More engine API work

UIXrender/Engine/ContextRegistry.cs

@@ -1,35 +1,21 @@
-using System;
 using System.Collections.Concurrent;
 using Microsoft.Iris.Render.Interop;
 
 namespace Microsoft.Iris.Render.Engine;
 
-// Maps a registered ContextID to the buffer-processing callback it should receive
-// deliveries on, via SpBufferOpen -- the smallest coherent slice of "Engine core" (see
-// logs/UIXrender/EngineCore.md) needed for SpRenderThreadInit and SpBufferOpen to mean
-// anything together. Callback stored as a raw IntPtr (not a typed function pointer
-// field) so nothing here needs to be unsafe/deal with function-pointer-as-generic-arg
-// concerns; callers cast at the point they actually invoke it.
+// Maps a registered ContextID to the handler it should receive deliveries on via
+// SendBuffer -- the smallest coherent slice of "Engine core" (see
+// logs/UIXrender/EngineCore.md) needed for StartRenderThread and SendBuffer to mean
+// anything together. Holds an ordinary delegate now (not a raw callback pointer) --
+// pointer marshaling, where it's still needed for native callers, lives entirely in
+// Interop/EngineApi.cs.
 internal static class ContextRegistry
 {
-    internal readonly struct Entry
-    {
-        public readonly IntPtr Callback;
-        public readonly IntPtr CallbackData;
+    private static readonly ConcurrentDictionary<uint, BufferReceivedHandler> s_contexts = new();
 
-        public Entry(IntPtr callback, IntPtr callbackData)
-        {
-            Callback = callback;
-            CallbackData = callbackData;
-        }
-    }
-
-    private static readonly ConcurrentDictionary<uint, Entry> s_contexts = new();
-
-    public static void Register(ContextID id, IntPtr callback, IntPtr callbackData)
-        => s_contexts[id.value] = new Entry(callback, callbackData);
+    public static void Register(ContextID id, BufferReceivedHandler handler) => s_contexts[id.value] = handler;
 
     public static void Unregister(ContextID id) => s_contexts.TryRemove(id.value, out _);
 
-    public static bool TryGet(ContextID id, out Entry entry) => s_contexts.TryGetValue(id.value, out entry);
+    public static bool TryGet(ContextID id, out BufferReceivedHandler handler) => s_contexts.TryGetValue(id.value, out handler);
 }