Clipboard: rich formats (image + HTML/MIME) beyond plain text

src/Skyline.Apple/AppKitWindowBackend.cs

@@ -129,6 +129,57 @@ public string? ClipboardText
         }
     }
 
+    // MIME type to macOS pasteboard UTI, for the formats a browser moves most.
+    private static readonly (string Mime, string Uti)[] ClipboardTypeMap =
+    [
+        ("text/plain", PasteboardText),
+        ("text/html", "public.html"),
+        ("image/png", "public.png"),
+    ];
+
+    private static string? MimeToUti(string mime)
+    {
+        foreach (var (m, uti) in ClipboardTypeMap)
+        {
+            if (m == mime)
+            {
+                return uti;
+            }
+        }
+        return null;
+    }
+
+    public IReadOnlyList<string> ClipboardFormats
+    {
+        get
+        {
+            var pb = NSPasteboard.GeneralPasteboard;
+            var formats = new List<string>();
+            foreach (var (mime, uti) in ClipboardTypeMap)
+            {
+                if (pb.GetDataForType(uti) is not null)
+                {
+                    formats.Add(mime);
+                }
+            }
+            return formats;
+        }
+    }
+
+    public byte[]? GetClipboardData(string mimeType) =>
+        MimeToUti(mimeType) is { } uti ? NSPasteboard.GeneralPasteboard.GetDataForType(uti)?.ToArray() : null;
+
+    public void SetClipboardData(string mimeType, byte[] data)
+    {
+        if (MimeToUti(mimeType) is not { } uti)
+        {
+            return;
+        }
+        var pb = NSPasteboard.GeneralPasteboard;
+        pb.ClearContents();
+        pb.SetDataForType(NSData.FromArray(data), uti);
+    }
+
     public bool IsClosing => _closing;
 
     public WindowSurfaceSource SurfaceSource => _surfaceSource;

src/Skyline/AppWindow.cs

@@ -158,6 +158,21 @@ public string? ClipboardText
         set => _backend.ClipboardText = value;
     }
 
+    /// <summary>The MIME types currently on the clipboard.</summary>
+    public IReadOnlyList<string> ClipboardFormats => _backend.ClipboardFormats;
+
+    /// <summary>
+    /// Read clipboard data for a MIME type (for example "image/png" or
+    /// "text/html"), or null if the clipboard holds no such type.
+    /// </summary>
+    public byte[]? GetClipboardData(string mimeType) => _backend.GetClipboardData(mimeType);
+
+    /// <summary>
+    /// Write clipboard data under a MIME type, replacing the clipboard. The
+    /// GLFW backend stores text only; other types are dropped there.
+    /// </summary>
+    public void SetClipboardData(string mimeType, byte[] data) => _backend.SetClipboardData(mimeType, data);
+
     public FrameInfo CurrentFrame => Frame(0);
 
     /// <summary>True when this window has been adopted by an <see cref="AppHost"/>. Hosted windows render on the host's thread, so use <c>AppHost.Run</c>, not <see cref="Run"/>.</summary>

src/Skyline/GlfwWindowBackend.cs

@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: Apache-2.0
+using System.Text;
 using Silk.NET.GLFW;
 using Silk.NET.Input;
 using Silk.NET.Maths;
@@ -88,6 +89,30 @@ public unsafe string? ClipboardText
         set => _glfw.SetClipboardString(_glfwHandle, value ?? string.Empty);
     }
 
+    // GLFW's clipboard is text only, so it reports and stores text/plain alone.
+    private static readonly string[] TextFormats = ["text/plain"];
+
+    public unsafe IReadOnlyList<string> ClipboardFormats =>
+        string.IsNullOrEmpty(_glfw.GetClipboardString(_glfwHandle)) ? [] : TextFormats;
+
+    public unsafe byte[]? GetClipboardData(string mimeType)
+    {
+        if (mimeType == "text/plain" && _glfw.GetClipboardString(_glfwHandle) is { Length: > 0 } s)
+        {
+            return Encoding.UTF8.GetBytes(s);
+        }
+        return null;
+    }
+
+    public unsafe void SetClipboardData(string mimeType, byte[] data)
+    {
+        // Other MIME types are dropped: GLFW has nowhere to put them.
+        if (mimeType == "text/plain")
+        {
+            _glfw.SetClipboardString(_glfwHandle, Encoding.UTF8.GetString(data));
+        }
+    }
+
     public bool IsClosing => _window.IsClosing;
 
     public WindowSurfaceSource SurfaceSource => _surfaceSource;

src/Skyline/IWindowBackend.cs

@@ -20,6 +20,15 @@ internal interface IWindowBackend : IDisposable
     string Title { get; set; }
     string? ClipboardText { get; set; }
 
+    /// <summary>The MIME types currently on the clipboard.</summary>
+    IReadOnlyList<string> ClipboardFormats { get; }
+
+    /// <summary>Read clipboard data for a MIME type, or null if absent.</summary>
+    byte[]? GetClipboardData(string mimeType);
+
+    /// <summary>Write clipboard data under a MIME type, replacing the clipboard.</summary>
+    void SetClipboardData(string mimeType, byte[] data);
+
     bool IsClosing { get; }
 
     /// <summary>How a presenter builds a surface for this window.</summary>

tests/Skyline.Tests/WindowBackendFactoryTests.cs

@@ -16,6 +16,9 @@ private sealed class FakeBackend : IWindowBackend
         public (int Width, int Height) LogicalSize => (100, 50);
         public string Title { get; set; } = "fake";
         public string? ClipboardText { get; set; }
+        public IReadOnlyList<string> ClipboardFormats => [];
+        public byte[]? GetClipboardData(string mimeType) => null;
+        public void SetClipboardData(string mimeType, byte[] data) { }
         public bool IsClosing => false;
         public WindowSurfaceSource SurfaceSource { get; } = new WindowSurfaceSource.MetalLayer(0x1234);
 

tests/Skyline.WindowedTests/Program.cs

@@ -42,6 +42,17 @@ void Check(bool condition, string what)
 win.ClipboardText = "skyline-test";
 Check(win.ClipboardText == "skyline-test", "clipboard round-trips");
 
+// Typed clipboard on the GLFW backend (text only there).
+using (var clipWin = new AppWindow(new AppWindowOptions { Title = "clip", Width = 160, Height = 120, ForceGlfw = true }))
+{
+    clipWin.SetClipboardData("text/plain", System.Text.Encoding.UTF8.GetBytes("typed-clip"));
+    var back = clipWin.GetClipboardData("text/plain");
+    Check(back is not null && System.Text.Encoding.UTF8.GetString(back) == "typed-clip", "typed text clipboard round-trips on GLFW");
+    Check(clipWin.GetClipboardData("image/png") is null, "GLFW reports no data for an unsupported type");
+    clipWin.SetClipboardData("image/png", [1, 2, 3]); // dropped, must not throw
+    Check(clipWin.ClipboardFormats.Contains("text/plain"), "ClipboardFormats lists text/plain when text is present");
+}
+
 win.PumpEvents(); // must not throw without a host
 
 // --- Chrome modes construct on the GLFW backend ------------------------