeStubs(extension_class);
if ( supported_extensions.contains(ext_name) ) {
try {
doInitNativeStubs(extension_class);
} catch (LWJGLException e) {
LWJGLUtil.log("Failed to initialize extension " + extension_class + " - exception: " + e);
supported_extensions.remove(ext_name);
}
}
}
static void doInitNativeStubs(final Class<?> extension_class) throws LWJGLException {
try {
AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
public Object run() throws Exception {
Method init_stubs_method = extension_class.getDeclaredMethod("initNativeStubs");
init_stubs_method.invoke(null);
return null;
}
});
} catch (PrivilegedActionException e) {
final Throwable c = e.getCause();
if ( c instanceof InvocationTargetException )
throw new LWJGLException(c.getCause());
else
throw new LWJGLException(c);
}
}
/**
* Makes a GL context the current LWJGL context by loading GL function pointers. The context must be current before a call to
* this method! Instead it simply ensures that the current context is reflected accurately by GLContext's extension caps and
* function pointers. Use useContext(null) when no context is active. <p>If the context is the same as last time, then this is
* a no-op. <p>If the context has not been encountered before it will be fully initialized from scratch. Otherwise a cached set
* of caps and function pointers will be used. <p>The reference to the context is held in a weak reference; therefore if no
* strong reference exists to the GL context it will automatically be forgotten by the VM at an indeterminate point in the
* future, freeing up a little RAM.
*
* @param context The context object, which uniquely identifies a GL context. If context is null, the native stubs are
* unloaded.
*
* @throws org.lwjgl.LWJGLException if context non-null, and the gl library can't be loaded or the basic GL11 functions can't be loaded
*/
public static synchronized void useContext(Object context) throws LWJGLException {
if ( context == null ) {
// Moved this to the shutdown hook
ContextCapabilities.unloadAllStubs();
setCapabilities(null);
if ( did_auto_load )
unloadOpenGLLibrary();
return;
}
if ( gl_ref_count == 0 ) {
loadOpenGLLibrary();
did_auto_load = true;
}
try {
ContextCapabilities capabilities = capability_cache.get(context);
if ( capabilities == null ) {
/*
* The capabilities object registers itself as current. This behaviour is caused
* by a chicken-and-egg situation where the constructor needs to call GL functions
* as part of its capability discovery, but GL functions cannot be called before
* a capabilities object has been set.
*/
new ContextCapabilities();
capability_cache.put(context, getCapabilities());
} else
setCapabilities(capabilities);
} catch (LWJGLException e) {
if ( did_auto_load )
unloadOpenGLLibrary();
throw e;
}
}
/** If the OpenGL reference count is 0, the library is loaded. The reference count is then incremented. */
public static synchronized void loadOpenGLLibrary() throws LWJGLException {
if ( gl_ref_count == 0 )
nLoadOpenGLLibrary();
gl_ref_count++;
}
private static native void nLoadOpenGLLibrary() throws LWJGLException;
/** The OpenGL library reference count is decremented, and if it reaches 0, the library is unloaded. */
public static synchronized void unloadOpenGLLibrary() {
gl_ref_count--;
/*
* Unload the native OpenGL library unless we're on linux, since
* some drivers (NVIDIA proprietary) crash on exit when unloading the library.
*/
if ( gl_ref_count == 0 && LWJGLUtil.getPlatform() != LWJGLUtil.PLATFORM_LINUX )
nUnloadOpenGLLibrary();
}
private static native void nUnloadOpenGLLibrary();
/** Native method to clear native stub bindings */
static native void resetNativeStubs(Class clazz);
private static final class CapabilitiesCacheEntry {
Thread owner;
ContextCapabilities capabilities;
}
}