SVG: Use cancellation token while reading SVG

Author: daniel-luberda

source/FFImageLoading.Svg.Shared/SkSvg.cs

@@ -9,6 +9,7 @@
 using System.Xml;
 using System.Xml.Linq;
 using SkiaSharp;
+using System.Threading;
 
 namespace FFImageLoading.Svg.Platform
 {
@@ -18,7 +19,6 @@ public class SKSvg
 		private const float DefaultPPI = 160f;
 		private const bool DefaultThrowOnUnsupportedElement = false;
 
-		private static readonly Random random = new Random();
 		private static readonly IFormatProvider icult = CultureInfo.InvariantCulture;
 		private static readonly XNamespace xlink = "http://www.w3.org/1999/xlink";
 		private static readonly XNamespace svg = "http://www.w3.org/2000/svg";
@@ -28,6 +28,7 @@ public class SKSvg
 		private static readonly Regex urlRe = new Regex(@"url\s*\(\s*#([^\)]+)\)");
 		private static readonly Regex keyValueRe = new Regex(@"\s*([\w-]+)\s*:\s*(.*)");
 		private static readonly Regex WSRe = new Regex(@"\s{2,}");
+
 		private readonly Dictionary<string, string> styles = new Dictionary<string, string>();
 		private readonly Dictionary<string, XElement> defs = new Dictionary<string, XElement>();
 		private readonly Dictionary<string, SKSvgMask> masks = new Dictionary<string, SKSvgMask>();
@@ -78,25 +79,25 @@ public SKSvg(float pixelsPerInch, SKSize canvasSize)
 
 		public string Version { get; private set; }
 
-		public SKPicture Load(string filename)
+		public SKPicture Load(string filename, CancellationToken token = default)
 		{
 			using (var stream = File.OpenRead(filename))
 			{
 				return Load(stream);
 			}
 		}
 
-		public SKPicture Load(Stream stream)
+		public SKPicture Load(Stream stream, CancellationToken token = default)
 		{
 			using (var reader = XmlReader.Create(stream, xmlReaderSettings, CreateSvgXmlContext()))
 			{
-				return Load(reader);
+				return Load(reader, token);
 			}
 		}
 
-		public SKPicture Load(XmlReader reader)
+		public SKPicture Load(XmlReader reader, CancellationToken token = default)
 		{
-			return Load(XDocument.Load(reader));
+			return Load(XDocument.Load(reader), token);
 		}
 
 		private static XmlParserContext CreateSvgXmlContext()
@@ -108,7 +109,7 @@ private static XmlParserContext CreateSvgXmlContext()
 			return new XmlParserContext(null, manager, null, XmlSpace.None);
 		}
 
-		private SKPicture Load(XDocument xdoc)
+		private SKPicture Load(XDocument xdoc, CancellationToken token = default)
 		{
 			var svg = xdoc.Root;
 			var ns = svg.Name.Namespace;
@@ -165,6 +166,8 @@ private SKPicture Load(XDocument xdoc)
 				CanvasSize = size;
 			}
 
+			token.ThrowIfCancellationRequested();
+
 			// create the picture from the elements
 			using (var recorder = new SKPictureRecorder())
 			using (var canvas = recorder.BeginRecording(SKRect.Create(CanvasSize)))
@@ -203,24 +206,26 @@ private SKPicture Load(XDocument xdoc)
 				var style = ReadPaints(svg, ref stroke, ref fill, true);
 
 				// read elements
-				LoadElements(svg.Elements(), canvas, stroke, fill);
+				LoadElements(svg.Elements(), canvas, stroke, fill, token);
 
 				Picture = recorder.EndRecording();
 			}
 
 			return Picture;
 		}
 
-		private void LoadElements(IEnumerable<XElement> elements, SKCanvas canvas, SKPaint stroke, SKPaint fill)
+		private void LoadElements(IEnumerable<XElement> elements, SKCanvas canvas, SKPaint stroke, SKPaint fill, CancellationToken token = default)
 		{
 			foreach (var e in elements)
 			{
 				ReadElement(e, canvas, stroke?.Clone(), fill?.Clone());
 			}
 		}
 
-		private void ReadElement(XElement e, SKCanvas canvas, SKPaint stroke, SKPaint fill, bool isMask = false)
+		private void ReadElement(XElement e, SKCanvas canvas, SKPaint stroke, SKPaint fill, bool isMask = false, CancellationToken token = default)
 		{
+			token.ThrowIfCancellationRequested();
+
 			if (e.Attribute("display")?.Value == "none")
 				return;
 

source/FFImageLoading.Svg.Shared/SvgDataResolver.cs

@@ -229,7 +229,7 @@ public async Task<DataResolverResult> Resolve(string identifier, TaskParameter p
             {
                 using (var svgStream = resolvedData.Stream)
                 {
-                    picture = svg.Load(svgStream);
+                    picture = svg.Load(svgStream, token);
                 }
             }
             else
@@ -253,13 +253,17 @@ public async Task<DataResolverResult> Resolve(string identifier, TaskParameter p
                         builder.Replace(map.Key, map.Value);
                     }
 
-                    using (var svgFinalStream = new MemoryStream(Encoding.UTF8.GetBytes(builder.ToString())))
+					token.ThrowIfCancellationRequested();
+
+					using (var svgFinalStream = new MemoryStream(Encoding.UTF8.GetBytes(builder.ToString())))
                     {
                         picture = svg.Load(svgFinalStream);
                     }
                 }
             }
 
+			token.ThrowIfCancellationRequested();
+
             double sizeX = VectorWidth;
             double sizeY = VectorHeight;
 
@@ -303,6 +307,8 @@ public async Task<DataResolverResult> Resolve(string identifier, TaskParameter p
                 canvas.DrawPicture(picture, ref matrix, paint);
                 canvas.Flush();
 
+				token.ThrowIfCancellationRequested();
+
 				return await Decode(picture, bitmap, resolvedData).ConfigureAwait(false);
 			}
         }