From 0befa22692d1fa32652f621042bc54188a7b5769 Mon Sep 17 00:00:00 2001
From: Nicolas Musset <musset.nicolas@gmail.com>
Date: Tue, 28 Aug 2018 21:49:34 +0900
Subject: [PATCH] Support invoking a task in the dispatcher.

---
 src/Avalonia.Base/Threading/Dispatcher.cs     | 14 ++++++++++++++
 src/Avalonia.Base/Threading/IDispatcher.cs    | 18 ++++++++++++++++++
 .../Avalonia.UnitTests/ImmediateDispatcher.cs | 19 ++++++++++++++++++-
 3 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Base/Threading/Dispatcher.cs b/src/Avalonia.Base/Threading/Dispatcher.cs
index aa2a7a7a8e..55a9b6984a 100644
--- a/src/Avalonia.Base/Threading/Dispatcher.cs
+++ b/src/Avalonia.Base/Threading/Dispatcher.cs
@@ -92,6 +92,20 @@ namespace Avalonia.Threading
             return _jobRunner.InvokeAsync(function, priority);
         }
 
+        /// <inheritdoc/>
+        public Task InvokeAsync(Func<Task> function, DispatcherPriority priority = DispatcherPriority.Normal)
+        {
+            Contract.Requires<ArgumentNullException>(function != null);
+            return _jobRunner.InvokeAsync(function, priority).Unwrap();
+        }
+
+        /// <inheritdoc/>
+        public Task<TResult> InvokeAsync<TResult>(Func<Task<TResult>> function, DispatcherPriority priority = DispatcherPriority.Normal)
+        {
+            Contract.Requires<ArgumentNullException>(function != null);
+            return _jobRunner.InvokeAsync(function, priority).Unwrap();
+        }
+
         /// <inheritdoc/>
         public void Post(Action action, DispatcherPriority priority = DispatcherPriority.Normal)
         {
diff --git a/src/Avalonia.Base/Threading/IDispatcher.cs b/src/Avalonia.Base/Threading/IDispatcher.cs
index 1fdc9da5fe..8f46f99283 100644
--- a/src/Avalonia.Base/Threading/IDispatcher.cs
+++ b/src/Avalonia.Base/Threading/IDispatcher.cs
@@ -40,5 +40,23 @@ namespace Avalonia.Threading
         /// <param name="function">The method.</param>
         /// <param name="priority">The priority with which to invoke the method.</param>
         Task<TResult> InvokeAsync<TResult>(Func<TResult> function, DispatcherPriority priority = DispatcherPriority.Normal);
+
+        /// <summary>
+        /// Queues the specified work to run on the dispatcher thread and returns a proxy for the
+        /// task returned by <paramref name="function"/>.
+        /// </summary>
+        /// <param name="function">The work to execute asynchronously.</param>
+        /// <param name="priority">The priority with which to invoke the method.</param>
+        /// <returns>A task that represents a proxy for the task returned by <paramref name="function"/>.</returns>
+        Task InvokeAsync(Func<Task> function, DispatcherPriority priority = DispatcherPriority.Normal);
+
+        /// <summary>
+        /// Queues the specified work to run on the dispatcher thread and returns a proxy for the
+        /// task returned by <paramref name="function"/>.
+        /// </summary>
+        /// <param name="function">The work to execute asynchronously.</param>
+        /// <param name="priority">The priority with which to invoke the method.</param>
+        /// <returns>A task that represents a proxy for the task returned by <paramref name="function"/>.</returns>
+        Task<TResult> InvokeAsync<TResult>(Func<Task<TResult>> function, DispatcherPriority priority = DispatcherPriority.Normal);
     }
 }
\ No newline at end of file
diff --git a/tests/Avalonia.UnitTests/ImmediateDispatcher.cs b/tests/Avalonia.UnitTests/ImmediateDispatcher.cs
index 44d8c78054..fac4ee64e7 100644
--- a/tests/Avalonia.UnitTests/ImmediateDispatcher.cs
+++ b/tests/Avalonia.UnitTests/ImmediateDispatcher.cs
@@ -9,28 +9,45 @@ namespace Avalonia.UnitTests
     /// </summary>
     public class ImmediateDispatcher : IDispatcher
     {
+        /// <inheritdoc/>
         public bool CheckAccess()
         {
             return true;
         }
 
+        /// <inheritdoc/>
         public void Post(Action action, DispatcherPriority priority = DispatcherPriority.Normal)
         {
             action();
         }
 
+        /// <inheritdoc/>
         public Task InvokeAsync(Action action, DispatcherPriority priority = DispatcherPriority.Normal)
         {
             action();
-            return Task.FromResult<object>(null);
+            return Task.CompletedTask;
         }
 
+        /// <inheritdoc/>
         public Task<TResult> InvokeAsync<TResult>(Func<TResult> function, DispatcherPriority priority = DispatcherPriority.Normal)
         {
             var result = function();
             return Task.FromResult(result);
         }
 
+        /// <inheritdoc/>
+        public Task InvokeAsync(Func<Task> function, DispatcherPriority priority = DispatcherPriority.Normal)
+        {
+            return function();
+        }
+        
+        /// <inheritdoc/>
+        public Task<TResult> InvokeAsync<TResult>(Func<Task<TResult>> function, DispatcherPriority priority = DispatcherPriority.Normal)
+        {
+            return function();
+        }
+        
+        /// <inheritdoc/>
         public void VerifyAccess()
         {
         }