Avalonia/src/Avalonia.X11/X11IconLoader.cs

using System;
using System.IO;
using System.Runtime.InteropServices;
using Avalonia.Controls.Platform.Surfaces;
using Avalonia.Media.Imaging;
using Avalonia.Platform;

namespace Avalonia.X11
{
    class X11IconLoader : IPlatformIconLoader
    {
        private readonly X11Info _x11;

        public X11IconLoader(X11Info x11)
        {
            _x11 = x11;
        }
        
        IWindowIconImpl LoadIcon(Bitmap bitmap)
        {
            var rv = new X11IconData(bitmap);
            bitmap.Dispose();
            return rv;
        }

        public IWindowIconImpl LoadIcon(string fileName) => LoadIcon(new Bitmap(fileName));

        public IWindowIconImpl LoadIcon(Stream stream) => LoadIcon(new Bitmap(stream));

        public IWindowIconImpl LoadIcon(IBitmapImpl bitmap)
        {
            var ms = new MemoryStream();
            bitmap.Save(ms);
            ms.Position = 0;
            return LoadIcon(ms);
        }
    }
    
    unsafe class X11IconData : IWindowIconImpl, IFramebufferPlatformSurface
    {
        private int _width;
        private int _height;
        private uint[] _bdata;
        public UIntPtr[]  Data { get; }
        
        public X11IconData(Bitmap bitmap)
        {
            _width = Math.Min(bitmap.PixelSize.Width, 128);
            _height = Math.Min(bitmap.PixelSize.Height, 128);
            _bdata = new uint[_width * _height];
            using(var rt = AvaloniaLocator.Current.GetService<IPlatformRenderInterface>().CreateRenderTarget(new[]{this}))
            using (var ctx = rt.CreateDrawingContext(null))
                ctx.DrawBitmap(bitmap.PlatformImpl, 1, new Rect(bitmap.Size),
                    new Rect(0, 0, _width, _height));
            Data = new UIntPtr[_width * _height + 2];
            Data[0] = new UIntPtr((uint)_width);
            Data[1] = new UIntPtr((uint)_height);
            for (var y = 0; y < _height; y++)
            {
                var r = y * _width;
                for (var x = 0; x < _width; x++)
                    Data[r + x + 2] = new UIntPtr(_bdata[r + x]);
            }

            _bdata = null;
        }

        public void Save(Stream outputStream)
        {
            using (var wr =
#pragma warning disable CS0618 // Type or member is obsolete
                new WriteableBitmap(new PixelSize(_width, _height), new Vector(96, 96), PixelFormat.Bgra8888))
#pragma warning restore CS0618 // Type or member is obsolete
            {
                using (var fb = wr.Lock())
                {
                    var fbp = (uint*)fb.Address;
                    for (var y = 0; y < _height; y++)
                    {
                        var r = y * _width;
                        var fbr = y * fb.RowBytes / 4;
                        for (var x = 0; x < _width; x++)
                            fbp[fbr + x] = Data[r + x + 2].ToUInt32();
                    }
                }
                wr.Save(outputStream);
            }
        }

        public ILockedFramebuffer Lock()
        {
            var h = GCHandle.Alloc(_bdata, GCHandleType.Pinned);
            return new LockedFramebuffer(h.AddrOfPinnedObject(), new PixelSize(_width, _height), _width * 4,
                new Vector(96, 96), PixelFormat.Bgra8888,
                () => h.Free());
        }
    }
}