libvlc_renderer_item_hold call is currently failing

LibVLCSharp.Tests/RendererDiscovererTests.cs

-using System.Threading.Tasks;
+using System.Linq;
+using System.Threading.Tasks;
 using NUnit.Framework;
 using VideoLAN.LibVLC;
 using static System.Diagnostics.Debug;
@@ -9,12 +10,13 @@ namespace LibVLCSharp.Tests
     public class RendererDiscovererTests
     {
         [Test]
-        public async Task T()
+        public async Task DiscoverItems()
         {
             var instance = new Instance();
 
             var rendererDiscoverer = new RendererDiscoverer(instance, "microdns");
             var em = rendererDiscoverer.EventManager;
+            var itemAdded = false;
 
             em.ItemAdded += (sender, args) =>
             {
@@ -23,12 +25,22 @@ namespace LibVLCSharp.Tests
                     WriteLine("Can render video");
                 if(args.RendererItem.CanRenderAudio)
                     WriteLine("Can render audio");
+                itemAdded = true;
             };
 
             if(!rendererDiscoverer.Start())
                 NUnit.Framework.Assert.Fail();
 
-            await Task.Delay(1000);
+            await Task.Delay(10000);
+
+            NUnit.Framework.Assert.True(itemAdded);
+        }
+
+        [Test]
+        public void RetrieveListInformation()
+        {
+            var rd = new RendererDiscoverer(new Instance(), "rd");
+            NUnit.Framework.Assert.Positive(rd.List.Length);
         }
     }
 }

LibVLCSharp/RendererDiscoverer.cs

@@ -6,6 +6,8 @@ namespace VideoLAN.LibVLC
 {
     public class RendererDiscoverer : Internal
     {
+        readonly IntPtr _instanceNativeReference;
+
         struct Native
         {
             [SuppressUnmanagedCodeSecurity]
@@ -36,17 +38,18 @@ namespace VideoLAN.LibVLC
             [SuppressUnmanagedCodeSecurity]
             [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl,
                 EntryPoint = "libvlc_renderer_discoverer_list_get")]
-            internal static extern UIntPtr LibVLCRendererDiscovererGetList(IntPtr instance, out IntPtr discovererList);
+            internal static extern ulong LibVLCRendererDiscovererGetList(IntPtr instance, ref IntPtr discovererList);
             
             [SuppressUnmanagedCodeSecurity]
             [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl,
                 EntryPoint = "libvlc_renderer_discoverer_list_release")]
-            internal static extern void LibVLCRendererDiscovererReleaseList(IntPtr discovererList, UIntPtr count);
+            internal static extern void LibVLCRendererDiscovererReleaseList(IntPtr discovererList, ulong count);
         }
 
         public RendererDiscoverer(Instance instance, string name) 
             : base(() => Native.LibVLCRendererDiscovererNew(instance.NativeReference, name), Native.LibVLCRendererDiscovererRelease)
         {
+            _instanceNativeReference = instance.NativeReference;
         }
 
         RendererDiscovererEventManager _eventManager;
@@ -67,6 +70,42 @@ namespace VideoLAN.LibVLC
         public bool Start() => Native.LibVLCRendererDiscovererStart(NativeReference) == 0;
 
         public void Stop() => Native.LibVLCRendererDiscovererStop(NativeReference);
+
+        public Description[] List
+        {
+            get
+            {
+                var discoverList = IntPtr.Zero;
+                var count = Native.LibVLCRendererDiscovererGetList(_instanceNativeReference, ref discoverList);
+
+                if (count == 0) return Array.Empty<Description>();
+
+                var rendererDiscovererDescription = new Description[(int)count];
+
+                for (var i = 0; i < (int)count; i++)
+                {
+                    var ptr = Marshal.ReadIntPtr(discoverList, i * IntPtr.Size);
+                    var managedStruct = (Description)Marshal.PtrToStructure(ptr, typeof(Description));
+                    rendererDiscovererDescription[i] = managedStruct;
+                }
+
+                Native.LibVLCRendererDiscovererReleaseList(discoverList, count);
+
+                return rendererDiscovererDescription;
+            }
+        }
+
+        public struct Description
+        {
+            public string Name { get; }
+            public string LongName { get; }
+
+            public Description(string name, string longName)
+            {
+                Name = name;
+                LongName = longName;
+            }
+        }
     }
 
     public class RendererItem : Internal
@@ -109,7 +148,7 @@ namespace VideoLAN.LibVLC
 
         public RendererItem(IntPtr reference) : base(() => reference, Native.LibVLCRendererItemRelease)
         {
-            Native.LibVLCRendererItemHold(reference);
+            Native.LibVLCRendererItemHold(reference); //fail
         }
 
         public string Name => Native.LibVLCRendererItemName(NativeReference);