Launch JVM through JNI_CreateJavaVM in OSX is console-only - cocoa

Question

I am trying to launch JVM from my C/ObjC program, but I have some issues displaying visual elements, like for example a window, on Catalina.
The part of the program that uses non-visual items, i.e. console & System.out works fine. But not any application window appears, although a proper Dock icon appears, which when clicked it does nothing.
I have written a helper function, to launch JVM. As arguments it has
the location of the libjvm.dylib
the JVM options
the size of the jvm options
the main arguments
the size of the main arguments
the main class
I looks to me that I am missing something, but I can't figure out what. Any ideas?
Here is the code:
typedef jint (*JNI_CreateJavaVM_f)(JavaVM **, void **, void *);
int launchjvm(char *jvmlib, char **jvmopts, int c_jvmopts, char **args, int c_args, char *mainclass)
{
JavaVM *vm;
JNIEnv *env;
JavaVMInitArgs vm_args;
JavaVMOption options[c_jvmopts];
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
memset(&vm_args, 0, sizeof(vm_args));
vm_args.version = JNI_VERSION_1_8;
vm_args.ignoreUnrecognized = JNI_TRUE;
for (int i = 0; i < c_jvmopts; i++)
options[i].optionString = jvmopts[i];
vm_args.options = options;
vm_args.nOptions = c_jvmopts;
void *lib_handle = dlopen(jvmlib, RTLD_LOCAL | RTLD_LAZY);
if (!lib_handle)
{
printf("[%s] Unable to load library: %s\n", __FILE__, dlerror());
return 1;
}
JNI_CreateJavaVM_f JNI_CreateJavaVM = dlsym(lib_handle, "JNI_CreateJavaVM");
if (!JNI_CreateJavaVM)
{
printf("[%s] Unable to get symbol: %s\n", __FILE__, dlerror());
return 1;
}
jint res = JNI_CreateJavaVM(&vm, (void **)&env, &vm_args);
if (res != JNI_OK)
{
printf("Failed to create Java VM\n");
return res;
}
jclass cls = (*env)->FindClass(env, mainclass);
if (cls == NULL)
{
printf("Failed to find %s class\n", mainclass);
return 1;
}
jmethodID mid = (*env)->GetStaticMethodID(env, cls, "main", "([Ljava/lang/String;)V");
if (mid == NULL)
{
printf("Failed to find main function in class %s\n", mainclass);
return 2;
}
jobjectArray main_args = (*env)->NewObjectArray(env, c_args, (*env)->FindClass(env, "java/lang/String"), NULL);
for(int i = 0 ; i < c_args ; i++)
(*env)->SetObjectArrayElement(env, main_args, i, (*env)->NewStringUTF(env, args[i]));
int result = 0;
(*env)->CallStaticVoidMethod(env, cls, mid, main_args);
if ((*env)->ExceptionOccurred(env)) { // check if an exception occurred
(*env)->ExceptionDescribe(env); // print the stack trace
result = -1;
}
(*vm)->DestroyJavaVM(vm);
[pool drain];
return result;
}