real async plugin loading

QuickLook/BackgroundListener.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Windows.Forms;
+using System.Windows.Threading;
 
 namespace QuickLook
 {
@@ -25,7 +26,8 @@ namespace QuickLook
             if (e.Modifiers != Keys.None)
                 return;
 
-            ViewWindowManager.GetInstance().InvokeRoutine(e);
+            Dispatcher.CurrentDispatcher.BeginInvoke(new Action(() => ViewWindowManager.GetInstance().InvokeRoutine(e)),
+                DispatcherPriority.ApplicationIdle);
         }
 
         private void InstallKeyHook(KeyEventHandler handler)

QuickLook/MainWindowTransparent.xaml.cs

@@ -16,9 +16,6 @@ namespace QuickLook
     /// </summary>
     public partial class MainWindowTransparent : Window
     {
-        private string _path = string.Empty;
-        private IViewer _plugin;
-
         internal MainWindowTransparent()
         {
             // this object should be initialized before loading UI components, because many of which are binding to it.
@@ -43,18 +40,21 @@ namespace QuickLook
                 ViewWindowManager.GetInstance().RunAndClosePreview();
         }
 
+        public string PreviewPath { get; private set; }
+        public IViewer Plugin { get; private set; }
+
         public ContextObject ContextObject { get; private set; }
 
         internal void RunAndHide()
         {
-            if (string.IsNullOrEmpty(_path))
+            if (string.IsNullOrEmpty(PreviewPath))
                 return;
 
             try
             {
-                Process.Start(new ProcessStartInfo(_path)
+                Process.Start(new ProcessStartInfo(PreviewPath)
                 {
-                    WorkingDirectory = Path.GetDirectoryName(_path)
+                    WorkingDirectory = Path.GetDirectoryName(PreviewPath)
                 });
             }
             catch (Exception e)
@@ -96,21 +96,21 @@ namespace QuickLook
 
             ContextObject.Reset();
 
-            _plugin?.Cleanup();
-            _plugin = null;
+            Plugin?.Cleanup();
+            Plugin = null;
 
             ProcessHelper.PerformAggressiveGC();
         }
 
-        internal void BeginShow(IViewer matchedPlugin, string path)
+        internal void BeginShow(IViewer matchedPlugin, string path, Action<ExceptionDispatchInfo> exceptionHandler)
         {
-            _path = path;
-            _plugin = matchedPlugin;
+            PreviewPath = path;
+            Plugin = matchedPlugin;
 
             ContextObject.ViewerWindow = this;
 
             // get window size before showing it
-            _plugin.Prepare(path, ContextObject);
+            Plugin.Prepare(path, ContextObject);
 
             SetOpenWithButtonAndPath();
 
@@ -129,31 +129,27 @@ namespace QuickLook
             //WindowHelper.SetActivate(new WindowInteropHelper(this), ContextObject.CanFocus);
 
             // load plugin, do not block UI
-            Exception thrown = null;
             Dispatcher.BeginInvoke(new Action(() =>
                 {
                     try
                     {
-                        _plugin.View(path, ContextObject);
+                        Plugin.View(path, ContextObject);
                     }
                     catch (Exception e)
                     {
-                        thrown = e;
+                        exceptionHandler(ExceptionDispatchInfo.Capture(e));
                     }
                 }),
-                DispatcherPriority.Render).Wait();
-
-            if (thrown != null)
-                ExceptionDispatchInfo.Capture(thrown).Throw();
+                DispatcherPriority.Input);
         }
 
         private void SetOpenWithButtonAndPath()
         {
-            var isExe = FileHelper.GetAssocApplication(_path, out string appFriendlyName);
+            var isExe = FileHelper.GetAssocApplication(PreviewPath, out string appFriendlyName);
 
             buttonOpenWith.Content = isExe == null
-                ? Directory.Exists(_path)
-                    ? $"Browse “{Path.GetFileName(_path)}”"
+                ? Directory.Exists(PreviewPath)
+                    ? $"Browse “{Path.GetFileName(PreviewPath)}”"
                     : "Open..."
                 : isExe == true
                     ? $"Run “{appFriendlyName}”"

QuickLook/PluginManager.cs

@@ -4,7 +4,6 @@ using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Reflection;
-using System.Threading.Tasks;
 using QuickLook.ExtensionMethods;
 using QuickLook.Plugin;
 using QuickLook.Plugin.InfoPanel;

QuickLook/ViewWindowManager.cs

@@ -4,6 +4,7 @@ using System.IO;
 using System.Runtime.ExceptionServices;
 using System.Windows;
 using System.Windows.Forms;
+using System.Windows.Threading;
 using QuickLook.Helpers;
 using QuickLook.Plugin;
 
@@ -123,8 +124,8 @@ namespace QuickLook
 
         private void SwitchPreviewRemoteInvoke(HeartbeatEventArgs e)
         {
-            // sleep for 1.5s
-            if (e.InvokeTick - _lastSwitchTick < 1.5 * TimeSpan.TicksPerSecond)
+            // sleep for 0.6s
+            if (e.InvokeTick - _lastSwitchTick < 0.6 * TimeSpan.TicksPerSecond)
                 return;
 
             if (e.FocusedFile == _path)
@@ -135,7 +136,7 @@ namespace QuickLook
             if (string.IsNullOrEmpty(e.FocusedFile))
                 return;
 
-            _currentMainWindow?.Dispatcher.Invoke(() => SwitchPreview());
+            _currentMainWindow?.Dispatcher.BeginInvoke(new Action(SwitchPreview), DispatcherPriority.ApplicationIdle);
         }
 
         private void RunFocusMonitor()
@@ -158,26 +159,24 @@ namespace QuickLook
 
         internal bool InvokeViewer(string path = null)
         {
-            if (path == null)
-                path = _path;
+            if (path != null)
+                _path = path;
 
-            if (string.IsNullOrEmpty(path))
+            if (string.IsNullOrEmpty(_path))
                 return false;
-            if (!Directory.Exists(path) && !File.Exists(path))
+            if (!Directory.Exists(_path) && !File.Exists(_path))
                 return false;
 
             RunFocusMonitor();
 
-            var matchedPlugin = PluginManager.GetInstance().FindMatch(path);
+            var matchedPlugin = PluginManager.GetInstance().FindMatch(_path);
 
-            BeginShowNewWindow(matchedPlugin, path);
+            BeginShowNewWindow(matchedPlugin);
 
             return true;
         }
 
-        private void BeginShowNewWindow(IViewer matchedPlugin, string path)
-        {
-            try
+        private void BeginShowNewWindow(IViewer matchedPlugin)
         {
             _currentMainWindow.UnloadPlugin();
 
@@ -189,28 +188,24 @@ namespace QuickLook
             if (!ReferenceEquals(oldWindow, _currentMainWindow))
                 oldWindow.BeginHide();
 
-                _currentMainWindow.BeginShow(matchedPlugin, path);
+            _currentMainWindow.BeginShow(matchedPlugin, _path, CurrentPluginFailed);
         }
-            catch (Exception e) // if current plugin failed, switch to default one.
+
+        private void CurrentPluginFailed(ExceptionDispatchInfo e)
         {
+            var plugin = _currentMainWindow.Plugin.GetType();
+
             _currentMainWindow.BeginHide();
 
-                TrayIconManager.GetInstance().ShowNotification("", $"Failed to preview {Path.GetFileName(path)}", true);
+            TrayIconManager.GetInstance().ShowNotification("", $"Failed to preview {Path.GetFileName(_path)}", true);
 
             Debug.WriteLine(e.ToString());
-                Debug.WriteLine(e.StackTrace);
+            Debug.WriteLine(e.SourceException.StackTrace);
 
-                if (matchedPlugin != PluginManager.GetInstance().DefaultPlugin)
-                {
-                    matchedPlugin.Cleanup();
-                    matchedPlugin = PluginManager.GetInstance().DefaultPlugin;
-                    BeginShowNewWindow(matchedPlugin, path);
-                }
+            if (plugin != PluginManager.GetInstance().DefaultPlugin.GetType())
+                BeginShowNewWindow(PluginManager.GetInstance().DefaultPlugin);
             else
-                {
-                    ExceptionDispatchInfo.Capture(e).Throw();
-                }
-            }
+                e.Throw();
         }
 
         internal static ViewWindowManager GetInstance()