A XAML based PictureMarkerSymbol for the ArcGIS Runtime .NET SDK

XamlMarkerSymbol.cs

using Esri.ArcGISRuntime.Symbology;
using System;
using System.IO;
using System.Threading.Tasks;
using System.Windows;
#if NETFX_CORE
using Windows.UI.Xaml.Markup;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.Foundation;
using Windows.UI.Xaml.Media.Imaging;
using System.Threading;
using System.Runtime.InteropServices.WindowsRuntime;
#else
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Markup;
#endif

namespace MortensGists
{
#if NETFX_CORE
	[ContentProperty(Name = "Template")]
#else
    [ContentProperty("Template")]
#endif
    public class XamlMarkerSymbol : PictureMarkerSymbol
	{
		private DataTemplate m_Template;
		public XamlMarkerSymbol()
		{
			Dpi = 96f;
		}

		
		public DataTemplate Template
		{
			get { return m_Template; }
			set
			{
				if (m_Template != value)
				{
					m_Template = value;
					Task t = RenderAsync(); //TODO: Handle fallback in case task doesn't succeed
				}
			}
		}
		/* Getting DPI (WPF):
		System.Windows.Media.Matrix m = 
		PresentationSource.FromVisual(MyMap).CompositionTarget.TransformToDevice;
		float dpi = 96f & m.M11;
		*/
		public float Dpi { get; set; }

		private async Task RenderAsync()
		{
			ContentControl content = new ContentControl();
			content.Content = this;
			content.ContentTemplate = this.Template;
			double w = this.Width / 72 * 96; //convert points to DIPs
			double h = this.Height / 72 * 96; //convert points to DIPs
			if (w == 0 || h == 0)
			{
				content.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
				w = content.DesiredSize.Width;
				h = content.DesiredSize.Height;
			}
			if (w < 0.5 || h < 0.5)
			{
#if NETFX_CORE
                await SetSourceAsync(null as Windows.Storage.Streams.IRandomAccessStream);
#else
				await SetSourceAsync(null as Stream);
#endif
                return;
			}
            content.Arrange(new Rect(0, 0, w, h));
            int pixelWidth = (int)(w * Dpi / 96); //DIPs to pixel
            int pixelHeight = (int)(h * Dpi / 96); //DIPs to pixel
			
#if WINDOWS_PHONE
			WriteableBitmap bmp = new WriteableBitmap(pixelWidth, pixelHeight);
			bmp.Render(content, null);
			bmp.Invalidate();

#elif NETFX_CORE 
            RenderTargetBitmap bmp = new RenderTargetBitmap();
            await bmp.RenderAsync(content, (int)pixelWidth, (int)pixelHeight).AsTask();
            var pixelBuffer = (await bmp.GetPixelsAsync().AsTask().ConfigureAwait(false)).AsStream();
            byte[] pixels = new byte[pixelBuffer.Length];
            pixelBuffer.Write(pixels, 0, pixels.Length);
            var png = new MemoryStream().AsRandomAccessStream();
            var encoder = await Windows.Graphics.Imaging.BitmapEncoder.CreateAsync(Windows.Graphics.Imaging.BitmapEncoder.PngEncoderId, png).AsTask();
            encoder.SetPixelData(Windows.Graphics.Imaging.BitmapPixelFormat.Rgba8, Windows.Graphics.Imaging.BitmapAlphaMode.Straight,
                (uint)pixelWidth, (uint)pixelHeight, Dpi, Dpi, pixels);
            await encoder.FlushAsync().AsTask();
            await SetSourceAsync(png);
#else //WPF
			RenderTargetBitmap bmp = new RenderTargetBitmap(pixelWidth, pixelHeight, Dpi, Dpi, PixelFormats.Default);
			bmp.Render(content);
			PngBitmapEncoder png = new PngBitmapEncoder();
			png.Frames.Add(BitmapFrame.Create(bmp));
			using (Stream stm = new MemoryStream())
			{
				png.Save(stm);
				stm.Seek(0, SeekOrigin.Begin);
				await SetSourceAsync(stm);
			}
#endif
		}
	}
}