GlueGen JavaCallback: Revised: Static Java callback dispatcher, dropping native heap, support Struct UserParam ...

Implementation now generates a static Java callback dispatcher for each defined SetCallbackFunction, which gets invoked by the generated native static counterpart with all arguments required.

The static callback utilizes its own synchronization for thread-safety and fetches the required data set stored at SetCallbackFunction to dispatch the call to the users' CallbackFunction.
In case the callback has been removed already, the static callback simply bails out quietly.

The native code does not create, release or manage heap memory and therefore is considered safe.

+++

Further Struct Type UserParam are now supported including Heterogeneous UserParam mapping (read GlueGen_Mapping.*).

+++

Cleaned up code by extracting all JavaCallback emitter code into JavaCallbackEmitter class in one place,
leaving JavaMethodbindingEmitter and CMethodbindingEmitter mostly in their original stage (non-convoluted).

In this regard, I had to refactor a few function, i.e. moving CMethodbindingEmitter.getJNIMangledArg(..)
into JavaType.appendDescriptor(..) and JavaType.appendJNIDescriptor(..) while reusing the toJNIMethodDescriptor(..) conversion.

Test4JavaCallback covers and passes all cases.

10 files changed, 1016 insertions, 768 deletions

diff --git a/src/java/com/jogamp/gluegen/CCodeUnit.java b/src/java/com/jogamp/gluegen/CCodeUnit.java
index c70df79..5c0db27 100644
--- a/src/java/com/jogamp/gluegen/CCodeUnit.java
+++ b/src/java/com/jogamp/gluegen/CCodeUnit.java
@@ -84,11 +84,6 @@ public class CCodeUnit extends CodeUnit {
         emitln( getJNIOnLoadJNIEnvCode(libraryBasename) );
     }
 
-    /** Emits {@link #JavaCallbackGlueDataDecl}. */
-    public void emitJavaCallbackGlueDataDecl() {
-        emitln( JavaCallbackGlueDataDecl );
-    }
-
     @Override
     public String toString() { return "CCodeUnit[unit "+cUnitName+", file "+filename+"]"; }
 
@@ -113,16 +108,6 @@ public class CCodeUnit extends CodeUnit {
         "    return jbyteBuffer;\n"+
         "}\n";
 
-    /** JavaCallback Glue Data typedef struct */
-    public static final String JavaCallbackGlueDataDecl =
-        "typedef struct {\n"+
-        "  jobject lockObj;\n"+
-        "  jobject cbFunc;\n"+
-        "  jmethodID cbMethodID;\n"+
-        "  jobject userParam;\n"+
-        "} T_JavaCallbackGlueData;\n"+
-        "\n";
-
     /**
      * Returns native JNI declarations for `JavaVM* {libraryBasename}_jvmHandle`
      * and `JVMUtil_GetJNIEnv(..)`.
diff --git a/src/java/com/jogamp/gluegen/CMethodBindingEmitter.java b/src/java/com/jogamp/gluegen/CMethodBindingEmitter.java
index 00cae13..9c7ed0b 100644
--- a/src/java/com/jogamp/gluegen/CMethodBindingEmitter.java
+++ b/src/java/com/jogamp/gluegen/CMethodBindingEmitter.java
@@ -113,15 +113,11 @@ public class CMethodBindingEmitter extends FunctionEmitter {
 
   protected static final String STRING_CHARS_PREFIX = "_strchars_";
 
-  protected static final String T_JavaCallbackGlueData = "T_JavaCallbackGlueData";
-
   // We need this in order to compute sizes of certain types
   protected MachineDataInfo machDesc;
 
-  private final JavaCallbackInfo javaCallback;
-  private final String jcbNativeBasename;
-  private final String jcbFriendlyBasename;
   private final CMethodBindingEmitter jcbCMethodEmitter;
+  private final JavaCallbackEmitter javaCallbackEmitter;
 
   /**
    * Constructs an emitter for the specified binding, and sets a default
@@ -155,18 +151,17 @@ public class CMethodBindingEmitter extends FunctionEmitter {
     this.forIndirectBufferAndArrayImplementation = forIndirectBufferAndArrayImplementation;
     this.machDesc = machDesc;
 
-    javaCallback = cfg.setFuncToJavaCallbackMap.get(binding.getName());
+    final JavaCallbackInfo javaCallback = cfg.setFuncToJavaCallbackMap.get(binding.getName());
     if( null != javaCallback ) {
-        jcbNativeBasename = CodeGenUtils.capitalizeString( javaCallback.setFuncName+javaCallback.cbSimpleClazzName.replace("_", "") );
-        jcbFriendlyBasename = javaCallback.setFuncName+"("+javaCallback.cbSimpleClazzName+")";
+        // jcbNativeBasename = CodeGenUtils.capitalizeString( javaCallback.setFuncName+javaCallback.cbSimpleClazzName.replace("_", "") );
         jcbCMethodEmitter = new CMethodBindingEmitter(javaCallback.cbFuncBinding,
                                                       unit, javaPackageName, javaClassName, isOverloadedBinding,
                                                       isJavaMethodStatic, forImplementingMethodCall,
                                                       forIndirectBufferAndArrayImplementation, machDesc, configuration);
+        javaCallbackEmitter = new JavaCallbackEmitter(cfg, binding, javaCallback, null);
     } else {
-        jcbNativeBasename = null;
-        jcbFriendlyBasename = null;
         jcbCMethodEmitter = null;
+        javaCallbackEmitter = null;
     }
     setCommentEmitter(defaultCommentEmitter);
   }
@@ -328,145 +323,25 @@ public class CMethodBindingEmitter extends FunctionEmitter {
    */
   public final MachineDataInfo getMachineDataInfo() { return machDesc; }
 
-  private static final boolean DEBUG_JAVACALLBACK = false;
-
   @Override
-  protected void emitReturnType()  {
-    if( null != javaCallback ) {
-        LOG.log(INFO, "BindCFunc.R.JavaCallback: {0}: {1}", binding.getName(), javaCallback);
-        final String staticCallbackName = "func"+jcbNativeBasename;
-
-        final Type userParamType = javaCallback.cbFuncBinding.getCArgumentType(javaCallback.cbFuncUserParamIdx);
-        final String userParamArgName = javaCallback.cbFuncBinding.getArgumentName(javaCallback.cbFuncUserParamIdx);
-        final Type cReturnType = javaCallback.cbFuncBinding.getCReturnType();
-        final JavaType jretType = javaCallback.cbFuncBinding.getJavaReturnType();
-        unit.emitln();
-        // javaCallback.cbFuncCEmitter.emitSignature();
-        unit.emit("static "+cReturnType.getCName()+" "+staticCallbackName+"(");
-        // javaCallback.cbFuncCEmitter.emitArguments();
-        unit.emit(javaCallback.cbFuncBinding.getCParameterList(new StringBuilder(), false, null).toString());
-        unit.emitln(") {");
-        // javaCallback.cbFuncCEmitter.emitBody();
-        {
-            unit.emitln("  JNIEnv* env = JVMUtil_GetJNIEnv();");
-            unit.emitln("  if( NULL == env ) {");
-            if( !cReturnType.isVoid() ) {
-                unit.emitln("    return 0;");
-            } else {
-                unit.emitln("    return;");
-            }
-            unit.emitln("  }");
-            // javaCallback.cbFuncCEmitter.emitBodyVariableDeclarations();
-            // javaCallback.cbFuncCEmitter.emitBodyUserVariableDeclarations();
-            // javaCallback.cbFuncCEmitter.emitBodyVariablePreCallSetup();
-            jcbCMethodEmitter.emitJavaCallbackBodyCToJavaPreCall(javaCallback);
-
-            // javaCallback.cbFuncCEmitter.emitBodyCallCFunction();
-            unit.emitln("  "+T_JavaCallbackGlueData+"* cb = ("+T_JavaCallbackGlueData+"*) "+userParamArgName+";");
-            unit.emitln("  // C Params: "+javaCallback.cbFuncBinding.getCParameterList(new StringBuilder(), false, null).toString());
-            unit.emitln("  // J Params: "+javaCallback.cbFuncBinding.getJavaParameterList(new StringBuilder()).toString());
-
-            final String returnStatement;
-            if( !cReturnType.isVoid() ) {
-                unit.emit("  "+cReturnType.getCName()+" _res = 0;");
-                returnStatement = "return _res;";
-            } else {
-                returnStatement = "return;";
-            }
-            unit.emitln("  if( NULL == cb ) { fprintf(stderr, \"Info: Callback '"+jcbFriendlyBasename+"': NULL "+userParamArgName+", skipping!\\n\"); "+returnStatement+" }");
-            unit.emitln();
-            unit.emitln("  // Use-after-free of '*cb' possible up until after GetObjectRefType() check for a brief moment!");
-            unit.emitln("  // Use a copy to avoid data-race between GetObjectRefType() and MonitorEnter()\");");
-            unit.emitln("  jobject lockObj = cb->lockObj;");
-            unit.emitln("  if( 0 == lockObj ) { fprintf(stderr, \"Info: Callback '"+jcbFriendlyBasename+"': NULL lock, skipping!\\n\"); "+returnStatement+" }");
-            unit.emitln();
-            unit.emitln("  jobjectRefType refType = (*env)->GetObjectRefType(env, lockObj);");
-            unit.emitln("  if( 0 == refType ) { fprintf(stderr, \"Info: Callback '"+jcbFriendlyBasename+"': User after free(lock), skipping!\\n\"); "+returnStatement+" }");
-            unit.emitln("  jint lockRes = (*env)->MonitorEnter(env, lockObj);");
-            unit.emitln("  if( 0 != lockRes ) { fprintf(stderr, \"Info: Callback '"+jcbFriendlyBasename+"': MonitorEnter failed %d, skipping!\\n\", lockRes); "+returnStatement+" }");
-            unit.emitln("  // synchronized block");
-            /**
-             * Since we have acquired the lock, in-sync w/ our Java code, cb->cbFunc and cb->userParam could not have been changed!
-             *
-            unit.emitln("  refType = (*env)->GetObjectRefType(env, cb->userParam);");
-            unit.emitln("  if( 0 == refType ) {");
-            unit.emitln("    fprintf(stderr, \"Info: Callback '"+staticCallbackName+"(..)': User after free(userParam), skipping!\\n\");");
-            unit.emitln("    lockRes = (*env)->MonitorExit(env, cb->lockObj);");
-            unit.emitln("    if( 0 != lockRes ) { fprintf(stderr, \"Info: Callback '"+staticCallbackName+"(..)': MonitorExit failed %d\\n\", lockRes); }");
-            unit.emitln("    "+returnStatement);
-            unit.emitln("  }");
-            */
-            if( !cReturnType.isVoid() ) {
-                unit.emit("  _res = ("+cReturnType.getCName()+") ");
-            } else {
-                unit.emit("  ");
-            }
-            unit.emit("(*env)->Call" + CodeGenUtils.capitalizeString( jretType.getName() ) +"Method(env, cb->cbFunc, cb->cbMethodID, ");
-            // javaCallback.cbFuncCEmitter.emitBodyPassCArguments();
-            jcbCMethodEmitter.emitJavaCallbackBodyPassJavaArguments(javaCallback, "cb->userParam");
-            unit.emitln(");");
-            unit.emitln("  if( (*env)->ExceptionCheck(env) ) {");
-            unit.emitln("    fprintf(stderr, \"Info: Callback '"+jcbFriendlyBasename+"': Exception in Java Callback caught:\\n\");");
-            unit.emitln("    (*env)->ExceptionDescribe(env);");
-            unit.emitln("    (*env)->ExceptionClear(env);");
-            unit.emitln("  }");
-
-            // javaCallback.cbFuncCEmitter.emitBodyUserVariableAssignments();
-            // javaCallback.cbFuncCEmitter.emitBodyVariablePostCallCleanup();
-            // javaCallback.cbFuncCEmitter.emitBodyMapCToJNIType(-1 /* return value */, true /* addLocalVar */)
-
-            unit.emitln("  lockRes = (*env)->MonitorExit(env, cb->lockObj);");
-            unit.emitln("  if( 0 != lockRes ) { fprintf(stderr, \"Info: Callback '"+jcbFriendlyBasename+"': MonitorExit failed %d\\n\", lockRes); }");
-            unit.emitln("  "+returnStatement);
-        }
-        unit.emitln("}");
-        unit.emitln();
-    }
-    unit.emit("JNIEXPORT ");
-    unit.emit(binding.getJavaReturnType().jniTypeName());
-    unit.emit(" JNICALL");
-  }
-  /* pp */ int emitJavaCallbackBodyCToJavaPreCall(final JavaCallbackInfo jcbi)  {
-    int count = 0;
-    for (int i = 0; i < binding.getNumArguments(); i++) {
-      if( i == jcbi.cbFuncUserParamIdx ) {
-        continue;
-      }
-      if( emitBodyMapCToJNIType(i, true /* addLocalVar */) ) {
-          ++count;
-      }
-    }
-    return count;
-  }
-  /* pp */ int emitJavaCallbackBodyPassJavaArguments(final JavaCallbackInfo jcbi, final String userParamVarName) {
-    int count = 0;
-    boolean needsComma = false;
-    for (int i = 0; i < binding.getNumArguments(); i++) {
-      if (needsComma) {
-        unit.emit(", ");
-        needsComma = false;
-      }
-      if( i == jcbi.cbFuncUserParamIdx ) {
-          unit.emit( userParamVarName );
-      } else {
-          unit.emit( binding.getArgumentName(i) + "_jni" );
-      }
-      needsComma = true;
-      ++count;
-    }
-    return count;
+  protected StringBuilder appendReturnType(final StringBuilder buf) {
+    buf.append("JNIEXPORT ");
+    buf.append(binding.getJavaReturnType().jniTypeName());
+    buf.append(" JNICALL");
+    return buf;
   }
 
   @Override
-  protected void emitName()  {
-    unit.emitln(); // start name on new line
-    unit.emit(JavaEmitter.getJNIMethodNamePrefix(getJavaPackageName(), getJavaClassName()));
-    unit.emit("_");
+  protected StringBuilder appendName(final StringBuilder buf)  {
+    buf.append(System.lineSeparator()); // start name on new line
+    buf.append(JavaEmitter.getJNIMethodNamePrefix(getJavaPackageName(), getJavaClassName()));
+    buf.append("_");
     if (isOverloadedBinding)    {
-      unit.emit(jniMangle(binding));
+      buf.append(jniMangle(binding));
     } else {
-      unit.emit(JavaEmitter.jniMangle(getImplName()));
+      buf.append(JavaEmitter.jniMangle(getImplName()));
     }
+    return buf;
   }
 
   protected String getImplSuffix() {
@@ -481,24 +356,24 @@ public class CMethodBindingEmitter extends FunctionEmitter {
   }
 
   @Override
-  protected int emitArguments()  {
-    unit.emit("JNIEnv *env, ");
+  protected int appendArguments(final StringBuilder buf) {
+    buf.append("JNIEnv *env, ");
     int numEmitted = 1; // initially just the JNIEnv
     if (isJavaMethodStatic && !binding.hasContainingType())    {
-      unit.emit("jclass");
+      buf.append("jclass");
     } else {
-      unit.emit("jobject");
+      buf.append("jobject");
     }
-    unit.emit(" _unused");
+    buf.append(" _unused");
     ++numEmitted;
 
     if( binding.isReturnCompoundByValue() ) {
-        unit.emit(", jclass _clazzBuffers");
+        buf.append(", jclass _clazzBuffers");
         ++numEmitted;
     }
     if (binding.hasContainingType())   {
       // "this" argument always comes down in argument 0 as direct buffer
-      unit.emit(", jobject " + JavaMethodBindingEmitter.javaThisArgumentName());
+      buf.append(", jobject " + JavaMethodBindingEmitter.javaThisArgumentName());
     }
     for (int i = 0; i < binding.getNumArguments(); i++) {
       final JavaType javaArgType = binding.getJavaArgumentType(i);
@@ -512,91 +387,47 @@ public class CMethodBindingEmitter extends FunctionEmitter {
       if (javaArgType.isJNIEnv() || binding.isArgumentThisPointer(i)) {
         continue;
       }
-      unit.emit(", ");
-      unit.emit(javaArgType.jniTypeName());
-      unit.emit(" ");
-      unit.emit(binding.getArgumentName(i));
+      buf.append(", ");
+      buf.append(javaArgType.jniTypeName());
+      buf.append(" ");
+      buf.append(binding.getArgumentName(i));
       ++numEmitted;
 
       if (javaArgType.isPrimitiveArray() ||
           javaArgType.isNIOBuffer()) {
-        unit.emit(", jint " + byteOffsetArgName(i));
+        buf.append(", jint " + byteOffsetArgName(i));
         if(forIndirectBufferAndArrayImplementation) {
-            unit.emit(", jboolean " + isNIOArgName(i));
+            buf.append(", jboolean " + isNIOArgName(i));
         }
       } else if (javaArgType.isNIOBufferArray()) {
-        unit.emit(", jintArray " +
+        buf.append(", jintArray " +
                      byteOffsetArrayArgName(i));
       }
     }
 
-    final JavaCallbackInfo jcb = this.javaCallback;
-    if( null != jcb ) {
-        LOG.log(INFO, "BindCFunc.A.JavaCallback: {0}: {1}", binding.getName(), jcb);
-        unit.emit(", jstring jcallbackSignature, jobject jlockObj, jlongArray jnativeUserParam");
-        numEmitted+=2;
-    } else {
-        LOG.log(INFO, "BindCFunc.JavaCallback: {0}: NONE", binding.getName());
+    if( null != javaCallbackEmitter ) {
+        numEmitted += javaCallbackEmitter.appendCAdditionalParameter(buf);
     }
     return numEmitted;
   }
 
 
   @Override
+  protected void emitAdditionalCode() {
+    if( null != javaCallbackEmitter ) {
+        javaCallbackEmitter.emitCAdditionalCode(unit, jcbCMethodEmitter);
+    }
+  }
+
+  @Override
   protected void emitBody()  {
     unit.emitln(" {");
 //    unit().emitln("printf(\" - - - - "+ getName() + getImplSuffix() +" - - - -\\n\");");
     emitBodyVariableDeclarations();
     emitBodyUserVariableDeclarations();
     emitBodyVariablePreCallSetup();
-    final JavaCallbackInfo jcb = this.javaCallback;
-    if( null != jcb ) {
-        LOG.log(INFO, "BindCFunc.B.JavaCallback: {0}: {1}", binding.getName(), jcb);
-        final String cbFuncArgName = binding.getArgumentName(jcb.setFuncCBParamIdx);
-        final String userParamArgName = binding.getArgumentName(jcb.setFuncUserParamIdx);
-        final String nativeCBFuncVarName = cbFuncArgName+"_native";
-        final String nativeUserParamVarName = userParamArgName+"_native";
-        unit.emitln();
-        unit.emitln("  // JavaCallback handling");
-        unit.emitln("  "+jcb.cbFuncTypeName+" "+nativeCBFuncVarName+";");
-        unit.emitln("  "+T_JavaCallbackGlueData+"* "+nativeUserParamVarName+";");
-        // unit.emit(", jstring jcallbackSignature, jobject jlockObj, jlongArray jnativeUserParam");
-        unit.emitln("  if( NULL == jlockObj ) { (*env)->FatalError(env, \"Null jlockObj in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("  if( NULL == jnativeUserParam ) { (*env)->FatalError(env, \"Null jnativeUserParam in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("  const size_t jnativeUserParam_size = (*env)->GetArrayLength(env, jnativeUserParam);");
-        unit.emitln("  if( 1 > jnativeUserParam_size ) { (*env)->FatalError(env, \"nativeUserParam size < 1 in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("  if( NULL != "+cbFuncArgName+" ) {");
-        unit.emitln("    if( NULL == "+userParamArgName+" ) { (*env)->FatalError(env, \"Null "+userParamArgName+" in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("    "+nativeUserParamVarName+" = ("+T_JavaCallbackGlueData+"*) calloc(1, sizeof("+T_JavaCallbackGlueData+"));");
-        unit.emitln("    if( NULL == "+nativeUserParamVarName+" ) { (*env)->FatalError(env, \"Can't alloc "+nativeUserParamVarName+" in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("    "+nativeUserParamVarName+"->lockObj = (*env)->NewGlobalRef(env, jlockObj);");
-        unit.emitln("    if( NULL == "+nativeUserParamVarName+"->lockObj ) { (*env)->FatalError(env, \"Failed NewGlobalRef(lock) in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("    "+nativeUserParamVarName+"->cbFunc = (*env)->NewGlobalRef(env, "+cbFuncArgName+");");
-        unit.emitln("    if( NULL == "+nativeUserParamVarName+"->cbFunc ) { (*env)->FatalError(env, \"Failed NewGlobalRef(func) in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("    "+nativeUserParamVarName+"->userParam = (*env)->NewGlobalRef(env, "+userParamArgName+");");
-        unit.emitln("    if( NULL == "+nativeUserParamVarName+"->userParam ) { (*env)->FatalError(env, \"Failed NewGlobalRef(userParam) in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("    {");
-        unit.emitln("      jclass cbClazz = (*env)->GetObjectClass(env, "+nativeUserParamVarName+"->cbFunc);");
-        unit.emitln("      if( NULL == cbClazz ) { (*env)->FatalError(env, \"Failed GetObjectClass in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("      const char* callbackSignature = (*env)->GetStringUTFChars(env, jcallbackSignature, (jboolean*)NULL);");
-        unit.emitln("      if( NULL == callbackSignature ) { (*env)->FatalError(env, \"Failed callbackSignature in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("      "+nativeUserParamVarName+"->cbMethodID = (*env)->GetMethodID(env, cbClazz, \"callback\", callbackSignature);");
-        unit.emitln("      (*env)->ReleaseStringUTFChars(env, jcallbackSignature, callbackSignature);");
-        unit.emitln("      if( NULL == "+nativeUserParamVarName+"->cbMethodID ) { (*env)->FatalError(env, \"Failed GetMethodID in '"+jcbFriendlyBasename+"'\"); }");
-        unit.emitln("    }");
-        unit.emitln("    "+nativeCBFuncVarName+" = func"+jcbNativeBasename+";");
-        unit.emitln("  } else {");
-        unit.emitln("    "+nativeCBFuncVarName+" = NULL;");
-        unit.emitln("    "+nativeUserParamVarName+" = NULL;");
-        unit.emitln("  }");
-        unit.emitln("  {");
-        unit.emitln("    jlong v = (jlong) (intptr_t) "+nativeUserParamVarName+";");
-        unit.emitln("    (*env)->SetLongArrayRegion(env, jnativeUserParam, 0, (jsize)1, &v);");
-        if( DEBUG_JAVACALLBACK ) {
-            unit.emitln("    fprintf(stderr, \"YYY user %p -> native %p\\n\", "+userParamArgName+", "+nativeUserParamVarName+");");
-        }
-        unit.emitln("  }");
-        unit.emitln();
+    if( null != javaCallbackEmitter ) {
+        javaCallbackEmitter.emitCSetFuncPreCall(unit);
     }
     emitBodyCallCFunction();
     emitBodyUserVariableAssignments();
@@ -606,24 +437,6 @@ public class CMethodBindingEmitter extends FunctionEmitter {
     }
     unit.emitln("}");
     unit.emitln();
-    if( null != jcb ) {
-        final String capIfaceName = CodeGenUtils.capitalizeString( getInterfaceName() );
-        unit.emitln("JNIEXPORT void JNICALL");
-        unit.emit(JavaEmitter.getJNIMethodNamePrefix(getJavaPackageName(), getJavaClassName()));
-        unit.emitln("_release"+capIfaceName+"Impl(JNIEnv *env, jobject _unused, jlong jnativeUserParam) {");
-        unit.emitln("  // already locked");
-        unit.emitln("  "+T_JavaCallbackGlueData+"* nativeUserParam = ("+T_JavaCallbackGlueData+"*) (intptr_t) jnativeUserParam;");
-        unit.emitln("  if( NULL != nativeUserParam ) {");
-        unit.emitln("    (*env)->DeleteGlobalRef(env, nativeUserParam->lockObj);");
-        unit.emitln("    (*env)->DeleteGlobalRef(env, nativeUserParam->cbFunc);");
-        unit.emitln("    (*env)->DeleteGlobalRef(env, nativeUserParam->userParam);");
-        unit.emitln("    // Ensure even w/ use-after-free jobject refs are NULL and invalid to avoid accidental reuse.");
-        unit.emitln("    memset(nativeUserParam, 0, sizeof("+T_JavaCallbackGlueData+"));");
-        unit.emitln("    free(nativeUserParam);");
-        unit.emitln("  }");
-        unit.emitln("}");
-        unit.emitln();
-    }
   }
 
   protected void emitBodyVariableDeclarations()  {
@@ -1173,9 +986,8 @@ public class CMethodBindingEmitter extends FunctionEmitter {
         } else {
           if (javaArgType.isString()) { unit.emit(STRING_CHARS_PREFIX); }
           unit.emit(binding.getArgumentName(i));
-          if( null != this.javaCallback &&
-              ( i == this.javaCallback.setFuncCBParamIdx || i == this.javaCallback.setFuncUserParamIdx ) ) {
-              unit.emit("_native");
+          if( null != javaCallbackEmitter ) {
+              javaCallbackEmitter.emitCOptArgumentSuffix(unit, i);
           }
         }
       }
@@ -1241,7 +1053,7 @@ public class CMethodBindingEmitter extends FunctionEmitter {
    * @param addLocalVar if true, emit instantiating the local JNI variable.
    * @return true if a non-void result has been produced, otherwise false
    */
-  protected boolean emitBodyMapCToJNIType(final int argIdx, final boolean addLocalVar)
+  public boolean emitBodyMapCToJNIType(final int argIdx, final boolean addLocalVar)
   {
     // WARNING: this code assumes that the return type has already been
     // typedef-resolved.
@@ -1436,12 +1248,11 @@ public class CMethodBindingEmitter extends FunctionEmitter {
     final StringBuilder buf = new StringBuilder();
     buf.append(JavaEmitter.jniMangle(getImplName()));
     buf.append(getImplSuffix());
-    if( null == this.javaCallback ) {
+    if( null == javaCallbackEmitter ) {
         buf.append("__");
-        getJNIMangledArgs(binding, forIndirectBufferAndArrayImplementation, buf);
-        if( null != this.javaCallback ) {
-            getJNIMangledArg(String.class, buf, false);  // to account for the additional 'jstring jcallbackSignature' parameter
-            getJNIMangledArg(long[].class, buf, false);  // to account for the additional 'long[] nativeUserParam' parameter
+        appendJNIMangledArgs(binding, forIndirectBufferAndArrayImplementation, buf);
+        if( null != javaCallbackEmitter ) {
+            javaCallbackEmitter.appendCAdditionalJNIDescriptor(buf);
         }
     }
     return buf.toString();
@@ -1454,13 +1265,13 @@ public class CMethodBindingEmitter extends FunctionEmitter {
    * @param buf
    * @return
    */
-  public static StringBuilder getJNIMangledArgs(final MethodBinding binding, final boolean forIndirectBufferAndArrayImplementation, final StringBuilder buf) {
+  public static StringBuilder appendJNIMangledArgs(final MethodBinding binding, final boolean forIndirectBufferAndArrayImplementation, final StringBuilder buf) {
     if (binding.isReturnCompoundByValue()) {
-        getJNIMangledArg(Class.class, buf, true);
+        JavaType.appendJNIDescriptor(buf, Class.class, true);
     }
     if (binding.hasContainingType()) {
       // "this" argument always comes down in argument 0 as direct buffer
-      getJNIMangledArg(java.nio.ByteBuffer.class, buf, true);
+      JavaType.appendJNIDescriptor(buf, java.nio.ByteBuffer.class, true);
     }
     for (int i = 0; i < binding.getNumArguments(); i++) {
       if (binding.isArgumentThisPointer(i)) {
@@ -1477,31 +1288,31 @@ public class CMethodBindingEmitter extends FunctionEmitter {
       } else {
         Class<?> c = type.getJavaClass();
         if (c != null) {
-          getJNIMangledArg(c, buf, false);
+          JavaType.appendJNIDescriptor(buf, c, false);
           // If Buffer offset arguments were added, we need to mangle the JNI for the
           // extra arguments
           if (type.isNIOBuffer()) {
-            getJNIMangledArg(Integer.TYPE, buf, false);
+            JavaType.appendJNIDescriptor(buf, Integer.TYPE, false);
             if(forIndirectBufferAndArrayImplementation) {
-                getJNIMangledArg(Boolean.TYPE, buf, false);
+                JavaType.appendJNIDescriptor(buf, Boolean.TYPE, false);
             }
           } else if (type.isNIOBufferArray())   {
             final int[] intArrayType = new int[0];
             c = intArrayType.getClass();
-            getJNIMangledArg(c , buf, true);
+            JavaType.appendJNIDescriptor(buf, c , true);
           }
           if (type.isPrimitiveArray()) {
-            getJNIMangledArg(Integer.TYPE, buf, false);
+            JavaType.appendJNIDescriptor(buf, Integer.TYPE, false);
           }
         } else if (type.isNamedClass()) {
           buf.append(type.getJNIMethodDesciptor());
         } else if (type.isCompoundTypeWrapper()) {
           // Mangle wrappers for C structs as ByteBuffer
-          getJNIMangledArg(java.nio.ByteBuffer.class, buf, true);
+          JavaType.appendJNIDescriptor(buf, java.nio.ByteBuffer.class, true);
         } else if (type.isArrayOfCompoundTypeWrappers()) {
           // Mangle arrays of C structs as ByteBuffer[]
           final java.nio.ByteBuffer[] tmp = new java.nio.ByteBuffer[0];
-          getJNIMangledArg(tmp.getClass(), buf, true);
+          JavaType.appendJNIDescriptor(buf, tmp.getClass(), true);
         } else if (type.isJNIEnv()) {
           // These are not exposed at the Java level
         } else {
@@ -1514,54 +1325,6 @@ public class CMethodBindingEmitter extends FunctionEmitter {
     return buf;
   }
 
-  public static void getJNIMangledArg(final Class<?> c, final StringBuilder res, final boolean syntheticArgument) {
-    if (c.isPrimitive()) {
-           if (c == Boolean.TYPE)   res.append("Z");
-      else if (c == Byte.TYPE)      res.append("B");
-      else if (c == Character.TYPE) res.append("C");
-      else if (c == Short.TYPE)     res.append("S");
-      else if (c == Integer.TYPE)   res.append("I");
-      else if (c == Long.TYPE)      res.append("J");
-      else if (c == Float.TYPE)     res.append("F");
-      else if (c == Double.TYPE)    res.append("D");
-      else throw new RuntimeException("Illegal primitive type \"" + c.getName() + "\"");
-    } else {
-      // Arrays and NIO Buffers are always passed down as java.lang.Object.
-      // The only arrays that show up as true arrays in the signature
-      // are the synthetic byte offset arrays created when passing
-      // down arrays of direct Buffers. Compound type wrappers are
-      // passed down as ByteBuffers (no good reason, just to avoid
-      // accidental conflation) so we mangle them differently.
-      if (syntheticArgument) {
-        if (c.isArray()) {
-          res.append("_3");
-          final Class<?> componentType = c.getComponentType();
-          // Handle arrays of compound type wrappers differently for
-          // convenience of the Java-level glue code generation
-          getJNIMangledArg(componentType, res,
-                    (componentType == java.nio.ByteBuffer.class));
-        } else {
-          res.append("L");
-          res.append(c.getName().replace('.', '_'));
-          res.append("_2");
-        }
-      } else {
-        if (c.isArray()) {
-          res.append("_3");
-          getJNIMangledArg(c.getComponentType(), res, false);
-        } else if (c == java.lang.String.class) {
-          res.append("L");
-          res.append(c.getName().replace('.', '_'));
-          res.append("_2");
-        } else {
-          res.append("L");
-          res.append("java_lang_Object");
-          res.append("_2");
-        }
-      }
-    }
-  }
-
   private void emitOutOfMemoryCheck(final String varName, final String errorMessage)  {
     unit.emitln("  if ( NULL == " + varName + " ) {");
     unit.emitln("      (*env)->ThrowNew(env, (*env)->FindClass(env, \"java/lang/OutOfMemoryError\"),");
diff --git a/src/java/com/jogamp/gluegen/FunctionEmitter.java b/src/java/com/jogamp/gluegen/FunctionEmitter.java
index a089a41..5037fc4 100644
--- a/src/java/com/jogamp/gluegen/FunctionEmitter.java
+++ b/src/java/com/jogamp/gluegen/FunctionEmitter.java
@@ -114,6 +114,7 @@ public abstract class FunctionEmitter {
    * Emit the function to the {@link #getUnit()}
    */
   public final void emit()  {
+    emitAdditionalCode();
     emitDocComment();
     //output.println("  // Emitter: " + getClass().getName());
     emitSignature();
@@ -139,6 +140,7 @@ public abstract class FunctionEmitter {
    */
   public CommentEmitter getCommentEmitter() { return commentEmitter; }
 
+  protected void emitAdditionalCode() { }
   protected void emitDocComment() {
 
     if (commentEmitter != null)    {
@@ -154,32 +156,42 @@ public abstract class FunctionEmitter {
     }
   }
 
-  protected void emitSignature()  {
+  protected final void emitSignature()  {
+    unit.emit(appendSignature(new StringBuilder()).toString());
+  }
 
-    unit.emit(getBaseIndentString()); // indent method
+  protected StringBuilder appendSignature(final StringBuilder buf)  {
+    buf.append(getBaseIndentString()); // indent method
 
-    final int numEmitted = emitModifiers();
+    final int numEmitted = appendModifiers(buf);
     if (numEmitted > 0)  {
-      unit.emit(" ");
+      buf.append(" ");
     }
 
-    emitReturnType();
-    unit.emit(" ");
+    appendReturnType(buf);
+    buf.append(" ");
 
-    emitName();
-    unit.emit("(");
+    appendName(buf);
+    buf.append("(");
 
-    emitArguments();
-    unit.emit(")");
+    appendArguments(buf);
+    buf.append(")");
+    return buf;
   }
 
-  protected int emitModifiers()  {
+  protected final int emitModifiers()  {
+      final StringBuilder buf = new StringBuilder();
+      final int n = appendModifiers(buf);
+      unit.emit(buf.toString());
+      return n;
+  }
+  protected int appendModifiers(final StringBuilder buf)  {
     int numEmitted = 0;
     for (final Iterator<EmissionModifier> it = getModifiers(); it.hasNext(); )   {
-      unit.emit(it.next().toString());
+      buf.append(it.next().toString());
       ++numEmitted;
       if (it.hasNext())  {
-        unit.emit(" ");
+        buf.append(" ");
       }
     }
     return numEmitted;
@@ -190,10 +202,23 @@ public abstract class FunctionEmitter {
   protected String getCommentStartString() { return "/* "; }
   protected String getCommentEndString() { return " */"; }
 
-  protected abstract void emitReturnType();
-  protected abstract void emitName();
+  protected final void emitReturnType() {
+      unit.emit(appendReturnType(new StringBuilder()).toString());
+  }
+  protected abstract StringBuilder appendReturnType(StringBuilder buf);
+  protected final void emitName() {
+      unit.emit(appendName(new StringBuilder()).toString());
+  }
+  protected abstract StringBuilder appendName(StringBuilder buf);
+  /** Returns the number of arguments emitted. */
+  protected final int emitArguments() {
+      final StringBuilder buf = new StringBuilder();
+      final int n = appendArguments(buf);
+      unit.emit(buf.toString());
+      return n;
+  }
   /** Returns the number of arguments emitted. */
-  protected abstract int emitArguments();
+  protected abstract int appendArguments(StringBuilder buf);
   protected abstract void emitBody();
 
   public static class EmissionModifier  {
diff --git a/src/java/com/jogamp/gluegen/JavaCallbackEmitter.java b/src/java/com/jogamp/gluegen/JavaCallbackEmitter.java
new file mode 100644
index 0000000..96e1e77
--- /dev/null
+++ b/src/java/com/jogamp/gluegen/JavaCallbackEmitter.java
@@ -0,0 +1,666 @@
+/**
+ * Copyright 2023 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.gluegen;
+
+import com.jogamp.gluegen.JavaConfiguration.JavaCallbackInfo;
+import com.jogamp.gluegen.cgram.types.Type;
+
+public final class JavaCallbackEmitter {
+    final JavaConfiguration cfg;
+    final MethodBinding binding;
+    final String setFuncSignature;
+    final JavaCallbackInfo info;
+    final String capIfaceName;
+    final String lowIfaceName;
+    final String lockInstanceName;
+    final String dataMapInstanceName;
+    final String dataInstanceName;
+    final String DataClassName;
+    final String fqUsrParamClassName;
+    final JavaType cbFuncJavaReturnType;
+    final String jcbNextIDVarName;
+
+    final String setFuncCBArgName;
+    final Type setFuncUserParamCType;
+    final JavaType setFuncUserParamJType;
+    final String setFuncUserParamTypeName;
+    final String setFuncUserParamArgName;
+
+    final boolean customKeyClass;
+    final String KeyClassName;
+    final boolean useDataMap;
+
+    public JavaCallbackEmitter(final JavaConfiguration cfg, final MethodBinding mb, final JavaCallbackInfo javaCallback, final String setFuncSignature) {
+        this.cfg = cfg;
+        this.binding = mb;
+        this.setFuncSignature = setFuncSignature;
+        this.info = javaCallback;
+
+        capIfaceName = CodeGenUtils.capitalizeString( mb.getInterfaceName() );
+        lowIfaceName = CodeGenUtils.decapitalizeString( mb.getInterfaceName() );
+        lockInstanceName = lowIfaceName+"Lock";
+        dataMapInstanceName = lowIfaceName+"DataMap";
+        dataInstanceName = lowIfaceName+"Data";
+        DataClassName = capIfaceName+"Data";
+        fqUsrParamClassName = cfg.packageName()+"."+cfg.className()+"."+DataClassName;
+        cbFuncJavaReturnType = javaCallback.cbFuncBinding.getJavaReturnType();
+        jcbNextIDVarName = "NEXT_"+capIfaceName+"_ID";
+
+        setFuncCBArgName = binding.getArgumentName(javaCallback.setFuncCBParamIdx);
+        setFuncUserParamCType = mb.getCArgumentType(javaCallback.setFuncUserParamIdx);
+        setFuncUserParamJType = mb.getJavaArgumentType(javaCallback.setFuncUserParamIdx);
+        setFuncUserParamTypeName = setFuncUserParamJType.getName();
+        setFuncUserParamArgName = binding.getArgumentName(javaCallback.setFuncUserParamIdx);
+
+        if( null != javaCallback.setFuncKeyClassName ) {
+            customKeyClass = true;;
+            KeyClassName = javaCallback.setFuncKeyClassName;
+            useDataMap = true;
+        } else {
+            customKeyClass = false;
+            KeyClassName = capIfaceName+"Key";
+            useDataMap = javaCallback.setFuncKeyIndices.size() > 0;
+        }
+    }
+
+    public void emitJavaSetFuncPreCall(final CodeUnit unit) {
+        unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+        unit.emit  ("      final long nativeUserParam = ");
+        if( setFuncUserParamJType.isLong() ) {
+            unit.emitln(" "+setFuncUserParamArgName+";");
+        } else if( setFuncUserParamJType.isCompoundTypeWrapper() ) {
+            unit.emitln(" null != "+setFuncUserParamArgName+" ? "+setFuncUserParamArgName+".getDirectBufferAddress() : 0;");
+        } else {
+            unit.emitln(""+jcbNextIDVarName+"++;");
+            unit.emitln("      if( 0 >= "+jcbNextIDVarName+" ) { "+jcbNextIDVarName+" = 1; }");
+        }
+        unit.emitln("      if( null != "+setFuncCBArgName+" ) {");
+        unit.emitln("        add"+capIfaceName+"("+binding.getJavaCallSelectArguments(new StringBuilder(), info.setFuncKeyIndices, true).toString()+
+                "new "+DataClassName+"("+setFuncCBArgName+", "+setFuncUserParamArgName+"));");
+        unit.emitln("      }");
+        unit.emitln();
+    }
+
+    public void emitJavaSetFuncPostCall(final CodeUnit unit) {
+        unit.emitln("      if( null == "+setFuncCBArgName+" ) {");
+        unit.emitln("          // callback released (null func) -> release a previously mapped instance ");
+        if( useDataMap ) {
+            unit.emitln("          release"+capIfaceName+"( new "+KeyClassName+"( "+binding.getJavaCallSelectArguments(new StringBuilder(), info.setFuncKeyIndices, false).toString()+" ) );");
+        } else {
+            unit.emitln("          release"+capIfaceName+"();");
+        }
+        unit.emitln("      }");
+        unit.emitln("    } // synchronized ");
+    }
+
+    public void emitJavaAdditionalCode(final CodeUnit unit, final boolean isInterface) {
+        if( isInterface ) {
+            if( useDataMap ) {
+                if( !customKeyClass && !info.keyClassEmitted ) {
+                    emitJavaKeyClass(unit);
+                    unit.emitln();
+                    info.keyClassEmitted = true;
+                }
+                emitJavaBriefAPIDoc(unit, "Returns ", "set of ", "", "for ");
+                unit.emitln("  public Set<"+KeyClassName+"> get"+capIfaceName+"Keys();");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Returns ", "whether callback ", "if callback ", "is mapped for ");
+                unit.emitln("  public boolean is"+capIfaceName+"Mapped("+KeyClassName+" key);");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Returns "+info.cbFuncTypeName+" callback ", "mapped to ", "", "for ");
+                unit.emitln("  public "+info.cbFuncTypeName+" get"+capIfaceName+"("+KeyClassName+" key);");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Returns user-param ", "mapped to ", "", "for ");
+                unit.emitln("  public Object get"+capIfaceName+"UserParam("+KeyClassName+" key);");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Releases all callback data ", "mapped via ", "", "skipping toolkit API. Favor passing `null` callback ref to ");
+                unit.emitln("  public int releaseAll"+capIfaceName+"();");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Releases callback data ", "mapped to ", "", "skipping toolkit API. Favor passing `null` callback ref to ");
+                unit.emitln("  public void release"+capIfaceName+"("+KeyClassName+" key);");
+                unit.emitln();
+            } else {
+                emitJavaBriefAPIDoc(unit, "Returns ", "whether callback ", "if callback ", "is mapped for ");
+                unit.emitln("  public boolean is"+capIfaceName+"Mapped();");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Returns "+info.cbFuncTypeName+" callback ", "mapped to ", "", "for ");
+                unit.emitln("  public "+info.cbFuncTypeName+" get"+capIfaceName+"();");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Returns user-param ", "mapped to ", "", "for ");
+                unit.emitln("  public Object get"+capIfaceName+"UserParam();");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Releases callback data ", "", "", "skipping toolkit API. Favor passing `null` callback ref to ");
+                unit.emitln("  public void release"+capIfaceName+"();");
+                unit.emitln();
+            }
+        } else {
+            if( useDataMap ) {
+                if( !customKeyClass && !info.keyClassEmitted ) {
+                    emitJavaKeyClass(unit);
+                    unit.emitln();
+                    info.keyClassEmitted = true;
+                }
+                emitJavaBriefAPIDoc(unit, "Returns ", "set of ", "", "for ");
+                unit.emitln("  public final Set<"+KeyClassName+"> get"+capIfaceName+"Keys() {");
+                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+                unit.emitln("      return "+dataMapInstanceName+".keySet();");
+                unit.emitln("    }");
+                unit.emitln("  }");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Returns ", "whether callback ", "if callback ", "is mapped for ");
+                unit.emitln("  public final boolean is"+capIfaceName+"Mapped("+KeyClassName+" key) {");
+                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+                unit.emitln("      return null != "+dataMapInstanceName+".get(key);");
+                unit.emitln("    }");
+                unit.emitln("  }");
+                unit.emitln();
+
+                emitJavaBriefAPIDoc(unit, "Returns "+info.cbFuncTypeName+" callback ", "mapped to ", "", "for ");
+                unit.emitln("  public final "+info.cbFuncTypeName+" get"+capIfaceName+"("+KeyClassName+" key) {");
+                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+                unit.emitln("      final "+DataClassName+" value = "+dataMapInstanceName+".get(key);");
+                unit.emitln("      return null != value ? value.func : null;");
+                unit.emitln("    }");
+                unit.emitln("  }");
+                unit.emitln();
+
+                emitJavaBriefAPIDoc(unit, "Returns user-param ", "mapped to ", "", "for ");
+                unit.emitln("  public final Object get"+capIfaceName+"UserParam("+KeyClassName+" key) {");
+                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+                unit.emitln("      final "+DataClassName+" value = "+dataMapInstanceName+".get(key);");
+                unit.emitln("      return null != value ? value.param : null;");
+                unit.emitln("    }");
+                unit.emitln("  }");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Releases all callback data ", "mapped via ", "", "skipping toolkit API. Favor passing `null` callback ref to ");
+                unit.emitln("  public final int releaseAll"+capIfaceName+"() {");
+                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+                unit.emitln("      final Set<"+KeyClassName+"> keySet = "+dataMapInstanceName+".keySet();");
+                unit.emitln("      final "+KeyClassName+"[] keys = keySet.toArray(new "+KeyClassName+"[keySet.size()]);");
+                unit.emitln("      for(int i=0; i<keys.length; ++i) {");
+                unit.emitln("        final "+KeyClassName+" key = keys[i];");
+                unit.emitln("          release"+capIfaceName+"(key);");
+                unit.emitln("      }");
+                unit.emitln("      return keys.length;");
+                unit.emitln("    }");
+                unit.emitln("  }");
+                unit.emitln();
+                emitJavaBriefAPIDoc(unit, "Releases callback data ", "mapped to ", "", "skipping toolkit API. Favor passing `null` callback ref to ");
+                unit.emitln("  public final void release"+capIfaceName+"("+KeyClassName+" key) {");
+                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+                unit.emitln("      /* final "+DataClassName+" value = */ "+dataMapInstanceName+".remove(key);");
+                unit.emitln("    }");
+                unit.emitln("  }");
+                unit.emitln();
+            } else {
+                emitJavaBriefAPIDoc(unit, "Returns ", "whether callback ", "if callback ", "is mapped for ");
+                unit.emitln("  public final boolean is"+capIfaceName+"Mapped() {");
+                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+                unit.emitln("      return null != "+dataInstanceName+";");
+                unit.emitln("    }");
+                unit.emitln("  }");
+                unit.emitln();
+
+                emitJavaBriefAPIDoc(unit, "Returns "+info.cbFuncTypeName+" callback ", "mapped to ", "", "for ");
+                unit.emitln("  public final "+info.cbFuncTypeName+" get"+capIfaceName+"() {");
+                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+                unit.emitln("      final "+DataClassName+" value = "+dataInstanceName+";");
+                unit.emitln("      return null != value ? value.func : null;");
+                unit.emitln("    }");
+                unit.emitln("  }");
+                unit.emitln();
+
+                emitJavaBriefAPIDoc(unit, "Returns user-param ", "mapped to ", "", "for ");
+                unit.emitln("  public final Object get"+capIfaceName+"UserParam() {");
+                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+                unit.emitln("      final "+DataClassName+" value = "+dataInstanceName+";");
+                unit.emitln("      return null != value ? value.param : null;");
+                unit.emitln("    }");
+                unit.emitln("  }");
+                unit.emitln();
+
+                emitJavaBriefAPIDoc(unit, "Releases callback data ", "", "", "skipping toolkit API. Favor passing `null` callback ref to ");
+                unit.emitln("  public final void release"+capIfaceName+"() {");
+                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+                unit.emitln("      // final "+DataClassName+" value = "+dataInstanceName+";");
+                unit.emitln("      "+dataInstanceName+" = null;");
+                unit.emitln("    }");
+                unit.emitln("  }");
+                unit.emitln();
+            }
+            unit.emitln("  private final void add"+capIfaceName+"("+binding.getJavaSelectParameter(new StringBuilder(), info.setFuncKeyIndices, true).toString()+DataClassName+" value) {");
+            if( useDataMap ) {
+                unit.emitln("    final "+KeyClassName+" key = new "+KeyClassName+"("+binding.getJavaCallSelectArguments(new StringBuilder(), info.setFuncKeyIndices, false).toString()+");");
+                unit.emitln("    /* final "+DataClassName+" old = */ "+dataMapInstanceName+".put(key, value);");
+            } else {
+                unit.emitln("    // final "+DataClassName+" old = "+dataInstanceName+";");
+                unit.emitln("    "+dataInstanceName+" = value;");
+            }
+            unit.emitln("  }");
+            unit.emitln();
+            if( !cfg.emittedJavaCallbackUserParamClasses.contains(fqUsrParamClassName) ) {
+                emitJavaDataClass(unit);
+                cfg.emittedJavaCallbackUserParamClasses.add(fqUsrParamClassName);
+            }
+            if( useDataMap ) {
+                unit.emitln("  private static final Map<"+KeyClassName+", "+DataClassName+"> "+dataMapInstanceName+" = new HashMap<"+KeyClassName+", "+DataClassName+">();");
+            } else {
+                unit.emitln("  private static "+DataClassName+" "+dataInstanceName+" = null;");
+            }
+            unit.emitln("  private static long "+jcbNextIDVarName+" = 1;");
+            unit.emitln("  private static final Object "+lockInstanceName+" = new Object();");
+            unit.emitln();
+            emitJavaStaticCallback(unit);
+        }
+    }
+
+    private final void emitJavaBriefAPIDoc(final CodeUnit unit, final String actionText, final String relationToKey, final String noKeyText, final String relationToFunc) {
+        unit.emit("  /** "+actionText);
+        if( info.setFuncKeyIndices.size() > 0 ) {
+            unit.emit(relationToKey);
+            unit.emit("Key { "+binding.getJavaSelectParameter(new StringBuilder(), info.setFuncKeyIndices, false).toString()+" } ");
+        } else {
+            unit.emit(noKeyText);
+        }
+        unit.emit(relationToFunc);
+        unit.emitln("<br> <code>"+setFuncSignature+"</code> */");
+    }
+
+    private final void emitJavaKeyClass(final CodeUnit unit) {
+        emitJavaBriefAPIDoc(unit, "", "", "", "for ");
+        unit.emitln("  public static class "+KeyClassName+" {");
+        binding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
+            if( !cType.isVoid() && info.setFuncKeyIndices.contains(idx) ) {
+                unit.emitln("    public final "+jType+" "+name+";");
+                return true;
+            } else {
+                return false;
+            }
+        } );
+        unit.emitln("    public "+KeyClassName+"("+binding.getJavaSelectParameter(new StringBuilder(), info.setFuncKeyIndices, false).toString()+") {");
+        binding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
+            if( !cType.isVoid() && info.setFuncKeyIndices.contains(idx) ) {
+                unit.emitln("      this."+name+" = "+name+";");
+                return true;
+            } else {
+                return false;
+            }
+        } );
+        unit.emitln("    }");
+        unit.emitln("    @Override");
+        unit.emitln("    public boolean equals(final Object o) {");
+        unit.emitln("      if( this == o ) {");
+        unit.emitln("        return true;");
+        unit.emitln("      }");
+        unit.emitln("      if( !(o instanceof "+KeyClassName+") ) {");
+        unit.emitln("        return false;");
+        unit.emitln("      }");
+        {
+            final int count = binding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
+                if( !cType.isVoid() && info.setFuncKeyIndices.contains(idx) ) {
+                    if( 0 == consumedCount ) {
+                        unit.emitln("      final "+KeyClassName+" o2 = ("+KeyClassName+")o;");
+                        unit.emit  ("      return ");
+                    } else {
+                        unit.emitln(" &&");
+                        unit.emit  ("             ");
+                    }
+                    if( jType.isPrimitive() || idx == info.setFuncUserParamIdx ) {
+                        unit.emit(name+" == o2."+name);
+                    } else {
+                        unit.emit(name+".equals( o2."+name+" )");
+                    }
+                    return true;
+                } else {
+                    return false;
+                }
+            } );
+            if( 0 == count ) {
+                unit.emit("      return true");
+            }
+            unit.emitln(";");
+        }
+        unit.emitln("    }");
+        unit.emitln("    @Override");
+        unit.emitln("    public int hashCode() {");
+        {
+            final int count = binding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
+                if( !cType.isVoid() && info.setFuncKeyIndices.contains(idx) ) {
+                    if( 0 == consumedCount ) {
+                        unit.emitln("      // 31 * x == (x << 5) - x");
+                        unit.emit  ("      int hash = ");
+                    } else {
+                        unit.emit  ("      hash = ((hash << 5) - hash) + ");
+                    }
+                    if( jType.isPrimitive() ) {
+                        if( jType.isLong() ) {
+                            unit.emitln("HashUtil.getAddrHash32_EqualDist( "+name+" );");
+                        } else {
+                            unit.emitln(name+";");
+                        }
+                    } else {
+                        if( idx == info.setFuncUserParamIdx ) {
+                            unit.emitln("System.identityHashCode( "+name+" );");
+                        } else {
+                            unit.emitln(name+".hashCode();");
+                        }
+                    }
+                    return true;
+                } else {
+                    return false;
+                }
+            } );
+            if( 0 == count ) {
+                unit.emitln("      return 0;");
+            } else {
+                unit.emitln("      return hash;");
+            }
+        }
+        unit.emitln("    }");
+        unit.emitln("  }");
+    }
+
+    private final void emitJavaDataClass(final CodeUnit unit) {
+        unit.emitln("  private static class "+DataClassName+" {");
+        unit.emitln("    // userParamArgCType "+setFuncUserParamCType);
+        unit.emitln("    // userParamArgJType "+setFuncUserParamJType);
+        unit.emitln("    final "+info.cbFuncTypeName+" func;");
+        unit.emitln("    final "+setFuncUserParamTypeName+" param;");
+        unit.emitln("    "+DataClassName+"("+info.cbFuncTypeName+" func, "+setFuncUserParamTypeName+" param) {");
+        unit.emitln("      this.func = func;");
+        unit.emitln("      this.param = param;");
+        unit.emitln("    }");
+        unit.emitln("  }");
+    }
+
+    public final String getJavaStaticCallbackSignature() {
+        final StringBuilder buf = new StringBuilder();
+        buf.append("(");
+        info.cbFuncBinding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
+            if( !cType.isVoid() ) {
+                if( idx == info.cbFuncUserParamIdx ) {
+                    buf.append("J");
+                } else {
+                    buf.append(jType.getDescriptor());
+                }
+                return true;
+            } else {
+                return false;
+            }
+        } );
+        buf.append(")");
+        buf.append(cbFuncJavaReturnType.getDescriptor());
+        return buf.toString();
+    }
+
+    public final int appendJavaAdditionalJNIParameter(final StringBuilder buf) {
+        buf.append("Class<?> clazz, String callbackSignature, long nativeUserParam");
+        return 3;
+    }
+    public final int appendJavaAdditionalJNIArguments(final StringBuilder buf) {
+        buf.append("this.getClass(), \"" + getJavaStaticCallbackSignature()+ "\", nativeUserParam");
+        return 3;
+    }
+    private final void emitJavaStaticCallback(final CodeUnit unit) {
+        unit.emitln("  /** Static callback invocation, dispatching to "+info.cbSimpleClazzName+" for callback <br> <code>"+
+                info.cbFuncType.toString(info.cbFuncTypeName, false, true)+"</code> */");
+        unit.emit  ("  /* pp */ static "+cbFuncJavaReturnType.getName()+" invoke"+capIfaceName+"(");
+        final boolean[] mapNativePtrToCompound = { false };
+        final JavaType[] origUserParamJType = { null };
+        info.cbFuncBinding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
+            if( !cType.isVoid() ) {
+                if( 0 < consumedCount ) { unit.emit(", "); }
+                if( idx == info.cbFuncUserParamIdx ) {
+                    unit.emit("long nativeUserParamPtr");
+                    if( jType.isCompoundTypeWrapper() ) {
+                        mapNativePtrToCompound[0] = true;
+                        origUserParamJType[0] = jType;
+                    }
+                } else {
+                    unit.emit(jType+" "+name);
+                }
+                return true;
+            } else {
+                return false;
+            }
+        } );
+        unit.emitln(") {");
+        if( mapNativePtrToCompound[0] ) {
+            unit.emitln("    final "+origUserParamJType[0]+" "+info.cbFuncUserParamName+" = "+origUserParamJType[0]+".derefPointer(nativeUserParamPtr);");
+        }
+        if( useDataMap ) {
+            unit.emitln("    final "+DataClassName+" value;");
+        } else {
+            unit.emitln("    final "+DataClassName+" value;");
+        }
+        unit.emitln("    synchronized( "+lockInstanceName+" ) {");
+        if( useDataMap ) {
+            unit.emitln("      final "+KeyClassName+" key = new "+KeyClassName+"("+binding.getJavaCallSelectArguments(new StringBuilder(), info.setFuncKeyIndices, false).toString()+");");
+            unit.emitln("      value = "+dataMapInstanceName+".get(key);");
+        } else {
+            unit.emitln("      value = "+dataInstanceName+";");
+        }
+        unit.emitln("    }");
+        unit.emitln("    if( null == value ) {");
+        if( !cbFuncJavaReturnType.isVoid() ) {
+            unit.emitln("      return 0;");
+        } else {
+            unit.emitln("      return;");
+        }
+        unit.emitln("    }");
+        if( !cbFuncJavaReturnType.isVoid() ) {
+            unit.emit("    return ");
+        } else {
+            unit.emit("    ");
+        }
+        unit.emit("value.func.callback(");
+        info.cbFuncBinding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
+            if( !cType.isVoid() ) {
+                if( 0 < consumedCount ) { unit.emit(", "); }
+                if( idx == info.cbFuncUserParamIdx && !mapNativePtrToCompound[0] ) {
+                    unit.emit("value.param");
+                } else {
+                    unit.emit(name);
+                }
+                return true;
+            } else {
+                return false;
+            }
+        } );
+        unit.emitln(");");
+        unit.emitln("  }");
+        unit.emitln();
+    }
+
+    //
+    // C JNI Code ..
+    //
+
+    public int appendCAdditionalParameter(final StringBuilder buf) {
+        buf.append(", jclass clazz, jstring jcallbackSignature, jlong jnativeUserParam");
+        return 3;
+    }
+
+    public void emitCOptArgumentSuffix(final CodeUnit unit, final int argIdx) {
+      if( ( argIdx == info.setFuncCBParamIdx || argIdx == info.setFuncUserParamIdx ) ) {
+          unit.emit("_native");
+      }
+    }
+
+    public void appendCAdditionalJNIDescriptor(final StringBuilder buf) {
+        JavaType.appendJNIDescriptor(buf, Class.class, false);  // to account for the additional 'jclass clazz' parameter
+        JavaType.appendJNIDescriptor(buf, String.class, false);  // to account for the additional 'jstring jcallbackSignature' parameter
+        JavaType.appendJNIDescriptor(buf, long.class, false);  // to account for the additional 'long nativeUserParam' parameter
+    }
+
+    public void emitCSetFuncPreCall(final CodeUnit unit) {
+        final String jcbNativeBasename = CodeGenUtils.capitalizeString( info.setFuncName );
+        final String jcbFriendlyBasename = info.setFuncName+"("+info.cbSimpleClazzName+")";
+        final String staticBindingMethodName = "invoke"+jcbNativeBasename;
+        final String staticBindingClazzVarName = "clazz"+jcbNativeBasename;
+        final String staticBindingMethodIDVarName = "method"+jcbNativeBasename;
+        final String cbFuncArgName = binding.getArgumentName(info.setFuncCBParamIdx);
+        final String userParamTypeName = info.cbFuncUserParamType.getCName();
+        final String userParamArgName = binding.getArgumentName(info.setFuncUserParamIdx);
+        final String nativeCBFuncVarName = cbFuncArgName+"_native";
+        final String nativeUserParamVarName = userParamArgName+"_native";
+        unit.emitln();
+        unit.emitln("  // JavaCallback handling");
+        unit.emitln("  if( NULL == clazz ) { (*env)->FatalError(env, \"NULL clazz passed to '"+jcbFriendlyBasename+"'\"); }");
+        unit.emitln("  "+info.cbFuncTypeName+" "+nativeCBFuncVarName+";");
+        unit.emitln("  "+userParamTypeName+"* "+nativeUserParamVarName+";");
+        unit.emitln("  if( NULL != "+cbFuncArgName+" ) {");
+        unit.emitln("    const char* callbackSignature = (*env)->GetStringUTFChars(env, jcallbackSignature, (jboolean*)NULL);");
+        unit.emitln("    if( NULL == callbackSignature ) { (*env)->FatalError(env, \"Failed callbackSignature in '"+jcbFriendlyBasename+"'\"); }");
+        unit.emitln("    jmethodID cbMethodID = (*env)->GetStaticMethodID(env, clazz, \""+staticBindingMethodName+"\", callbackSignature);");
+        unit.emitln("    if( NULL == cbMethodID ) {");
+        unit.emitln("      char cmsg[400];");
+        unit.emitln("      snprintf(cmsg, 400, \"Failed GetStaticMethodID of '"+staticBindingMethodName+"(%s)' in '"+jcbFriendlyBasename+"'\", callbackSignature);");
+        unit.emitln("      (*env)->FatalError(env, cmsg);");
+        unit.emitln("    }");
+        unit.emitln("    (*env)->ReleaseStringUTFChars(env, jcallbackSignature, callbackSignature);");
+        unit.emitln("    "+staticBindingClazzVarName+" = clazz;");
+        unit.emitln("    "+staticBindingMethodIDVarName+" = cbMethodID;");
+        unit.emitln("    "+nativeCBFuncVarName+" = func"+jcbNativeBasename+";");
+        unit.emitln("    "+nativeUserParamVarName+" = ("+userParamTypeName+"*) jnativeUserParam;");
+        unit.emitln("  } else {");
+        unit.emitln("    "+nativeCBFuncVarName+" = NULL;");
+        unit.emitln("    "+nativeUserParamVarName+" = NULL;");
+        unit.emitln("  }");
+        unit.emitln();
+
+    }
+
+    public void emitCAdditionalCode(final CodeUnit unit, final CMethodBindingEmitter jcbCMethodEmitter) {
+        final String jcbNativeBasename = CodeGenUtils.capitalizeString( info.setFuncName );
+        final String jcbFriendlyBasename = info.setFuncName+"("+info.cbSimpleClazzName+")";
+        final String staticBindingClazzVarName = "clazz"+jcbNativeBasename;
+        final String staticBindingMethodIDVarName = "method"+jcbNativeBasename;
+        final String staticCallbackName = "func"+jcbNativeBasename;
+        // final Type userParamType = javaCallback.cbFuncBinding.getCArgumentType(javaCallback.cbFuncUserParamIdx);
+        final String userParamTypeName = info.cbFuncUserParamType.getCName();
+        final String userParamArgName = info.cbFuncBinding.getArgumentName(info.cbFuncUserParamIdx);
+        final Type cReturnType = info.cbFuncBinding.getCReturnType();
+        final JavaType jretType = info.cbFuncBinding.getJavaReturnType();
+        unit.emitln();
+        unit.emitln("static jclass "+staticBindingClazzVarName+" = NULL;");
+        unit.emitln("static jmethodID "+staticBindingMethodIDVarName+" = NULL;");
+        unit.emitln();
+        // javaCallback.cbFuncCEmitter.emitSignature();
+        unit.emit("static "+cReturnType.getCName()+" "+staticCallbackName+"(");
+        // javaCallback.cbFuncCEmitter.emitArguments();
+        unit.emit(info.cbFuncBinding.getCParameterList(new StringBuilder(), false, null).toString());
+        unit.emitln(") {");
+        // javaCallback.cbFuncCEmitter.emitBody();
+        {
+            unit.emitln("  JNIEnv* env = JVMUtil_GetJNIEnv();");
+            unit.emitln("  jclass cbClazz = "+staticBindingClazzVarName+";");
+            unit.emitln("  jmethodID cbMethod = "+staticBindingMethodIDVarName+";");
+            unit.emitln("  if( NULL == env || NULL == cbClazz || NULL == cbMethod ) {");
+            if( !cReturnType.isVoid() ) {
+                unit.emitln("    return 0;");
+            } else {
+                unit.emitln("    return;");
+            }
+            unit.emitln("  }");
+            // javaCallback.cbFuncCEmitter.emitBodyVariableDeclarations();
+            // javaCallback.cbFuncCEmitter.emitBodyUserVariableDeclarations();
+            // javaCallback.cbFuncCEmitter.emitBodyVariablePreCallSetup();
+            emitJavaCallbackBodyCToJavaPreCall(jcbCMethodEmitter);
+
+            // javaCallback.cbFuncCEmitter.emitBodyCallCFunction();
+            unit.emitln("  "+userParamTypeName+"* "+userParamArgName+"_jni = ("+userParamTypeName+"*) "+userParamArgName+";");
+            unit.emitln("  // C Params: "+info.cbFuncBinding.getCParameterList(new StringBuilder(), false, null).toString());
+            unit.emitln("  // J Params: "+info.cbFuncBinding.getJavaParameterList(new StringBuilder()).toString());
+
+            final String returnStatement;
+            if( !cReturnType.isVoid() ) {
+                unit.emit("  "+cReturnType.getCName()+" _res = 0;");
+                returnStatement = "return _res;";
+            } else {
+                returnStatement = "return;";
+            }
+            if( !cReturnType.isVoid() ) {
+                unit.emit("  _res = ("+cReturnType.getCName()+") ");
+            } else {
+                unit.emit("  ");
+            }
+            unit.emit("(*env)->CallStatic" + CodeGenUtils.capitalizeString( jretType.getName() ) +"Method(env, cbClazz, cbMethod, ");
+            // javaCallback.cbFuncCEmitter.emitBodyPassCArguments();
+            emitJavaCallbackBodyPassJavaArguments(unit, jcbCMethodEmitter.binding, null); //"NULL");
+            unit.emitln(");");
+            unit.emitln("  if( (*env)->ExceptionCheck(env) ) {");
+            unit.emitln("    fprintf(stderr, \"Info: Callback '"+jcbFriendlyBasename+"': Exception in Java Callback caught:\\n\");");
+            unit.emitln("    (*env)->ExceptionDescribe(env);");
+            unit.emitln("    (*env)->ExceptionClear(env);");
+            unit.emitln("  }");
+
+            // javaCallback.cbFuncCEmitter.emitBodyUserVariableAssignments();
+            // javaCallback.cbFuncCEmitter.emitBodyVariablePostCallCleanup();
+            // javaCallback.cbFuncCEmitter.emitBodyMapCToJNIType(-1 /* return value */, true /* addLocalVar */)
+
+            unit.emitln("  "+returnStatement);
+        }
+        unit.emitln("}");
+        unit.emitln();
+    }
+
+    /* pp */ int emitJavaCallbackBodyCToJavaPreCall(final CMethodBindingEmitter ce)  {
+        int count = 0;
+        for (int i = 0; i < ce.binding.getNumArguments(); i++) {
+            if( i == info.cbFuncUserParamIdx ) {
+                continue;
+            }
+            if( ce.emitBodyMapCToJNIType(i, true /* addLocalVar */) ) {
+                ++count;
+            }
+        }
+        return count;
+    }
+
+    /* pp */ int emitJavaCallbackBodyPassJavaArguments(final CodeUnit unit, final MethodBinding binding, final String userParamVarName) {
+        int count = 0;
+        boolean needsComma = false;
+        for (int i = 0; i < binding.getNumArguments(); i++) {
+            if (needsComma) {
+                unit.emit(", ");
+                needsComma = false;
+            }
+            if( i == info.cbFuncUserParamIdx && null != userParamVarName ) {
+                unit.emit( userParamVarName );
+            } else {
+                unit.emit( binding.getArgumentName(i) + "_jni" );
+            }
+            needsComma = true;
+            ++count;
+        }
+        return count;
+    }
+
+
+}
diff --git a/src/java/com/jogamp/gluegen/JavaConfiguration.java b/src/java/com/jogamp/gluegen/JavaConfiguration.java
index 3e2e680..10f43a7 100644
--- a/src/java/com/jogamp/gluegen/JavaConfiguration.java
+++ b/src/java/com/jogamp/gluegen/JavaConfiguration.java
@@ -156,17 +156,19 @@ public class JavaConfiguration {
       final int cbFuncUserParamIdx;
       final String setFuncName;
       final List<Integer> setFuncKeyIndices = new ArrayList<Integer>();
+      final int setFuncUserParamIdx; // optional
       final String setFuncKeyClassName; // optional
-      JavaCallbackDef(final String cbFuncTypeName, final int cbFuncUserParamIdx, final String setFuncName, final String setFuncKeyClassName) {
+      JavaCallbackDef(final String cbFuncTypeName, final int cbFuncUserParamIdx, final String setFuncName, final int setFuncUserParamIdx, final String setFuncKeyClassName) {
           this.cbFuncTypeName = cbFuncTypeName;
           this.cbFuncUserParamIdx = cbFuncUserParamIdx;
           this.setFuncName = setFuncName;
+          this.setFuncUserParamIdx = setFuncUserParamIdx;
           this.setFuncKeyClassName = setFuncKeyClassName;
       }
       @Override
       public String toString() {
-          return String.format("JavaCallbackDef[cbFunc[type %s, userParamIdx %d], set[%s, keys %s, KeyClass %s]]",
-                  cbFuncTypeName, cbFuncUserParamIdx, setFuncName, setFuncKeyIndices.toString(), setFuncKeyClassName);
+          return String.format("JavaCallbackDef[cbFunc[type %s, userParamIdx %d], set[%s, keys %s, userParamIdx %d, KeyClass %s]]",
+                  cbFuncTypeName, cbFuncUserParamIdx, setFuncName, setFuncKeyIndices.toString(), setFuncUserParamIdx, setFuncKeyClassName);
       }
     }
     private final List<JavaCallbackDef> javaCallbackList = new ArrayList<JavaCallbackDef>();
@@ -1630,7 +1632,25 @@ public class JavaConfiguration {
   protected void readJavaCallbackDef(final StringTokenizer tok, final String filename, final int lineNo) {
     try {
       final String setFuncName = tok.nextToken();
-      final String cbFuncTypeName = tok.nextToken();
+      final int setFuncUserParamIdx;
+      final String cbFuncTypeName;
+      {
+          final String stok = tok.nextToken();
+          int ival = -1;
+          String sval = null;
+          try {
+              ival = Integer.valueOf(stok);
+          } catch(final NumberFormatException nfe) {
+              sval = stok;
+          }
+          if( null == sval ) {
+              setFuncUserParamIdx = ival;
+              cbFuncTypeName = tok.nextToken();
+          } else {
+              setFuncUserParamIdx = -1;
+              cbFuncTypeName = sval;
+          }
+      }
       final Integer cbFuncUserParamIdx = Integer.valueOf(tok.nextToken());
       final String cbFuncKeyClassName;
       if( tok.hasMoreTokens() ) {
@@ -1638,7 +1658,7 @@ public class JavaConfiguration {
       } else {
           cbFuncKeyClassName = null;
       }
-      final JavaCallbackDef jcd = new JavaCallbackDef(cbFuncTypeName, cbFuncUserParamIdx, setFuncName, cbFuncKeyClassName);
+      final JavaCallbackDef jcd = new JavaCallbackDef(cbFuncTypeName, cbFuncUserParamIdx, setFuncName, setFuncUserParamIdx, cbFuncKeyClassName);
       javaCallbackList.add(jcd);
       javaCallbackSetFuncToDef.put(setFuncName, jcd);
     } catch (final NoSuchElementException e) {
@@ -2279,13 +2299,12 @@ public class JavaConfiguration {
       final String cbFuncTypeName;
       final String cbSimpleClazzName;
       final String cbFQClazzName;
-      final String cbMethodSignature;
+      final String staticCBMethodSignature;
       final FunctionType cbFuncType;
       final MethodBinding cbFuncBinding;
       final int cbFuncUserParamIdx;
-
-      final Type userParamType;
-      final String userParamName;
+      final String cbFuncUserParamName;
+      final Type cbFuncUserParamType;
 
       final String setFuncName;
       final List<Integer> setFuncKeyIndices;
@@ -2295,38 +2314,38 @@ public class JavaConfiguration {
       int setFuncUserParamIdx;
       boolean keyClassEmitted;
 
-      public JavaCallbackInfo(final String cbFuncTypeName, final String cbSimpleClazzName, final String cbFQClazzName, final String cbMethodSignature,
+      public JavaCallbackInfo(final String cbFuncTypeName, final String cbSimpleClazzName, final String cbFQClazzName, final String staticCBMethodSignature,
                               final FunctionType cbFuncType, final MethodBinding cbFuncBinding, final int cbFuncUserParamIdx,
-                              final String setFuncName, final List<Integer> setFuncKeyIndices, final String setFuncKeyClassName) {
+                              final String setFuncName, final int setFuncUserParamIdx, final List<Integer> setFuncKeyIndices, final String setFuncKeyClassName) {
           this.cbFuncTypeName = cbFuncTypeName;
           this.cbSimpleClazzName = cbSimpleClazzName;
           this.cbFQClazzName = cbFQClazzName;
-          this.cbMethodSignature = cbMethodSignature;
+          this.staticCBMethodSignature = staticCBMethodSignature;
           this.cbFuncType = cbFuncType;
           this.cbFuncBinding = cbFuncBinding;
-          int paramIdx = -2;
-          Type paramType = null;
-          String paramName = null;
-          if( 0 <= cbFuncUserParamIdx && cbFuncUserParamIdx < cbFuncType.getNumArguments() ) {
-              final Type t = cbFuncType.getArgumentType(cbFuncUserParamIdx);
-              if( null != t && t.isPointer() ) {
-                  // OK '<something>*'
-                  paramIdx = cbFuncUserParamIdx;
-                  paramName = cbFuncType.getArgumentName(cbFuncUserParamIdx);
-                  paramType = t.getTargetType();
+          {
+              int paramIdx = -2;
+              Type paramType = null;
+              String paramName = null;
+              if( 0 <= cbFuncUserParamIdx && cbFuncUserParamIdx < cbFuncType.getNumArguments() ) {
+                  final Type t = cbFuncType.getArgumentType(cbFuncUserParamIdx);
+                  if( null != t && t.isPointer() ) {
+                      // OK '<something>*'
+                      paramIdx = cbFuncUserParamIdx;
+                      paramName = cbFuncType.getArgumentName(cbFuncUserParamIdx);
+                      paramType = t.getTargetType();
+                  }
               }
+              this.cbFuncUserParamIdx = paramIdx;
+              this.cbFuncUserParamName = paramName;
+              this.cbFuncUserParamType = paramType;
           }
-          this.cbFuncUserParamIdx = paramIdx;
-
-          this.userParamType = paramType;
-          this.userParamName = paramName;
-
           this.setFuncName = setFuncName;
           this.setFuncKeyIndices = setFuncKeyIndices;
           this.setFuncKeyClassName = setFuncKeyClassName;
           this.setFuncProcessed = false;
           this.setFuncCBParamIdx = -1;
-          this.setFuncUserParamIdx = -1;
+          this.setFuncUserParamIdx = setFuncUserParamIdx;
           this.keyClassEmitted = false;
       }
 
@@ -2335,7 +2354,13 @@ public class JavaConfiguration {
             if( 0 <= cbParamIdx && 0 <= userParamIdx ) {
                 setFuncProcessed = true;
                 setFuncCBParamIdx = cbParamIdx;
-                setFuncUserParamIdx = userParamIdx;
+                if( 0 <= setFuncUserParamIdx ) {
+                    if( setFuncUserParamIdx != userParamIdx ) {
+                        throw new IllegalArgumentException("Mismatch pre-set setFuncUserParamIdx "+setFuncUserParamIdx+", given "+userParamIdx+": "+toString());
+                    }
+                } else {
+                    setFuncUserParamIdx = userParamIdx;
+                }
             } else {
                 setFuncCBParamIdx = -1;
                 setFuncUserParamIdx = -1;
@@ -2346,8 +2371,8 @@ public class JavaConfiguration {
       @Override
       public String toString() {
           return String.format("JavaCallbackInfo[cbFunc[%s%s, userParam[idx %d, '%s', %s], set[%s(ok %b, cbIdx %d, upIdx %d, keys %s, KeyClass '%s'], %s]",
-                  cbFuncTypeName, cbMethodSignature,
-                  cbFuncUserParamIdx, userParamName, userParamType.getSignature(null).toString(),
+                  cbFuncTypeName, staticCBMethodSignature,
+                  cbFuncUserParamIdx, cbFuncUserParamName, cbFuncUserParamType.getSignature(null).toString(),
                   setFuncName, setFuncProcessed, setFuncCBParamIdx, setFuncUserParamIdx,
                   setFuncKeyIndices.toString(), setFuncKeyClassName,
                   cbFuncType.toString(cbFuncTypeName, false, true));
diff --git a/src/java/com/jogamp/gluegen/JavaEmitter.java b/src/java/com/jogamp/gluegen/JavaEmitter.java
index 2ea8d30..4a81a01 100644
--- a/src/java/com/jogamp/gluegen/JavaEmitter.java
+++ b/src/java/com/jogamp/gluegen/JavaEmitter.java
@@ -1471,9 +1471,9 @@ public class JavaEmitter implements GlueEmitter {
               throw new UnsupportedOperationException("Reused FuncTypeName "+jcbd.cbFuncTypeName+" used with different FuncUserParamIdx "+jcbi0.cbFuncUserParamIdx+" -> "+jcbd.cbFuncUserParamIdx+". Func "+
                       funcType.toString(jcbd.cbFuncTypeName, false, true));
           }
-          final JavaCallbackInfo jcbi1 = new JavaCallbackInfo(jcbd.cbFuncTypeName, cbSimpleClazzName, cbFQClazzName, jcbi0.cbMethodSignature,
+          final JavaCallbackInfo jcbi1 = new JavaCallbackInfo(jcbd.cbFuncTypeName, cbSimpleClazzName, cbFQClazzName, jcbi0.staticCBMethodSignature,
                                                               funcType, jcbi0.cbFuncBinding, jcbi0.cbFuncUserParamIdx,
-                                                              jcbd.setFuncName, jcbd.setFuncKeyIndices, jcbd.setFuncKeyClassName);
+                                                              jcbd.setFuncName, jcbd.setFuncUserParamIdx, jcbd.setFuncKeyIndices, jcbd.setFuncKeyClassName);
           cfg.setFuncToJavaCallbackMap.put(jcbd.setFuncName, jcbi1);
           LOG.log(INFO, "JavaCallbackInfo: Reusing {0} -> {1}", jcbd.setFuncName, jcbi0);
       } else {
@@ -1493,7 +1493,7 @@ public class JavaEmitter implements GlueEmitter {
           }
           final JavaCallbackInfo jcbi1 = new JavaCallbackInfo(jcbd.cbFuncTypeName, cbSimpleClazzName, cbFQClazzName, cbMethodSignature.toString(),
                                                               funcType, cbFuncBinding, jcbd.cbFuncUserParamIdx,
-                                                              jcbd.setFuncName, jcbd.setFuncKeyIndices, jcbd.setFuncKeyClassName);
+                                                              jcbd.setFuncName, jcbd.setFuncUserParamIdx, jcbd.setFuncKeyIndices, jcbd.setFuncKeyClassName);
           cfg.setFuncToJavaCallbackMap.put(jcbd.setFuncName, jcbi1);
           javaCallbackInterfaceMap.put(cbFQClazzName, jcbi1);
           LOG.log(INFO, "JavaCallbackInfo: Added {0} -> {1}", jcbd.setFuncName, jcbi1);
@@ -3019,9 +3019,6 @@ public class JavaEmitter implements GlueEmitter {
             LOG.log(WARNING, "JavaCallback used, but no 'LibraryOnLoad' basename specified for JNI_OnLoad(..). Exactly one native code-unit for the library must specify 'LibraryOnLoad' basename");
         }
         cUnit().emitHeader(cfg.libraryOnLoadName(), getImplPackageName(), cfg.implClassName(), cfg.customCCode());
-        if( cfg.getJavaCallbackList().size() > 0 ) {
-            cUnit().emitJavaCallbackGlueDataDecl();
-        }
       }
     } catch (final Exception e) {
       throw new RuntimeException(
@@ -3114,13 +3111,29 @@ public class JavaEmitter implements GlueEmitter {
           // Replace JavaCallback type with generated interface name
           jcbiSetFuncCBParamIdx=i;
           mappedType = JavaType.createForNamedClass( jcbi.cbFQClazzName );
-      } else if( null != jcbi && jcbi.userParamName.equals( cArgName ) &&
+      } else if( null != jcbi && i == jcbi.setFuncUserParamIdx && cArgType.isPointer() ) {
+          // Replace userParam argument '<userParamType>*' if 'void*' with Object
+          jcbiSetFuncUserParamIdx=i;
+          if( cArgType.getTargetType().isVoid() ) {
+              if( jcbi.cbFuncUserParamType.isCompound() ) {
+                  mappedType = JavaType.createForClass(long.class);
+              } else {
+                  mappedType = JavaType.forObjectClass();
+              }
+          }
+      } else if( null != jcbi && jcbi.cbFuncUserParamName.equals( cArgName ) &&
                  ( !jcbi.setFuncProcessed || i == jcbi.setFuncUserParamIdx ) &&
-                 cArgType.isPointer() && jcbi.userParamType.equals( cArgType.getTargetType() ) )
+                 cArgType.isPointer() && jcbi.cbFuncUserParamType.equals( cArgType.getTargetType() ) )
       {
-          // Replace optional userParam argument '<userParamType>*' with Object
+          // Replace userParam argument '<userParamType>*' if 'void*' with Object
           jcbiSetFuncUserParamIdx=i;
-          mappedType = JavaType.forObjectClass();
+          if( cArgType.getTargetType().isVoid() ) {
+              if( jcbi.cbFuncUserParamType.isCompound() ) {
+                  mappedType = JavaType.createForClass(long.class);
+              } else {
+                  mappedType = JavaType.forObjectClass();
+              }
+          }
       } else if (stringArgIndices != null && stringArgIndices.contains(i)) {
         // Take into account any ArgumentIsString configuration directives that apply
         // System.out.println("Forcing conversion of " + binding.getName() + " arg #" + i + " from byte[] to String ");
@@ -3153,7 +3166,8 @@ public class JavaEmitter implements GlueEmitter {
     }
     if( null != jcbi ) {
         jcbi.setFuncProcessed(jcbiSetFuncCBParamIdx, jcbiSetFuncUserParamIdx);
-        LOG.log(INFO, "BindFunc.JavaCallback: {0}: {1}, {2}", sym.getName(), sym.getType().toString(sym.getName(), false, true), jcbi);
+        LOG.log(INFO, "BindFunc.JavaCallback: {0}: set[cbParamIdx {1}, userParamIdx {2}], {3}, {4}",
+                sym.getName(), jcbiSetFuncCBParamIdx, jcbiSetFuncUserParamIdx, sym.getType().toString(sym.getName(), false, true), jcbi);
     }
     final MethodBinding mb = new MethodBinding(sym, delegationImplName,
                                                javaReturnType, javaArgumentTypes,
diff --git a/src/java/com/jogamp/gluegen/JavaMethodBindingEmitter.java b/src/java/com/jogamp/gluegen/JavaMethodBindingEmitter.java
index 6a93973..fe4f82a 100644
--- a/src/java/com/jogamp/gluegen/JavaMethodBindingEmitter.java
+++ b/src/java/com/jogamp/gluegen/JavaMethodBindingEmitter.java
@@ -95,7 +95,7 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
   private String returnedArrayLengthExpression;
   private boolean returnedArrayLengthExpressionOnlyForComments = false;
 
-  private final JavaCallbackInfo javaCallback;
+  private final JavaCallbackEmitter javaCallbackEmitter;
 
   // A suffix used to create a temporary outgoing array of Buffers to
   // represent an array of compound type wrappers
@@ -134,7 +134,12 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
     } else {
       setCommentEmitter(defaultInterfaceCommentEmitter);
     }
-    javaCallback = cfg.setFuncToJavaCallbackMap.get(binding.getName());
+    final JavaCallbackInfo javaCallback = cfg.setFuncToJavaCallbackMap.get(binding.getName());
+    if( null != javaCallback ) {
+        javaCallbackEmitter = new JavaCallbackEmitter(cfg, binding, javaCallback, appendSignature(new StringBuilder()).toString());
+    } else {
+        javaCallbackEmitter = null;
+    }
     // !forImplementingMethodCall && !isInterface
   }
 
@@ -156,7 +161,7 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
     epilogue                      = arg.epilogue;
     returnedArrayLengthExpression = arg.returnedArrayLengthExpression;
     returnedArrayLengthExpressionOnlyForComments = arg.returnedArrayLengthExpressionOnlyForComments;
-    javaCallback                  = arg.javaCallback;
+    javaCallbackEmitter           = arg.javaCallbackEmitter;
   }
 
   public boolean isNativeMethod() { return isNativeMethod; }
@@ -262,8 +267,8 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
   }
 
   @Override
-  protected void emitReturnType()  {
-    unit.emit(getReturnTypeString(false));
+  protected StringBuilder appendReturnType(final StringBuilder buf) {
+    return buf.append(getReturnTypeString(false));
   }
 
   protected String erasedTypeString(final JavaType type, final boolean skipBuffers) {
@@ -335,33 +340,34 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
   }
 
   @Override
-  protected void emitName()  {
+  protected StringBuilder appendName(final StringBuilder buf)  {
     if (isPrivateNativeMethod) {
-      unit.emit(getNativeImplMethodName());
+      buf.append(getNativeImplMethodName());
     } else if( isInterface()) {
-      unit.emit(getInterfaceName());
+      buf.append(getInterfaceName());
     } else {
-      unit.emit(getImplName());
+      buf.append(getImplName());
     }
+    return buf;
   }
 
   @Override
-  protected int emitArguments() {
+  protected int appendArguments(final StringBuilder buf) {
     boolean needComma = false;
     int numEmitted = 0;
 
     if( hasModifier(JavaMethodBindingEmitter.NATIVE) && binding.isReturnCompoundByValue() ) {
-      unit.emit("final Class<?> _clazzBuffers");
+      buf.append("final Class<?> _clazzBuffers");
       ++numEmitted;
       needComma = true;
     }
     if (isPrivateNativeMethod  && binding.hasContainingType()) {
       // Always emit outgoing "this" argument
       if (needComma) {
-        unit.emit(", ");
+        buf.append(", ");
       }
-      unit.emit("ByteBuffer ");
-      unit.emit(javaThisArgumentName());
+      buf.append("ByteBuffer ");
+      buf.append(javaThisArgumentName());
       ++numEmitted;
       needComma = true;
     }
@@ -385,12 +391,12 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
       }
 
       if (needComma) {
-        unit.emit(", ");
+        buf.append(", ");
       }
 
-      unit.emit(erasedTypeString(type, false));
-      unit.emit(" ");
-      unit.emit(getArgumentName(i));
+      buf.append(erasedTypeString(type, false));
+      buf.append(" ");
+      buf.append(getArgumentName(i));
 
       ++numEmitted;
       needComma = true;
@@ -398,12 +404,12 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
       // Add Buffer and array index offset arguments after each associated argument
       if (forDirectBufferImplementation || forIndirectBufferAndArrayImplementation) {
         if (type.isNIOBuffer()) {
-          unit.emit(", int " + byteOffsetArgName(i));
+          buf.append(", int " + byteOffsetArgName(i));
           if(!useNIODirectOnly) {
-              unit.emit(", boolean " + isNIOArgName(i));
+              buf.append(", boolean " + isNIOArgName(i));
           }
         } else if (type.isNIOBufferArray()) {
-          unit.emit(", int[] " +  byteOffsetArrayArgName(i));
+          buf.append(", int[] " +  byteOffsetArrayArgName(i));
         }
       }
 
@@ -412,17 +418,16 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
         if(useNIOOnly) {
             throw new RuntimeException("NIO[Direct]Only "+binding+" is set, but "+getArgumentName(i)+" is a primitive array");
         }
-        unit.emit(", int " + offsetArgName(i));
+        buf.append(", int " + offsetArgName(i));
       }
     }
     if( hasModifier(JavaMethodBindingEmitter.NATIVE) &&
-        null != javaCallback )
+        null != javaCallbackEmitter )
     {
         if (needComma) {
-            unit.emit(", ");
+            buf.append(", ");
         }
-        unit.emit("String callbackSignature, Object lockObj, long[/*1*/] nativeUserParam");
-        ++numEmitted;
+        numEmitted += javaCallbackEmitter.appendJavaAdditionalJNIParameter(buf);
     }
     return numEmitted;
   }
@@ -455,125 +460,11 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
     return getArgumentName(i) + "_offset";
   }
 
-  private static final boolean DEBUG_JAVACALLBACK = false;
-
-  private final void emitJavaCallbackBirefAPIDoc(final String actionText, final String relationToKey, final String noKeyText, final String relationToFunc) {
-      unit.emit("  /** "+actionText);
-      if( javaCallback.setFuncKeyIndices.size() > 0 ) {
-          unit.emit(relationToKey);
-          unit.emit("Key { "+binding.getJavaSelectParameter(new StringBuilder(), javaCallback.setFuncKeyIndices, false).toString()+" } ");
-      } else {
-          unit.emit(noKeyText);
-      }
-      unit.emit(relationToFunc);
-      unit.emit("<br> <code>");
-      emitSignature();
-      unit.emitln("</code> **/");
-  }
-  private final void emitJavaCallbackKeyClass(final String capIfaceName, final String keyClassName) {
-      emitJavaCallbackBirefAPIDoc("", "", "", "for ");
-      unit.emitln("  public static class "+keyClassName+" {");
-      binding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
-          if( !cType.isVoid() && javaCallback.setFuncKeyIndices.contains(idx) ) {
-              unit.emitln("    public final "+jType+" "+name+";");
-              return true;
-          } else {
-              return false;
-          }
-      } );
-      unit.emitln("    public "+keyClassName+"("+binding.getJavaSelectParameter(new StringBuilder(), javaCallback.setFuncKeyIndices, false).toString()+") {");
-      binding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
-          if( !cType.isVoid() && javaCallback.setFuncKeyIndices.contains(idx) ) {
-              unit.emitln("      this."+name+" = "+name+";");
-              return true;
-          } else {
-              return false;
-          }
-      } );
-      unit.emitln("    }");
-      unit.emitln("    @Override");
-      unit.emitln("    public boolean equals(final Object o) {");
-      unit.emitln("      if( this == o ) {");
-      unit.emitln("        return true;");
-      unit.emitln("      }");
-      unit.emitln("      if( !(o instanceof "+keyClassName+") ) {");
-      unit.emitln("        return false;");
-      unit.emitln("      }");
-      {
-          final int count = binding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
-              if( !cType.isVoid() && javaCallback.setFuncKeyIndices.contains(idx) ) {
-                  if( 0 == consumedCount ) {
-                      unit.emitln("      final "+keyClassName+" o2 = ("+keyClassName+")o;");
-                      unit.emit  ("      return ");
-                  } else {
-                      unit.emitln(" &&");
-                      unit.emit  ("             ");
-                  }
-                  if( jType.isPrimitive() || idx == javaCallback.setFuncUserParamIdx ) {
-                      unit.emit(name+" == o2."+name);
-                  } else {
-                      unit.emit(name+".equals( o2."+name+" )");
-                  }
-                  return true;
-              } else {
-                  return false;
-              }
-          } );
-          if( 0 == count ) {
-              unit.emit("      return true");
-          }
-          unit.emitln(";");
-      }
-      unit.emitln("    }");
-      unit.emitln("    @Override");
-      unit.emitln("    public int hashCode() {");
-      {
-          final int count = binding.forEachParameter( ( final int idx, final int consumedCount, final Type cType, final JavaType jType, final String name ) -> {
-              if( !cType.isVoid() && javaCallback.setFuncKeyIndices.contains(idx) ) {
-                  if( 0 == consumedCount ) {
-                      unit.emitln("      // 31 * x == (x << 5) - x");
-                      unit.emit  ("      int hash = ");
-                  } else {
-                      unit.emit  ("      hash = ((hash << 5) - hash) + ");
-                  }
-                  if( jType.isPrimitive() ) {
-                      if( jType.isLong() ) {
-                          unit.emitln("HashUtil.getAddrHash32_EqualDist( "+name+" );");
-                      } else {
-                          unit.emitln(name+";");
-                      }
-                  } else {
-                      if( idx == javaCallback.setFuncUserParamIdx ) {
-                          unit.emitln("System.identityHashCode( "+name+" );");
-                      } else {
-                          unit.emitln(name+".hashCode();");
-                      }
-                  }
-                  return true;
-              } else {
-                  return false;
-              }
-          } );
-          if( 0 == count ) {
-              unit.emitln("      return 0;");
-          } else {
-              unit.emitln("      return hash;");
-          }
-      }
-      unit.emitln("    }");
-      unit.emitln("  }");
-  }
-  private final void emitJavaCallbackDataClass(final String capIfaceName, final String dataClassName) {
-      unit.emitln("  private static class "+dataClassName+" {");
-      unit.emitln("    final "+javaCallback.cbFuncTypeName+" func;");
-      unit.emitln("    final Object param;");
-      unit.emitln("    final long nativeParam;");
-      unit.emitln("    "+dataClassName+"("+javaCallback.cbFuncTypeName+" func, Object param, long nativeParam) {");
-      unit.emitln("      this.func = func;");
-      unit.emitln("      this.param = param;");
-      unit.emitln("      this.nativeParam = nativeParam;");
-      unit.emitln("    }");
-      unit.emitln("  }");
+  @Override
+  protected void emitAdditionalCode() {
+    if( null != javaCallbackEmitter && !isPrivateNativeMethod ) {
+        javaCallbackEmitter.emitJavaAdditionalCode(unit, isInterface());
+    }
   }
 
   @Override
@@ -594,201 +485,6 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
       }
       unit.emitln("  }");
     }
-    if( null != javaCallback && !isPrivateNativeMethod ) {
-        final String capIfaceName = CodeGenUtils.capitalizeString( getInterfaceName() );
-        final String lowIfaceName = CodeGenUtils.decapitalizeString( getInterfaceName() );
-        final String lockInstanceName = lowIfaceName+"Lock";
-        final String dataMapInstanceName = lowIfaceName+"DataMap";
-        final String dataInstanceName = lowIfaceName+"Data";
-        final boolean customKeyClass;
-        final String KeyClassName;
-        final boolean useDataMap;
-        if( null != javaCallback.setFuncKeyClassName ) {
-            customKeyClass = true;;
-            KeyClassName = javaCallback.setFuncKeyClassName;
-            useDataMap = true;
-        } else {
-            customKeyClass = false;
-            KeyClassName = CodeGenUtils.capitalizeString(capIfaceName+"Key");
-            useDataMap = javaCallback.setFuncKeyIndices.size() > 0;
-        }
-        final String DataClassName = CodeGenUtils.capitalizeString( javaCallback.cbFuncTypeName+"Data" );
-        final String fqUsrParamClassName = cfg.packageName()+"."+cfg.className()+"."+DataClassName;
-        unit.emitln();
-        if( isInterface() ) {
-            if( useDataMap ) {
-                if( !customKeyClass && !javaCallback.keyClassEmitted ) {
-                    emitJavaCallbackKeyClass(capIfaceName, KeyClassName);
-                    unit.emitln();
-                    javaCallback.keyClassEmitted = true;
-                }
-                emitJavaCallbackBirefAPIDoc("Returns ", "set of ", "", "for ");
-                unit.emitln("  public Set<"+KeyClassName+"> get"+capIfaceName+"Keys();");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Returns ", "whether callback ", "if callback ", "is mapped for ");
-                unit.emitln("  public boolean is"+capIfaceName+"Mapped("+KeyClassName+" key);");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Returns "+javaCallback.cbFuncTypeName+" callback ", "mapped to ", "", "for ");
-                unit.emitln("  public "+javaCallback.cbFuncTypeName+" get"+capIfaceName+"("+KeyClassName+" key);");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Returns user-param ", "mapped to ", "", "for ");
-                unit.emitln("  public Object get"+capIfaceName+"UserParam("+KeyClassName+" key);");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Releases all callback data ", "mapped via ", "", "skipping toolkit API. Favor passing `null` callback ref to ");
-                unit.emitln("  public int releaseAll"+capIfaceName+"();");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Releases callback data ", "mapped to ", "", "skipping toolkit API. Favor passing `null` callback ref to ");
-                unit.emitln("  public void release"+capIfaceName+"("+KeyClassName+" key);");
-                unit.emitln();
-            } else {
-                emitJavaCallbackBirefAPIDoc("Returns ", "whether callback ", "if callback ", "is mapped for ");
-                unit.emitln("  public boolean is"+capIfaceName+"Mapped();");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Returns "+javaCallback.cbFuncTypeName+" callback ", "mapped to ", "", "for ");
-                unit.emitln("  public "+javaCallback.cbFuncTypeName+" get"+capIfaceName+"();");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Returns user-param ", "mapped to ", "", "for ");
-                unit.emitln("  public Object get"+capIfaceName+"UserParam();");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Releases callback data ", "", "", "skipping toolkit API. Favor passing `null` callback ref to ");
-                unit.emitln("  public void release"+capIfaceName+"();");
-                unit.emitln();
-            }
-        } else {
-            if( useDataMap ) {
-                if( !customKeyClass && !javaCallback.keyClassEmitted ) {
-                    emitJavaCallbackKeyClass(capIfaceName, KeyClassName);
-                    unit.emitln();
-                    javaCallback.keyClassEmitted = true;
-                }
-                emitJavaCallbackBirefAPIDoc("Returns ", "set of ", "", "for ");
-                unit.emitln("  public final Set<"+KeyClassName+"> get"+capIfaceName+"Keys() {");
-                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-                unit.emitln("      return "+dataMapInstanceName+".keySet();");
-                unit.emitln("    }");
-                unit.emitln("  }");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Returns ", "whether callback ", "if callback ", "is mapped for ");
-                unit.emitln("  public final boolean is"+capIfaceName+"Mapped("+KeyClassName+" key) {");
-                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-                unit.emitln("      return null != "+dataMapInstanceName+".get(key);");
-                unit.emitln("    }");
-                unit.emitln("  }");
-                unit.emitln();
-
-                emitJavaCallbackBirefAPIDoc("Returns "+javaCallback.cbFuncTypeName+" callback ", "mapped to ", "", "for ");
-                unit.emitln("  public final "+javaCallback.cbFuncTypeName+" get"+capIfaceName+"("+KeyClassName+" key) {");
-                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-                unit.emitln("      final "+DataClassName+" value = "+dataMapInstanceName+".get(key);");
-                unit.emitln("      return null != value ? value.func : null;");
-                unit.emitln("    }");
-                unit.emitln("  }");
-                unit.emitln();
-
-                emitJavaCallbackBirefAPIDoc("Returns user-param ", "mapped to ", "", "for ");
-                unit.emitln("  public final Object get"+capIfaceName+"UserParam("+KeyClassName+" key) {");
-                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-                unit.emitln("      final "+DataClassName+" value = "+dataMapInstanceName+".get(key);");
-                unit.emitln("      return null != value ? value.param : null;");
-                unit.emitln("    }");
-                unit.emitln("  }");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Releases all callback data ", "mapped via ", "", "skipping toolkit API. Favor passing `null` callback ref to ");
-                unit.emitln("  public final int releaseAll"+capIfaceName+"() {");
-                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-                unit.emitln("      final Set<"+KeyClassName+"> keySet = "+dataMapInstanceName+".keySet();");
-                unit.emitln("      final "+KeyClassName+"[] keys = keySet.toArray(new "+KeyClassName+"[keySet.size()]);");
-                unit.emitln("      for(int i=0; i<keys.length; ++i) {");
-                unit.emitln("        final "+KeyClassName+" key = keys[i];");
-                unit.emitln("          release"+capIfaceName+"(key);");
-                unit.emitln("      }");
-                unit.emitln("      return keys.length;");
-                unit.emitln("    }");
-                unit.emitln("  }");
-                unit.emitln();
-                emitJavaCallbackBirefAPIDoc("Releases callback data ", "mapped to ", "", "skipping toolkit API. Favor passing `null` callback ref to ");
-                unit.emitln("  public final void release"+capIfaceName+"("+KeyClassName+" key) {");
-                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-                unit.emitln("      final "+DataClassName+" value = "+dataMapInstanceName+".remove(key);");
-                if( DEBUG_JAVACALLBACK ) {
-                    unit.emitln("      System.err.println(\"ZZZ Release \"+key+\" -> value.nativeParam 0x\"+Long.toHexString(null!=value?value.nativeParam:0));");
-                }
-                unit.emitln("      if( null != value ) {");
-                unit.emitln("        release"+capIfaceName+"Impl(value.nativeParam);");
-                unit.emitln("      }");
-                unit.emitln("    }");
-                unit.emitln("  }");
-            } else {
-                emitJavaCallbackBirefAPIDoc("Returns ", "whether callback ", "if callback ", "is mapped for ");
-                unit.emitln("  public final boolean is"+capIfaceName+"Mapped() {");
-                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-                unit.emitln("      return null != "+dataInstanceName+";");
-                unit.emitln("    }");
-                unit.emitln("  }");
-                unit.emitln();
-
-                emitJavaCallbackBirefAPIDoc("Returns "+javaCallback.cbFuncTypeName+" callback ", "mapped to ", "", "for ");
-                unit.emitln("  public final "+javaCallback.cbFuncTypeName+" get"+capIfaceName+"() {");
-                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-                unit.emitln("      final "+DataClassName+" value = "+dataInstanceName+";");
-                unit.emitln("      return null != value ? value.func : null;");
-                unit.emitln("    }");
-                unit.emitln("  }");
-                unit.emitln();
-
-                emitJavaCallbackBirefAPIDoc("Returns user-param ", "mapped to ", "", "for ");
-                unit.emitln("  public final Object get"+capIfaceName+"UserParam() {");
-                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-                unit.emitln("      final "+DataClassName+" value = "+dataInstanceName+";");
-                unit.emitln("      return null != value ? value.param : null;");
-                unit.emitln("    }");
-                unit.emitln("  }");
-                unit.emitln();
-
-                emitJavaCallbackBirefAPIDoc("Releases callback data ", "", "", "skipping toolkit API. Favor passing `null` callback ref to ");
-                unit.emitln("  public final void release"+capIfaceName+"() {");
-                unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-                unit.emitln("      final "+DataClassName+" value = "+dataInstanceName+";");
-                unit.emitln("      "+dataInstanceName+" = null;");
-                if( DEBUG_JAVACALLBACK ) {
-                    unit.emitln("      System.err.println(\"ZZZ Release \"+key+\" -> value.nativeParam 0x\"+Long.toHexString(null!=value?value.nativeParam:0));");
-                }
-                unit.emitln("      if( null != value ) {");
-                unit.emitln("        release"+capIfaceName+"Impl(value.nativeParam);");
-                unit.emitln("      }");
-                unit.emitln("    }");
-                unit.emitln("  }");
-            }
-            unit.emitln("  private native void release"+capIfaceName+"Impl(long nativeUserParam);");
-            unit.emitln();
-            unit.emitln("  private final void add"+capIfaceName+"("+binding.getJavaSelectParameter(new StringBuilder(), javaCallback.setFuncKeyIndices, true).toString()+DataClassName+" value) {");
-            if( useDataMap ) {
-                unit.emitln("    final "+KeyClassName+" key = new "+KeyClassName+"("+binding.getJavaCallSelectArguments(new StringBuilder(), javaCallback.setFuncKeyIndices, false).toString()+");");
-                unit.emitln("    final "+DataClassName+" old = "+dataMapInstanceName+".put(key, value);");
-            } else {
-                unit.emitln("    final "+DataClassName+" old = "+dataInstanceName+";");
-                unit.emitln("    "+dataInstanceName+" = value;");
-            }
-            if( DEBUG_JAVACALLBACK ) {
-                unit.emitln("    System.err.println(\"ZZZ Map \"+key+\" -> value.nativeParam 0x\"+Long.toHexString(null!=value?value.nativeParam:0));");
-            }
-            unit.emitln("    if( null != old ) {");
-            unit.emitln("      release"+capIfaceName+"Impl(old.nativeParam);");
-            unit.emitln("    }");
-            unit.emitln("  }");
-            if( !cfg.emittedJavaCallbackUserParamClasses.contains(fqUsrParamClassName) ) {
-                emitJavaCallbackDataClass(capIfaceName, DataClassName);
-                cfg.emittedJavaCallbackUserParamClasses.add(fqUsrParamClassName);
-            }
-            if( useDataMap ) {
-                unit.emitln("  private final Map<"+KeyClassName+", "+DataClassName+"> "+dataMapInstanceName+" = new HashMap<"+KeyClassName+", "+DataClassName+">();");
-            } else {
-                unit.emitln("  private "+DataClassName+" "+dataInstanceName+" = null;");
-            }
-            unit.emitln("  private final Object "+lockInstanceName+" = new Object();");
-            unit.emitln();
-        }
-    }
   }
 
   protected void emitPrologueOrEpilogue(final List<String> code) {
@@ -901,15 +597,11 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
 
   protected void emitReturnVariableSetupAndCall(final MethodBinding binding) {
     final JavaType returnType = binding.getJavaReturnType();
+
     boolean needsResultAssignment = false;
-    final String capIfaceName = CodeGenUtils.capitalizeString( getInterfaceName() );
 
-    if( null != javaCallback ) {
-        final String lowIfaceName = CodeGenUtils.decapitalizeString( getInterfaceName() );
-        final String lockInstanceName = lowIfaceName+"Lock";
-        unit.emitln("    synchronized( "+lockInstanceName+" ) {");
-        unit.emitln("      final long[] nativeUserParam = { 0 };");
-        unit.emitln();
+    if( null != javaCallbackEmitter ) {
+        javaCallbackEmitter.emitJavaSetFuncPreCall(unit);
     }
     if (!returnType.isVoid()) {
       unit.emit("      ");
@@ -941,36 +633,9 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
     emitCall(binding);
     unit.emitln();
 
-    if( null != javaCallback ) {
-        final String funcArgName = binding.getArgumentName(javaCallback.setFuncCBParamIdx);
-        final String userParamArgName = binding.getArgumentName(javaCallback.setFuncUserParamIdx);
-        final String DataClassName = CodeGenUtils.capitalizeString( javaCallback.cbFuncTypeName+"Data" );
-        final String KeyClassName;
-        final boolean useDataMap;
-        if( null != javaCallback.setFuncKeyClassName ) {
-            KeyClassName = javaCallback.setFuncKeyClassName;
-            useDataMap = true;
-        } else {
-            KeyClassName = CodeGenUtils.capitalizeString(capIfaceName+"Key");
-            useDataMap = javaCallback.setFuncKeyIndices.size() > 0;
-        }
-        if( DEBUG_JAVACALLBACK ) {
-            unit.emitln("    System.err.println(\"ZZZ returned nativeUserParam 0x\"+Long.toHexString(nativeUserParam[0]));");
-        }
+    if( null != javaCallbackEmitter ) {
         unit.emitln();
-        unit.emitln("      if( 0 != nativeUserParam[0] ) {");
-        unit.emitln("          // callback registrated -> add will release a previously mapped instance ");
-        unit.emitln("          add"+capIfaceName+"("+binding.getJavaCallSelectArguments(new StringBuilder(), javaCallback.setFuncKeyIndices, true).toString()+
-                                                   "new "+DataClassName+"("+funcArgName+", "+userParamArgName+", nativeUserParam[0]));");
-        unit.emitln("      } else {");
-        unit.emitln("          // callback released (null func) -> release a previously mapped instance ");
-        if( useDataMap ) {
-            unit.emitln("          release"+capIfaceName+"( new "+KeyClassName+"( "+binding.getJavaCallSelectArguments(new StringBuilder(), javaCallback.setFuncKeyIndices, false).toString()+" ) );");
-        } else {
-            unit.emitln("          release"+capIfaceName+"();");
-        }
-        unit.emitln("      }");
-        unit.emitln("    } // synchronized ");
+        javaCallbackEmitter.emitJavaSetFuncPostCall(unit);
     }
 
     emitPostCallCleanup(binding);
@@ -1094,14 +759,13 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
       needComma = true;
       ++numArgsEmitted;
     }
-    if( null != javaCallback ) {
-        final String lowIfaceName = CodeGenUtils.decapitalizeString( getInterfaceName() );
-        final String lockInstanceName = lowIfaceName+"Lock";
+    if( null != javaCallbackEmitter ) {
         if (needComma) {
             unit.emit(", ");
         }
-        unit.emit("\"" + javaCallback.cbMethodSignature + "\", "+lockInstanceName+", nativeUserParam");
-        ++numArgsEmitted;
+        final StringBuilder buf = new StringBuilder();
+        numArgsEmitted += javaCallbackEmitter.appendJavaAdditionalJNIArguments(buf);
+        unit.emit(buf.toString());
     }
     return numArgsEmitted;
   }
@@ -1301,12 +965,11 @@ public class JavaMethodBindingEmitter extends FunctionEmitter {
     }
   }
 
-    protected class InterfaceCommentEmitter extends JavaMethodBindingEmitter.DefaultCommentEmitter {
-
-        @Override
-        protected void emitBeginning(final FunctionEmitter emitter, final PrintWriter writer) {
-            writer.print("Interface to C language function: <br> ");
-        }
+  protected class InterfaceCommentEmitter extends JavaMethodBindingEmitter.DefaultCommentEmitter {
+    @Override
+    protected void emitBeginning(final FunctionEmitter emitter, final PrintWriter writer) {
+        writer.print("Interface to C language function: <br> ");
     }
+  }
 }
 
diff --git a/src/java/com/jogamp/gluegen/JavaType.java b/src/java/com/jogamp/gluegen/JavaType.java
index 682a95a..3d6d839 100644
--- a/src/java/com/jogamp/gluegen/JavaType.java
+++ b/src/java/com/jogamp/gluegen/JavaType.java
@@ -334,6 +334,84 @@ public class JavaType {
   }
 
   /**
+   * Appends the descriptor (internal type signature) corresponding to the given Class<?> c.
+   * @param buf the StringBuilder sink
+   * @param c the Class<?> to append the descriptor for
+   * @param useTrueType if true, use the actual Class<?> name for non primitives, otherwise java.lang.Object will be used (flattened)
+   * @return the given StringBuilder sink for chaining
+   */
+  public static StringBuilder appendDescriptor(final StringBuilder buf, final Class<?> c, final boolean useTrueType) {
+    if (c.isPrimitive()) {
+           if (c == Boolean.TYPE)   buf.append("Z");
+      else if (c == Byte.TYPE)      buf.append("B");
+      else if (c == Character.TYPE) buf.append("C");
+      else if (c == Short.TYPE)     buf.append("S");
+      else if (c == Integer.TYPE)   buf.append("I");
+      else if (c == Long.TYPE)      buf.append("J");
+      else if (c == Float.TYPE)     buf.append("F");
+      else if (c == Double.TYPE)    buf.append("D");
+      else throw new RuntimeException("Illegal primitive type \"" + c.getName() + "\"");
+    } else {
+      // Arrays and NIO Buffers are always passed down as java.lang.Object.
+      // The only arrays that show up as true arrays in the signature
+      // are the synthetic byte offset arrays created when passing
+      // down arrays of direct Buffers. Compound type wrappers are
+      // passed down as ByteBuffers (no good reason, just to avoid
+      // accidental conflation) so we mangle them differently.
+      if (useTrueType) {
+        if (c.isArray()) {
+          buf.append("[");
+          final Class<?> componentType = c.getComponentType();
+          // Handle arrays of compound type wrappers differently for
+          // convenience of the Java-level glue code generation
+          appendDescriptor(buf, componentType,
+                    (componentType == java.nio.ByteBuffer.class));
+        } else {
+          buf.append("L");
+          buf.append(c.getName().replace('.', '/'));
+          buf.append(";");
+        }
+      } else {
+        if (c.isArray()) {
+          buf.append("[");
+          appendDescriptor(buf, c.getComponentType(), false);
+        } else if (c == java.lang.String.class) {
+          buf.append("L");
+          buf.append(c.getName().replace('.', '/'));
+          buf.append(";");
+        } else {
+          buf.append("L");
+          buf.append("java_lang_Object");
+          buf.append(";");
+        }
+      }
+    }
+    return buf;
+  }
+
+  /**
+   * Appends the native (JNI) method-name descriptor corresponding to the given Class<?> c,
+   * i.e. replacing chars {@link #appendDescriptor(StringBuilder, Class, boolean)} as follows
+   * <ul>
+   *   <li>`_` -> `_1`</li>
+   *   <li>`/` ->  `_`</li>
+   *   <li>`;` -> `_2`</li>
+   *   <li>`[` -> `_3`</li>
+   * </ul>
+   * Only the newly appended segment to the StringBuilder sink will be converted to (JNI) method-name using {@link #toJNIMethodDescriptor(StringBuilder, int)}.
+   * @param buf the StringBuilder sink
+   * @param c the Class<?> to append the descriptor for
+   * @param useTrueType if true, use the actual Class<?> name for non primitives, otherwise java.lang.Object will be used (flattened)
+   * @return the given StringBuilder sink for chaining
+   * @see JNI Spec 2, Chapter 2, Resolving Native Method Names
+   * @see #toJNIMethodDescriptor(StringBuilder)
+   */
+  public static StringBuilder appendJNIDescriptor(final StringBuilder res, final Class<?> c, final boolean useTrueType) {
+      final int start = res.length();
+      return toJNIMethodDescriptor( appendDescriptor(res, c, useTrueType), start );
+  }
+
+  /**
    * Converts the assumed descriptor (internal type signature) to a native (JNI) method-name descriptor,
    * i.e. replacing chars {@link #getDescriptor()} as follows
    * <ul>
@@ -342,6 +420,7 @@ public class JavaType {
    *   <li>`;` -> `_2`</li>
    *   <li>`[` -> `_3`</li>
    * </ul>
+   * @param descriptor the char sequence holding the original descriptor
    * @see JNI Spec 2, Chapter 2, Resolving Native Method Names
    */
   public static String toJNIMethodDescriptor(final String descriptor) {
@@ -351,6 +430,36 @@ public class JavaType {
                        .replace("[", "_3");
   }
 
+  /**
+   * Converts the assumed descriptor (internal type signature) to a native (JNI) method-name descriptor,
+   * i.e. replacing chars {@link #getDescriptor()} as follows
+   * <ul>
+   *   <li>`_` -> `_1`</li>
+   *   <li>`/` ->  `_`</li>
+   *   <li>`;` -> `_2`</li>
+   *   <li>`[` -> `_3`</li>
+   * </ul>
+   * @param descriptor the char buffer holding the original descriptor
+   * @param start start position of the segment to convert, use 0 if whole buffr shall be converted
+   * @return returns passed descriptor buffer for chaining
+   * @see JNI Spec 2, Chapter 2, Resolving Native Method Names
+   */
+  public static StringBuilder toJNIMethodDescriptor(final StringBuilder descriptor, final int start) {
+      replace(descriptor, start, "_", "_1");
+      replace(descriptor, start, "/",  "_");
+      replace(descriptor, start, ";", "_2");
+      replace(descriptor, start, "[", "_3");
+      return descriptor;
+  }
+  private static StringBuilder replace(final StringBuilder buf, int start, final String target, final String replacement) {
+      start = buf.indexOf(target, start);
+      while( 0 <= start ) {
+          buf.replace(start, start + target.length(), replacement);
+          start = buf.indexOf(target, start + replacement.length());
+      }
+      return buf;
+  }
+
   /** Returns the String corresponding to the JNI type for this type,
       or NULL if it can't be represented (i.e., it's a boxing class
       that we need to call getBuffer() on.) */
diff --git a/src/java/com/jogamp/gluegen/procaddress/ProcAddressCMethodBindingEmitter.java b/src/java/com/jogamp/gluegen/procaddress/ProcAddressCMethodBindingEmitter.java
index a280d6e..c20b07a 100644
--- a/src/java/com/jogamp/gluegen/procaddress/ProcAddressCMethodBindingEmitter.java
+++ b/src/java/com/jogamp/gluegen/procaddress/ProcAddressCMethodBindingEmitter.java
@@ -102,17 +102,16 @@ public class ProcAddressCMethodBindingEmitter extends CMethodBindingEmitter {
     }
 
     @Override
-    protected int emitArguments() {
-        int numEmitted = super.emitArguments();
+    protected int appendArguments(final StringBuilder buf) {
+        int numEmitted = super.appendArguments(buf);
         if (callThroughProcAddress) {
             if (numEmitted > 0) {
-                unit.emit(", ");
+                buf.append(", ");
             }
-            unit.emit(procAddressJavaTypeName);
-            unit.emit(" procAddress");
+            buf.append(procAddressJavaTypeName);
+            buf.append(" procAddress");
             ++numEmitted;
         }
-
         return numEmitted;
     }
 
@@ -224,7 +223,7 @@ public class ProcAddressCMethodBindingEmitter extends CMethodBindingEmitter {
     protected String jniMangle(final MethodBinding binding) {
         final StringBuilder buf = new StringBuilder(super.jniMangle(binding));
         if (callThroughProcAddress && 0 <= buf.indexOf("__") ) {
-            getJNIMangledArg(Long.TYPE, buf, false);  // to account for the additional _addr_ parameter
+            JavaType.appendJNIDescriptor(buf, Long.TYPE, false);  // to account for the additional _addr_ parameter
         }
         return buf.toString();
     }
diff --git a/src/java/com/jogamp/gluegen/procaddress/ProcAddressJavaMethodBindingEmitter.java b/src/java/com/jogamp/gluegen/procaddress/ProcAddressJavaMethodBindingEmitter.java
index 0d5de1c..b6ed21b 100644
--- a/src/java/com/jogamp/gluegen/procaddress/ProcAddressJavaMethodBindingEmitter.java
+++ b/src/java/com/jogamp/gluegen/procaddress/ProcAddressJavaMethodBindingEmitter.java
@@ -91,19 +91,18 @@ public class ProcAddressJavaMethodBindingEmitter extends JavaMethodBindingEmitte
     }
 
     @Override
-    protected int emitArguments() {
-        int numEmitted = super.emitArguments();
+    protected int appendArguments(final StringBuilder buf) {
+        int numEmitted = super.appendArguments(buf);
         if (callThroughProcAddress) {
             if (changeNameAndArguments) {
                 if (numEmitted > 0) {
-                    unit.emit(", ");
+                    buf.append(", ");
                 }
 
-                unit.emit("long procAddress");
+                buf.append("long procAddress");
                 ++numEmitted;
             }
         }
-
         return numEmitted;
     }