Implement RenderImage and Image for Sky

sky/sdk/lib/framework/rendering/image.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:sky' as sky;
+import 'package:sky/framework/net/image_cache.dart' as image_cache;
+import 'render_node.dart';
+import 'render_box.dart';
+
+class RenderImage extends RenderBox {

[abarth-chromium, 2015/06/03 00:16:31]

We probably should just put the class in box.dart.

[jackson, 2015/06/03 17:41:43]

Done.

+
+  RenderImage(String src, num width, num height) {
+    configure(src, width, height);
+  }
+
+  sky.Image _image;
+  sky.Size requestedSize;
+  final sky.Paint _paint = new sky.Paint();
+
+  void configure(String src, num width, num height) {
+    sky.Size newSize = new sky.Size(width, height);
+    if (requestedSize != newSize) {
+      requestedSize = newSize;
+      markNeedsLayout();
+      markNeedsPaint();
+    }
+    image_cache.load(src, (result) {
+      if (_image != result) {
+        _image = result;
+        _updateSizeFromImage();
+        markNeedsLayout();
+        markNeedsPaint();
+      }
+    });
+  }
+
+  void _updateSizeFromImage() {
+    // If both height and width are specified, we don't care about image dimensions
+    if (requestedSize.width != null && requestedSize.height != null)
+      size = constraints.constrain(requestedSize);
+
+    // If there's no image, we can't size ourselves
+    if (_image == null)
+      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 {
+        num width = requestedSize.height * _image.width / _image.height;
+        size = constraints.constrain(new sky.Size(width, requestedSize.height));
+      }
+    } else if (requestedSize.height == null) {
+      num height = requestedSize.width * _image.height / _image.width;
+      size = constraints.constrain(new sky.Size(requestedSize.width, height));
+    } else {
+      size = constraints.constrain(requestedSize);
+    }
+  }
+
+  void performLayout() {
+    _updateSizeFromImage();
+  }
+
+  void paint(RenderNodeDisplayList canvas) {
+    if (_image == null) return;
+    double widthScale = size.width / _image.width;
+    double heightScale = size.height / _image.height;
+    canvas.save();
+    canvas.scale(widthScale, heightScale);
+    canvas.drawImage(_image, 0.0, 0.0, _paint);
+    canvas.restore();
+  }
+}