ClipPath.shape and related fixes (#24816)

packages/flutter/lib/src/material/material.dart

@@ -357,8 +357,14 @@ class _MaterialState extends State<Material> with TickerProviderStateMixin {
 
     final ShapeBorder shape = _getShape();
 
-    if (widget.type == MaterialType.transparency)
-      return _transparentInterior(shape: shape, clipBehavior: widget.clipBehavior, contents: contents);
+    if (widget.type == MaterialType.transparency) {
+      return _transparentInterior(
+        context: context,
+        shape: shape,
+        clipBehavior: widget.clipBehavior,
+        contents: contents,
+      );
+    }
 
     return _MaterialInterior(
       curve: Curves.fastOutSlowIn,
@@ -372,7 +378,12 @@ class _MaterialState extends State<Material> with TickerProviderStateMixin {
     );
   }
 
-  static Widget _transparentInterior({ShapeBorder shape, Clip clipBehavior, Widget contents}) {
+  static Widget _transparentInterior({
+    @required BuildContext context,
+    @required ShapeBorder shape,
+    @required Clip clipBehavior,
+    @required Widget contents,
+  }) {
     final _ShapeBorderPaint child = _ShapeBorderPaint(
       child: contents,
       shape: shape,
@@ -382,7 +393,10 @@ class _MaterialState extends State<Material> with TickerProviderStateMixin {
     }
     return ClipPath(
       child: child,
-      clipper: ShapeBorderClipper(shape: shape),
+      clipper: ShapeBorderClipper(
+        shape: shape,
+        textDirection: Directionality.of(context),
+      ),
       clipBehavior: clipBehavior,
     );
   }

packages/flutter/lib/src/rendering/proxy_box.dart

@@ -1053,7 +1053,7 @@ class RenderBackdropFilter extends RenderProxyBox {
 /// information.
 ///
 /// The most efficient way to update the clip provided by this class is to
-/// supply a reclip argument to the constructor of the [CustomClipper]. The
+/// supply a `reclip` argument to the constructor of the [CustomClipper]. The
 /// custom object will listen to this animation and update the clip whenever the
 /// animation ticks, avoiding both the build and layout phases of the pipeline.
 ///
@@ -1063,6 +1063,7 @@ class RenderBackdropFilter extends RenderProxyBox {
 ///  * [ClipRRect], which can be customized with a [CustomClipper<RRect>].
 ///  * [ClipOval], which can be customized with a [CustomClipper<Rect>].
 ///  * [ClipPath], which can be customized with a [CustomClipper<Path>].
+///  * [ShapeBorderClipper], for specifying a clip path using a [ShapeBorder].
 abstract class CustomClipper<T> {
   /// Creates a custom clipper.
   ///
@@ -1141,7 +1142,8 @@ class ShapeBorderClipper extends CustomClipper<Path> {
     if (oldClipper.runtimeType != ShapeBorderClipper)
       return true;
     final ShapeBorderClipper typedOldClipper = oldClipper;
-    return typedOldClipper.shape != shape;
+    return typedOldClipper.shape != shape
+        || typedOldClipper.textDirection != textDirection;
   }
 }
 

packages/flutter/lib/src/widgets/basic.dart

@@ -690,6 +690,10 @@ class ClipOval extends SingleChildRenderObjectWidget {
 ///  * To clip to a rectangle, consider [ClipRect].
 ///  * To clip to an oval or circle, consider [ClipOval].
 ///  * To clip to a rounded rectangle, consider [ClipRRect].
+///
+/// To clip to a particular [ShapeBorder], consider using either the
+/// [ClipPath.shape] static method or the [ShapeBorderClipper] custom clipper
+/// class.
 class ClipPath extends SingleChildRenderObjectWidget {
   /// Creates a path clip.
   ///
@@ -697,7 +701,38 @@ class ClipPath extends SingleChildRenderObjectWidget {
   /// size and location of the child. However, rather than use this default,
   /// consider using a [ClipRect], which can achieve the same effect more
   /// efficiently.
-  const ClipPath({ Key key, this.clipper, this.clipBehavior = Clip.antiAlias, Widget child }) : super(key: key, child: child);
+  const ClipPath({
+    Key key,
+    this.clipper,
+    this.clipBehavior = Clip.antiAlias,
+    Widget child,
+  }) : super(key: key, child: child);
+
+  /// Creates a shape clip.
+  ///
+  /// Uses a [ShapeBorderClipper] to configure the [ClipPath] to clip to the
+  /// given [ShapeBorder].
+  static Widget shape({
+    Key key,
+    @required ShapeBorder shape,
+    Clip clipBehavior = Clip.antiAlias,
+    Widget child,
+  }) {
+    assert(shape != null);
+    return Builder(
+      key: key,
+      builder: (BuildContext context) {
+        return ClipPath(
+          clipper: ShapeBorderClipper(
+            shape: shape,
+            textDirection: Directionality.of(context),
+          ),
+          clipBehavior: clipBehavior,
+          child: child,
+        );
+      },
+    );
+  }
 
   /// If non-null, determines which clip to use.
   ///

packages/flutter/lib/src/widgets/container.dart

@@ -20,6 +20,9 @@ import 'image.dart';
 ///
 /// Commonly used with [BoxDecoration].
 ///
+/// The [child] is not clipped. To clip a child to the shape of a particular
+/// [ShapeDecoration], consider using a [ClipPath] widget.
+///
 /// {@tool sample}
 ///
 /// This sample shows a radial gradient that draws a moon on a night sky:
@@ -313,6 +316,9 @@ class Container extends StatelessWidget {
   /// A shorthand for specifying just a solid color is available in the
   /// constructor: set the `color` argument instead of the `decoration`
   /// argument.
+  ///
+  /// The [child] is not clipped to the decoration. To clip a child to the shape
+  /// of a particular [ShapeDecoration], consider using a [ClipPath] widget.
   final Decoration decoration;
 
   /// The decoration to paint in front of the [child].

packages/flutter/test/material/material_test.dart

@@ -8,6 +8,7 @@ import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import '../rendering/mock_canvas.dart';
+import '../widgets/shape_decoration_test.dart' show TestBorder;
 
 class NotifyMaterial extends StatelessWidget {
   @override
@@ -237,6 +238,69 @@ void main() {
         ),
       );
     });
+
+    testWidgets('supports directional clips', (WidgetTester tester) async {
+      final List<String> logs = <String>[];
+      final ShapeBorder shape = TestBorder((String message) { logs.add(message); });
+      Widget buildMaterial() {
+        return Material(
+          type: MaterialType.transparency,
+          shape: shape,
+          child: const SizedBox(width: 100.0, height: 100.0),
+          clipBehavior: Clip.antiAlias,
+        );
+      }
+      final Widget material = buildMaterial();
+      // verify that a regular clip works as one would expect
+      logs.add('--0');
+      await tester.pumpWidget(material);
+      // verify that pumping again doesn't recompute the clip
+      // even though the widget itself is new (the shape doesn't change identity)
+      logs.add('--1');
+      await tester.pumpWidget(buildMaterial());
+      // verify that Material passes the TextDirection on to its shape when it's transparent
+      logs.add('--2');
+      await tester.pumpWidget(Directionality(
+        textDirection: TextDirection.ltr,
+        child: material,
+      ));
+      // verify that changing the text direction from LTR to RTL has an effect
+      // even though the widget itself is identical
+      logs.add('--3');
+      await tester.pumpWidget(Directionality(
+        textDirection: TextDirection.rtl,
+        child: material,
+      ));
+      // verify that pumping again with a text direction has no effect
+      logs.add('--4');
+      await tester.pumpWidget(Directionality(
+        textDirection: TextDirection.rtl,
+        child: buildMaterial(),
+      ));
+      logs.add('--5');
+      // verify that changing the text direction and the widget at the same time
+      // works as expected
+      await tester.pumpWidget(Directionality(
+        textDirection: TextDirection.ltr,
+        child: material,
+      ));
+      expect(logs, <String>[
+        '--0',
+        'getOuterPath Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) null',
+        'paint Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) null',
+        '--1',
+        '--2',
+        'getOuterPath Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) TextDirection.ltr',
+        'paint Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) TextDirection.ltr',
+        '--3',
+        'getOuterPath Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) TextDirection.rtl',
+        'paint Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) TextDirection.rtl',
+        '--4',
+        '--5',
+        'getOuterPath Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) TextDirection.ltr',
+        'paint Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) TextDirection.ltr',
+      ]);
+    });
   });
 
   group('PhysicalModels', () {

packages/flutter/test/widgets/clip_test.dart

@@ -7,6 +7,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 
 import '../rendering/mock_canvas.dart';
+import 'shape_decoration_test.dart' show TestBorder;
 
 final List<String> log = <String>[];
 
@@ -686,4 +687,61 @@ void main() {
       matchesGoldenFile('clip.PhysicalShape.default.png'),
     );
   });
+
+  testWidgets('ClipPath.shape', (WidgetTester tester) async {
+    final List<String> logs = <String>[];
+    final ShapeBorder shape = TestBorder((String message) { logs.add(message); });
+    Widget buildClipPath() {
+      return ClipPath.shape(
+        shape: shape,
+        child: const SizedBox(width: 100.0, height: 100.0),
+      );
+    }
+    final Widget clipPath = buildClipPath();
+    // verify that a regular clip works as one would expect
+    logs.add('--0');
+    await tester.pumpWidget(clipPath);
+    // verify that pumping again doesn't recompute the clip
+    // even though the widget itself is new (the shape doesn't change identity)
+    logs.add('--1');
+    await tester.pumpWidget(buildClipPath());
+    // verify that ClipPath passes the TextDirection on to its shape
+    logs.add('--2');
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.ltr,
+      child: clipPath,
+    ));
+    // verify that changing the text direction from LTR to RTL has an effect
+    // even though the widget itself is identical
+    logs.add('--3');
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.rtl,
+      child: clipPath,
+    ));
+    // verify that pumping again with a text direction has no effect
+    logs.add('--4');
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.rtl,
+      child: buildClipPath(),
+    ));
+    logs.add('--5');
+    // verify that changing the text direction and the widget at the same time
+    // works as expected
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.ltr,
+      child: clipPath,
+    ));
+    expect(logs, <String>[
+      '--0',
+      'getOuterPath Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) null',
+      '--1',
+      '--2',
+      'getOuterPath Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) TextDirection.ltr',
+      '--3',
+      'getOuterPath Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) TextDirection.rtl',
+      '--4',
+      '--5',
+      'getOuterPath Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) TextDirection.ltr',
+    ]);
+  });
 }