From 56a56503d630a64cb7b468c4f5b8b9c15a78c441 Mon Sep 17 00:00:00 2001
From: Elias Naur <elias.naur@gmail.com>
Date: Sun, 23 Oct 2005 19:41:09 +0000
Subject: [PATCH] Linux: Don't assume JAWT Lock()/Unlock() are re-entrant,
 fixing a hang with GCJ 4

---
 src/java/org/lwjgl/opengl/LinuxDisplay.java | 51 +++++++++++++++++++--
 src/native/linux/org_lwjgl_opengl_Display.c |  9 ++--
 2 files changed, 52 insertions(+), 8 deletions(-)

diff --git a/src/java/org/lwjgl/opengl/LinuxDisplay.java b/src/java/org/lwjgl/opengl/LinuxDisplay.java
index a14d6f16..64ea9d14 100644
--- a/src/java/org/lwjgl/opengl/LinuxDisplay.java
+++ b/src/java/org/lwjgl/opengl/LinuxDisplay.java
@@ -49,16 +49,61 @@ import org.lwjgl.input.Keyboard;
 final class LinuxDisplay implements DisplayImplementation {
 	private static final int NUM_BUTTONS = 3;
 
+	/** Keep track on the current awt lock owner to avoid
+	 * depending on JAWT locking to be re-entrant (This is a
+	 * problem with GCJ). JAWT locking is not that well specified
+	 * anyway so it is probably best to avoid assuming too much
+	 * about it.
+	 */
+	private static Thread current_awt_lock_owner;
+	private static int awt_lock_count;
+	
 	private static int display_connection_usage_count = 0;
 
 	private static PeerInfo peer_info;
 
 	/* Since Xlib is not guaranteed to be thread safe, we need a way to synchronize LWJGL
-	 * Xlib calls with AWT Xlib calls. Fortunately, JAWT implements LockAWT and UnlockAWT() to
+	 * Xlib calls with AWT Xlib calls. Fortunately, JAWT implements Lock()/Unlock() to
 	 * do just that.
 	 */
-	static native void lockAWT();
-	static native void unlockAWT();
+	static synchronized void lockAWT() {
+		Thread this_thread = Thread.currentThread();
+		while (current_awt_lock_owner != null && current_awt_lock_owner != this_thread) {
+			try {
+				LinuxDisplay.class.wait();
+			} catch (InterruptedException e) {
+				LWJGLUtil.log("Interrupted while waiting for awt lock: " + e);
+			}
+		}
+		if (awt_lock_count == 0) {
+			current_awt_lock_owner = this_thread;
+			try {
+				nLockAWT();
+			} catch (LWJGLException e) {
+				LWJGLUtil.log("Caught exception while locking AWT: " + e);
+			}
+		}
+		awt_lock_count++;
+	}
+	private static native void nLockAWT() throws LWJGLException;
+	
+	static synchronized void unlockAWT() {
+		if (awt_lock_count <= 0)
+			throw new IllegalStateException("AWT not locked!");
+		if (Thread.currentThread() != current_awt_lock_owner)
+			throw new IllegalStateException("AWT already locked by " + current_awt_lock_owner);
+		awt_lock_count--;
+		if (awt_lock_count == 0) {
+			try {
+				nUnlockAWT();
+			} catch (LWJGLException e) {
+				LWJGLUtil.log("Caught exception while unlocking AWT: " + e);
+			}
+			current_awt_lock_owner = null;
+			LinuxDisplay.class.notify();
+		}
+	}
+	private static native void nUnlockAWT() throws LWJGLException;
 
 	/**
 	 * increment and decrement display usage.
diff --git a/src/native/linux/org_lwjgl_opengl_Display.c b/src/native/linux/org_lwjgl_opengl_Display.c
index 6e3bfd40..efc99f0d 100644
--- a/src/native/linux/org_lwjgl_opengl_Display.c
+++ b/src/native/linux/org_lwjgl_opengl_Display.c
@@ -124,7 +124,6 @@ static int errorHandler(Display *disp, XErrorEvent *error) {
 	return 0;
 }
 
-
 Display *getDisplay(void) {
 	return display_connection;
 }
@@ -556,21 +555,21 @@ JNIEXPORT jboolean JNICALL Java_org_lwjgl_opengl_LinuxDisplay_nIsActive
 	return focused || isLegacyFullscreen() ? JNI_TRUE : JNI_FALSE;
 }
 
-JNIEXPORT void JNICALL Java_org_lwjgl_opengl_LinuxDisplay_lockAWT(JNIEnv *env, jclass clazz) {
+JNIEXPORT void JNICALL Java_org_lwjgl_opengl_LinuxDisplay_nLockAWT(JNIEnv *env, jclass clazz) {
 	JAWT jawt;
 	jawt.version = JAWT_VERSION_1_4;
 	if (JAWT_GetAWT(env, &jawt) != JNI_TRUE) {
-		throwGeneralException(env, "java/lang/RuntimeException", "GetAWT failed");
+		throwException(env, "GetAWT failed");
 		return;
 	}
 	jawt.Lock(env);
 }
 
-JNIEXPORT void JNICALL Java_org_lwjgl_opengl_LinuxDisplay_unlockAWT(JNIEnv *env, jclass clazz) {
+JNIEXPORT void JNICALL Java_org_lwjgl_opengl_LinuxDisplay_nUnlockAWT(JNIEnv *env, jclass clazz) {
 	JAWT jawt;
 	jawt.version = JAWT_VERSION_1_4;
 	if (JAWT_GetAWT(env, &jawt) != JNI_TRUE) {
-		throwGeneralException(env, "java/lang/RuntimeException", "GetAWT failed");
+		throwException(env, "GetAWT failed");
 		return;
 	}
 	jawt.Unlock(env);