Make Border more general (#12619)

packages/flutter/lib/painting.dart

@@ -36,6 +36,7 @@ export 'src/painting/gradient.dart';
 export 'src/painting/images.dart';
 export 'src/painting/matrix_utils.dart';
 export 'src/painting/rounded_rectangle_border.dart';
+export 'src/painting/shape_decoration.dart';
 export 'src/painting/text_painter.dart';
 export 'src/painting/text_span.dart';
 export 'src/painting/text_style.dart';

packages/flutter/lib/src/painting/box_border.dart

@@ -57,8 +57,26 @@ abstract class BoxBorder extends ShapeBorder {
   /// const constructors so that they can be used in const expressions.
   const BoxBorder();
 
+  /// The top side of this border.
+  ///
+  /// This getter is available on both [Border] and [BorderDirectional]. If
+  /// [isUniform] is true, then this is the same style as all the other sides.
+  BorderSide get top;
+
+  /// The bottom side of this border.
+  BorderSide get bottom;
+
+  /// Whether all four sides of the border are identical. Uniform borders are
+  /// typically more efficient to paint.
+  ///
+  /// A uniform border by definition has no text direction dependency and
+  /// therefore could be expressed as a [Border], even if it is currently a
+  /// [BorderDirectional]. A uniform border can also be expressed as a
+  /// [RoundedRectangleBorder].
+  bool get isUniform;
+
   // We override this to tighten the return value, so that callers can assume
-  // that we'll return a BoxBorder.
+  // that we'll return a [BoxBorder].
   @override
   BoxBorder add(ShapeBorder other, { bool reversed: false }) => null;
 
@@ -315,13 +333,13 @@ class Border extends BoxBorder {
     );
   }
 
-  /// The top side of this border.
+  @override
   final BorderSide top;
 
   /// The right side of this border.
   final BorderSide right;
 
-  /// The bottom side of this border.
+  @override
   final BorderSide bottom;
 
   /// The left side of this border.
@@ -332,8 +350,7 @@ class Border extends BoxBorder {
     return new EdgeInsets.fromLTRB(left.width, top.width, right.width, bottom.width);
   }
 
-  /// Whether all four sides of the border are identical. Uniform borders are
-  /// typically more efficient to paint.
+  @override
   bool get isUniform {
     final Color topColor = top.color;
     if (right.color != topColor ||
@@ -572,7 +589,7 @@ class BorderDirectional extends BoxBorder {
     );
   }
 
-  /// The top side of this border.
+  @override
   final BorderSide top;
 
   /// The start side of this border.
@@ -595,7 +612,7 @@ class BorderDirectional extends BoxBorder {
   ///  * [TextDirection], which is used to describe the reading direction.
   final BorderSide end;
 
-  /// The bottom side of this border.
+  @override
   final BorderSide bottom;
 
   @override
@@ -603,8 +620,7 @@ class BorderDirectional extends BoxBorder {
     return new EdgeInsetsDirectional.fromSTEB(start.width, top.width, end.width, bottom.width);
   }
 
-  /// Whether all four sides of the border are identical. Uniform borders are
-  /// typically more efficient to paint.
+  @override
   bool get isUniform {
     final Color topColor = top.color;
     if (start.color != topColor ||

packages/flutter/lib/src/painting/box_decoration.dart

@@ -206,7 +206,7 @@ class BoxDecoration extends Decoration {
   ///  * [Decoration.lerp], which can interpolate between any two types of
   ///    [Decoration]s, not just [BoxDecoration]s.
   ///  * [lerpFrom] and [lerpTo], which are used to implement [Decoration.lerp]
-  ///     and which use [BoxDecoration.lerp] when interpolating two
+  ///    and which use [BoxDecoration.lerp] when interpolating two
   ///    [BoxDecoration]s or a [BoxDecoration] to or from null.
   static BoxDecoration lerp(BoxDecoration a, BoxDecoration b, double t) {
     if (a == null && b == null)

packages/flutter/lib/src/painting/circle_border.dart

@@ -25,7 +25,7 @@ class CircleBorder extends ShapeBorder {
   /// Create a circle border.
   ///
   /// The [side] argument must not be null.
-  const CircleBorder(this.side) : assert(side != null);
+  const CircleBorder([ this.side = BorderSide.none ]) : assert(side != null);
 
   /// The style of this border.
   final BorderSide side;

packages/flutter/lib/src/painting/rounded_rectangle_border.dart

@@ -28,7 +28,7 @@ class RoundedRectangleBorder extends ShapeBorder {
   /// Creates a rounded rectangle border.
   ///
   /// The arguments must not be null.
-  RoundedRectangleBorder({
+  const RoundedRectangleBorder({
     this.side: BorderSide.none,
     this.borderRadius: BorderRadius.zero,
   }) : assert(side != null),

packages/flutter/test/painting/shape_decoration_test.dart

+// Copyright 2017 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 'package:flutter/painting.dart';
+
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  test('ShapeDecoration constructor', () {
+    final Color colorR = const Color(0xffff0000);
+    final Color colorG = const Color(0xff00ff00);
+    final Gradient gradient = new LinearGradient(colors: <Color>[colorR, colorG]);
+    expect(const ShapeDecoration(shape: const Border()), const ShapeDecoration(shape: const Border()));
+    expect(() => new ShapeDecoration(color: colorR, gradient: gradient, shape: const Border()), throwsAssertionError);
+    expect(() => new ShapeDecoration(color: colorR, shape: null), throwsAssertionError);
+    expect(
+      new ShapeDecoration.fromBoxDecoration(const BoxDecoration(shape: BoxShape.circle)),
+      const ShapeDecoration(shape: const CircleBorder(BorderSide.none)),
+    );
+    expect(
+      new ShapeDecoration.fromBoxDecoration(new BoxDecoration(shape: BoxShape.rectangle, borderRadius: new BorderRadiusDirectional.circular(100.0))),
+      new ShapeDecoration(shape: new RoundedRectangleBorder(borderRadius: new BorderRadiusDirectional.circular(100.0))),
+    );
+    expect(
+      new ShapeDecoration.fromBoxDecoration(new BoxDecoration(shape: BoxShape.circle, border: new Border.all(color: colorG))),
+      new ShapeDecoration(shape: new CircleBorder(new BorderSide(color: colorG))),
+    );
+    expect(
+      new ShapeDecoration.fromBoxDecoration(new BoxDecoration(shape: BoxShape.rectangle, border: new Border.all(color: colorR))),
+      new ShapeDecoration(shape: new Border.all(color: colorR)),
+    );
+    expect(
+      new ShapeDecoration.fromBoxDecoration(const BoxDecoration(shape: BoxShape.rectangle, border: const BorderDirectional(start: const BorderSide()))),
+      const ShapeDecoration(shape: const BorderDirectional(start: const BorderSide())),
+    );
+  });
+
+  test('ShapeDecoration.lerp and hit test', () {
+    final Decoration a = const ShapeDecoration(shape: const CircleBorder());
+    final Decoration b = const ShapeDecoration(shape: const RoundedRectangleBorder());
+    expect(Decoration.lerp(a, b, 0.0), a);
+    expect(Decoration.lerp(a, b, 1.0), b);
+    const Size size = const Size(200.0, 100.0); // at t=0.5, width will be 150 (x=25 to x=175).
+    expect(a.hitTest(size, const Offset(20.0, 50.0)), isFalse);
+    expect(Decoration.lerp(a, b, 0.1).hitTest(size, const Offset(20.0, 50.0)), isFalse);
+    expect(Decoration.lerp(a, b, 0.5).hitTest(size, const Offset(20.0, 50.0)), isFalse);
+    expect(Decoration.lerp(a, b, 0.9).hitTest(size, const Offset(20.0, 50.0)), isTrue);
+    expect(b.hitTest(size, const Offset(20.0, 50.0)), isTrue);
+  });
+}