Merge remote-tracking branch 'origin/master'

Assets/UIWidgets/Tests/CanvasAndLayers.cs

 using System;
+using System.Collections.Generic;
 using System.Linq;
 using UIWidgets.painting;
 using UIWidgets.ui;
 
         private int _selected;
 
+        private PaintingBinding paintingBinding;
+
+        private ImageStream _stream;
+
+                this.drawImageRect,
                 this.drawPicture,
                 this.clipRect,
                 this.clipRRect,
         void OnGUI() {
             this._selected = EditorGUILayout.Popup("test case", this._selected, this._optionStrings);
 
+            if (_selected == 3) {
+                if (GUI.Button(new UnityEngine.Rect(20, 50, 100, 20), "Image 1")) {
+                    LoadImage(
+                        "http://a.hiphotos.baidu.com/image/h%3D300/sign=10b374237f0e0cf3bff748fb3a47f23d/adaf2edda3cc7cd90df1ede83401213fb80e9127.jpg");
+                }
+
+                if (GUI.Button(new UnityEngine.Rect(20, 150, 100, 20), "Image 2")) {
+                    LoadImage(
+                        "http://a.hiphotos.baidu.com/image/pic/item/cf1b9d16fdfaaf519b4aa960875494eef11f7a47.jpg");
+                }
+
+                if (GUI.Button(new UnityEngine.Rect(20, 250, 100, 20), "Image 3")) {
+                    LoadImage(
+                        "http://a.hiphotos.baidu.com/image/pic/item/2f738bd4b31c8701c1e721dd2a7f9e2f0708ffbc.jpg");
+                }
+            }
+
+        private void OnEnable() {
+            this.paintingBinding = new PaintingBinding(null);
+            paintingBinding.initInstances();
+        }
+
+        private void LoadImage(string url) {
+            Dictionary<string, string> headers = new Dictionary<string, string>();
+            NetworkImage networkImage = new NetworkImage(url, headers);
+            ImageConfiguration imageConfig = new ImageConfiguration();
+            _stream = networkImage.resolve(imageConfig);
+        }
+
         void drawPloygon4() {
             var canvas = new CanvasImpl();
 
             editorCanvas.drawPicture(picture);
         }
 
+        void drawImageRect() {
+            if (_stream == null || _stream.completer == null || _stream.completer._currentImgae == null) {
+                return;
+            }
+
+            var canvas = new CanvasImpl();
+
+            var paint = new Paint {
+                color = new Color(0xFFFF0000),
+            };
+
+            canvas.drawImageRect(
+                Rect.fromLTWH(150, 50, 250, 250),
+                Rect.fromLTWH(150, 50, 250, 250),
+                paint,
+                _stream.completer._currentImgae.image
+            );
+        }
+
         void clipRect() {
             var pictureRecorder = new PictureRecorder();
             var canvas = new RecorderCanvas(pictureRecorder);
                 paint);
 
             var picture = pictureRecorder.endRecording();
-            Debug.Log("picture.paintBounds: " + picture.paintBounds);
 
             var editorCanvas = new CanvasImpl();
             editorCanvas.concat(Matrix4x4.Rotate(Quaternion.Euler(0, 0, -5)));

Assets/UIWidgets/painting/alignment.cs

-using System;
+using System;
 using UIWidgets.ui;
 
 namespace UIWidgets.painting {
             this.y = y;
         }
 
-        private readonly double x;
+        public readonly double x;
-        private readonly double y;
+        public readonly double y;
 
         public static readonly Alignment topLeft = new Alignment(-1.0, -1.0);
         public static readonly Alignment topCenter = new Alignment(0, -1.0);
             );
         }
 
-        Rect inscribe(Size size, Rect rect) {
+        public Rect inscribe(Size size, Rect rect) {
             double halfWidthDelta = (rect.width - size.width) / 2.0;
             double halfHeightDelta = (rect.height - size.height) / 2.0;
             return Rect.fromLTWH(

Assets/UIWidgets/painting/alignment.cs.meta

-fileFormatVersion: 2
-guid: d34b191577d24c30b0fd2a99022b8a88
-timeCreated: 1535002958
+fileFormatVersion: 2
+guid: 52b90656e86c4a39af38d0518a67f68b
+timeCreated: 1534820611

Assets/UIWidgets/painting/binding.cs

+using UIWidgets.ui;
+
-    public abstract class PaintingBinding {
+    public class PaintingBinding {
+
+        public PaintingBinding(Window window) {
+            this._window = window;
+        }
+        private static PaintingBinding _instance;
+        public readonly Window _window;
+
+        public static PaintingBinding instance {
+            get { return _instance; }
+        }
+
+        private ImageCache _imageCache;
+
+        public ImageCache imageCache {
+            get { return _imageCache; }
+        }
+
+        public ImageCache createImageCache() {
+            return new ImageCache();
+        }
+
+        public void initInstances() {
+            _instance = this;
+            _imageCache = createImageCache();
+        }
     }
 }

Assets/UIWidgets/painting/box_border.cs

             }
         }
     }
-
-    public class ImageConfiguration {
-        public ImageConfiguration(Size size = null) {
-            this.size = size;
-        }
-
-        public static readonly ImageConfiguration empty = new ImageConfiguration();
-
-        public ImageConfiguration copyWith(
-            Size size = null) {
-            return new ImageConfiguration(
-                size: size ?? this.size
-            );
-        }
-
-        public readonly Size size;
-    }
 }

Assets/UIWidgets/painting/decoration_image.cs

-
+using System;
+using UIWidgets.ui;
+using System.Collections.Generic;
+    /// How to paint any portions of a box not covered by an image.
+    public enum ImageRepeat {
+        /// Repeat the image in both the x and y directions until the box is filled.
+        repeat,
+
+        /// Repeat the image in the x direction until the box is filled horizontally.
+        repeatX,
+
+        /// Repeat the image in the y direction until the box is filled vertically.
+        repeatY,
+
+        /// Leave uncovered portions of the box transparent.
+        noRepeat,
+    }
+
-        
+        public DecorationImage() {
+        }
+    }
+
+    public static class DecorationImageUtil {
+        public static void paintImage(Canvas canvas, Rect rect, ui.Image image, BoxFit fit, Rect centerSlice,
+            Alignment alignment = null,
+            ImageRepeat repeat = ImageRepeat.noRepeat) {
+            if (rect.isEmpty)
+                return;
+            alignment = alignment ?? Alignment.center;
+            Size outputSize = rect.size;
+            Size inputSize = new Size(image.width, image.height);
+            Offset sliceBorder = null;
+            if (centerSlice != null) {
+                sliceBorder = new Offset(
+                    centerSlice.left + inputSize.width - centerSlice.right,
+                    centerSlice.top + inputSize.height - centerSlice.bottom
+                );
+                outputSize -= sliceBorder;
+                inputSize -= sliceBorder;
+            }
+
+            fit = centerSlice == null ? BoxFit.scaleDown : BoxFit.fill;
+            FittedSizes fittedSizes = FittedSizes.applyBoxFit(fit, inputSize, outputSize);
+            Size sourceSize = fittedSizes.source;
+            Size destinationSize = fittedSizes.destination;
+            if (centerSlice != null) {
+                outputSize += sliceBorder;
+                destinationSize += sliceBorder;
+            }
+
+            if (repeat != ImageRepeat.noRepeat && destinationSize == outputSize) {
+                repeat = ImageRepeat.noRepeat;
+            }
+
+            Paint paint = new Paint(); // ..isAntiAlias = false;
+//            if (colorFilter != null)
+//                paint.colorFilter = colorFilter;
+            if (sourceSize != destinationSize) {
+                // Use the "low" quality setting to scale the image, which corresponds to
+                // bilinear interpolation, rather than the default "none" which corresponds
+                // to nearest-neighbor.
+//                paint.filterQuality = FilterQuality.low;
+            }
+
+            double halfWidthDelta = (outputSize.width - destinationSize.width) / 2.0;
+            double halfHeightDelta = (outputSize.height - destinationSize.height) / 2.0;
+            double dx = halfWidthDelta + alignment.x * halfWidthDelta;
+            double dy = halfHeightDelta + alignment.y * halfHeightDelta;
+            Offset destinationPosition = rect.topLeft.translate(dx, dy);
+            Rect destinationRect = destinationPosition & destinationSize;
+            bool needSave = repeat != ImageRepeat.noRepeat;
+            if (needSave)
+                canvas.save();
+            if (repeat != ImageRepeat.noRepeat)
+                canvas.clipRect(rect);
+            if (centerSlice == null) {
+                Rect sourceRect = alignment.inscribe(
+                    fittedSizes.source, Offset.zero & inputSize
+                );
+                foreach (Rect tileRect in _generateImageTileRects(rect, destinationRect, repeat)) {
+                    canvas.drawImageRect(sourceRect, tileRect, paint, image);
+                }
+            }
+            else {
+                // todo
+                foreach (Rect tileRect in _generateImageTileRects(rect, destinationRect, repeat)) {
+//                canvas.drawImageNine(image, centerSlice, tileRect, paint);
+                }
+            }
+
+            if (needSave)
+                canvas.restore();
+        }
+
+        public static List<Rect> _generateImageTileRects(Rect outputRect, Rect fundamentalRect,
+            ImageRepeat repeat) {
+            List<Rect> tileRects = new List<Rect>();
+            if (repeat == ImageRepeat.noRepeat) {
+                tileRects.Add(fundamentalRect);
+                return tileRects;
+            }
+
+            int startX = 0;
+            int startY = 0;
+            int stopX = 0;
+            int stopY = 0;
+            double strideX = fundamentalRect.width;
+            double strideY = fundamentalRect.height;
+
+            if (repeat == ImageRepeat.repeat || repeat == ImageRepeat.repeatX) {
+                startX = (int) Math.Floor((outputRect.left - fundamentalRect.left) / strideX);
+                stopX = (int) Math.Ceiling((outputRect.right - fundamentalRect.right) / strideX);
+            }
+
+            if (repeat == ImageRepeat.repeat || repeat == ImageRepeat.repeatY) {
+                startY = (int) Math.Floor((outputRect.top - fundamentalRect.top) / strideY);
+                stopY = (int) Math.Ceiling((outputRect.bottom - fundamentalRect.bottom) / strideY);
+            }
+
+            for (int i = startX; i <= stopX; ++i) {
+                for (int j = startY; j <= stopY; ++j)
+                    tileRects.Add(fundamentalRect.shift(new Offset(i * strideX, j * strideY)));
+            }
+
+            return tileRects;
+        }
     }
 }

Assets/UIWidgets/rendering/box.cs

             );
         }
 
+        public static BoxConstraints tightFor(double width, double height) {
+            return new BoxConstraints(
+                width,
+                width,
+                height,
+                height
+            );
+        }
+
         public static BoxConstraints tightFor(
             double? width = null,
             double? height = null
         : ContainerRenderObjectMixinRenderBox<ChildType, ParentDataType>
         where ChildType : RenderBox
         where ParentDataType : ContainerParentDataMixinBoxParentData<ChildType> {
-        
         public double? defaultComputeDistanceToFirstActualBaseline(TextBaseline baseline) {
             var child = this.firstChild;
             while (child != null) {
                     candidate += childParentData.offset.dy;
                     if (result != null) {
                         result = Math.Min(result.Value, candidate.Value);
-                    } else {
+                    }
+                    else {
                         result = candidate;
                     }
                 }

Assets/UIWidgets/ui/geometry.cs

             get { return this.width <= 0.0 || this.height <= 0.0; }
         }
 
-        public static Size operator +(Size a, Offset b) {
-            return new Size(a.width + b.dx, a.height + b.dy);
-        }
-
+        }
+
+        public static Size operator +(Size a, Offset b) {
+            return new Size(a.width + b.dx, a.height + b.dy);
         }
 
         public static Offset operator -(Size a, Size b) {

Assets/UIWidgets/ui/painting/canvas.cs

 
         void drawPicture(Picture picture);
 
+        void drawImageRect(Rect src, Rect dst, Paint paint, Image image);
+
         void concat(Matrix4x4 transform);
 
         void save();
         public void drawPicture(Picture picture) {
             this._recorder.addDrawCmd(new DrawPicture {
                 picture = picture,
+            });
+        }
+
+        public void drawImageRect(Rect src, Rect dst, Paint paint, Image image) {
+            this._recorder.addDrawCmd(new DrawImageRect
+            {
+                image = image,
+                src = src,
+                dst = dst,
             });
         }
 

Assets/UIWidgets/ui/painting/canvas_impl.cs

                 if (drawCmd is DrawPloygon4) {
                     var drawPloygon4 = (DrawPloygon4) drawCmd;
                     this.drawPloygon4(drawPloygon4.points, drawPloygon4.paint);
-                } else if (drawCmd is DrawRect) {
+                }
+                else if (drawCmd is DrawRect) {
-                } else if (drawCmd is DrawRectShadow) {
+                }
+                else if (drawCmd is DrawRectShadow) {
-                } else if (drawCmd is DrawPicture) {
+                }
+                else if (drawCmd is DrawPicture) {
-                } else if (drawCmd is DrawConcat) {
+                }
+                else if (drawCmd is DrawConcat) {
-                } else if (drawCmd is DrawSave) {
+                }
+                else if (drawCmd is DrawSave) {
-                } else if (drawCmd is DrawSaveLayer) {
+                }
+                else if (drawCmd is DrawSaveLayer) {
-                } else if (drawCmd is DrawRestore) {
+                }
+                else if (drawCmd is DrawRestore) {
                     saveCount--;
                     if (saveCount < 0) {
                         throw new Exception("unmatched save/restore in picture");
-                } else if (drawCmd is DrawClipRect) {
+                }
+                else if (drawCmd is DrawClipRect) {
-                } else if (drawCmd is DrawClipRRect) {
+                }
+                else if (drawCmd is DrawClipRRect) {
-                } else {
+                }
+                else {
                     throw new Exception("unknown drawCmd: " + drawCmd);
                 }
             }
             }
 
             this.restore();
+        }
+
+        public void drawImageRect(Rect src, Rect dst, Paint paint, Image image) {
+            if (image != null) {
+                Texture2D _texture = new Texture2D(0, 0);
+                _texture.LoadImage(image.rawData);
+                Graphics.DrawTexture(dst.toRect(), _texture);
+            }
         }
 
         public void concat(Matrix4x4 transform) {
                         (float) rect.width,
                         (float) rect.height));
                     mat.SetVector("UIWidgets_GUIClipRectRadius", new Vector4(0, 0, 0, 0));
-                } else {
+                }
+                else {
                     var rrect = this._clipRec.rrect;
                     var rect = rrect.outerRect;
                     mat.SetVector("UIWidgets_GUIClipRect", new Vector4(
                             (float) rrect.brRadius,
                             (float) rrect.blRadius));
                 }
-            } else {
+            }
+            else {
                 mat.SetMatrix("UIWidgets_GUIClipMatrix", Matrix4x4.identity);
                 var rect = Rect.largest;
                 mat.SetVector("UIWidgets_GUIClipRect", new Vector4(

Assets/UIWidgets/ui/painting/draw_cmd.cs

 using UIWidgets.painting;
 using UnityEngine;
+using UnityEngine.UI;
 
 namespace UIWidgets.ui {
     public interface DrawCmd {
 
     public class DrawPicture : DrawCmd {
         public Picture picture;
+    }
+
+    public class DrawImageRect : DrawCmd {
+        public Image image;
+        public Rect src;
+        public Rect dst;
     }
 
     public class DrawConcat : DrawCmd {

Assets/UIWidgets/ui/painting/painting.cs

             };
         }
     }
+
+    public class ColorFilter {
+        public ColorFilter(Color color, BlendMode blendMode) {
+            _color = color;
+            _blendMode = blendMode;
+        }
+
+        Color _color;
+        BlendMode _blendMode;
+    }
+
+    public enum BlendMode {
+        None = 0, // explicitly assign zero to make it more clear
+        clear,
+        src,
+        dst,
+        dstOver,
+        srcIn,
+        dstIn,
+        srcOut,
+        dstOut,
+        srcATop,
+        dstATop,
+        xor,
+        plus,
+        modulate,
+        screen, // The last coeff mode.
+        overlay,
+        darken,
+        lighten,
+        colorDodge,
+        colorBurn,
+        hardLight,
+        softLight,
+        difference,
+        exclusion,
+        multiply, // The last separable mode.
+        hue,
+        saturation,
+        color,
+        luminosity,
+    }
 }

Assets/UIWidgets/painting/box_fit.cs

+using UIWidgets.ui;
+using System;
+
+namespace UIWidgets.painting {
+    public enum BoxFit {
+        fill,
+        contain,
+        cover,
+        fitWidth,
+        fitHeight,
+        none,
+        scaleDown,
+    }
+
+    public class FittedSizes {
+        public FittedSizes(Size source, Size destination) {
+            this.source = source;
+            this.destination = destination;
+        }
+
+        public Size source;
+        public Size destination;
+
+        public static FittedSizes applyBoxFit(BoxFit fit, Size inputSize, Size outputSize) {
+            if (inputSize.height <= 0.0 || inputSize.width <= 0.0 || outputSize.height <= 0.0 ||
+                outputSize.width <= 0.0)
+                return new FittedSizes(Size.zero, Size.zero);
+            Size sourceSize = null;
+            Size destinationSize = null;
+            switch (fit) {
+                case BoxFit.fill:
+                    sourceSize = inputSize;
+                    destinationSize = outputSize;
+                    break;
+                case BoxFit.contain:
+                    sourceSize = inputSize;
+                    if (outputSize.width / outputSize.height > sourceSize.width / sourceSize.height)
+                        destinationSize = new Size(sourceSize.width * outputSize.height / sourceSize.height,
+                            outputSize.height);
+                    else
+                        destinationSize = new Size(outputSize.width,
+                            sourceSize.height * outputSize.width / sourceSize.width);
+                    break;
+                case BoxFit.cover:
+                    if (outputSize.width / outputSize.height > inputSize.width / inputSize.height) {
+                        sourceSize = new Size(inputSize.width, inputSize.width * outputSize.height / outputSize.width);
+                    }
+                    else {
+                        sourceSize = new Size(inputSize.height * outputSize.width / outputSize.height,
+                            inputSize.height);
+                    }
+
+                    destinationSize = outputSize;
+                    break;
+                case BoxFit.fitWidth:
+                    sourceSize = new Size(inputSize.width, inputSize.width * outputSize.height / outputSize.width);
+                    destinationSize = new Size(outputSize.width,
+                        sourceSize.height * outputSize.width / sourceSize.width);
+                    break;
+                case BoxFit.fitHeight:
+                    sourceSize = new Size(inputSize.height * outputSize.width / outputSize.height, inputSize.height);
+                    destinationSize = new Size(sourceSize.width * outputSize.height / sourceSize.height,
+                        outputSize.height);
+                    break;
+                case BoxFit.none:
+                    sourceSize = new Size(Math.Min(inputSize.width, outputSize.width),
+                        Math.Min(inputSize.height, outputSize.height));
+                    destinationSize = sourceSize;
+                    break;
+                case BoxFit.scaleDown:
+                    sourceSize = inputSize;
+                    destinationSize = inputSize;
+                    double aspectRatio = inputSize.width / inputSize.height;
+                    if (destinationSize.height > outputSize.height)
+                        destinationSize = new Size(outputSize.height * aspectRatio, outputSize.height);
+                    if (destinationSize.width > outputSize.width)
+                        destinationSize = new Size(outputSize.width, outputSize.width / aspectRatio);
+                    break;
+            }
+
+            return new FittedSizes(sourceSize, destinationSize);
+        }
+    }
+}

Assets/UIWidgets/painting/box_fit.cs.meta

+fileFormatVersion: 2
+guid: 4d75ec15a75b4a7baca1968978b1eec9
+timeCreated: 1534820694

Assets/UIWidgets/painting/image_cache.cs

+using System.Collections.Generic;
+using Object = System.Object;
+
+namespace UIWidgets.painting {
+    public class ImageCache {
+        private const int _kDefaultSize = 1000;
+        private const int _kDefaultSizeBytes = 20 << 20; // 20 MiB
+
+        public Dictionary<Object, ImageStreamCompleter> _pendingImages =
+            new Dictionary<Object, ImageStreamCompleter>();
+
+        public Dictionary<Object, _CachedImage> _cache = new Dictionary<Object, _CachedImage>();
+        public LinkedList<Object> _lruKeys = new LinkedList<Object>();
+
+        private int _maximumSize = _kDefaultSize;
+
+        public int maximumSize {
+            get { return _maximumSize; }
+            set {
+                if (value == maximumSize) {
+                    return;
+                }
+
+                _maximumSize = value;
+                if (maximumSize == 0) {
+                    _cache.Clear();
+                    _lruKeys.Clear();
+                    _currentSizeBytes = 0;
+                }
+                else {
+                    _checkCacheSize();
+                }
+            }
+        }
+
+        public int currentSize {
+            get { return _cache.Count; }
+        }
+
+        private int _maximumSizeBytes = _kDefaultSizeBytes;
+
+        public int maximumSizeBytes {
+            get { return _maximumSizeBytes; }
+            set {
+                if (value == _maximumSizeBytes) {
+                    return;
+                }
+
+                _maximumSizeBytes = value;
+                if (_maximumSizeBytes == 0) {
+                    _cache.Clear();
+                    _lruKeys.Clear();
+                    _currentSizeBytes = 0;
+                }
+                else {
+                    _checkCacheSize();
+                }
+            }
+        }
+
+        private int _currentSizeBytes;
+
+        public int currentSizeBytes {
+            get { return _currentSizeBytes; }
+        }
+
+        public void clear() {
+            _cache.Clear();
+            _lruKeys.Clear();
+            _currentSizeBytes = 0;
+        }
+
+        public delegate ImageStreamCompleter Loader();
+
+        public ImageStreamCompleter putIfAbsent(Object key, Loader loader) {
+            ImageStreamCompleter result;
+            if (_pendingImages.TryGetValue(key, out result)) {
+                return result;
+            }
+
+            _CachedImage image;
+            if (_cache.TryGetValue(key, out image)) {
+                // put to the MRU position
+                _lruKeys.Remove(key);
+                _lruKeys.AddLast(key);
+            }
+
+            if (image != null) {
+                return image.completer;
+            }
+
+            result = loader();
+
+            if (maximumSize > 0 && maximumSizeBytes > 0) {
+                _pendingImages[key] = result;
+                result.addListener((info, syncCall) => {
+//                    int imageSize = info.image == null ? 0 : info.image.height * info.image.width * 4;
+                    // now we use length or raw bytes array as image size
+                    int imageSize = info.image == null ? 0 : info.image.rawData.Length;
+                    _CachedImage cachedImage = new _CachedImage(result, imageSize);
+                    if (maximumSizeBytes > 0 && imageSize > maximumSizeBytes) {
+                        _maximumSize = imageSize + 1000;
+                    }
+
+                    _currentSizeBytes += imageSize;
+                    _pendingImages.Remove(key);
+                    _cache[key] = cachedImage;
+                    _lruKeys.AddLast(key);
+                    this._checkCacheSize();
+                }, null);
+            }
+
+            return result;
+        }
+
+        void _checkCacheSize() {
+            while (_currentSizeBytes > _maximumSizeBytes || _cache.Count > _maximumSize) {
+                Object key = _lruKeys.First.Value; // get the LRU item
+                _CachedImage image = _cache[key];
+                bool removed = _cache.Remove(key);
+                if (image != null && removed) {
+                    _currentSizeBytes -= image.sizeBytes;
+                    _lruKeys.Remove(key);
+                }
+            }
+        }
+    }
+
+    public class _CachedImage {
+        public _CachedImage(ImageStreamCompleter completer, int sizeBytes) {
+            this.completer = completer;
+            this.sizeBytes = sizeBytes;
+        }
+
+        public ImageStreamCompleter completer;
+        public int sizeBytes;
+    }
+}

Assets/UIWidgets/painting/image_cache.cs.meta

+fileFormatVersion: 2
+guid: 80732e4248ce48ec92e1463ddc59451d
+timeCreated: 1534833891

Assets/UIWidgets/painting/image_provider.cs

+using System.Collections.Generic;
+using RSG;
+using System.Net;
+using System;
+using System.IO;
+using UIWidgets.ui;
+using UnityEngine;
+
+namespace UIWidgets.painting {
+    public abstract class ImageProvider<T> {
+        public ImageStream resolve(ImageConfiguration configuration) {
+            ImageStream stream = new ImageStream();
+            T obtainedKey;
+            obtainedKey = obtainKey(configuration);
+            stream.setCompleter(PaintingBinding.instance.imageCache.putIfAbsent(obtainedKey, () => load(obtainedKey)));
+            return stream;
+        }
+
+        public abstract ImageStreamCompleter load(T key);
+
+        public abstract T obtainKey(ImageConfiguration configuration);
+    }
+
+    public class NetworkImage : ImageProvider<NetworkImage> {
+        public NetworkImage(string url, Dictionary<string, string> headers, double scale = 1.0) {
+            this.url = url;
+            this.headers = headers;
+            this.scale = scale;
+        }
+
+        /// The URL from which the image will be fetched.
+        string url;
+
+        /// The scale to place in the [ImageInfo] object of the image.
+        double scale;
+
+        /// The HTTP headers that will be used with [HttpClient.get] to fetch image from network.
+        Dictionary<string, string> headers;
+
+        public override NetworkImage obtainKey(ImageConfiguration configuration) {
+            return this;
+        }
+
+        public override ImageStreamCompleter load(NetworkImage key) {
+            return new OneFrameImageStreamCompleter(_loadAsync(key));
+        }
+
+        public static IPromise<ImageInfo> _loadAsync(NetworkImage key) {
+            var promise = new Promise<ImageInfo>(); // Create promise.
+            using (var client = new WebClient()) {
+                client.DownloadDataCompleted += // Monitor event for download completed.
+                    (s, ev) => {
+                        if (ev.Error != null) {
+                            promise.Reject(ev.Error); // Error during download, reject the promise.
+                        }
+                        else {
+                            var bytes = ev.Result;
+                            var imageInfo = new ImageInfo(new ui.Image(
+                                bytes
+                            ));
+                            promise.Resolve(imageInfo); // Downloaded completed successfully, resolve the promise.
+                        }
+                    };
+
+                client.DownloadDataAsync(new Uri(key.url)); // Initiate async op.
+            }
+
+            return promise; // Return the promise so the caller can await resolution (or error).
+        }
+
+        public override string ToString() {
+            return "NetworkImage with Url: " + this.url;
+        }
+
+        public bool Equals(NetworkImage other) {
+            return this.url.Equals(other.url) && this.scale.Equals(other.scale);
+        }
+
+        public override bool Equals(object obj) {
+            if (object.ReferenceEquals(null, obj)) return false;
+            if (object.ReferenceEquals(this, obj)) return true;
+            return obj is NetworkImage && this.Equals((NetworkImage) obj);
+        }
+
+        public override int GetHashCode() {
+            unchecked {
+                var hashCode = this.url.GetHashCode();
+                hashCode = (hashCode * 397) ^ this.scale.GetHashCode();
+                return hashCode;
+            }
+        }
+    }
+
+    public class ImageConfiguration {
+        public ImageConfiguration(Size size = null) {
+            this.size = size;
+        }
+
+        public static readonly ImageConfiguration empty = new ImageConfiguration();
+
+        public ImageConfiguration copyWith(Size size = null) {
+            return new ImageConfiguration(
+                size: size ?? this.size
+            );
+        }
+
+        public readonly Size size;
+    }
+}

Assets/UIWidgets/painting/image_provider.cs.meta

+fileFormatVersion: 2
+guid: 858587f8fb5d435e8a07a0ff46e5bc95
+timeCreated: 1534820746

Assets/UIWidgets/painting/image_stream.cs

+using RSG;
+using UIWidgets.ui;
+using UnityEngine;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace UIWidgets.painting {
+    public delegate void ImageListener(ImageInfo image, bool synchronousCall);
+
+    public delegate void ImageErrorListerner(System.Object exception, string stackTrack);
+
+    public class ImageInfo {
+        public ImageInfo(Image image, double scale = 1.0) {
+            this.image = image;
+            this.scale = scale;
+        }
+
+        public Image image;
+        public double scale;
+    }
+
+    public class ImageStream {
+        public ImageStream() {
+        }
+
+        private ImageStreamCompleter _completer;
+        private List<_ImageListenerPair> _listeners;
+
+        public ImageStreamCompleter completer {
+            get { return _completer; }
+        }
+
+        public void setCompleter(ImageStreamCompleter value) {
+            _completer = value;
+            if (_listeners != null) {
+                List<_ImageListenerPair> initialListeners = _listeners;
+                _listeners = null;
+                foreach (_ImageListenerPair listenerPair in initialListeners) {
+                    _completer.addListener(
+                        listenerPair.listener,
+                        listenerPair.errorListener
+                    );
+                }
+            }
+        }
+    }
+
+    public abstract class ImageStreamCompleter {
+        public List<_ImageListenerPair> _listeners = new List<_ImageListenerPair>();
+        public ImageInfo _currentImgae;
+
+        public void addListener(ImageListener listener, ImageErrorListerner onError) {
+            this._listeners.Add(new _ImageListenerPair(listener, onError));
+            if (_currentImgae != null) {
+                try {
+                    listener(_currentImgae, true);
+                    this.removeListener(listener);
+                }
+                catch (Exception e) {
+                    Console.WriteLine("{0} Exception caught.", e);
+                }
+            }
+
+            // todo call onError
+        }
+
+        public void removeListener(ImageListener listener) {
+            var pairToRemove = this._listeners.Single(lp => lp.listener == listener);
+            this._listeners.Remove(pairToRemove);
+        }
+
+        public void setImage(ImageInfo image) {
+            _currentImgae = image;
+            if (_listeners.Count == 0) {
+                return;
+            }
+
+            foreach (var lp in _listeners.ToList()) {
+                // todo refine
+                var listener = lp.listener;
+                try {
+                    listener(image, false);
+                    this.removeListener(listener);
+                }
+                catch (Exception e) {
+                    Console.WriteLine("{0} Exception caught.", e);
+                }
+
+                // todo call onError
+            }
+        }
+    }
+
+    public class OneFrameImageStreamCompleter : ImageStreamCompleter {
+        public OneFrameImageStreamCompleter(IPromise<ImageInfo> image) {
+            image.Then(result => { setImage(result); }).Catch(err => { Debug.Log(err); });
+        }
+    }
+
+    public class _ImageListenerPair {
+        public _ImageListenerPair(ImageListener listener, ImageErrorListerner errorListener) {
+            this.listener = listener;
+            this.errorListener = errorListener;
+        }
+
+        public ImageListener listener;
+        public ImageErrorListerner errorListener;
+    }
+}

Assets/UIWidgets/painting/image_stream.cs.meta

+fileFormatVersion: 2
+guid: 462d84cff25d484895d1a81e7ebd2a24
+timeCreated: 1534820764

Assets/UIWidgets/promise.meta

+fileFormatVersion: 2
+guid: e2adb93c961cc4d4e8d94fce276c0b57
+folderAsset: yes
+DefaultImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Assets/UIWidgets/rendering/image.cs

+using UIWidgets.ui;
+using UIWidgets.painting;
+using UnityEngine.Rendering;
+using BlendMode = UIWidgets.ui.BlendMode;
+
+namespace UIWidgets.rendering {
+    class RenderImage : RenderBox {
+        public RenderImage(ui.Image image,
+            double width,
+            double height,
+            Color color,
+            ui.BlendMode colorBlendMode,
+            BoxFit fit,
+            ImageRepeat repeat,
+            Rect centerSlice,
+            Alignment alignment = null,
+            double scale = 1.0
+        ) {
+            this._image = image;
+            this._width = width;
+            this._height = height;
+            this._scale = scale;
+            this._color = color;
+            this._colorBlendMode = colorBlendMode;
+            this._fit = fit;
+            this._repeat = repeat;
+            this._centerSlice = centerSlice;
+            this._alignment = alignment ?? Alignment.center;
+        }
+
+        Alignment _resolvedAlignment;
+
+        void _resolve() {
+            if (_resolvedAlignment != null)
+                return;
+            _resolvedAlignment = alignment;
+        }
+
+        void _markNeedsResolution() {
+            _resolvedAlignment = null;
+            markNeedsPaint();
+        }
+
+        private ui.Image _image;
+
+        public ui.Image image {
+            get { return this._image; }
+            set {
+                if (value == _image)
+                    return;
+                _image = value;
+                markNeedsPaint();
+                if (_width == 0.0 || _height == 0.0)
+                    markNeedsLayout();
+            }
+        }
+
+        private double _width;
+
+        public double width {
+            get { return _width; }
+            set {
+                if (value == _width)
+                    return;
+                _width = value;
+                markNeedsLayout();
+            }
+        }
+
+        private double _height;
+
+        public double height {
+            get { return _height; }
+            set {
+                if (value == _height)
+                    return;
+                _height = value;
+                markNeedsLayout();
+            }
+        }
+
+        private double _scale;
+
+        public double scale {
+            get { return _scale; }
+            set {
+                if (value == _scale)
+                    return;
+                _scale = value;
+                markNeedsLayout();
+            }
+        }
+
+        private Color _color;
+
+        public Color color {
+            get { return _color; }
+            set {
+                if (value == _color)
+                    return;
+                _color = value;
+                markNeedsPaint();
+            }
+        }
+
+        private ui.BlendMode _colorBlendMode;
+
+        public ui.BlendMode colorBlendMode {
+            get { return _colorBlendMode; }
+            set {
+                if (value == _colorBlendMode)
+                    return;
+                _colorBlendMode = value;
+                markNeedsPaint();
+            }
+        }
+
+        private BoxFit _fit;
+
+        public BoxFit fit {
+            get { return _fit; }
+            set {
+                if (value == _fit)
+                    return;
+                _fit = value;
+                markNeedsPaint();
+            }
+        }
+
+        private Alignment _alignment;
+
+        public Alignment alignment {
+            get { return _alignment; }
+            set {
+                if (value == _alignment)
+                    return;
+                _alignment = value;
+                _markNeedsResolution();
+            }
+        }
+
+        private ImageRepeat _repeat;
+
+        public ImageRepeat repeat {
+            get { return _repeat; }
+            set {
+                if (value == _repeat)
+                    return;
+                _repeat = value;
+                markNeedsPaint();
+            }
+        }
+
+        private Rect _centerSlice;
+
+        public Rect centerSlice {
+            get { return _centerSlice; }
+            set {
+                if (value == _centerSlice)
+                    return;
+                _centerSlice = value;
+                markNeedsPaint();
+            }
+        }
+
+        Size _sizeForConstraints(BoxConstraints constraints) {
+            // Folds the given |width| and |height| into |constraints| so they can all
+            // be treated uniformly.
+            constraints = BoxConstraints.tightFor(
+                _width,
+                _height
+            );
+            constraints = constraints.enforce(constraints);
+
+            if (_image == null)
+                return constraints.smallest;
+
+            return constraints.constrainSizeAndAttemptToPreserveAspectRatio(new Size(
+                _image.width / _scale,
+                _image.height / _scale
+            ));
+        }
+
+        public override void paint(PaintingContext context, Offset offset) {
+            if (_image == null)
+                return;
+            _resolve();
+            DecorationImageUtil.paintImage(
+                context.canvas,
+                offset & size,
+                _image,
+                _fit,
+                _centerSlice,
+                _resolvedAlignment,
+                _repeat
+            );
+        }
+    }
+}

Assets/UIWidgets/rendering/image.cs.meta

+fileFormatVersion: 2
+guid: d0413272d07e4c958f45f9c7597fe2b7
+timeCreated: 1534820838

Assets/UIWidgets/ui/painting/image.cs

+using System;
+using System.Collections.Generic;
+using UIWidgets.painting;
+using UnityEngine;
+
+namespace UIWidgets.ui
+{
+    public class Image
+    {
+        public Image(byte[] raw, int height = 100, int width = 100) {
+            this.rawData = raw;
+            this.height = height;
+            this.width = width;
+        }
+
+        public byte[] rawData;
+        public int height;
+        public int width;
+    }
+}

Assets/UIWidgets/ui/painting/image.cs.meta

+fileFormatVersion: 2
+guid: bfd6fdb0d13948d6acbc528589ebef33
+timeCreated: 1534821698

Assets/UIWidgets/promise/EnumerableExt.cs.meta

+fileFormatVersion: 2
+guid: bb9a3c5b387541cb800b11c84121f7f3
+timeCreated: 1534828260

Assets/UIWidgets/promise/Promise.cs.meta

+fileFormatVersion: 2
+guid: ffdd174fa01b47d99dae6b8b38945413
+timeCreated: 1534828022

Assets/UIWidgets/promise/PromiseException.cs

+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace RSG.Exceptions
+{
+    /// <summary>
+    /// Base class for promise exceptions.
+    /// </summary>
+    public class PromiseException : Exception
+    {
+        public PromiseException() { }
+
+        public PromiseException(string message) : base(message) { }
+
+        public PromiseException(string message, Exception inner) : base(message, inner) { }
+    }
+}

Assets/UIWidgets/promise/PromiseException.cs.meta

+fileFormatVersion: 2
+guid: ef24fa8abd794ec9ad904f149ade425b
+timeCreated: 1534828173

Assets/UIWidgets/promise/PromiseHelpers.cs.meta

+fileFormatVersion: 2
+guid: 07f0b3c08d53427992f828dd9c4f0f15
+timeCreated: 1534828078

Assets/UIWidgets/promise/PromiseStateException.cs.meta

+fileFormatVersion: 2
+guid: d922956f02bc4ff2a82f9404787380b0
+timeCreated: 1534828191

Assets/UIWidgets/promise/PromiseTimer.cs.meta

+fileFormatVersion: 2
+guid: e47ddf579a9a45f48fd9203faf93b52f
+timeCreated: 1534828095

Assets/UIWidgets/promise/Promise_NonGeneric.cs.meta

+fileFormatVersion: 2
+guid: fad6eb2d15b84c7cb92f115245ac09f8
+timeCreated: 1534828106

Assets/UIWidgets/promise/Tuple.cs.meta

+fileFormatVersion: 2
+guid: 2e1ff13e974447a080559101999e17d9
+timeCreated: 1534828127

Assets/UIWidgets/promise/EnumerableExt.cs

+using System;
+using System.Collections.Generic;
+
+namespace RSG.Promises {
+    /// <summary>
+    /// General extensions to LINQ.
+    /// </summary>
+    public static class EnumerableExt {
+        public static void Each<T>(this IEnumerable<T> source, Action<T> fn) {
+            foreach (var item in source) {
+                fn.Invoke(item);
+            }
+        }
+
+        public static void Each<T>(this IEnumerable<T> source, Action<T, int> fn) {
+            int index = 0;
+
+            foreach (T item in source) {
+                fn.Invoke(item, index);
+                index++;
+            }
+        }
+
+        /// <summary>
+        /// Convert a variable length argument list of items to an enumerable.
+        /// </summary>
+        public static IEnumerable<T> FromItems<T>(params T[] items) {
+            foreach (var item in items) {
+                yield return item;
+            }
+        }
+    }
+}

Assets/UIWidgets/promise/PromiseHelpers.cs

+namespace RSG {
+    public static class PromiseHelpers {
+        /// <summary>
+        /// Returns a promise that resolves with all of the specified promises have resolved.
+        /// Returns a promise of a tuple of the resolved results.
+        /// </summary>
+        public static IPromise<Tuple<T1, T2>> All<T1, T2>(IPromise<T1> p1, IPromise<T2> p2) {
+            var val1 = default(T1);
+            var val2 = default(T2);
+            var numUnresolved = 2;
+            var alreadyRejected = false;
+            var promise = new Promise<Tuple<T1, T2>>();
+
+            p1
+                .Then(val => {
+                    val1 = val;
+                    numUnresolved--;
+                    if (numUnresolved <= 0) {
+                        promise.Resolve(Tuple.Create(val1, val2));
+                    }
+                })
+                .Catch(e => {
+                    if (!alreadyRejected) {
+                        promise.Reject(e);
+                    }
+
+                    alreadyRejected = true;
+                })
+                .Done();
+
+            p2
+                .Then(val => {
+                    val2 = val;
+                    numUnresolved--;
+                    if (numUnresolved <= 0) {
+                        promise.Resolve(Tuple.Create(val1, val2));
+                    }
+                })
+                .Catch(e => {
+                    if (!alreadyRejected) {
+                        promise.Reject(e);
+                    }
+
+                    alreadyRejected = true;
+                })
+                .Done();
+
+            return promise;
+        }
+
+        /// <summary>
+        /// Returns a promise that resolves with all of the specified promises have resolved.
+        /// Returns a promise of a tuple of the resolved results.
+        /// </summary>
+        public static IPromise<Tuple<T1, T2, T3>> All<T1, T2, T3>(IPromise<T1> p1, IPromise<T2> p2, IPromise<T3> p3) {
+            return All(All(p1, p2), p3)
+                .Then(vals => Tuple.Create(vals.Item1.Item1, vals.Item1.Item2, vals.Item2));
+        }
+
+        /// <summary>
+        /// Returns a promise that resolves with all of the specified promises have resolved.
+        /// Returns a promise of a tuple of the resolved results.
+        /// </summary>
+        public static IPromise<Tuple<T1, T2, T3, T4>> All<T1, T2, T3, T4>(IPromise<T1> p1, IPromise<T2> p2,
+            IPromise<T3> p3, IPromise<T4> p4) {
+            return All(All(p1, p2), All(p3, p4))
+                .Then(vals => Tuple.Create(vals.Item1.Item1, vals.Item1.Item2, vals.Item2.Item1, vals.Item2.Item2));
+        }
+    }
+}

Assets/UIWidgets/promise/PromiseStateException.cs

+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace RSG.Exceptions {
+    /// <summary>
+    /// Exception thrown when an operation is performed on a promise that is in an invalid
+    /// state for it to handle.
+    /// </summary>
+    public class PromiseStateException : PromiseException {
+        public PromiseStateException() {
+        }
+
+        public PromiseStateException(string message) : base(message) {
+        }
+
+        public PromiseStateException(string message, Exception inner)
+            : base(message, inner) {
+        }
+    }
+}

Assets/UIWidgets/promise/PromiseTimer.cs

+using System;
+using System.Collections.Generic;
+
+namespace RSG {
+    public class PromiseCancelledException : Exception {
+        /// <summary>
+        /// Just create the exception
+        /// </summary>
+        public PromiseCancelledException() {
+        }
+
+        /// <summary>
+        /// Create the exception with description
+        /// </summary>
+        /// <param name="message">Exception description</param>
+        public PromiseCancelledException(String message) : base(message) {
+        }
+    }
+
+    /// <summary>
+    /// A class that wraps a pending promise with it's predicate and time data
+    /// </summary>
+    internal class PredicateWait {
+        /// <summary>
+        /// Predicate for resolving the promise
+        /// </summary>
+        public Func<TimeData, bool> predicate;
+
+        /// <summary>
+        /// The time the promise was started
+        /// </summary>
+        public float timeStarted;
+
+        /// <summary>
+        /// The pending promise which is an interface for a promise that can be rejected or resolved.
+        /// </summary>
+        public IPendingPromise pendingPromise;
+
+        /// <summary>
+        /// The time data specific to this pending promise. Includes elapsed time and delta time.
+        /// </summary>
+        public TimeData timeData;
+
+        /// <summary>
+        /// The frame the promise was started
+        /// </summary>
+        public int frameStarted;
+    }
+
+    /// <summary>
+    /// Time data specific to a particular pending promise.
+    /// </summary>
+    public struct TimeData {
+        /// <summary>
+        /// The amount of time that has elapsed since the pending promise started running
+        /// </summary>
+        public float elapsedTime;
+
+        /// <summary>
+        /// The amount of time since the last time the pending promise was updated.
+        /// </summary>
+        public float deltaTime;
+
+        /// <summary>
+        /// The amount of times that update has been called since the pending promise started running
+        /// </summary>
+        public int elapsedUpdates;
+    }
+
+    public interface IPromiseTimer {
+        /// <summary>
+        /// Resolve the returned promise once the time has elapsed
+        /// </summary>
+        IPromise WaitFor(float seconds);
+
+        /// <summary>
+        /// Resolve the returned promise once the predicate evaluates to true
+        /// </summary>
+        IPromise WaitUntil(Func<TimeData, bool> predicate);
+
+        /// <summary>
+        /// Resolve the returned promise once the predicate evaluates to false
+        /// </summary>
+        IPromise WaitWhile(Func<TimeData, bool> predicate);
+
+        /// <summary>
+        /// Update all pending promises. Must be called for the promises to progress and resolve at all.
+        /// </summary>
+        void Update(float deltaTime);
+
+        /// <summary>
+        /// Cancel a waiting promise and reject it immediately.
+        /// </summary>
+        bool Cancel(IPromise promise);
+    }
+
+    public class PromiseTimer : IPromiseTimer {
+        /// <summary>
+        /// The current running total for time that this PromiseTimer has run for
+        /// </summary>
+        private float curTime;
+
+        /// <summary>
+        /// The current running total for the amount of frames the PromiseTimer has run for
+        /// </summary>
+        private int curFrame;
+
+        /// <summary>
+        /// Currently pending promises
+        /// </summary>
+        private readonly LinkedList<PredicateWait> waiting = new LinkedList<PredicateWait>();
+
+        /// <summary>
+        /// Resolve the returned promise once the time has elapsed
+        /// </summary>
+        public IPromise WaitFor(float seconds) {
+            return WaitUntil(t => t.elapsedTime >= seconds);
+        }
+
+        /// <summary>
+        /// Resolve the returned promise once the predicate evaluates to false
+        /// </summary>
+        public IPromise WaitWhile(Func<TimeData, bool> predicate) {
+            return WaitUntil(t => !predicate(t));
+        }
+
+        /// <summary>
+        /// Resolve the returned promise once the predicate evalutes to true
+        /// </summary>
+        public IPromise WaitUntil(Func<TimeData, bool> predicate) {
+            var promise = new Promise();
+
+            var wait = new PredicateWait() {
+                timeStarted = curTime,
+                pendingPromise = promise,
+                timeData = new TimeData(),
+                predicate = predicate,
+                frameStarted = curFrame
+            };
+
+            waiting.AddLast(wait);
+
+            return promise;
+        }
+
+        public bool Cancel(IPromise promise) {
+            var node = FindInWaiting(promise);
+
+            if (node == null) {
+                return false;
+            }
+
+            node.Value.pendingPromise.Reject(new PromiseCancelledException("Promise was cancelled by user."));
+            waiting.Remove(node);
+
+            return true;
+        }
+
+        LinkedListNode<PredicateWait> FindInWaiting(IPromise promise) {
+            for (var node = waiting.First; node != null; node = node.Next) {
+                if (node.Value.pendingPromise.Id.Equals(promise.Id)) {
+                    return node;
+                }
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Update all pending promises. Must be called for the promises to progress and resolve at all.
+        /// </summary>
+        public void Update(float deltaTime) {
+            curTime += deltaTime;
+            curFrame += 1;
+
+            var node = waiting.First;
+            while (node != null) {
+                var wait = node.Value;
+
+                var newElapsedTime = curTime - wait.timeStarted;
+                wait.timeData.deltaTime = newElapsedTime - wait.timeData.elapsedTime;
+                wait.timeData.elapsedTime = newElapsedTime;
+                var newElapsedUpdates = curFrame - wait.frameStarted;
+                wait.timeData.elapsedUpdates = newElapsedUpdates;
+
+                bool result;
+                try {
+                    result = wait.predicate(wait.timeData);
+                }
+                catch (Exception ex) {
+                    wait.pendingPromise.Reject(ex);
+
+                    node = RemoveNode(node);
+                    continue;
+                }
+
+                if (result) {
+                    wait.pendingPromise.Resolve();
+
+                    node = RemoveNode(node);
+                }
+                else {
+                    node = node.Next;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Removes the provided node and returns the next node in the list.
+        /// </summary>
+        private LinkedListNode<PredicateWait> RemoveNode(LinkedListNode<PredicateWait> node) {
+            var currentNode = node;
+            node = node.Next;
+
+            waiting.Remove(currentNode);
+
+            return node;
+        }
+    }
+}

Assets/UIWidgets/promise/Tuple.cs

+namespace RSG {
+    /// <summary>
+    /// Provides static methods for creating tuple objects.
+    /// 
+    /// Tuple implementation for .NET 3.5
+    /// </summary>
+    public class Tuple {
+        /// <summary>
+        /// Create a new 2-tuple, or pair.
+        /// </summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <typeparam name="T2">The type of the second component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <param name="item2">The value of the second component of the tuple.</param>
+        /// <returns>A 2-tuple whose value is (item1, item2)</returns>
+        public static Tuple<T1, T2> Create<T1, T2>(T1 item1, T2 item2) {
+            return new Tuple<T1, T2>(item1, item2);
+        }
+
+        /// <summary>
+        /// Create a new 3-tuple, or triple.
+        /// </summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <typeparam name="T2">The type of the second component of the tuple.</typeparam>
+        /// <typeparam name="T3">The type of the third component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <param name="item2">The value of the second component of the tuple.</param>
+        /// <param name="item3">The value of the third component of the tuple.</param>
+        /// <returns>A 3-tuple whose value is (item1, item2, item3)</returns>
+        public static Tuple<T1, T2, T3> Create<T1, T2, T3>(T1 item1, T2 item2, T3 item3) {
+            return new Tuple<T1, T2, T3>(item1, item2, item3);
+        }
+
+        /// <summary>
+        /// Create a new 4-tuple, or quadruple.
+        /// </summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <typeparam name="T2">The type of the second component of the tuple.</typeparam>
+        /// <typeparam name="T3">The type of the third component of the tuple.</typeparam>
+        /// <typeparam name="T4">The type of the fourth component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <param name="item2">The value of the second component of the tuple.</param>
+        /// <param name="item3">The value of the third component of the tuple.</param>
+        /// <param name="item4">The value of the fourth component of the tuple.</param>
+        /// <returns>A 3-tuple whose value is (item1, item2, item3, item4)</returns>
+        public static Tuple<T1, T2, T3, T4> Create<T1, T2, T3, T4>(T1 item1, T2 item2, T3 item3, T4 item4) {
+            return new Tuple<T1, T2, T3, T4>(item1, item2, item3, item4);
+        }
+    }
+
+    /// <summary>
+    /// Represents a 2-tuple, or pair.
+    /// </summary>
+    /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
+    /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
+    public class Tuple<T1, T2> {
+        internal Tuple(T1 item1, T2 item2) {
+            Item1 = item1;
+            Item2 = item2;
+        }
+
+        /// <summary>
+        /// Gets the value of the current tuple's first component.
+        /// </summary>
+        public T1 Item1 { get; private set; }
+
+        /// <summary>
+        /// Gets the value of the current tuple's second component.
+        /// </summary>
+        public T2 Item2 { get; private set; }
+    }
+
+    /// <summary>
+    /// Represents a 3-tuple, or triple.
+    /// </summary>
+    /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
+    /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
+    /// <typeparam name="T3">The type of the tuple's third component.</typeparam>
+    public class Tuple<T1, T2, T3> {
+        internal Tuple(T1 item1, T2 item2, T3 item3) {
+            Item1 = item1;
+            Item2 = item2;
+            Item3 = item3;
+        }
+
+        /// <summary>
+        /// Gets the value of the current tuple's first component.
+        /// </summary>
+        public T1 Item1 { get; private set; }
+
+        /// <summary>
+        /// Gets the value of the current tuple's second component.
+        /// </summary>
+        public T2 Item2 { get; private set; }
+
+        /// <summary>
+        /// Gets the value of the current tuple's third component.
+        /// </summary>
+        public T3 Item3 { get; private set; }
+    }
+
+    /// <summary>
+    /// Represents a 4-tuple, or quadruple.
+    /// </summary>
+    /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
+    /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
+    /// <typeparam name="T3">The type of the tuple's third component.</typeparam>
+    /// <typeparam name="T4">The type of the tuple's fourth component.</typeparam>
+    public class Tuple<T1, T2, T3, T4> {
+        internal Tuple(T1 item1, T2 item2, T3 item3, T4 item4) {
+            Item1 = item1;
+            Item2 = item2;
+            Item3 = item3;
+            Item4 = item4;
+        }
+
+        /// <summary>
+        /// Gets the value of the current tuple's first component.
+        /// </summary>
+        public T1 Item1 { get; private set; }
+
+        /// <summary>
+        /// Gets the value of the current tuple's second component.
+        /// </summary>
+        public T2 Item2 { get; private set; }
+
+        /// <summary>
+        /// Gets the value of the current tuple's third component.
+        /// </summary>
+        public T3 Item3 { get; private set; }
+
+        /// <summary>
+        /// Gets the value of the current tuple's fourth component.
+        /// </summary>
+        public T4 Item4 { get; private set; }
+    }
+}