gzdoom/wadsrc/static/zscript/events.txt

class EventHandler : Object native
{
	static native EventHandler Create(class<EventHandler> type);
	static native EventHandler CreateOnce(class<EventHandler> type);
	static native EventHandler Find(class<EventHandler> type);

	static native bool Register(EventHandler handler);
	static native bool Unregister(EventHandler handler);

	virtual native void MapLoaded();
	virtual native void MapUnloading();

	virtual native void RenderFrame();
	virtual native void RenderCamera();
	virtual native void RenderBeforeThing();
	virtual native void RenderAfterThing();
}

class RenderEventHandler : EventHandler native
{
	// for frame and camera
	native readonly Vector3 ViewPos;
	native readonly double ViewAngle;
	native readonly double ViewPitch;
	native readonly double ViewRoll;
	native readonly double FracTic;
	// for camera
	native readonly Actor Camera;
	// for thing
	native readonly Actor CurrentThing;
}