From 05c087eddd689940bf58efcea6b98d959d5a198c Mon Sep 17 00:00:00 2001
From: Dan Siegel <me@dansiegel.net>
Date: Mon, 20 Feb 2023 21:04:40 -0600
Subject: [PATCH] fix: issue with WASM not loading

---
 .../DependencyObjectExtensions.Uno.cs         | 49 ++++++++++---------
 1 file changed, 25 insertions(+), 24 deletions(-)

diff --git a/src/Uno/Prism.Uno/Extensions/DependencyObjectExtensions.Uno.cs b/src/Uno/Prism.Uno/Extensions/DependencyObjectExtensions.Uno.cs
index 462a89c988..7d6541f1f7 100644
--- a/src/Uno/Prism.Uno/Extensions/DependencyObjectExtensions.Uno.cs
+++ b/src/Uno/Prism.Uno/Extensions/DependencyObjectExtensions.Uno.cs
@@ -1,43 +1,44 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
+using System.Runtime.InteropServices;
 using Microsoft.UI.Xaml;
-using Microsoft.UI.Xaml.Data;
-using Windows.Foundation.Metadata;
 
 namespace Prism
 {
     internal static partial class DependencyObjectExtensions
     {
+#if HAS_UNO_WINUI
+        // Related to :
+        // https://github.com/dotnet/runtime/issues/76959
+        // https://github.com/unoplatform/uno/blob/56d3f6ece16b2dba51776e95a3c847c9c4b68e8b/src/Uno.UI.Dispatching/Core/CoreDispatcher.wasm.cs#L17
+        private static bool IsWebAssemblyThreadingSupported { get; }
+            = Environment.GetEnvironmentVariable("UNO_BOOTSTRAP_MONO_RUNTIME_FEATURES")
+                ?.Split(',').Any(v => v.Equals("threads", StringComparison.OrdinalIgnoreCase)) ?? false;
+
+        private static bool IsWebAssembly { get; }
+            = RuntimeInformation.IsOSPlatform(OSPlatform.Create("BROWSER"));
+#endif
+
         /// <summary>
         /// Compatibility method to determine if the current thread can access a <see cref="DependencyObject"/>
         /// </summary>
         /// <param name="instance">The instance to check</param>
         /// <returns><c>true</c> if the current thread has access to the instance, otherwise <c>false</c></returns>
         public static bool CheckAccess(this DependencyObject instance)
-#if __WASM__
-            // This needs to evolve, once threading is supported
-            // See https://github.com/unoplatform/uno/issues/2302
-            => System.Threading.Thread.CurrentThread.ManagedThreadId == 1;
-#elif HAS_WINUI
-#if NETCOREAPP
-            => instance.DispatcherQueue.HasThreadAccess;
-#else
+#if HAS_WINUI
+#if HAS_UNO_WINUI
+        {
+            if (IsWebAssembly && !IsWebAssemblyThreadingSupported)
             {
-                // Dispatcher queue HasThreadAccess is not yet implemented in Uno, we can fall back on CoreDispatcher
-                // See https://github.com/unoplatform/uno/issues/5818
-                if(ApiInformation.IsPropertyPresent("Microsoft.UI.Dispatching.DispatcherQueue", nameof(Microsoft.UI.Dispatching.DispatcherQueue.HasThreadAccess)))
-                {
-                    return instance.DispatcherQueue.HasThreadAccess;
-                }
-                else
-                {
-                    return instance.Dispatcher.HasThreadAccess;
-                }
+                // When threading is disabled, we need to return true 
+                return true;
             }
+
+            return instance.DispatcherQueue.HasThreadAccess;
+        }
+#else
+        => instance.DispatcherQueue.HasThreadAccess;
 #endif
 #else
-            => instance.Dispatcher.HasThreadAccess;
+        => instance.Dispatcher.HasThreadAccess;
 #endif
     }
 }