Made it possible to create event args externally for testing.

NTwain/Data/TwainTypesExtended.cs

@@ -1730,12 +1730,13 @@ namespace NTwain.Data
         public string ProductName { get { return _productName; } set { value.VerifyLengthUnder(TwainConst.String32 - 1); _productName = value; } }
 
         /// <summary>
-        /// Creates a <see cref="TWIdentity"/> from assembly values.
+        /// Creates a <see cref="TWIdentity" /> from assembly values.
         /// </summary>
         /// <param name="supportedGroups">The supported groups.</param>
         /// <param name="assembly">The assembly.</param>
         /// <returns></returns>
-        /// <exception cref="ArgumentNullException">assembly</exception>
+        /// <exception cref="System.ArgumentNullException">assembly</exception>
+        /// <exception cref="System.ArgumentException"></exception>
         public static TWIdentity CreateFromAssembly(DataGroups supportedGroups, Assembly assembly)
         {
             if (assembly == null) { throw new ArgumentNullException("assembly"); }
@@ -1755,10 +1756,16 @@ namespace NTwain.Data
         /// <param name="productName">Name of the product.</param>
         /// <param name="productDescription">The product description.</param>
         /// <returns></returns>
-        /// <exception cref="ArgumentNullException">version</exception>
+        /// <exception cref="System.ArgumentNullException">assembly</exception>
+        /// <exception cref="System.ArgumentException"></exception>
         public static TWIdentity Create(DataGroups supportedGroups, Version version,
             string manufacturer, string productFamily, string productName, string productDescription)
         {
+            if ((supportedGroups & DataGroups.Image) == 0 &&
+                (supportedGroups & DataGroups.Audio) == 0)
+            {
+                throw new ArgumentException(Resources.BadDataGroupsForAppId);
+            }
             if (version == null) { throw new ArgumentNullException("version"); }
 
             return new TWIdentity

NTwain/DataTransferredEventArgs.cs

@@ -8,6 +8,37 @@ namespace NTwain
     /// </summary>
     public class DataTransferredEventArgs : EventArgs
     {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DataTransferredEventArgs"/> class.
+        /// </summary>
+        /// <param name="nativeData">The native data.</param>
+        /// <param name="imageInfo">The image information.</param>
+        public DataTransferredEventArgs(IntPtr nativeData, TWImageInfo imageInfo)
+        {
+            NativeData = nativeData;
+            ImageInfo = imageInfo;
+        }
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DataTransferredEventArgs"/> class.
+        /// </summary>
+        /// <param name="fileDataPath">The file data path.</param>
+        /// <param name="imageInfo">The image information.</param>
+        public DataTransferredEventArgs(string fileDataPath, TWImageInfo imageInfo)
+        {
+            FileDataPath = fileDataPath;
+            ImageInfo = imageInfo;
+        }
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DataTransferredEventArgs"/> class.
+        /// </summary>
+        /// <param name="memoryData">The memory data.</param>
+        /// <param name="imageInfo">The image information.</param>
+        public DataTransferredEventArgs(byte[] memoryData, TWImageInfo imageInfo)
+        {
+            MemoryData = memoryData;
+            ImageInfo = imageInfo;
+        }
+
         /// <summary>
         /// Gets pointer to the complete data if the transfer was native.
         /// The data will be freed once the event handler ends
@@ -16,7 +47,7 @@ namespace NTwain
         /// This pointer is already locked for the duration of this event.
         /// </summary>
         /// <value>The data pointer.</value>
-        public IntPtr NativeData { get; internal set; }
+        public IntPtr NativeData { get; private set; }
 
         /// <summary>
         /// Gets the file path to the complete data if the transfer was file or memory-file.
@@ -24,7 +55,7 @@ namespace NTwain
         /// <value>
         /// The file path.
         /// </value>
-        public string FileDataPath { get; internal set; }
+        public string FileDataPath { get; private set; }
 
         /// <summary>
         /// Gets the raw memory data if the transfer was memory.
@@ -35,7 +66,7 @@ namespace NTwain
         /// The memory data.
         /// </value>
         [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays")]
-        public byte[] MemoryData { get; internal set; }
+        public byte[] MemoryData { get; private set; }
 
         /// <summary>
         /// Gets the final image information if applicable.
@@ -43,7 +74,7 @@ namespace NTwain
         /// <value>
         /// The final image information.
         /// </value>
-        public TWImageInfo ImageInfo { get; internal set; }
+        public TWImageInfo ImageInfo { get; private set; }
 
         ///// <summary>
         ///// Gets the extended image information if applicable.

NTwain/Internals/TransferLogic.cs

@@ -39,14 +39,7 @@ namespace NTwain.Internals
                 }
 
                 // ask consumer for xfer details
-                var preXferArgs = new TransferReadyEventArgs
+                var preXferArgs = new TransferReadyEventArgs(pending.Count, pending.EndOfJob == 0, imgInfo, audInfo); ;
-                {
-                    AudioInfo = audInfo,
-                    PendingImageInfo = imgInfo,
-                    PendingTransferCount = pending.Count,
-                    EndOfJob = pending.EndOfJob == 0
-                };
-
                 session.SafeSyncableRaiseEvent(preXferArgs);
 
                 #endregion
@@ -144,16 +137,16 @@ namespace NTwain.Internals
                         lockedPtr = Platform.MemoryManager.Lock(dataPtr);
                     }
 
-                    session.SafeSyncableRaiseEvent(new DataTransferredEventArgs { NativeData = lockedPtr });
+                    session.SafeSyncableRaiseEvent(new DataTransferredEventArgs(lockedPtr, null));
                 }
                 else
                 {
-                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.CurrentSource.GetStatus() });
+                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs(xrc, session.CurrentSource.GetStatus()));
                 }
             }
             catch (Exception ex)
             {
-                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { Exception = ex });
+                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs(ex));
             }
             finally
             {
@@ -184,11 +177,11 @@ namespace NTwain.Internals
             var xrc = session.DGAudio.AudioFileXfer.Get();
             if (xrc == ReturnCode.XferDone)
             {
-                session.SafeSyncableRaiseEvent(new DataTransferredEventArgs { FileDataPath = filePath });
+                session.SafeSyncableRaiseEvent(new DataTransferredEventArgs(filePath, null));
             }
             else
             {
-                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.CurrentSource.GetStatus() });
+                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs(xrc, session.CurrentSource.GetStatus()));
             }
         }
 
@@ -214,12 +207,12 @@ namespace NTwain.Internals
                 }
                 else
                 {
-                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.CurrentSource.GetStatus() });
+                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs(xrc, session.CurrentSource.GetStatus()));
                 }
             }
             catch (Exception ex)
             {
-                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { Exception = ex });
+                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs(ex));
             }
             finally
             {
@@ -254,7 +247,7 @@ namespace NTwain.Internals
             }
             else
             {
-                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.CurrentSource.GetStatus() });
+                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs(xrc, session.CurrentSource.GetStatus()));
             }
         }
 
@@ -317,13 +310,13 @@ namespace NTwain.Internals
                         }
                         else
                         {
-                            session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.CurrentSource.GetStatus() });
+                            session.SafeSyncableRaiseEvent(new TransferErrorEventArgs(xrc, session.CurrentSource.GetStatus()));
                         }
                     }
                 }
                 catch (Exception ex)
                 {
-                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { Exception = ex });
+                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs(ex));
                 }
                 finally
                 {
@@ -396,12 +389,12 @@ namespace NTwain.Internals
                     }
                     else
                     {
-                        session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.CurrentSource.GetStatus() });
+                        session.SafeSyncableRaiseEvent(new TransferErrorEventArgs(xrc, session.CurrentSource.GetStatus()));
                     }
                 }
                 catch (Exception ex)
                 {
-                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { Exception = ex });
+                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs(ex));
                 }
                 finally
                 {
@@ -425,6 +418,7 @@ namespace NTwain.Internals
 
         static void DoImageXferredEventRoutine(ITwainSessionInternal session, IntPtr dataPtr, byte[] dataArray, string filePath)
         {
+            DataTransferredEventArgs args = null;
             TWImageInfo imgInfo;
             //TWExtImageInfo extInfo = null;
             //if (session.CurrentSource.SupportedCaps.Contains(CapabilityId.ICapExtImageInfo))
@@ -438,14 +432,19 @@ namespace NTwain.Internals
             {
                 imgInfo = null;
             }
-            session.SafeSyncableRaiseEvent(new DataTransferredEventArgs
+            if (dataPtr != IntPtr.Zero)
             {
-                NativeData = dataPtr,
+                args = new DataTransferredEventArgs(dataPtr, imgInfo);
-                MemoryData = dataArray,
+            }
-                FileDataPath = filePath,
+            else if (dataArray != null)
-                ImageInfo = imgInfo,
+            {
-                //ExImageInfo = extInfo
+                args = new DataTransferredEventArgs(dataArray, imgInfo);
-            });
+            }
+            else
+            {
+                args = new DataTransferredEventArgs(filePath, imgInfo);
+            }
+            session.SafeSyncableRaiseEvent(args);
             //if (extInfo != null) { extInfo.Dispose(); }
         }
 

NTwain/MessageLoopHooks.cs

@@ -113,7 +113,6 @@ namespace NTwain
             //{
             System.Windows.Forms.Application.RemoveMessageFilter(this);
             _filter = null;
-            Handle = IntPtr.Zero;
             //});
         }
 
@@ -191,9 +190,9 @@ namespace NTwain
             if (_hooker != null)
             {
                 _hooker.RemoveHook(FilterMessage);
-                _hooker.Dispose();
+                // cannot really dispose _hook or the window will also dispose
+                //_hooker.Dispose();
                 _hooker = null;
-                Handle = IntPtr.Zero;
             }
         }
     }

NTwain/Properties/Resources.Designer.cs

@@ -8,10 +8,10 @@
 // </auto-generated>
 //------------------------------------------------------------------------------
 
-namespace NTwain.Properties
+namespace NTwain.Properties {
-{
+    using System;
-
+    
-
+    
     /// <summary>
     ///   A strongly-typed resource class, for looking up localized strings, etc.
     /// </summary>
@@ -60,6 +60,15 @@ namespace NTwain.Properties
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Data group for application must contain either Image or Audio..
+        /// </summary>
+        internal static string BadDataGroupsForAppId {
+            get {
+                return ResourceManager.GetString("BadDataGroupsForAppId", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Invalid value type for {0}..
         /// </summary>

NTwain/Properties/Resources.resx

@@ -112,11 +112,14 @@
     <value>2.0</value>
   </resheader>
   <resheader name="reader">
-    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
   </resheader>
   <resheader name="writer">
-    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
   </resheader>
+  <data name="BadDataGroupsForAppId" xml:space="preserve">
+    <value>Data group for application must contain either Image or Audio.</value>
+  </data>
   <data name="BadValueType" xml:space="preserve">
     <value>Invalid value type for {0}.</value>
   </data>

NTwain/TransferErrorEventArgs.cs

@@ -8,13 +8,33 @@ namespace NTwain
     /// </summary>
     public class TransferErrorEventArgs : EventArgs
     {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="TransferErrorEventArgs"/> class.
+        /// </summary>
+        /// <param name="error">The error.</param>
+        public TransferErrorEventArgs(Exception error)
+        {
+            Exception = error;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="TransferErrorEventArgs"/> class.
+        /// </summary>
+        /// <param name="code">The code.</param>
+        /// <param name="status">The status.</param>
+        public TransferErrorEventArgs(ReturnCode code, TWStatus status)
+        {
+            ReturnCode = code;
+            SourceStatus = status;
+        }
+
         /// <summary>
         /// Gets the return code from the transfer.
         /// </summary>
         /// <value>
         /// The return code.
         /// </value>
-        public ReturnCode ReturnCode { get; internal set; }
+        public ReturnCode ReturnCode { get; private set; }
 
         /// <summary>
         /// Gets the source status.
@@ -22,7 +42,7 @@ namespace NTwain
         /// <value>
         /// The source status.
         /// </value>
-        public TWStatus SourceStatus { get; internal set; }
+        public TWStatus SourceStatus { get; private set; }
 
         /// <summary>
         /// Gets the exception if the error is from some exception.
@@ -30,6 +50,6 @@ namespace NTwain
         /// <value>
         /// The exception.
         /// </value>
-        public Exception Exception { get; internal set; }
+        public Exception Exception { get; private set; }
     }
 }

NTwain/TransferReadyEventArgs.cs

@@ -8,6 +8,21 @@ namespace NTwain
     /// </summary>
     public class TransferReadyEventArgs : EventArgs
     {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="TransferReadyEventArgs"/> class.
+        /// </summary>
+        /// <param name="pendingCount">The pending count.</param>
+        /// <param name="endOfJob">if set to <c>true</c> [end of job].</param>
+        /// <param name="imageInfo">The image information.</param>
+        /// <param name="audioInfo">The audio information.</param>
+        public TransferReadyEventArgs(int pendingCount, bool endOfJob, TWImageInfo imageInfo, TWAudioInfo audioInfo)
+        {
+            PendingTransferCount = pendingCount;
+            EndOfJob = endOfJob;
+            PendingImageInfo = imageInfo;
+            AudioInfo = audioInfo;
+        }
+
         /// <summary>
         /// Gets or sets a value indicating whether the current transfer should be canceled
         /// and continue next transfer if there are more data.
@@ -25,14 +40,14 @@ namespace NTwain
         /// Gets a value indicating whether current transfer signifies an end of job in TWAIN world.
         /// </summary>
         /// <value><c>true</c> if transfer is end of job; otherwise, <c>false</c>.</value>
-        public bool EndOfJob { get; internal set; }
+        public bool EndOfJob { get; private set; }
 
         /// <summary>
         /// Gets the known pending transfer count. This may not be appilicable 
         /// for certain scanning modes.
         /// </summary>
         /// <value>The pending count.</value>
-        public int PendingTransferCount { get; internal set; }
+        public int PendingTransferCount { get; private set; }
 
         /// <summary>
         /// Gets the tentative image information for the current transfer if applicable.
@@ -41,7 +56,7 @@ namespace NTwain
         /// <value>
         /// The image info.
         /// </value>
-        public TWImageInfo PendingImageInfo { get; internal set; }
+        public TWImageInfo PendingImageInfo { get; private set; }
 
         /// <summary>
         /// Gets the audio information for the current transfer if applicable.
@@ -49,7 +64,7 @@ namespace NTwain
         /// <value>
         /// The audio information.
         /// </value>
-        public TWAudioInfo AudioInfo { get; internal set; }
+        public TWAudioInfo AudioInfo { get; private set; }
 
     }
 }

NTwain/TwainSession.cs

@@ -18,7 +18,7 @@ namespace NTwain
     /// <summary>
     /// Basic class for interfacing with TWAIN. You should only have one of this per application process.
     /// </summary>
-    public partial class TwainSession : ITwainSessionInternal, IWinMessageFilter
+    public partial class TwainSession 
     {
         /// <summary>
         /// Initializes a new instance of the <see cref="TwainSession"/> class.
@@ -557,114 +557,5 @@ namespace NTwain
         protected virtual void OnTransferError(TransferErrorEventArgs e) { }
 
         #endregion
-
-        #region handle twain ds message
-
-
-        #region IWinMessageFilter Members
-
-        /// <summary>
-        /// Checks and handle the message if it's a TWAIN message.
-        /// </summary>
-        /// <param name="hwnd">The window handle.</param>
-        /// <param name="msg">The message.</param>
-        /// <param name="wParam">The w parameter.</param>
-        /// <param name="lParam">The l parameter.</param>
-        /// <returns>
-        /// true if handled internally.
-        /// </returns>
-        public bool IsTwainMessage(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam)
-        {
-            bool handled = false;
-            // this handles the message from a typical WndProc message loop and check if it's from the TWAIN source.
-            if (_state >= 5)
-            {
-                // transform it into a pointer for twain
-                IntPtr msgPtr = IntPtr.Zero;
-                try
-                {
-                    var winMsg = new NTwain.Internals.MESSAGE(hwnd, msg, wParam, lParam);
-
-                    // no need to do another lock call when using marshal alloc
-                    msgPtr = Marshal.AllocHGlobal(Marshal.SizeOf(winMsg));
-                    Marshal.StructureToPtr(winMsg, msgPtr, false);
-
-                    var evt = new TWEvent();
-                    evt.pEvent = msgPtr;
-                    if (handled = (((ITwainSessionInternal)this).DGControl.Event.ProcessEvent(evt) == ReturnCode.DSEvent))
-                    {
-                        Debug.WriteLine(string.Format(CultureInfo.InvariantCulture, "Thread {0}: HandleWndProcMessage at state {1} with MSG={2}.", Thread.CurrentThread.ManagedThreadId, State, evt.TWMessage));
-
-                        HandleSourceMsg(evt.TWMessage);
-                    }
-                }
-                finally
-                {
-                    if (msgPtr != IntPtr.Zero) { Marshal.FreeHGlobal(msgPtr); }
-                }
-            }
-            return handled;
-        }
-
-        #endregion
-
-        ReturnCode HandleCallback(TWIdentity origin, TWIdentity destination, DataGroups dg, DataArgumentType dat, Message msg, IntPtr data)
-        {
-            if (origin != null && CurrentSource != null && origin.Id == CurrentSource.Identity.Id && _state >= 5)
-            {
-                Debug.WriteLine(string.Format(CultureInfo.InvariantCulture, "Thread {0}: CallbackHandler at state {1} with MSG={2}.", Thread.CurrentThread.ManagedThreadId, State, msg));
-                // spec says we must handle this on the thread that enabled the DS.
-                // by using the internal dispatcher this will be the case.
-
-                _msgLoopHook.BeginInvoke(() =>
-                {
-                    HandleSourceMsg(msg);
-                });
-                return ReturnCode.Success;
-            }
-            return ReturnCode.Failure;
-        }
-
-        // final method that handles msg from the source, whether it's from wndproc or callbacks
-        void HandleSourceMsg(Message msg)
-        {
-            switch (msg)
-            {
-                case Message.XferReady:
-                    if (State < 6)
-                    {
-                        State = 6;
-                    }
-                    TransferLogic.DoTransferRoutine(this);
-                    break;
-                case Message.DeviceEvent:
-                    TWDeviceEvent de;
-                    var rc = ((ITwainSessionInternal)this).DGControl.DeviceEvent.Get(out de);
-                    if (rc == ReturnCode.Success)
-                    {
-                        SafeSyncableRaiseOnEvent(OnDeviceEvent, DeviceEvent, new DeviceEventArgs(de));
-                    }
-                    break;
-                case Message.CloseDSReq:
-                case Message.CloseDSOK:
-                    Debug.WriteLine("Got msg " + msg);
-                    // even though it says closeDS it's really disable.
-                    // dsok is sent if source is enabled with uionly
-
-                    // some sources send this at other states so do a step down
-                    if (State > 5)
-                    {
-                        ForceStepDown(4);
-                    }
-                    else if (State == 5)
-                    {
-                        // needs this state check since some source sends this more than once
-                        ((ITwainSessionInternal)this).DisableSource();
-                    }
-                    break;
-            }
-        }
-
-        #endregion
     }
 }

NTwain/TwainSessionInternal.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Globalization;
 using System.Linq;
+using System.Runtime.InteropServices;
 using System.Text;
 using System.Threading;
 
@@ -13,7 +14,7 @@ namespace NTwain
 {
     // for internal pieces since the main twain session file is getting too long
 
-    partial class TwainSession
+    partial class TwainSession : ITwainSessionInternal, IWinMessageFilter
     {
         #region ITwainSessionInternal Members
 
@@ -196,5 +197,114 @@ namespace NTwain
 
         #endregion
 
+        #region IWinMessageFilter Members
+
+        /// <summary>
+        /// Checks and handle the message if it's a TWAIN message.
+        /// </summary>
+        /// <param name="hwnd">The window handle.</param>
+        /// <param name="msg">The message.</param>
+        /// <param name="wParam">The w parameter.</param>
+        /// <param name="lParam">The l parameter.</param>
+        /// <returns>
+        /// true if handled internally.
+        /// </returns>
+        public bool IsTwainMessage(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam)
+        {
+            bool handled = false;
+            // this handles the message from a typical WndProc message loop and check if it's from the TWAIN source.
+            if (_state >= 5)
+            {
+                // transform it into a pointer for twain
+                IntPtr msgPtr = IntPtr.Zero;
+                try
+                {
+                    var winMsg = new NTwain.Internals.MESSAGE(hwnd, msg, wParam, lParam);
+
+                    // no need to do another lock call when using marshal alloc
+                    msgPtr = Marshal.AllocHGlobal(Marshal.SizeOf(winMsg));
+                    Marshal.StructureToPtr(winMsg, msgPtr, false);
+
+                    var evt = new TWEvent();
+                    evt.pEvent = msgPtr;
+                    if (handled = (((ITwainSessionInternal)this).DGControl.Event.ProcessEvent(evt) == ReturnCode.DSEvent))
+                    {
+                        Debug.WriteLine(string.Format(CultureInfo.InvariantCulture, "Thread {0}: HandleWndProcMessage at state {1} with MSG={2}.", Thread.CurrentThread.ManagedThreadId, State, evt.TWMessage));
+
+                        HandleSourceMsg(evt.TWMessage);
+                    }
+                }
+                finally
+                {
+                    if (msgPtr != IntPtr.Zero) { Marshal.FreeHGlobal(msgPtr); }
+                }
+            }
+            return handled;
+        }
+
+        #endregion
+
+        #region handle twain ds message
+
+
+        ReturnCode HandleCallback(TWIdentity origin, TWIdentity destination, DataGroups dg, DataArgumentType dat, Message msg, IntPtr data)
+        {
+            if (origin != null && CurrentSource != null && origin.Id == CurrentSource.Identity.Id && _state >= 5)
+            {
+                Debug.WriteLine(string.Format(CultureInfo.InvariantCulture, "Thread {0}: CallbackHandler at state {1} with MSG={2}.", Thread.CurrentThread.ManagedThreadId, State, msg));
+                // spec says we must handle this on the thread that enabled the DS.
+                // by using the internal dispatcher this will be the case.
+
+                _msgLoopHook.BeginInvoke(() =>
+                {
+                    HandleSourceMsg(msg);
+                });
+                return ReturnCode.Success;
+            }
+            return ReturnCode.Failure;
+        }
+
+        // final method that handles msg from the source, whether it's from wndproc or callbacks
+        void HandleSourceMsg(Message msg)
+        {
+            switch (msg)
+            {
+                case Message.XferReady:
+                    if (State < 6)
+                    {
+                        State = 6;
+                    }
+                    TransferLogic.DoTransferRoutine(this);
+                    break;
+                case Message.DeviceEvent:
+                    TWDeviceEvent de;
+                    var rc = ((ITwainSessionInternal)this).DGControl.DeviceEvent.Get(out de);
+                    if (rc == ReturnCode.Success)
+                    {
+                        SafeSyncableRaiseOnEvent(OnDeviceEvent, DeviceEvent, new DeviceEventArgs(de));
+                    }
+                    break;
+                case Message.CloseDSReq:
+                case Message.CloseDSOK:
+                    Debug.WriteLine("Got msg " + msg);
+                    // even though it says closeDS it's really disable.
+                    // dsok is sent if source is enabled with uionly
+
+                    // some sources send this at other states so do a step down
+                    if (State > 5)
+                    {
+                        ForceStepDown(4);
+                    }
+                    else if (State == 5)
+                    {
+                        // needs this state check since some source sends this more than once
+                        ((ITwainSessionInternal)this).DisableSource();
+                    }
+                    break;
+            }
+        }
+
+        #endregion
+
     }
 }