Fixed stuck in Invoke.

NTwain/MessageLoop.cs

@@ -0,0 +1,98 @@
+using NTwain.Triplets;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Windows.Interop;
+using System.Windows.Threading;
+
+namespace NTwain
+{
+    /// <summary>
+    /// Provides a message loop for old TWAIN to post or new TWAIN to synchronize callbacks.
+    /// </summary>
+    class MessageLoop
+    {
+        // mostly wraps around a dispatcher?
+        static MessageLoop _instance = new MessageLoop();
+        public static MessageLoop Instance { get { return _instance; } }
+
+        Dispatcher _dispatcher;
+        bool _started;
+        HwndSource _dummyWindow;
+
+        private MessageLoop() { }
+        public void EnsureStarted()
+        {
+            if (!_started)
+            {
+                var loopThread = new Thread(new ThreadStart(() =>
+                {
+                    _dispatcher = Dispatcher.CurrentDispatcher;
+                    if (Dsm.IsWin)
+                    {
+                        // start a windows msg loop for old twain to post msgs
+                        // the style values are purely guesses here with
+                        // CS_NOCLOSE, WS_DISABLED, and WS_EX_NOACTIVATE
+                        _dummyWindow = new HwndSource(0x0200, 0x8000000, 0x8000000, 0, 0, "NTWAIN_LOOPER", IntPtr.Zero);
+                    }
+                    Dispatcher.Run();
+                }));
+                loopThread.IsBackground = true;
+                loopThread.SetApartmentState(ApartmentState.STA);
+                loopThread.Start();
+                _started = true;
+            }
+        }
+
+        public IntPtr LoopHandle
+        {
+            get
+            {
+                return _dummyWindow == null ? IntPtr.Zero : _dummyWindow.Handle;
+            }
+        }
+
+        public void BeginInvoke(Action action)
+        {
+            if (_dispatcher != null)
+            {
+                _dispatcher.BeginInvoke(DispatcherPriority.Normal, action);
+            }
+        }
+
+        public void Invoke(Action action)
+        {
+            if (_dispatcher != null)
+            {
+                if (_dispatcher.CheckAccess())
+                {
+                    action();
+                }
+                else
+                {
+                    //_dispatcher.Invoke(DispatcherPriority.Normal, action);
+
+                    var man = new ManualResetEvent(false);
+                    _dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action(() =>
+                    {
+                        action();
+                        man.Set();
+                    }));
+                    man.WaitOne();
+                    man.Close();
+                }
+            }
+        }
+
+        public void AddHook(HwndSourceHook hook)
+        {
+            if (_dummyWindow != null) { _dummyWindow.AddHook(hook); }
+        }
+        public void RemoveHook(HwndSourceHook hook)
+        {
+            if (_dummyWindow != null) { _dummyWindow.RemoveHook(hook); }
+        }
+    }
+}

NTwain/TwainSession.cs

@@ -211,10 +211,13 @@ namespace NTwain
         /// </summary>
         /// <returns></returns>
         public ReturnCode OpenManager()
+        {
+            ReturnCode rc = ReturnCode.Success;
+            MessageLoop.Instance.Invoke(() =>
             {
                 Debug.WriteLine(string.Format("Thread {0}: OpenManager.", Thread.CurrentThread.ManagedThreadId));
 
-            var rc = DGControl.Parent.OpenDsm(MessageLoop.Instance.LoopHandle);
+                rc = DGControl.Parent.OpenDsm(MessageLoop.Instance.LoopHandle);
                 if (rc == ReturnCode.Success)
                 {
                     // if twain2 then get memory management functions
@@ -233,6 +236,7 @@ namespace NTwain
                         }
                     }
                 }
+            });
             return rc;
         }
 
@@ -241,10 +245,14 @@ namespace NTwain
         /// </summary>
         /// <returns></returns>
         public ReturnCode CloseManager()
+        {
+            ReturnCode rc = ReturnCode.Success;
+            MessageLoop.Instance.Invoke(() =>
             {
                 Debug.WriteLine(string.Format("Thread {0}: CloseManager.", Thread.CurrentThread.ManagedThreadId));
 
-            var rc = DGControl.Parent.CloseDsm(MessageLoop.Instance.LoopHandle);
+                rc = DGControl.Parent.CloseDsm(MessageLoop.Instance.LoopHandle);
+            });
             return rc;
         }
 
@@ -260,15 +268,16 @@ namespace NTwain
         {
             if (string.IsNullOrEmpty(sourceProductName)) { throw new ArgumentException("Source name is required.", "sourceProductName"); }
 
+            ReturnCode rc = ReturnCode.Success;
+            MessageLoop.Instance.Invoke(() =>
+            {
                 Debug.WriteLine(string.Format("Thread {0}: OpenSource.", Thread.CurrentThread.ManagedThreadId));
 
                 var source = new TWIdentity();
                 source.ProductName = sourceProductName;
 
-            var rc = DGControl.Identity.OpenDS(source);
+                rc = DGControl.Identity.OpenDS(source);
-            if (rc == ReturnCode.Success)
+            });
-            {
-            }
             return rc;
         }
 
@@ -280,16 +289,20 @@ namespace NTwain
         /// </summary>
         /// <returns></returns>
         public ReturnCode CloseSource()
+        {
+            ReturnCode rc = ReturnCode.Success;
+            MessageLoop.Instance.Invoke(() =>
             {
                 Debug.WriteLine(string.Format("Thread {0}: CloseSource.", Thread.CurrentThread.ManagedThreadId));
 
-            var rc = DGControl.Identity.CloseDS();
+                rc = DGControl.Identity.CloseDS();
                 if (rc == ReturnCode.Success)
                 {
                     MessageLoop.Instance.RemoveHook(HandleWndProcMessage);
                     _callbackObj = null;
                     SupportedCaps = null;
                 }
+            });
             return rc;
         }
 
@@ -303,12 +316,12 @@ namespace NTwain
         /// <exception cref="ArgumentNullException">context</exception>
         public ReturnCode EnableSource(SourceEnableMode mode, bool modal, IntPtr windowHandle)
         {
-            Debug.WriteLine(string.Format("Thread {0}: EnableSource.", Thread.CurrentThread.ManagedThreadId));
-
             ReturnCode rc = ReturnCode.Success;
 
             MessageLoop.Instance.Invoke(() =>
             {
+                Debug.WriteLine(string.Format("Thread {0}: EnableSource.", Thread.CurrentThread.ManagedThreadId));
+
                 // app v2.2 or higher uses callback2
                 if (_appId.ProtocolMajor >= 2 && _appId.ProtocolMinor >= 2)
                 {
@@ -363,12 +376,12 @@ namespace NTwain
         /// <returns></returns>
         protected ReturnCode DisableSource()
         {
-            Debug.WriteLine(string.Format("Thread {0}: DisableSource.", Thread.CurrentThread.ManagedThreadId));
-
             ReturnCode rc = ReturnCode.Success;
 
             MessageLoop.Instance.Invoke(() =>
             {
+                Debug.WriteLine(string.Format("Thread {0}: DisableSource.", Thread.CurrentThread.ManagedThreadId));
+
                 rc = DGControl.UserInterface.DisableDS(_twui);
                 if (rc == ReturnCode.Success)
                 {
@@ -386,8 +399,7 @@ namespace NTwain
         public void ForceStepDown(int targetState)
         {
             Debug.WriteLine(string.Format("Thread {0}: ForceStepDown.", Thread.CurrentThread.ManagedThreadId));
-            MessageLoop.Instance.Invoke(() =>
+
-            {
             bool origFlag = EnforceState;
             EnforceState = false;
 
@@ -427,7 +439,6 @@ namespace NTwain
                 CloseManager();
             }
             EnforceState = origFlag;
-            });
         }
 
         #endregion
@@ -609,10 +620,7 @@ namespace NTwain
                     {
                         Debug.WriteLine(string.Format("Thread {0}: HandleWndProcMessage at state {1} with MSG={2}.", Thread.CurrentThread.ManagedThreadId, State, evt.TWMessage));
 
-                        MessageLoop.Instance.BeginInvoke(() =>
-                        {
                         HandleSourceMsg(evt.TWMessage);
-                        });
                     }
                 }
                 finally

Tests/Tester.WPF/MainWindow.xaml.cs

@@ -49,8 +49,18 @@ namespace Tester.WPF
             if (!DesignerProperties.GetIsInDesignMode(this))
             {
                 Messenger.Default.Register<DialogMessage>(this, msg =>
+                {
+                    if (Dispatcher.CheckAccess())
                     {
                         ModernMessageBox.Show(this, msg.Content, msg.Caption, msg.Button, msg.Icon, msg.DefaultResult);
+                    }
+                    else
+                    {
+                        Dispatcher.BeginInvoke(new Action(() =>
+                        {
+                            ModernMessageBox.Show(this, msg.Content, msg.Caption, msg.Button, msg.Icon, msg.DefaultResult);
+                        }));
+                    }
                 });
             }
         }