Merge pull request #46 from AArnott/fix43

Sleep the WinForms thread without spinning
AArnott · May 16, 2020 · 3f3c5c5 · 3f3c5c5
2 parents 68790c2 + 5a0b218
commit 3f3c5c5
Showing 1 changed file with 20 additions and 1 deletion.
diff --git a/src/Xunit.StaFact/Sdk.Desktop/WinFormsSynchronizationContextAdapter.cs b/src/Xunit.StaFact/Sdk.Desktop/WinFormsSynchronizationContextAdapter.cs
@@ -4,6 +4,8 @@
 namespace Xunit.Sdk
 {
     using System;
+    using System.ComponentModel;
+    using System.Runtime.InteropServices;
     using System.Threading;
     using System.Threading.Tasks;
     using System.Windows.Forms;
@@ -12,6 +14,12 @@ internal class WinFormsSynchronizationContextAdapter : SyncContextAdapter
     {
         internal static readonly SyncContextAdapter Default = new WinFormsSynchronizationContextAdapter();
 
+#pragma warning disable SA1310 // Field names should not contain underscore
+        private const uint MWMO_INPUTAVAILABLE = 0x0004;
+        private const uint QS_ALLINPUT = 0x04FF;
+        private const uint WAIT_FAILED = 0xFFFFFFFF;
+#pragma warning restore SA1310 // Field names should not contain underscore
+
         private WinFormsSynchronizationContextAdapter()
         {
         }
@@ -30,10 +38,21 @@ internal override void PumpTill(SynchronizationContext synchronizationContext, T
             while (!task.IsCompleted)
             {
                 Application.DoEvents();
-                Thread.Sleep(0); // give up thread to OS so we don't spin CPU too hard
+                if (MsgWaitForMultipleObjectsEx(0, IntPtr.Zero, 250, QS_ALLINPUT, MWMO_INPUTAVAILABLE) == WAIT_FAILED)
+                {
+                    throw new Win32Exception();
+                }
             }
         }
 
         internal override void InitializeThread() => Application.OleRequired();
+
+        [DllImport("user32", SetLastError = true)]
+        private static extern uint MsgWaitForMultipleObjectsEx(
+            uint nCount,
+            IntPtr pHandles,
+            uint dwMilliseconds,
+            uint dwWakeMask,
+            uint dwFlags);
     }
 }