Rename BannerLocation enum values (#11960)

* Rename BannerLocation enum values

 * topLeft -> topStart
 * topRight -> topEnd
 * bottomLeft -> bottomStart
 * bottomRight -> bottomEnd

These names will make it easier for us to adjust the location of the
banner in right-to-left mode.

See the discussion on flutter-dev.

* Add RTL support for Banner

Fixes #11905

examples/flutter_gallery/lib/gallery/home.dart

@@ -197,7 +197,7 @@ class GalleryHomeState extends State<GalleryHome> with SingleTickerProviderState
             opacity: new CurvedAnimation(parent: _controller, curve: Curves.easeInOut),
             child: const Banner(
               message: 'PREVIEW',
-              location: BannerLocation.topRight,
+              location: BannerLocation.topEnd,
             )
           ),
         ]

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

@@ -24,17 +24,25 @@ const TextStyle _kTextStyle = const TextStyle(
 
 /// Where to show a [Banner].
 enum BannerLocation {
-  /// Show the banner in the top right corner.
+  /// Show the banner in the top-right corner when the ambient [Directionality]
-  topRight,
+  /// is [TextDirection.rtl] and in the top-left corner when the ambient
+  /// [Directionality] is [TextDirection.ltr].
+  topStart,
 
-  /// Show the banner in the top left corner.
+  /// Show the banner in the top-left corner when the ambient [Directionality]
-  topLeft,
+  /// is [TextDirection.rtl] and in the top-right corner when the ambient
+  /// [Directionality] is [TextDirection.ltr].
+  topEnd,
 
-  /// Show the banner in the bottom right corner.
+  /// Show the banner in the bottom-right corner when the ambient
-  bottomRight,
+  /// [Directionality] is [TextDirection.rtl] and in the bottom-left corner when
+  /// the ambient [Directionality] is [TextDirection.ltr].
+  bottomStart,
 
-  /// Show the banner in the bottom left corner.
+  /// Show the banner in the bottom-left corner when the ambient
-  bottomLeft,
+  /// [Directionality] is [TextDirection.rtl] and in the bottom-right corner when
+  /// the ambient [Directionality] is [TextDirection.ltr].
+  bottomEnd,
 }
 
 /// Paints a [Banner].
@@ -59,12 +67,14 @@ class BannerPainter extends CustomPainter {
 
   /// The directionality of the text.
   ///
-  /// This is used to disambiguate how to render bidirectional text. For
+  /// This value is used to disambiguate how to render bidirectional text. For
   /// example, if the message is an English phrase followed by a Hebrew phrase,
   /// in a [TextDirection.ltr] context the English phrase will be on the left
   /// and the Hebrew phrase to its right, while in a [TextDirection.rtl]
   /// context, the English phrase will be on the right and the Hebrow phrase on
   /// its left.
+  ///
+  /// This value is also used to interpret the [location] of the banner.
   final TextDirection textDirection;
 
   /// Where to show the banner (e.g., the upper right corder).
@@ -126,15 +136,32 @@ class BannerPainter extends CustomPainter {
 
   double _translationX(double width) {
     assert(location != null);
-    switch (location) {
+    assert(textDirection != null);
-      case BannerLocation.bottomRight:
+    switch (textDirection) {
-        return width - _kBottomOffset;
+      case TextDirection.rtl:
-      case BannerLocation.topRight:
+        switch (location) {
-        return width;
+          case BannerLocation.bottomEnd:
-      case BannerLocation.bottomLeft:
+            return _kBottomOffset;
-        return _kBottomOffset;
+          case BannerLocation.topEnd:
-      case BannerLocation.topLeft:
+            return 0.0;
-        return 0.0;
+          case BannerLocation.bottomStart:
+            return width - _kBottomOffset;
+          case BannerLocation.topStart:
+            return width;
+        }
+        break;
+      case TextDirection.ltr:
+        switch (location) {
+          case BannerLocation.bottomEnd:
+            return width - _kBottomOffset;
+          case BannerLocation.topEnd:
+            return width;
+          case BannerLocation.bottomStart:
+            return _kBottomOffset;
+          case BannerLocation.topStart:
+            return 0.0;
+        }
+        break;
     }
     return null;
   }
@@ -142,11 +169,11 @@ class BannerPainter extends CustomPainter {
   double _translationY(double height) {
     assert(location != null);
     switch (location) {
-      case BannerLocation.bottomRight:
+      case BannerLocation.bottomStart:
-      case BannerLocation.bottomLeft:
+      case BannerLocation.bottomEnd:
         return height - _kBottomOffset;
-      case BannerLocation.topRight:
+      case BannerLocation.topStart:
-      case BannerLocation.topLeft:
+      case BannerLocation.topEnd:
         return 0.0;
     }
     return null;
@@ -154,13 +181,28 @@ class BannerPainter extends CustomPainter {
 
   double get _rotation {
     assert(location != null);
-    switch (location) {
+    assert(textDirection != null);
-      case BannerLocation.bottomLeft:
+    switch (textDirection) {
-      case BannerLocation.topRight:
+      case TextDirection.rtl:
-        return math.PI / 4.0;
+        switch (location) {
-      case BannerLocation.bottomRight:
+          case BannerLocation.bottomStart:
-      case BannerLocation.topLeft:
+          case BannerLocation.topEnd:
-        return -math.PI / 4.0;
+            return -math.PI / 4.0;
+          case BannerLocation.bottomEnd:
+          case BannerLocation.topStart:
+            return math.PI / 4.0;
+        }
+        break;
+      case TextDirection.ltr:
+        switch (location) {
+          case BannerLocation.bottomStart:
+          case BannerLocation.topEnd:
+            return math.PI / 4.0;
+          case BannerLocation.bottomEnd:
+          case BannerLocation.topStart:
+            return -math.PI / 4.0;
+        }
+        break;
     }
     return null;
   }
@@ -265,7 +307,7 @@ class CheckedModeBanner extends StatelessWidget {
         child: result,
         message: 'SLOW MODE',
         textDirection: TextDirection.ltr,
-        location: BannerLocation.topRight,
+        location: BannerLocation.topEnd,
       );
       return true;
     });

packages/flutter/test/widgets/banner_test.dart

@@ -17,11 +17,11 @@ class TestCanvas implements Canvas {
 }
 
 void main() {
-  test('A Banner with a location of topLeft paints in the top left', () {
+  test('A Banner with a location of topStart paints in the top left (LTR)', () {
     final BannerPainter bannerPainter = new BannerPainter(
       message: 'foo',
       textDirection: TextDirection.ltr,
-      location: BannerLocation.topLeft
+      location: BannerLocation.topStart
     );
 
     final TestCanvas canvas = new TestCanvas();
@@ -44,11 +44,11 @@ void main() {
     expect(rotateCommand.positionalArguments[0], equals(-math.PI / 4.0));
   });
 
-  test('A Banner with a location of topRight paints in the top right', () {
+  test('A Banner with a location of topStart paints in the top right (RTL)', () {
     final BannerPainter bannerPainter = new BannerPainter(
       message: 'foo',
-      textDirection: TextDirection.ltr,
+      textDirection: TextDirection.rtl,
-      location: BannerLocation.topRight
+      location: BannerLocation.topStart,
     );
 
     final TestCanvas canvas = new TestCanvas();
@@ -71,11 +71,65 @@ void main() {
     expect(rotateCommand.positionalArguments[0], equals(math.PI / 4.0));
   });
 
-  test('A Banner with a location of bottomLeft paints in the bottom left', () {
+  test('A Banner with a location of topEnd paints in the top right (LTR)', () {
     final BannerPainter bannerPainter = new BannerPainter(
       message: 'foo',
       textDirection: TextDirection.ltr,
-      location: BannerLocation.bottomLeft
+      location: BannerLocation.topEnd
+    );
+
+    final TestCanvas canvas = new TestCanvas();
+
+    bannerPainter.paint(canvas, const Size(1000.0, 1000.0));
+
+    final Invocation translateCommand = canvas.invocations.firstWhere((Invocation invocation) {
+      return invocation.memberName == #translate;
+    });
+
+    expect(translateCommand, isNotNull);
+    expect(translateCommand.positionalArguments[0], greaterThan(900.0));
+    expect(translateCommand.positionalArguments[1], lessThan(100.0));
+
+    final Invocation rotateCommand = canvas.invocations.firstWhere((Invocation invocation) {
+      return invocation.memberName == #rotate;
+    });
+
+    expect(rotateCommand, isNotNull);
+    expect(rotateCommand.positionalArguments[0], equals(math.PI / 4.0));
+  });
+
+  test('A Banner with a location of topEnd paints in the top left (RTL)', () {
+    final BannerPainter bannerPainter = new BannerPainter(
+      message: 'foo',
+      textDirection: TextDirection.rtl,
+      location: BannerLocation.topEnd,
+    );
+
+    final TestCanvas canvas = new TestCanvas();
+
+    bannerPainter.paint(canvas, const Size(1000.0, 1000.0));
+
+    final Invocation translateCommand = canvas.invocations.firstWhere((Invocation invocation) {
+      return invocation.memberName == #translate;
+    });
+
+    expect(translateCommand, isNotNull);
+    expect(translateCommand.positionalArguments[0], lessThan(100.0));
+    expect(translateCommand.positionalArguments[1], lessThan(100.0));
+
+    final Invocation rotateCommand = canvas.invocations.firstWhere((Invocation invocation) {
+      return invocation.memberName == #rotate;
+    });
+
+    expect(rotateCommand, isNotNull);
+    expect(rotateCommand.positionalArguments[0], equals(-math.PI / 4.0));
+  });
+
+  test('A Banner with a location of bottomStart paints in the bottom left (LTR)', () {
+    final BannerPainter bannerPainter = new BannerPainter(
+      message: 'foo',
+      textDirection: TextDirection.ltr,
+      location: BannerLocation.bottomStart
     );
 
     final TestCanvas canvas = new TestCanvas();
@@ -98,11 +152,11 @@ void main() {
     expect(rotateCommand.positionalArguments[0], equals(math.PI / 4.0));
   });
 
-  test('A Banner with a location of bottomRight paints in the bottom right', () {
+  test('A Banner with a location of bottomStart paints in the bottom right (RTL)', () {
     final BannerPainter bannerPainter = new BannerPainter(
       message: 'foo',
-      textDirection: TextDirection.ltr,
+      textDirection: TextDirection.rtl,
-      location: BannerLocation.bottomRight
+      location: BannerLocation.bottomStart,
     );
 
     final TestCanvas canvas = new TestCanvas();
@@ -124,4 +178,59 @@ void main() {
     expect(rotateCommand, isNotNull);
     expect(rotateCommand.positionalArguments[0], equals(-math.PI / 4.0));
   });
+
+  test('A Banner with a location of bottomEnd paints in the bottom right (LTR)', () {
+    final BannerPainter bannerPainter = new BannerPainter(
+      message: 'foo',
+      textDirection: TextDirection.ltr,
+      location: BannerLocation.bottomEnd
+    );
+
+    final TestCanvas canvas = new TestCanvas();
+
+    bannerPainter.paint(canvas, const Size(1000.0, 1000.0));
+
+    final Invocation translateCommand = canvas.invocations.firstWhere((Invocation invocation) {
+      return invocation.memberName == #translate;
+    });
+
+    expect(translateCommand, isNotNull);
+    expect(translateCommand.positionalArguments[0], greaterThan(900.0));
+    expect(translateCommand.positionalArguments[1], greaterThan(900.0));
+
+    final Invocation rotateCommand = canvas.invocations.firstWhere((Invocation invocation) {
+      return invocation.memberName == #rotate;
+    });
+
+    expect(rotateCommand, isNotNull);
+    expect(rotateCommand.positionalArguments[0], equals(-math.PI / 4.0));
+  });
+
+  test('A Banner with a location of bottomEnd paints in the bottom left (RTL)', () {
+    final BannerPainter bannerPainter = new BannerPainter(
+      message: 'foo',
+      textDirection: TextDirection.rtl,
+      location: BannerLocation.bottomEnd,
+    );
+
+    final TestCanvas canvas = new TestCanvas();
+
+    bannerPainter.paint(canvas, const Size(1000.0, 1000.0));
+
+    final Invocation translateCommand = canvas.invocations.firstWhere((Invocation invocation) {
+      return invocation.memberName == #translate;
+    });
+
+    expect(translateCommand, isNotNull);
+    expect(translateCommand.positionalArguments[0], lessThan(100.0));
+    expect(translateCommand.positionalArguments[1], greaterThan(900.0));
+
+    final Invocation rotateCommand = canvas.invocations.firstWhere((Invocation invocation) {
+      return invocation.memberName == #rotate;
+    });
+
+    expect(rotateCommand, isNotNull);
+    expect(rotateCommand.positionalArguments[0], equals(math.PI / 4.0));
+  });
+
 }