static void OverridePrePushFrame(GLib.GType gtype, PrePushFrameNativeDelegate callback)
 {
     unsafe {
         IntPtr *raw_ptr = (IntPtr *)(((long)gtype.GetClassPtr()) + (long)class_abi.GetFieldOffset("pre_push_frame"));
         *raw_ptr = Marshal.GetFunctionPointerForDelegate((Delegate)callback);
     }
 }
        private Gst.FlowReturn InternalPrePushFrame(Gst.Base.BaseParseFrame frame)
        {
            PrePushFrameNativeDelegate unmanaged = null;

            unsafe {
                IntPtr *raw_ptr = (IntPtr *)(((long)this.LookupGType().GetThresholdType().GetClassPtr()) + (long)class_abi.GetFieldOffset("pre_push_frame"));
                unmanaged = (PrePushFrameNativeDelegate)Marshal.GetDelegateForFunctionPointer(*raw_ptr, typeof(PrePushFrameNativeDelegate));
            }
            if (unmanaged == null)
            {
                return((Gst.FlowReturn) 0);
            }

            IntPtr native_frame = GLib.Marshaller.StructureToPtrAlloc(frame);
            int    __result     = unmanaged(this.Handle, native_frame);

            Marshal.FreeHGlobal(native_frame);
            return((Gst.FlowReturn)__result);
        }