Added DAT_XFERGROUP calls

README.md

@@ -4,7 +4,7 @@
 
 This is a library created to make working with 
 [TWAIN](http://twain.org/) easier in dotnet. 
-This project has these goals:
+V4 of this lib is a work in progress and has these goals:
 
 * Targets latest TWAIN version (2.4 as of this writing)
 * Supports all the TWAIN functions in the spec

src/NTwain/Data/Delegates.cs

@@ -0,0 +1,11 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace NTwain.Data
+{
+    delegate ReturnCode Callback32(TW_IDENTITY origin, TW_IDENTITY destination,
+            DataGroups dg, DataArgumentType dat, Message msg, IntPtr data);
+
+}

src/NTwain/Triplets/Control/XferGroup.cs

@@ -0,0 +1,82 @@
+using NTwain.Data;
+using NTwain.Internals;
+
+namespace NTwain.Triplets.Control
+{
+    /// <summary>
+    /// Represents <see cref="DataArgumentType.XferGroup"/>.
+    /// </summary>
+    public sealed class XferGroup : BaseTriplet
+	{
+		internal XferGroup(TwainSession session) : base(session) { }
+
+		/// <summary>
+		/// Returns the Data Group (the type of data) for the upcoming transfer. The Source is required to
+		/// only supply one of the DGs specified in the SupportedGroups field of origin.
+		/// </summary>
+		/// <param name="value">The value.</param>
+		/// <returns></returns>
+        public ReturnCode Get(ref DataGroups value)
+        {
+            if (Is32Bit)
+            {
+                if (IsWin)
+                    return NativeMethods.DsmWin32(Session.Config.App32, Session.CurrentSource.Identity32,
+                        DataGroups.Control, DataArgumentType.XferGroup, Message.Get, ref value);
+                if (IsLinux)
+                    return NativeMethods.DsmLinux32(Session.Config.App32, Session.CurrentSource.Identity32,
+                        DataGroups.Control, DataArgumentType.XferGroup, Message.Get, ref value);
+                if (IsMac)
+                    return NativeMethods.DsmMac32(Session.Config.App32, Session.CurrentSource.Identity32,
+                        DataGroups.Control, DataArgumentType.XferGroup, Message.Get, ref value);
+            }
+
+            if (IsWin)
+                return NativeMethods.DsmWin64(Session.Config.App32, Session.CurrentSource.Identity32,
+                    DataGroups.Control, DataArgumentType.XferGroup, Message.Get, ref value);
+            if (IsLinux)
+                return NativeMethods.DsmLinux64(Session.Config.App32, Session.CurrentSource.Identity32,
+                    DataGroups.Control, DataArgumentType.XferGroup, Message.Get, ref value);
+            if (IsMac)
+                return NativeMethods.DsmMac64(Session.Config.App32, Session.CurrentSource.Identity32,
+                    DataGroups.Control, DataArgumentType.XferGroup, Message.Get, ref value);
+
+            return ReturnCode.Failure;
+		}
+
+        /// <summary>
+        /// The transfer group determines the kind of data being passed from the Source to the Application.
+        /// By default a TWAIN Source must default to DG_IMAGE. Currently the only other data group
+        /// supported is DG_AUDIO, which is a feature supported by some digital cameras.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        /// <returns></returns>
+        public ReturnCode Set(DataGroups value)
+        {
+            if (Is32Bit)
+            {
+                if (IsWin)
+                    return NativeMethods.DsmWin32(Session.Config.App32, Session.CurrentSource.Identity32,
+                        DataGroups.Control, DataArgumentType.XferGroup, Message.Set, ref value);
+                if (IsLinux)
+                    return NativeMethods.DsmLinux32(Session.Config.App32, Session.CurrentSource.Identity32,
+                        DataGroups.Control, DataArgumentType.XferGroup, Message.Set, ref value);
+                if (IsMac)
+                    return NativeMethods.DsmMac32(Session.Config.App32, Session.CurrentSource.Identity32,
+                        DataGroups.Control, DataArgumentType.XferGroup, Message.Set, ref value);
+            }
+
+            if (IsWin)
+                return NativeMethods.DsmWin64(Session.Config.App32, Session.CurrentSource.Identity32,
+                    DataGroups.Control, DataArgumentType.XferGroup, Message.Set, ref value);
+            if (IsLinux)
+                return NativeMethods.DsmLinux64(Session.Config.App32, Session.CurrentSource.Identity32,
+                    DataGroups.Control, DataArgumentType.XferGroup, Message.Set, ref value);
+            if (IsMac)
+                return NativeMethods.DsmMac64(Session.Config.App32, Session.CurrentSource.Identity32,
+                    DataGroups.Control, DataArgumentType.XferGroup, Message.Set, ref value);
+
+            return ReturnCode.Failure;
+        }
+	}
+}

src/NTwain/Triplets/DGControl.cs

@@ -38,5 +38,11 @@ namespace NTwain.Triplets
 
         DeviceEvent _devEvent;
         internal DeviceEvent DeviceEvent => _devEvent ?? (_devEvent = new DeviceEvent(Session));
+
+        XferGroup _xferGroup;
+        /// <summary>
+        /// Gets the operations defined for DAT_XFERGROUP.
+        /// </summary>
+        public XferGroup XferGroup => _xferGroup ?? (_xferGroup = new XferGroup(Session));
     }
 }

src/NTwain/TwainSession.cs

@@ -11,10 +11,6 @@ using System.Threading;
 
 namespace NTwain
 {
-    //[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
-    delegate ReturnCode CallbackDelegate(TW_IDENTITY origin, TW_IDENTITY destination,
-            DataGroups dg, DataArgumentType dat, Message msg, IntPtr data);
-
     /// <summary>
     /// Manages a TWAIN session.
     /// </summary>
@@ -26,7 +22,7 @@ namespace NTwain
         // cache generated twain sources so if you get same source from same session it'll return the same object
         readonly Dictionary<string, DataSource> _ownedSources = new Dictionary<string, DataSource>();
         // need to keep delegate around to prevent GC?
-        readonly CallbackDelegate _callbackDelegate;
+        readonly Callback32 _callback32Delegate;
 
 
         /// <summary>
@@ -41,7 +37,7 @@ namespace NTwain
                 case PlatformID.MacOSX:
                 case PlatformID.Unix:
                 default:
-                    _callbackDelegate = new CallbackDelegate(Handle32BitCallback);
+                    _callback32Delegate = new Callback32(Handle32BitCallback);
                     break;
             }
         }
@@ -107,7 +103,8 @@ namespace NTwain
 
         internal void RegisterCallback()
         {
-            var callbackPtr = Marshal.GetFunctionPointerForDelegate(_callbackDelegate);
+            // TODO: support other platforms
+            var callbackPtr = Marshal.GetFunctionPointerForDelegate(_callback32Delegate);
 
             // try new callback first
             var cb2 = new TW_CALLBACK2 { CallBackProc = callbackPtr };