Timing hack for file transfer.

samples/WinConsole32/Program.cs

@@ -36,7 +36,9 @@ namespace WinConsole32
                 Console.WriteLine($"Default data source = {defaultSrc}");
                 Console.WriteLine();
 
-                twain.ShowUserSelect();
+                sts = twain.ShowUserSelect();
+                if (sts.IsSuccess)
+                {
                     Console.WriteLine($"Selected data source = {twain.DefaultSource}");
                     Console.WriteLine();
 
@@ -58,6 +60,7 @@ namespace WinConsole32
                     Console.ReadLine();
                     twain.TryStepdown(STATE.S1);
                 }
+            }
             else
             {
                 Console.WriteLine("Failed to attach: " + sts);
@@ -115,7 +118,7 @@ namespace WinConsole32
 
                 TW_SETUPFILEXFER setup = new()
                 {
-                    FileName = targetName,
+                    FileName = Path.Combine("Images", targetName),
                     Format = format,
                 };
                 e.SetupFileTransfer(ref setup);
@@ -171,9 +174,11 @@ namespace WinConsole32
         {
             watch.Stop();
             var elapsed = watch.Elapsed;
-            Console.WriteLine($"Session source disabled, took {elapsed}.");
+            Console.WriteLine($"Session source disabled, took {elapsed}, will retest in 3 sec...");
 
-            //TestThisSource(twain, e);
+            Thread.Sleep(3000);
+            if (twain.State > STATE.S3)
+                TestThisSource(twain, e);
         }
 
         private static void TestThisSource(TwainAppSession twain, TW_IDENTITY_LEGACY source)

src/Directory.Build.props

@@ -2,7 +2,7 @@
   <PropertyGroup>
     <!--change these in each release-->
     <VersionPrefix>4.0.0.0</VersionPrefix>
-    <VersionSuffix>alpha.7</VersionSuffix>
+    <VersionSuffix>alpha.8</VersionSuffix>
     
     <!--keep it the same until major # changes-->
     <AssemblyVersion>4.0.0.0</AssemblyVersion>

src/NTwain/MessagePumpThread.cs

@@ -9,8 +9,7 @@ using System.Windows.Forms;
 namespace NTwain
 {
   /// <summary>
-  /// For use under Windows to host a message pump in non-winform/wpf apps.
+  /// For use under Windows to host a message pump.
-  /// This is highly experimental.
   /// </summary>
   class MessagePumpThread
   {

src/NTwain/TwainAppSession.Callbacks.cs

@@ -98,6 +98,13 @@ namespace NTwain
             switch (msg)
             {
                 case MSG.XFERREADY:
+                    if (_transferInCallbackThread)
+                    {
+                        EnterTransferRoutine();
+                    }
+                    else
+                    {
+                        // use bg thread to process transfer.
                         // some sources spam this even during transfer so we gate it
                         if (!_inTransfer)
                         {
@@ -105,6 +112,7 @@ namespace NTwain
                             _xferReady.Set();
                             //_bgPendingMsgs.Add(msg);
                         }
+                    }
                     break;
                 case MSG.CLOSEDSOK:
                 case MSG.CLOSEDSREQ:

src/NTwain/TwainAppSession.Xfers.cs

@@ -2,9 +2,11 @@
 using NTwain.Native;
 using NTwain.Triplets;
 using System;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Runtime.InteropServices;
+using System.Threading;
 
 namespace NTwain
 {
@@ -161,7 +163,7 @@ namespace NTwain
                                             break;
                                     }
                                 }
-                                HandleXferCode(ref sts, ref pending);
+                                HandleXferCode(ref sts, ref pending, isEnd: false);
                             }
                         }
                         catch (Exception ex)
@@ -176,7 +178,7 @@ namespace NTwain
                 } while (sts.RC == TWRC.SUCCESS && pending.Count != 0);
             }
 
-            HandleXferCode(ref sts, ref pending);
+            HandleXferCode(ref sts, ref pending, isEnd: true);
 
             if (State >= STATE.S5)
             {
@@ -185,13 +187,17 @@ namespace NTwain
             _inTransfer = false;
         }
 
-        private void HandleXferCode(ref STS sts, ref TW_PENDINGXFERS pending)
+        private void HandleXferCode(ref STS sts, ref TW_PENDINGXFERS pending, bool isEnd)
         {
             switch (sts.RC)
             {
                 case TWRC.SUCCESS:
                 case TWRC.XFERDONE:
                     // ok to keep going
+                    if (isEnd)
+                    {
+                        //DGControl.PendingXfers.EndXfer(ref _appIdentity, ref _currentDS, ref pending);
+                    }
                     break;
                 case TWRC.CANCEL:
                     // might eventually have option to cancel this or all like transfer ready
@@ -210,6 +216,18 @@ namespace NTwain
                     // TODO: raise error event
                     switch (sts.STATUS.ConditionCode)
                     {
+                        case TWCC.SEQERROR:
+                            if (isEnd)
+                            {
+                                // special break down to state 5
+                                pending = TW_PENDINGXFERS.DONTCARE();
+                                sts = WrapInSTS(DGControl.PendingXfers.EndXfer(ref _appIdentity, ref _currentDS, ref pending));
+                                State = STATE.S6;
+                                pending = TW_PENDINGXFERS.DONTCARE();
+                                sts = WrapInSTS(DGControl.PendingXfers.Reset(ref _appIdentity, ref _currentDS, ref pending));
+                                State = STATE.S5;
+                            }
+                            break;
                         case TWCC.DAMAGEDCORNER:
                         case TWCC.DOCTOODARK:
                         case TWCC.DOCTOOLIGHT:
@@ -245,6 +263,7 @@ namespace NTwain
 
             // and just start it
             var sts = WrapInSTS(DGAudio.AudioFileXfer.Get(ref _appIdentity, ref _currentDS));
+
             if (sts.RC == TWRC.XFERDONE)
             {
                 State = STATE.S7;
@@ -475,7 +494,11 @@ namespace NTwain
             // get what will be transferred
             DGControl.SetupFileXfer.Get(ref _appIdentity, ref _currentDS, out TW_SETUPFILEXFER fileSetup);
             // and just start it
+
+            int tries = 0;
+        RETRY:
             var sts = WrapInSTS(DGImage.ImageFileXfer.Get(ref _appIdentity, ref _currentDS));
+
             if (sts.RC == TWRC.XFERDONE)
             {
                 State = STATE.S7;
@@ -494,6 +517,23 @@ namespace NTwain
                     State = pending.Count == 0 ? STATE.S5 : STATE.S6;
                 }
             }
+            else
+            {
+                // sometimes it errors only due to timing so wait a bit and try again
+                if (sts.RC == TWRC.FAILURE && (sts.ConditionCode == TWCC.None || sts.ConditionCode == TWCC.SEQERROR))
+                {
+                    if (tries++ < 3)
+                    {
+                        Debug.WriteLine($"Using fileXfer timing workaround try {tries}.");
+                        Thread.Sleep(500);
+                        goto RETRY;
+                    }
+                }
+                else
+                {
+                    Debugger.Break();
+                }
+            }
             return sts;
         }
 

src/NTwain/TwainAppSession.cs

@@ -50,6 +50,7 @@ namespace NTwain
         bool _inTransfer;
         readonly AutoResetEvent _xferReady = new(false);
         private bool disposedValue;
+        bool _transferInCallbackThread = true;
 
         void StartTransferThread()
         {
@@ -114,7 +115,7 @@ namespace NTwain
 #if WINDOWS || NETFRAMEWORK
         /// <summary>
         /// Loads and opens the TWAIN data source manager in a self-hosted message queue thread.
-    /// Highly experimental and only use if necessary. Must close with <see cref="CloseDSMAsync"/>
+        /// Must close with <see cref="CloseDSMAsync"/>
         /// if used.
         /// </summary>
         /// <returns></returns>
@@ -122,6 +123,7 @@ namespace NTwain
         {
             if (_selfPump == null)
             {
+                _transferInCallbackThread = true;
                 var pump = new MessagePumpThread();
                 var sts = await pump.AttachAsync(this);
                 if (sts.IsSuccess)
@@ -162,6 +164,7 @@ namespace NTwain
             var rc = DGControl.Parent.OpenDSM(ref _appIdentity, hwnd);
             if (rc == TWRC.SUCCESS)
             {
+                _transferInCallbackThread = true;
                 _hwnd = hwnd;
                 _pumpThreadMarshaller = uiThreadMarshaller;
                 State = STATE.S3;
@@ -296,7 +299,14 @@ namespace NTwain
                 {
                     // todo: finish
                     case STATE.S7:
+                        var pending = TW_PENDINGXFERS.DONTCARE();
+                        DGControl.PendingXfers.EndXfer(ref _appIdentity, ref _currentDS, ref pending);
+                        _state = STATE.S6;
+                        break;
                     case STATE.S6:
+                        pending = TW_PENDINGXFERS.DONTCARE();
+                        DGControl.PendingXfers.Reset(ref _appIdentity, ref _currentDS, ref pending);
+                        _state = STATE.S5;
                         break;
                     case STATE.S5:
                         DisableSource();