Factor BoxPainter out of RenderDecoratedBox

sky/sdk/lib/framework/painting/box_painter.dart

Index: sky/sdk/lib/framework/painting/box_painter.dart
diff --git a/sky/sdk/lib/framework/painting/box_painter.dart b/sky/sdk/lib/framework/painting/box_painter.dart
new file mode 100644
index 0000000000000000000000000000000000000000..0b5747da5021f8e5e4785f303bbac408cb93b121
--- /dev/null
+++ b/sky/sdk/lib/framework/painting/box_painter.dart
@@ -0,0 +1,252 @@
+// 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 'dart:sky' show Point, Size, Rect, Color, Paint, Path;
+import 'shadows.dart';
+
+class BorderSide {
+  const BorderSide({
+    this.color: const Color(0xFF000000),
+    this.width: 1.0
+  });
+  final Color color;
+  final double width;
+
+  static const none = const BorderSide(width: 0.0);
+
+  int get hashCode {
+    int value = 373;
+    value = 37 * value * color.hashCode;
+    value = 37 * value * width.hashCode;
+    return value;
+  }
+  String toString() => 'BorderSide($color, $width)';
+}
+
+class Border {
+  const Border({
+    this.top: BorderSide.none,
+    this.right: BorderSide.none,
+    this.bottom: BorderSide.none,
+    this.left: BorderSide.none
+  });
+
+  const Border.all(BorderSide side) :
+    top = side,
+    right = side,
+    bottom = side,
+    left = side;
+
+  final BorderSide top;
+  final BorderSide right;
+  final BorderSide bottom;
+  final BorderSide left;
+
+  int get hashCode {
+    int value = 373;
+    value = 37 * value * top.hashCode;
+    value = 37 * value * right.hashCode;
+    value = 37 * value * bottom.hashCode;
+    value = 37 * value * left.hashCode;
+    return value;
+  }
+  String toString() => 'Border($top, $right, $bottom, $left)';
+}
+
+class BoxShadow {
+  const BoxShadow({
+    this.color,
+    this.offset,
+    this.blur
+  });
+
+  final Color color;
+  final Size offset;
+  final double blur;
+
+  String toString() => 'BoxShadow($color, $offset, $blur)';
+}
+
+abstract class Gradient {
+  sky.Shader createShader();
+}
+
+class LinearGradient extends Gradient {
+  LinearGradient({
+    this.endPoints,
+    this.colors,
+    this.colorStops,
+    this.tileMode: sky.TileMode.clamp
+  });
+
+  String toString() =>
+      'LinearGradient($endPoints, $colors, $colorStops, $tileMode)';
+
+  sky.Shader createShader() {
+    return new sky.Gradient.Linear(this.endPoints, this.colors, this.colorStops,
+                                   this.tileMode);
+  }
+
+  final List<Point> endPoints;
+  final List<Color> colors;
+  final List<double> colorStops;
+  final sky.TileMode tileMode;
+}
+
+class RadialGradient extends Gradient {
+  RadialGradient({
+    this.center,
+    this.radius,
+    this.colors,
+    this.colorStops,
+    this.tileMode: sky.TileMode.clamp
+  });
+
+  String toString() =>
+      'RadialGradient($center, $radius, $colors, $colorStops, $tileMode)';
+
+  sky.Shader createShader() {
+    return new sky.Gradient.Radial(this.center, this.radius, this.colors,
+                                   this.colorStops, this.tileMode);
+  }
+
+  final Point center;
+  final double radius;
+  final List<Color> colors;
+  final List<double> colorStops;
+  final sky.TileMode tileMode;
+}
+
+// This must be immutable, because we won't notice when it changes
+class BoxDecoration {
+  const BoxDecoration({
+    this.backgroundColor,
+    this.border,
+    this.borderRadius,
+    this.boxShadow,
+    this.gradient
+  });
+
+  final Color backgroundColor;
+  final double borderRadius;
+  final Border border;
+  final List<BoxShadow> boxShadow;
+  final Gradient gradient;
+
+  String toString([String prefix = '']) {
+    List<String> result = [];
+    if (backgroundColor != null)
+      result.add('${prefix}backgroundColor: $backgroundColor');
+    if (border != null)
+      result.add('${prefix}border: $border');
+    if (borderRadius != null)
+      result.add('${prefix}borderRadius: $borderRadius');
+    if (boxShadow != null)
+      result.add('${prefix}boxShadow: ${boxShadow.map((shadow) => shadow.toString())}');
+    if (gradient != null)
+      result.add('${prefix}gradient: $gradient');
+    if (result.isEmpty)
+      return '${prefix}<no decorations specified>';
+    return result.join('\n');
+  }
+}
+
+class BoxPainter {
+  BoxPainter(BoxDecoration decoration) : _decoration = decoration {
+    assert(decoration != null);
+  }
+
+  BoxDecoration _decoration;
+  BoxDecoration get decoration => _decoration;
+  void set decoration (BoxDecoration value) {
+    assert(value != null);
+    if (value == _decoration)
+      return;
+    _decoration = value;
+    _cachedBackgroundPaint = null;
+  }
+
+  Paint _cachedBackgroundPaint;
+  Paint get _backgroundPaint {
+    if (_cachedBackgroundPaint == null) {
+      Paint paint = new Paint();
+
+      if (_decoration.backgroundColor != null)
+        paint.color = _decoration.backgroundColor;
+
+      if (_decoration.boxShadow != null) {
+        var builder = new ShadowDrawLooperBuilder();
+        for (BoxShadow boxShadow in _decoration.boxShadow)
+          builder.addShadow(boxShadow.offset, boxShadow.color, boxShadow.blur);
+        paint.setDrawLooper(builder.build());
+      }
+
+      if (_decoration.gradient != null)
+        paint.setShader(_decoration.gradient.createShader());
+
+      _cachedBackgroundPaint = paint;
+    }
+
+    return _cachedBackgroundPaint;
+  }
+
+  void paint(sky.Canvas canvas, Rect rect) {
+    if (_decoration.backgroundColor != null || _decoration.boxShadow != null ||
+        _decoration.gradient != null) {
+      if (_decoration.borderRadius == null)
+        canvas.drawRect(rect, _backgroundPaint);
+      else
+        canvas.drawRRect(new sky.RRect()..setRectXY(rect, _decoration.borderRadius, _decoration.borderRadius), _backgroundPaint);
+    }
+
+    if (_decoration.border != null) {
+      assert(_decoration.borderRadius == null); // TODO(abarth): Implement borders with border radius.
+
+      assert(_decoration.border.top != null);
+      assert(_decoration.border.right != null);
+      assert(_decoration.border.bottom != null);
+      assert(_decoration.border.left != null);
+
+      Paint paint = new Paint();
+      Path path;
+
+      paint.color = _decoration.border.top.color;
+      path = new Path();
+      path.moveTo(rect.left, rect.top);
+      path.lineTo(rect.left + _decoration.border.left.width, rect.top + _decoration.border.top.width);
+      path.lineTo(rect.right - _decoration.border.right.width, rect.top + _decoration.border.top.width);
+      path.lineTo(rect.right, rect.top);
+      path.close();
+      canvas.drawPath(path, paint);
+
+      paint.color = _decoration.border.right.color;
+      path = new Path();
+      path.moveTo(rect.right, rect.top);
+      path.lineTo(rect.right - _decoration.border.right.width, rect.top + _decoration.border.top.width);
+      path.lineTo(rect.right - _decoration.border.right.width, rect.bottom - _decoration.border.bottom.width);
+      path.lineTo(rect.right, rect.bottom);
+      path.close();
+      canvas.drawPath(path, paint);
+
+      paint.color = _decoration.border.bottom.color;
+      path = new Path();
+      path.moveTo(rect.right, rect.bottom);
+      path.lineTo(rect.right - _decoration.border.right.width, rect.bottom - _decoration.border.bottom.width);
+      path.lineTo(rect.left + _decoration.border.left.width, rect.bottom - _decoration.border.bottom.width);
+      path.lineTo(rect.left, rect.bottom);
+      path.close();
+      canvas.drawPath(path, paint);
+
+      paint.color = _decoration.border.left.color;
+      path = new Path();
+      path.moveTo(rect.left, rect.bottom);
+      path.lineTo(rect.left + _decoration.border.left.width, rect.bottom - _decoration.border.bottom.width);
+      path.lineTo(rect.left + _decoration.border.left.width, rect.top + _decoration.border.top.width);
+      path.lineTo(rect.left, rect.top);
+      path.close();
+      canvas.drawPath(path, paint);
+    }
+  }
+}