Merge pull request ppy#6254 from Susko3/sdl-clipboard-data

Add support for deferred SDL3 clipboard callbacks (and use it for images)

osu.Framework/Allocation/ObjectHandle.cs

@@ -29,7 +29,7 @@ public struct ObjectHandle<T> : IDisposable
 
         private GCHandle handle;
 
-        private readonly bool fromPointer;
+        private readonly bool canFree;
 
         /// <summary>
         /// Wraps the provided object with a <see cref="GCHandle" />, using the given <see cref="GCHandleType" />.
@@ -39,18 +39,19 @@ public struct ObjectHandle<T> : IDisposable
         public ObjectHandle(T target, GCHandleType handleType)
         {
             handle = GCHandle.Alloc(target, handleType);
-            fromPointer = false;
+            canFree = true;
         }
 
         /// <summary>
         /// Recreates an <see cref="ObjectHandle{T}" /> based on the passed <see cref="IntPtr" />.
-        /// Disposing this object will not free the handle, the original object must be disposed instead.
+        /// If <paramref name="ownsHandle"/> is <c>true</c>, disposing this object will free the handle.
         /// </summary>
-        /// <param name="handle">Handle.</param>
-        public ObjectHandle(IntPtr handle)
+        /// <param name="handle"><see cref="Handle"/> from a previously constructed <see cref="ObjectHandle{T}(T, GCHandleType)"/>.</param>
+        /// <param name="ownsHandle">Whether this instance owns the underlying <see cref="GCHandle"/>.</param>
+        public ObjectHandle(IntPtr handle, bool ownsHandle = false)
         {
             this.handle = GCHandle.FromIntPtr(handle);
-            fromPointer = true;
+            canFree = ownsHandle;
         }
 
         /// <summary>
@@ -87,7 +88,7 @@ public bool GetTarget(out T target)
 
         public void Dispose()
         {
-            if (!fromPointer && handle.IsAllocated)
+            if (canFree && handle.IsAllocated)
                 handle.Free();
         }
 

osu.Framework/Platform/SDL/SDL3Clipboard.cs

@@ -1,13 +1,42 @@
 // Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
+using System.Buffers;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+using osu.Framework.Allocation;
+using osu.Framework.Logging;
 using SDL;
 using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.Formats;
 
 namespace osu.Framework.Platform.SDL
 {
     public class SDL3Clipboard : Clipboard
     {
+        /// <summary>
+        /// Supported formats for decoding images from the clipboard.
+        /// </summary>
+        // It's possible for a format to not have a registered decoder, but all default formats will have one:
+        // https://github.com/SixLabors/ImageSharp/discussions/1353#discussioncomment-9142056
+        private static IEnumerable<string> supportedImageMimeTypes => SixLabors.ImageSharp.Configuration.Default.ImageFormats.SelectMany(f => f.MimeTypes);
+
+        /// <summary>
+        /// Format used for encoding (saving) images to the clipboard.
+        /// </summary>
+        private readonly IImageFormat imageFormat;
+
+        public SDL3Clipboard(IImageFormat imageFormat)
+        {
+            this.imageFormat = imageFormat;
+        }
+
         // SDL cannot differentiate between string.Empty and no text (eg. empty clipboard or an image)
         // doesn't matter as text editors don't really allow copying empty strings.
         // assume that empty text means no text.
@@ -17,12 +46,175 @@ public class SDL3Clipboard : Clipboard
 
         public override Image<TPixel>? GetImage<TPixel>()
         {
+            foreach (string mimeType in supportedImageMimeTypes)
+            {
+                if (tryGetData(mimeType, Image.Load<TPixel>, out var image))
+                {
+                    Logger.Log($"Decoded {mimeType} from clipboard.");
+                    return image;
+                }
+            }
+
             return null;
         }
 
         public override bool SetImage(Image image)
         {
-            return false;
+            ReadOnlyMemory<byte> memory;
+
+            // we can't save the image in the callback as the caller owns the image and might dispose it from under us.
+
+            using (var stream = new MemoryStream())
+            {
+                image.Save(stream, imageFormat);
+
+                // The buffer is allowed to escape the lifetime of the MemoryStream.
+                // https://learn.microsoft.com/en-us/dotnet/api/system.io.memorystream.getbuffer?view=net-8.0
+                // "This method works when the memory stream is closed."
+                memory = new ReadOnlyMemory<byte>(stream.GetBuffer(), 0, (int)stream.Length);
+            }
+
+            return trySetData(imageFormat.DefaultMimeType, () => memory);
+        }
+
+        /// <summary>
+        /// Decodes data from a native memory span. Return null or throw an exception if the data couldn't be decoded.
+        /// </summary>
+        /// <typeparam name="T">Type of decoded data.</typeparam>
+        private delegate T? SpanDecoder<out T>(ReadOnlySpan<byte> span);
+
+        private static unsafe bool tryGetData<T>(string mimeType, SpanDecoder<T> decoder, out T? data)
+        {
+            if (SDL3.SDL_HasClipboardData(mimeType) == SDL_bool.SDL_FALSE)
+            {
+                data = default;
+                return false;
+            }
+
+            UIntPtr nativeSize;
+            IntPtr pointer = SDL3.SDL_GetClipboardData(mimeType, &nativeSize);
+
+            if (pointer == IntPtr.Zero)
+            {
+                Logger.Log($"Failed to get SDL clipboard data for {mimeType}. SDL error: {SDL3.SDL_GetError()}");
+                data = default;
+                return false;
+            }
+
+            try
+            {
+                var nativeMemory = new ReadOnlySpan<byte>((void*)pointer, (int)nativeSize);
+                data = decoder(nativeMemory);
+                return data != null;
+            }
+            catch (Exception e)
+            {
+                Logger.Error(e, $"Failed to decode clipboard data for {mimeType}.");
+                data = default;
+                return false;
+            }
+            finally
+            {
+                SDL3.SDL_free(pointer);
+            }
+        }
+
+        private static unsafe bool trySetData(string mimeType, Func<ReadOnlyMemory<byte>> dataProvider)
+        {
+            var callbackContext = new ClipboardCallbackContext(mimeType, dataProvider);
+            var objectHandle = new ObjectHandle<ClipboardCallbackContext>(callbackContext, GCHandleType.Normal);
+
+            // TODO: support multiple mime types in a single callback
+            fixed (byte* ptr = Encoding.UTF8.GetBytes(mimeType + '\0'))
+            {
+                int ret = SDL3.SDL_SetClipboardData(&dataCallback, &cleanupCallback, objectHandle.Handle, &ptr, 1);
+
+                if (ret < 0)
+                {
+                    objectHandle.Dispose();
+                    Logger.Log($"Failed to set clipboard data callback. SDL error: {SDL3.SDL_GetError()}");
+                }
+
+                return ret == 0;
+            }
+        }
+
+        [UnmanagedCallersOnly(CallConvs = new[] { typeof(CallConvCdecl) })]
+        private static unsafe IntPtr dataCallback(IntPtr userdata, byte* mimeType, UIntPtr* length)
+        {
+            using var objectHandle = new ObjectHandle<ClipboardCallbackContext>(userdata);
+
+            if (!objectHandle.GetTarget(out var context) || context.MimeType != SDL3.PtrToStringUTF8(mimeType))
+            {
+                *length = 0;
+                return IntPtr.Zero;
+            }
+
+            context.EnsureDataValid();
+            *length = context.DataLength;
+            return context.Address;
+        }
+
+        [UnmanagedCallersOnly(CallConvs = new[] { typeof(CallConvCdecl) })]
+        private static void cleanupCallback(IntPtr userdata)
+        {
+            using var objectHandle = new ObjectHandle<ClipboardCallbackContext>(userdata, true);
+
+            if (objectHandle.GetTarget(out var context))
+            {
+                context.Dispose();
+            }
+        }
+
+        private class ClipboardCallbackContext : IDisposable
+        {
+            public readonly string MimeType;
+
+            /// <summary>
+            /// Provider of data suitable for the <see cref="MimeType"/>.
+            /// </summary>
+            /// <remarks>Called when another application requests that mime type from the OS clipboard.</remarks>
+            private Func<ReadOnlyMemory<byte>>? dataProvider;
+
+            private MemoryHandle memoryHandle;
+
+            /// <summary>
+            /// Address of the <see cref="ReadOnlyMemory{T}"/> returned by the <see cref="dataProvider"/>.
+            /// </summary>
+            /// <remarks>Pinned and suitable for passing to unmanaged code.</remarks>
+            public unsafe IntPtr Address => (IntPtr)memoryHandle.Pointer;
+
+            /// <summary>
+            /// Length of the <see cref="ReadOnlyMemory{T}"/> returned by the <see cref="dataProvider"/>.
+            /// </summary>
+            public UIntPtr DataLength { get; private set; }
+
+            public ClipboardCallbackContext(string mimeType, Func<ReadOnlyMemory<byte>> dataProvider)
+            {
+                MimeType = mimeType;
+                this.dataProvider = dataProvider;
+            }
+
+            public void EnsureDataValid()
+            {
+                if (dataProvider == null)
+                {
+                    Debug.Assert(Address != IntPtr.Zero);
+                    Debug.Assert(DataLength != 0);
+                    return;
+                }
+
+                var data = dataProvider();
+                dataProvider = null!;
+                DataLength = (UIntPtr)data.Length;
+                memoryHandle = data.Pin();
+            }
+
+            public void Dispose()
+            {
+                memoryHandle.Dispose();
+                DataLength = 0;
+            }
         }
     }
 }

osu.Framework/Platform/SDL3GameHost.cs

@@ -11,6 +11,7 @@
 using osu.Framework.Input.Handlers.Tablet;
 using osu.Framework.Input.Handlers.Touch;
 using osu.Framework.Platform.SDL;
+using SixLabors.ImageSharp.Formats.Png;
 
 namespace osu.Framework.Platform
 {
@@ -31,7 +32,8 @@ protected override TextInputSource CreateTextInput()
             return base.CreateTextInput();
         }
 
-        protected override Clipboard CreateClipboard() => new SDL3Clipboard();
+        // PNG works well on linux
+        protected override Clipboard CreateClipboard() => new SDL3Clipboard(PngFormat.Instance);
 
         protected override IEnumerable<InputHandler> CreateAvailableInputHandlers() =>
             new InputHandler[]