Fix AWTGLCanvas to create context and make it current in paint(). GL usage can then only happen from an overidden paintGL().

src/java/org/lwjgl/opengl/AWTGLCanvas.java

@@ -136,22 +136,13 @@ public class AWTGLCanvas extends Canvas implements Drawable {
 	 */
 	public void addNotify() {
 		super.addNotify();
-		try {
-			createContext();
-		} catch (LWJGLException e) {
-			throw new RuntimeException(e);
-		}
 	}
 	
 	/* (non-Javadoc)
 	 * @see java.awt.Component#removeNotify()
 	 */
 	public void removeNotify() {
-		try {
-			destroyContext();
-		} catch (LWJGLException e) {
-			throw new RuntimeException(e);
-		}
+		destroyContext();
 		super.removeNotify();
 	} 
 	
@@ -190,27 +181,41 @@ public class AWTGLCanvas extends Canvas implements Drawable {
 		context.makeCurrent();
 	}
 	
-	/**
-	 * Create the OpenGL context. This occurs when the component becomes displayable
-	 * @throws LWJGLException
-	 */
-	private synchronized void createContext() throws LWJGLException {
-		if (context == null)
-			context = new Context(peer_info, drawable != null ? drawable.getContext() : null);
-	}
-	
 	/**
 	 * Destroy the OpenGL context. This happens when the component becomes undisplayable
 	 */
-	private synchronized void destroyContext() throws LWJGLException {
-		context.forceDestroy();
-		context = null;
+	private synchronized void destroyContext() {
+		try {
+			if (context != null) {
+				context.forceDestroy();
+				context = null;
+			}
+		} catch (LWJGLException e) {
+			throw new RuntimeException(e);
+		}
 	}
 
 	/**
-	 * Empty paint to avoid clearing
+	 * Override this to do painting
 	 */
-	public void paint(Graphics g) {
+	protected void paintGL() {
+	}
+
+	public final void paint(Graphics g) {
+		try {
+			peer_info.lockAndGetHandle();
+			try {
+				if (context == null)
+					context = new Context(peer_info, drawable != null ? drawable.getContext() : null);
+				if (!context.isCurrent())
+					context.makeCurrent();
+				paintGL();
+			} finally {
+				peer_info.unlock();
+			}
+		} catch (LWJGLException e) {
+			throw new RuntimeException(e);
+		}
 	}
 
 	/**

src/java/org/lwjgl/opengl/PeerInfo.java

@@ -44,6 +44,8 @@ import org.lwjgl.Sys;
  */
 abstract class PeerInfo {
 	private final ByteBuffer handle;
+	private Thread locking_thread; // Thread that has locked this PeerInfo
+	private int lock_count;
 
 	protected PeerInfo(ByteBuffer handle) {
 		this.handle = handle;
@@ -54,14 +56,29 @@ abstract class PeerInfo {
 	}
 	
 	public synchronized final void unlock() throws LWJGLException {
-		doUnlock();
+		if (lock_count <= 0)
+			throw new IllegalStateException("PeerInfo not locked!");
+		if (Thread.currentThread() != locking_thread)
+			throw new IllegalStateException("PeerInfo already locked by " + locking_thread);
+		lock_count--;
+		if (lock_count == 0) {
+			doUnlock();
+			locking_thread = null;
+		}
 	}
 
 	protected abstract void doLockAndInitHandle() throws LWJGLException;
 	protected abstract void doUnlock() throws LWJGLException;
 
 	public synchronized final ByteBuffer lockAndGetHandle() throws LWJGLException {
-		lockAndInitHandle();
+		Thread this_thread = Thread.currentThread();
+		if (locking_thread != null && locking_thread != this_thread)
+			throw new IllegalStateException("PeerInfo already locked by " + locking_thread);
+		if (lock_count == 0) {
+			locking_thread = this_thread;
+			doLockAndInitHandle();
+		}
+		lock_count++;
 		return getHandle();
 	}
 

src/java/org/lwjgl/test/opengl/awt/AWTTest.java

@@ -37,7 +37,7 @@ public class AWTTest extends Frame {
 		setSize(640, 320);
 		setLayout(null);
 		add(canvas0 = new AWTGLCanvas() {
-			public void paint(Graphics g) {
+			public void paintGL() {
 				try {
 					makeCurrent();
 					GL11.glViewport(0, 0, getWidth(), getHeight());
@@ -61,7 +61,7 @@ public class AWTTest extends Frame {
 		});
 		canvas0.setBounds(0, 0, 320, 320);
 		add(canvas1 = new AWTGLCanvas() {
-			public void paint(Graphics g) {
+			public void paintGL() {
 				try {
 					makeCurrent();
 					GL11.glViewport(0, 0, getWidth(), getHeight());