Use NamedPipe, instead of second instance, to invoke preview from command line

QuickLook/App.xaml.cs

@@ -1,10 +1,10 @@
 using System;
-using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Threading;
 using System.Windows;
-using QuickLook.Helpers;
+using System.Windows.Threading;
 
 namespace QuickLook
 {
@@ -16,9 +16,9 @@ namespace QuickLook
         public static readonly bool Is64Bit = Environment.Is64BitProcess;
         public static readonly string AppFullPath = Assembly.GetExecutingAssembly().Location;
         public static readonly string AppPath = Path.GetDirectoryName(AppFullPath);
-        public static bool RunningAsViewer;
 
-        private static bool _duplicated;
+        private bool _isFirstInstance;
+        private Mutex _isRunning;
 
         protected override void OnStartup(StartupEventArgs e)
         {
@@ -27,7 +27,7 @@ namespace QuickLook
                 MessageBox.Show(((Exception) args.ExceptionObject).Message + Environment.NewLine +
                                 ((Exception) args.ExceptionObject).StackTrace);
 
-                Current.Shutdown();
+                Shutdown();
             };
 
             base.OnStartup(e);
@@ -35,65 +35,60 @@ namespace QuickLook
 
         private void Application_Startup(object sender, StartupEventArgs e)
         {
-            if (e.Args.Any())
-                if (Directory.Exists(e.Args.First()) || File.Exists(e.Args.First()))
-                    RunAsViewer(e);
+            EnsureFirstInstance();
+
+            if (!_isFirstInstance)
+            {
+                // second instance: preview this file
+                if (e.Args.Any() && (Directory.Exists(e.Args.First()) || File.Exists(e.Args.First())))
+                    RemoteCallShowPreview(e);
+                // second instance: duplicate
                 else
-                    RunAsListener(e);
-            else
-                RunAsListener(e);
-        }
+                    MessageBox.Show("QuickLook is already running in the background.");
 
-        private void RunAsViewer(StartupEventArgs e)
-        {
-            RunningAsViewer = true;
-
-            var runningPid = PidHelper.GetRunningInstance();
-            if (runningPid != -1)
-            {
-                Process.GetProcessById(runningPid).Kill();
-
-                Current.Shutdown();
+                Shutdown();
                 return;
             }
 
-            PidHelper.WritePid();
+            RunListener(e);
 
-            ViewWindowManager.GetInstance().InvokeViewer(e.Args.First());
+            // second instance: run and preview this file
+            if (e.Args.Any() && (Directory.Exists(e.Args.First()) || File.Exists(e.Args.First())))
+                RemoteCallShowPreview(e);
         }
 
-        private void RunAsListener(StartupEventArgs e)
+        private void RemoteCallShowPreview(StartupEventArgs e)
         {
-            RunningAsViewer = false;
-
-            if (PidHelper.GetRunningInstance() != -1)
-            {
-                _duplicated = true;
-
-                MessageBox.Show("QuickLook is already running in the background.");
-
-                Current.Shutdown();
-                return;
-            }
-
-            PidHelper.WritePid();
+            PipeServerManager.SendMessage(e.Args.First());
+        }
 
+        private void RunListener(StartupEventArgs e)
+        {
             TrayIconManager.GetInstance();
             if (!e.Args.Contains("/autorun"))
                 TrayIconManager.GetInstance().ShowNotification("", "QuickLook is running in the background.");
 
             PluginManager.GetInstance();
-
             BackgroundListener.GetInstance();
+            PipeServerManager.GetInstance().MessageReceived +=
+                (msg, ea) => Dispatcher.BeginInvoke(
+                    new Action(() => ViewWindowManager.GetInstance().InvokeViewer(msg as string)),
+                    DispatcherPriority.ApplicationIdle);
         }
 
         private void App_OnExit(object sender, ExitEventArgs e)
         {
-            TrayIconManager.GetInstance().Dispose();
-            BackgroundListener.GetInstance().Dispose();
+            if (_isFirstInstance)
+            {
+                PipeServerManager.GetInstance().Dispose();
+                TrayIconManager.GetInstance().Dispose();
+                BackgroundListener.GetInstance().Dispose();
+            }
+        }
 
-            if (!_duplicated)
-                PidHelper.DeletePid();
+        private void EnsureFirstInstance()
+        {
+            _isRunning = new Mutex(true, "QuickLook.App.Mutex", out _isFirstInstance);
         }
     }
 }

QuickLook/Helpers/PidHelper.cs

@@ -1,59 +0,0 @@
-using System.Diagnostics;
-using System.IO;
-
-namespace QuickLook.Helpers
-{
-    internal static class PidHelper
-    {
-        private static FileStream _pidLocker;
-
-        private static readonly string PidListener =
-            Path.Combine(Path.GetTempPath(), "QuickLook.App.Listener.D6EC3F8DDF6B.pid");
-
-        private static readonly string PidViewer =
-            Path.Combine(Path.GetTempPath(), "QuickLook.App.Viewer.A6FA53E93515.pid");
-
-        internal static int GetRunningInstance()
-        {
-            var pid = App.RunningAsViewer ? PidViewer : PidListener;
-
-            if (!File.Exists(pid))
-                return -1;
-
-            var ppid = -1;
-            using (var file = File.Open(pid, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
-            using (var sr = new StreamReader(file))
-            {
-                int.TryParse(sr.ReadToEnd(), out ppid);
-            }
-
-            try
-            {
-                Process.GetProcessById(ppid);
-            }
-            catch
-            {
-                return -1;
-            }
-
-            return ppid;
-        }
-
-        internal static void WritePid()
-        {
-            var pidFile = App.RunningAsViewer ? PidViewer : PidListener;
-
-            File.WriteAllText(pidFile, Process.GetCurrentProcess().Id.ToString());
-
-            _pidLocker = File.Open(pidFile, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.Read);
-        }
-
-        internal static void DeletePid()
-        {
-            _pidLocker?.Close();
-            _pidLocker = null;
-
-            File.Delete(App.RunningAsViewer ? PidViewer : PidListener);
-        }
-    }
-}

QuickLook/PipeServerManager.cs

@@ -0,0 +1,89 @@
+using System;
+using System.Diagnostics;
+using System.IO;
+using System.IO.Pipes;
+using System.Threading.Tasks;
+
+namespace QuickLook
+{
+    internal class PipeServerManager : IDisposable
+    {
+        private const string PipeName = "QuickLook.App.Pipe";
+        private const string PipeCloseMessage = "QuickLook.App.Pipe.QuitSingal";
+        private static PipeServerManager _instance;
+
+        private NamedPipeServerStream _server;
+
+        public PipeServerManager()
+        {
+            _server = new NamedPipeServerStream(PipeName, PipeDirection.In);
+
+            new Task(() =>
+            {
+                using (var reader = new StreamReader(_server))
+                {
+                    while (true)
+                    {
+                        Debug.WriteLine("PipeManager: WaitForConnection");
+
+                        _server.WaitForConnection();
+                        var msg = reader.ReadLine();
+
+                        Debug.WriteLine($"PipeManager: {msg}");
+
+                        if (msg == PipeCloseMessage)
+                            return;
+
+                        // dispatch message
+                        MessageReceived?.Invoke(msg, new EventArgs());
+
+                        _server.Disconnect();
+                    }
+                }
+            }).Start();
+        }
+
+        public void Dispose()
+        {
+            GC.SuppressFinalize(this);
+
+            if (_server != null)
+                SendMessage(PipeCloseMessage);
+            _server?.Dispose();
+            _server = null;
+        }
+
+        public event EventHandler MessageReceived;
+
+        public static void SendMessage(string msg)
+        {
+            try
+            {
+                using (var client = new NamedPipeClientStream(".", PipeName, PipeDirection.Out))
+                {
+                    client.Connect();
+
+                    using (var writer = new StreamWriter(client))
+                    {
+                        writer.WriteLine(msg);
+                        writer.Flush();
+                    }
+                }
+            }
+            catch (Exception e)
+            {
+                Debug.WriteLine(e.ToString());
+            }
+        }
+
+        ~PipeServerManager()
+        {
+            Dispose();
+        }
+
+        public static PipeServerManager GetInstance()
+        {
+            return _instance ?? (_instance = new PipeServerManager());
+        }
+    }
+}

QuickLook/QuickLook.csproj

@@ -134,7 +134,7 @@
     <Compile Include="Helpers\FileHelper.cs" />
     <Compile Include="Helpers\ProcessHelper.cs" />
     <Compile Include="MainWindowNoTransparent.cs" />
-    <Compile Include="Helpers\PidHelper.cs" />
+    <Compile Include="PipeServerManager.cs" />
     <Compile Include="PluginManager.cs" />
     <Compile Include="Plugin\InfoPanel\DpiHelpers.cs" />
     <Compile Include="Plugin\InfoPanel\Extensions.cs" />