Implement RenderImage and Image for Sky

sky/sdk/lib/framework/rendering/box.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 import 'dart:typed_data';
 import 'node.dart';
 import 'package:vector_math/vector_math.dart';
+import 'package:sky/framework/net/image_cache.dart' as image_cache;
 
 // GENERIC BOX RENDERING
 // Anything that has a concept of x, y, width, height is going to derive from this
 
 class EdgeDims {
   // used for e.g. padding
   const EdgeDims(this.top, this.right, this.bottom, this.left);
   const EdgeDims.all(double value)
       : top = value, right = value, bottom = value, left = value;
 
@@ skipping 228 matching lines @@
       sky.Rect childBounds = new sky.Rect.fromPointAndSize(child.parentData.position, child.size);
       if (childBounds.contains(position)) {
         child.hitTest(result, position: new sky.Point(position.x - child.parentData.position.x,
                                                       position.y - child.parentData.position.y));
       }
     }
   }
 
 }
 
+class RenderImage extends RenderBox {
+
+  RenderImage(String url, sky.Size dimensions) {
+    requestedSize = dimensions;
+    src = url;
+  }
+
+  sky.Image _image;
+  String _src;
+  String get src => _src;
+  void set src (String value) {
+    if (value == _src)
+      return;
+    _src = value;
+    image_cache.load(_src, (result) {
+      _image = result;
+      if (requestedSize.width == null || requestedSize.height == null)
+        markNeedsLayout();
+      markNeedsPaint();
+    });
+  }
+
+  sky.Size _requestedSize;
+  sky.Size get requestedSize => _requestedSize;
+  void set requestedSize (sky.Size value) {
+    if (value == _requestedSize)
+      return;
+    _requestedSize = value;
+    markNeedsLayout();
+  }
+
+  void performLayout() {
+    // If there's no image, we can't size ourselves automatically
+    if (_image == null) {
+      double width = requestedSize.width == null ? 0.0 : requestedSize.width;
+      double height = requestedSize.height == null ? 0.0 : requestedSize.height;
+      size = constraints.constrain(new sky.Size(width, height));
+      return;
+    }
+
+    // If neither height nor width are specified, use inherent image dimensions
+    // If only one dimension is specified, adjust the other dimension to
+    // maintain the aspect ratio
+    if (requestedSize.width == null) {
+      if (requestedSize.height == null) {
+        size = constraints.constrain(new sky.Size(_image.width, _image.height));
+      } else {
+        double width = requestedSize.height * _image.width / _image.height;
+        size = constraints.constrain(new sky.Size(width, requestedSize.height));
+      }
+    } else if (requestedSize.height == null) {
+      double height = requestedSize.width * _image.height / _image.width;
+      size = constraints.constrain(new sky.Size(requestedSize.width, height));
+    } else {
+      size = constraints.constrain(requestedSize);
+    }
+  }
+
+  void paint(RenderNodeDisplayList canvas) {
+    if (_image == null) return;
+    bool needsScale = size.width != _image.width || size.height != _image.height;
+    if (needsScale) {
+      double widthScale = size.width / _image.width;
+      double heightScale = size.height / _image.height;
+      canvas.save();
+      canvas.scale(widthScale, heightScale);
+    }
+    sky.Paint paint = new sky.Paint();
+    canvas.drawImage(_image, 0.0, 0.0, paint);
+    if (needsScale)
+      canvas.restore();
+  }
+}
+
 // This must be immutable, because we won't notice when it changes
 class BoxDecoration {
   const BoxDecoration({this.backgroundColor});
 
   final sky.Color backgroundColor;
 }
 
 class RenderDecoratedBox extends RenderProxyBox {
 
   RenderDecoratedBox({
@@ skipping 195 matching lines @@
 
   void defaultPaint(RenderNodeDisplayList canvas) {
     RenderBox child = firstChild;
     while (child != null) {
       assert(child.parentData is ParentDataType);
       canvas.paintChild(child, child.parentData.position);
       child = child.parentData.nextSibling;
     }
   }
 }