From 7ec33b1bc5c37544e1b59be65298544f780b6796 Mon Sep 17 00:00:00 2001
From: Daniel Grunwald <daniel@danielgrunwald.de>
Date: Fri, 20 Mar 2009 13:02:22 +0000
Subject: [PATCH] Don't constantly create new threads to poll the clipboard.

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/branches/3.0@3892 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61
---
 .../Project/ICSharpCode.SharpDevelop.csproj   |   1 +
 .../Src/TextEditor/ClipboardHandling.cs       |  34 +++---
 .../Base/Project/Src/Util/WorkerThread.cs     | 105 ++++++++++++++++++
 3 files changed, 124 insertions(+), 16 deletions(-)
 create mode 100644 src/Main/Base/Project/Src/Util/WorkerThread.cs

diff --git a/src/Main/Base/Project/ICSharpCode.SharpDevelop.csproj b/src/Main/Base/Project/ICSharpCode.SharpDevelop.csproj
index 013f671baa..159bc2e922 100644
--- a/src/Main/Base/Project/ICSharpCode.SharpDevelop.csproj
+++ b/src/Main/Base/Project/ICSharpCode.SharpDevelop.csproj
@@ -717,6 +717,7 @@
     <Compile Include="Src\Util\GenericConverter.cs" />
     <Compile Include="Src\Internal\Templates\TemplateLoadException.cs" />
     <Compile Include="Src\Util\UnclosableStream.cs" />
+    <Compile Include="Src\Util\WorkerThread.cs" />
     <EmbeddedResource Include="Resources\DefaultManifest.manifest" />
     <EmbeddedResource Include="Src\Gui\Dialogs\ExtractInterfaceDialog.resx">
       <DependentUpon>ExtractInterfaceDialog.cs</DependentUpon>
diff --git a/src/Main/Base/Project/Src/TextEditor/ClipboardHandling.cs b/src/Main/Base/Project/Src/TextEditor/ClipboardHandling.cs
index 82a2117efa..83575e204c 100644
--- a/src/Main/Base/Project/Src/TextEditor/ClipboardHandling.cs
+++ b/src/Main/Base/Project/Src/TextEditor/ClipboardHandling.cs
@@ -5,9 +5,10 @@
 //     <version>$Revision$</version>
 // </file>
 
-using ICSharpCode.Core.WinForms;
+using ICSharpCode.SharpDevelop.Util;
 using System;
 using System.Threading;
+using ICSharpCode.Core.WinForms;
 using ICSharpCode.SharpDevelop.Gui;
 
 namespace ICSharpCode.SharpDevelop.DefaultEditor
@@ -36,7 +37,7 @@ namespace ICSharpCode.SharpDevelop.DefaultEditor
 			UpdateClipboardContainsText();
 		}
 		
-		static bool clipboardContainsText;
+		static volatile bool clipboardContainsText;
 		
 		public static bool GetClipboardContainsText()
 		{
@@ -47,28 +48,29 @@ namespace ICSharpCode.SharpDevelop.DefaultEditor
 			return clipboardContainsText;
 		}
 		
-		static volatile Thread updateThread;
+		static WorkerThread workerThread;
+		static IAsyncResult currentWorker;
 		
 		static void UpdateClipboardContainsText()
 		{
-			if (updateThread != null)
+			if (currentWorker != null && !currentWorker.IsCompleted)
 				return;
-			Thread t = new Thread(new ThreadStart(DoUpdate));
-			t.SetApartmentState(ApartmentState.STA);
-			t.IsBackground = true;
-			t.Name = "clipboard access";
-			updateThread = t;
-			t.Start();
-			t.Join(50); // wait a few ms in case the clipboard can be accessed without problems
+			if (workerThread == null) {
+				workerThread = new WorkerThread();
+				Thread t = new Thread(new ThreadStart(workerThread.RunLoop));
+				t.SetApartmentState(ApartmentState.STA);
+				t.IsBackground = true;
+				t.Name = "clipboard access";
+				t.Start();
+			}
+			currentWorker = workerThread.Enqueue(DoUpdate);
+			// wait a few ms in case the clipboard can be accessed without problems
+			currentWorker.AsyncWaitHandle.WaitOne(50);
 		}
 		
 		static void DoUpdate()
 		{
-			try {
-				clipboardContainsText = ClipboardWrapper.ContainsText;
-			} finally {
-				updateThread = null;
-			}
+			clipboardContainsText = ClipboardWrapper.ContainsText;
 		}
 	}
 }
diff --git a/src/Main/Base/Project/Src/Util/WorkerThread.cs b/src/Main/Base/Project/Src/Util/WorkerThread.cs
new file mode 100644
index 0000000000..ad60da065b
--- /dev/null
+++ b/src/Main/Base/Project/Src/Util/WorkerThread.cs
@@ -0,0 +1,105 @@
+// <file>
+//     <copyright see="prj:///doc/copyright.txt"/>
+//     <license see="prj:///doc/license.txt"/>
+//     <author name="Daniel Grunwald"/>
+//     <version>$Revision$</version>
+// </file>
+
+using System;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace ICSharpCode.SharpDevelop.Util
+{
+	/// <summary>
+	/// A worker thread that normally sleeps, but can run a queue of commands.
+	/// </summary>
+	public class WorkerThread
+	{
+		sealed class AsyncTask : IAsyncResult
+		{
+			internal readonly ManualResetEvent manualResetEvent = new ManualResetEvent(false);
+			internal readonly Action method;
+			volatile bool isCompleted;
+			
+			internal AsyncTask(Action method)
+			{
+				this.method = method;
+			}
+			
+			internal void SetCompleted()
+			{
+				isCompleted = true;
+				manualResetEvent.Set();
+			}
+			
+			public bool IsCompleted {
+				get { return isCompleted; }
+			}
+			
+			public WaitHandle AsyncWaitHandle {
+				get { return manualResetEvent; }
+			}
+			
+			public object AsyncState { get; set; }
+			public bool CompletedSynchronously { get { return false; } }
+		}
+		
+		/// <summary>
+		/// Runs <paramref name="method"/> on the worker thread.
+		/// </summary>
+		/// <param name="method">The method to run.</param>
+		/// <returns></returns>
+		public IAsyncResult Enqueue(Action method)
+		{
+			if (method == null)
+				throw new ArgumentNullException("method");
+			AsyncTask task = new AsyncTask(method);
+			lock (lockObject) {
+				taskQueue.Enqueue(task);
+				Monitor.Pulse(lockObject);
+			}
+			return task;
+		}
+		
+		readonly object lockObject = new object();
+		Queue<AsyncTask> taskQueue = new Queue<AsyncTask>();
+		bool workerRunning = false;
+		
+		/// <summary>
+		/// Runs the worker thread loop on the current thread.
+		/// </summary>
+		public void RunLoop()
+		{
+			lock (lockObject) {
+				if (workerRunning)
+					throw new InvalidOperationException("There already is a worker running");
+				workerRunning = true;
+			}
+			try {
+				while (workerRunning) {
+					AsyncTask task;
+					lock (lockObject) {
+						while (taskQueue.Count == 0)
+							Monitor.Wait(lockObject);
+						task = taskQueue.Dequeue();
+					}
+					task.method();
+					task.SetCompleted();
+				}
+			} finally {
+				lock (lockObject) {
+					workerRunning = false;
+				}
+			}
+		}
+		
+		/// <summary>
+		/// Exits running the worker thread.
+		/// </summary>
+		public void ExitWorkerThread()
+		{
+			Enqueue(delegate { workerRunning = false; });
+		}
+	}
+}