xash3d-fwgs/Documentation/extensions/native-object.md

GetNativeObject API

To be able to use platform-specific features or get optional engine interfaces, we've added a simple call to MobilityAPI on client DLL and PhysicsAPI for server DLL and extended MenuAPI for menu DLL.

It's defined like this:

void *pfnGetNativeObject( const char *name );

Cross-platform objects

Only these objects are guaranteed to be available on all targets.

Object name	Interface
VFileSystem009	Provides C++ interface to filesystem, binary-compatible with Valve's VFileSystem009.
XashFileSystemXXX	Provides C interface to filesystem. This interface is unstable and not recommended for generic use, outside of engine internals. For more info about current version look into filesystem.h.
MenuFactory	Returns a CreateInterface function pointer (pfnCreateInterface_t) for the currently loaded menu library.

Android-specific objects

Object name	Interface
JNIEnv	Allows interfacing with Java Native Interface.
ActivityClass	Returns JNI object for engine Android activity class.