Fix Win32 clipboard not returning bitmaps in some cases (#20506)

* Fix Win32 clipboard not returning bitmap in some cases

* Make ClipboardFormatRegistry fields read-only

src/Windows/Avalonia.Win32/ClipboardFormatRegistry.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Diagnostics;
 using Avalonia.Input;
 using Avalonia.Media.Imaging;
 using Avalonia.Utilities;
@@ -12,19 +13,15 @@ namespace Avalonia.Win32
     {
         private const int MaxFormatNameLength = 260;
         private const string AppPrefix = "avn-app-fmt:";
-        public const string PngFormatMimeType = "image/png";
-        public const string PngFormatSystemType = "PNG";
-        public const string BitmapFormat = "CF_BITMAP";
-        public const string DibFormat = "CF_DIB";
-        public const string DibV5Format = "CF_DIBV5";
         private static readonly List<(DataFormat Format, ushort Id)> s_formats = [];
 
-        public static DataFormat PngSystemDataFormat = DataFormat.FromSystemName<Bitmap>(PngFormatSystemType, AppPrefix);
+        public static readonly DataFormat PngSystemDataFormat = new DataFormat<Bitmap>(DataFormatKind.Platform, "PNG");
-        public static DataFormat PngMimeDataFormat = DataFormat.FromSystemName<Bitmap>(PngFormatMimeType, AppPrefix);
+        public static readonly DataFormat PngMimeDataFormat = new DataFormat<Bitmap>(DataFormatKind.Platform, "image/png");
-        public static DataFormat HBitmapDataFormat = DataFormat.FromSystemName<Bitmap>(BitmapFormat, AppPrefix);
+        public static readonly DataFormat HBitmapDataFormat = new DataFormat<Bitmap>(DataFormatKind.Platform, "CF_BITMAP");
-        public static DataFormat DibDataFormat = DataFormat.FromSystemName<Bitmap>(DibFormat, AppPrefix);
+        public static readonly DataFormat DibDataFormat = new DataFormat<Bitmap>(DataFormatKind.Platform, "CF_DIB");
-        public static DataFormat DibV5DataFormat = DataFormat.FromSystemName<Bitmap>(DibV5Format, AppPrefix);
+        public static readonly DataFormat DibV5DataFormat = new DataFormat<Bitmap>(DataFormatKind.Platform, "CF_DIBV5");
 
+        // Ordered from the most preferred to the least preferred
         public static DataFormat[] ImageFormats = [PngMimeDataFormat, PngSystemDataFormat, DibDataFormat, DibV5DataFormat, HBitmapDataFormat];
 
         static ClipboardFormatRegistry()
@@ -44,12 +41,12 @@ namespace Avalonia.Win32
             var buffer = StringBuilderCache.Acquire(MaxFormatNameLength);
             if (UnmanagedMethods.GetClipboardFormatName(id, buffer, buffer.Capacity) > 0)
                 return StringBuilderCache.GetStringAndRelease(buffer);
-            if (Enum.IsDefined(typeof(UnmanagedMethods.ClipboardFormat), (int)id))
+            if (Enum.IsDefined(typeof(UnmanagedMethods.ClipboardFormat), id))
-                return Enum.GetName(typeof(UnmanagedMethods.ClipboardFormat), (int)id)!;
+                return Enum.GetName(typeof(UnmanagedMethods.ClipboardFormat), id)!;
             return $"Unknown_Format_{id}";
         }
 
-        public static DataFormat GetFormatById(ushort id)
+        public static DataFormat GetOrAddFormat(ushort id)
         {
             lock (s_formats)
             {
@@ -66,30 +63,12 @@ namespace Avalonia.Win32
             }
         }
 
-        public static ushort GetFormatId(DataFormat format)
+        public static ushort GetOrAddFormat(DataFormat format)
         {
+            Debug.Assert(format != DataFormat.Bitmap); // Callers must pass an effective platform type
+
             lock (s_formats)
             {
-                if (DataFormat.Bitmap.Equals(format))
-                {
-                    (DataFormat, ushort)? pngFormat = null;
-                    (DataFormat, ushort)? dibFormat = null;
-
-                    foreach (var currentFormat in s_formats)
-                    {
-                        if (currentFormat.Id == (ushort)UnmanagedMethods.ClipboardFormat.CF_DIB)
-                            dibFormat = currentFormat;
-                        else if (currentFormat.Format.Identifier == PngFormatMimeType)
-                            pngFormat = currentFormat;
-                    }
-                    var imageFormatId = pngFormat?.Item2 ?? dibFormat?.Item2 ?? 0;
-
-                    if (imageFormatId != 0)
-                    {
-                        return imageFormatId;
-                    }
-                }
-
                 for (var i = 0; i < s_formats.Count; ++i)
                 {
                     if (s_formats[i].Format.Equals(format))

src/Windows/Avalonia.Win32/DataTransferToOleDataObjectWrapper.cs

@@ -30,25 +30,9 @@ internal class DataTransferToOleDataObjectWrapper(IDataTransfer dataTransfer)
             _current = current;
         }
 
-        public FormatEnumerator(IReadOnlyList<DataFormat> dataFormats)
+        public FormatEnumerator(ushort[] formatIds)
         {
-            List<FORMATETC> formats = new List<FORMATETC>();
+            _formats = formatIds.Select(OleDataObjectHelper.ToFormatEtc).ToArray();
-
-            if (dataFormats.Contains(DataFormat.Bitmap))
-            {
-                // We add extra formats for bitmaps
-                formats.Add(OleDataObjectHelper.ToFormatEtc(ClipboardFormatRegistry.PngMimeDataFormat));
-                formats.Add(OleDataObjectHelper.ToFormatEtc(ClipboardFormatRegistry.PngSystemDataFormat));
-                formats.Add(OleDataObjectHelper.ToFormatEtc(ClipboardFormatRegistry.DibDataFormat));
-                formats.Add(OleDataObjectHelper.ToFormatEtc(ClipboardFormatRegistry.DibV5DataFormat));
-                formats.Add(OleDataObjectHelper.ToFormatEtc(ClipboardFormatRegistry.HBitmapDataFormat, true));
-            }
-            else
-            {
-                formats.AddRange(dataFormats.Select(x => OleDataObjectHelper.ToFormatEtc(x)));
-            }
-
-            _formats = formats.ToArray();
             _current = 0;
         }
 
@@ -98,6 +82,9 @@ internal class DataTransferToOleDataObjectWrapper(IDataTransfer dataTransfer)
     public bool IsDisposed
         => DataTransfer is null;
 
+    private ushort[] FormatIds
+        => field ??= CalcFormatIds();
+
     public event Action? OnDestroyed;
 
     unsafe int Win32Com.IDataObject.DAdvise(FORMATETC* pFormatetc, int advf, void* adviseSink)
@@ -115,7 +102,7 @@ internal class DataTransferToOleDataObjectWrapper(IDataTransfer dataTransfer)
             throw new COMException(nameof(COR_E_OBJECTDISPOSED), unchecked((int)HRESULT.E_NOTIMPL));
 
         if ((DATADIR)direction == DATADIR.DATADIR_GET)
-            return new FormatEnumerator(DataTransfer.Formats);
+            return new FormatEnumerator(FormatIds);
 
         throw new COMException(nameof(HRESULT.E_NOTIMPL), unchecked((int)HRESULT.E_NOTIMPL));
     }
@@ -166,7 +153,8 @@ internal class DataTransferToOleDataObjectWrapper(IDataTransfer dataTransfer)
     {
         dataFormat = null;
 
-        if (!(format->tymed.HasAllFlags(TYMED.TYMED_HGLOBAL) || format->cfFormat == (ushort)ClipboardFormat.CF_BITMAP && format->tymed == TYMED.TYMED_GDI))
+        if (!(format->tymed == TYMED.TYMED_HGLOBAL ||
+            (format->tymed == TYMED.TYMED_GDI && format->cfFormat == (ushort)ClipboardFormat.CF_BITMAP)))
         {
             result = DV_E_TYMED;
             dataFormat = null;
@@ -185,17 +173,38 @@ internal class DataTransferToOleDataObjectWrapper(IDataTransfer dataTransfer)
             return false;
         }
 
-        dataFormat = ClipboardFormatRegistry.GetFormatById(format->cfFormat);
+        if (!FormatIds.Contains(format->cfFormat))
-        if (!DataTransfer.Contains(dataFormat) && !ClipboardFormatRegistry.ImageFormats.Contains(dataFormat))
         {
             result = DV_E_FORMATETC;
             return false;
         }
 
+        dataFormat = ClipboardFormatRegistry.GetOrAddFormat(format->cfFormat);
         result = (uint)HRESULT.S_OK;
         return true;
     }
 
+    private ushort[] CalcFormatIds()
+    {
+        if (DataTransfer is null)
+            return [];
+
+        var formatIds = new List<ushort>(DataTransfer.Formats.Count);
+
+        foreach (var dataFormat in DataTransfer.Formats)
+        {
+            if (DataFormat.Bitmap.Equals(dataFormat))
+            {
+                // We add extra formats for bitmaps
+                formatIds.AddRange(ClipboardFormatRegistry.ImageFormats.Select(ClipboardFormatRegistry.GetOrAddFormat));
+            }
+            else
+                formatIds.Add(ClipboardFormatRegistry.GetOrAddFormat(dataFormat));
+        }
+
+        return formatIds.ToArray();
+    }
+
     unsafe uint Win32Com.IDataObject.SetData(FORMATETC* pformatetc, STGMEDIUM* pmedium, int fRelease)
         => (uint)HRESULT.E_NOTIMPL;
 

src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs

@@ -2297,7 +2297,7 @@ namespace Avalonia.Win32.Interop
             MDT_DEFAULT = MDT_EFFECTIVE_DPI
         }
 
-        public enum ClipboardFormat
+        public enum ClipboardFormat : ushort
         {
             /// <summary>
             /// A handle to a bitmap

src/Windows/Avalonia.Win32/OleDataObjectHelper.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Runtime.InteropServices;
@@ -24,39 +25,26 @@ internal static class OleDataObjectHelper
 {
     private const int SRCCOPY = 0x00CC0020;
 
-    public static FORMATETC ToFormatEtc(this DataFormat format, bool isGdi = false)
+    public static FORMATETC ToFormatEtc(ushort formatId)
         => new()
         {
-            cfFormat = ClipboardFormatRegistry.GetFormatId(format),
+            cfFormat = formatId,
             dwAspect = DVASPECT.DVASPECT_CONTENT,
             ptd = IntPtr.Zero,
             lindex = -1,
-            tymed = isGdi ? TYMED.TYMED_GDI : TYMED.TYMED_HGLOBAL
+            tymed = formatId == (ushort)ClipboardFormat.CF_BITMAP ? TYMED.TYMED_GDI : TYMED.TYMED_HGLOBAL
         };
 
     public static unsafe object? TryGet(this Win32Com.IDataObject oleDataObject, DataFormat format)
     {
-        var formatEtc = format.ToFormatEtc();
+        if (TryGetContainedFormat(oleDataObject, format) is not { } formatId)
-
-        if (oleDataObject.QueryGetData(&formatEtc) != (uint)HRESULT.S_OK)
             return null;
 
         var medium = new STGMEDIUM();
+        var formatEtc = ToFormatEtc(formatId);
         var result = oleDataObject.GetData(&formatEtc, &medium);
         if (result != (uint)HRESULT.S_OK)
-        {
+            return null;
-            if (result == DV_E_TYMED)
-            {
-                formatEtc.tymed = TYMED.TYMED_GDI;
-
-                if (oleDataObject.GetData(&formatEtc, &medium) != (uint)HRESULT.S_OK)
-                {
-                    return null;
-                }
-            }
-            else
-                return null;
-        }
 
         try
         {
@@ -82,6 +70,32 @@ internal static class OleDataObjectHelper
         return null;
     }
 
+    private static ushort? TryGetContainedFormat(Win32Com.IDataObject oleDataObject, DataFormat format)
+    {
+        // Bitmap is not a real format, find the first matching platform format, if any.
+        if (DataFormat.Bitmap.Equals(format))
+        {
+            foreach (var imageFormat in ClipboardFormatRegistry.ImageFormats)
+            {
+                if (TryGetContainedFormatCore(oleDataObject, imageFormat) is { } formatId)
+                    return formatId;
+            }
+
+            return null;
+        }
+
+        return TryGetContainedFormatCore(oleDataObject, format);
+
+        static unsafe ushort? TryGetContainedFormatCore(Win32Com.IDataObject oleDataObject, DataFormat format)
+        {
+            Debug.Assert(format != DataFormat.Bitmap);
+
+            var formatId = ClipboardFormatRegistry.GetOrAddFormat(format);
+            var formatEtc = ToFormatEtc(formatId);
+            return oleDataObject.QueryGetData(&formatEtc) == (uint)HRESULT.S_OK ? formatId : null;
+        }
+    }
+
     private static unsafe object? ReadDataFromGdi(nint bitmapHandle)
     {
         var bitmap = new BITMAP();

src/Windows/Avalonia.Win32/OleDataObjectToDataTransferWrapper.cs

@@ -36,11 +36,7 @@ internal sealed class OleDataObjectToDataTransferWrapper(Win32Com.IDataObject ol
 
         foreach (var format in formats)
         {
-            if (format.Identifier is ClipboardFormatRegistry.DibFormat 
+            if (ClipboardFormatRegistry.ImageFormats.Contains(format)) {
-                or ClipboardFormatRegistry.BitmapFormat 
-                or ClipboardFormatRegistry.PngFormatMimeType
-                or ClipboardFormatRegistry.PngFormatSystemType)
-            {
                 hasSupportedImageFormat = true;
                 break;
             }
@@ -65,7 +61,7 @@ internal sealed class OleDataObjectToDataTransferWrapper(Win32Com.IDataObject ol
             if (formatEtc.ptd != IntPtr.Zero)
                 Marshal.FreeCoTaskMem(formatEtc.ptd);
 
-            return ClipboardFormatRegistry.GetFormatById(formatEtc.cfFormat);
+            return ClipboardFormatRegistry.GetOrAddFormat(formatEtc.cfFormat);
         }
     }