CupertinoActionSheet (#19232)

Adding CupertinoActionSheet, showCupertinoModalPopup

packages/flutter/lib/cupertino.dart

@@ -7,6 +7,7 @@
 /// To use, import `package:flutter/cupertino.dart`.
 library cupertino;
 
+export 'src/cupertino/action_sheet.dart';
 export 'src/cupertino/activity_indicator.dart';
 export 'src/cupertino/app.dart';
 export 'src/cupertino/bottom_tab_bar.dart';

packages/flutter/lib/src/cupertino/route.dart

@@ -14,6 +14,9 @@ const double _kMinFlingVelocity = 1.0; // Screen widths per second.
 // Barrier color for a Cupertino modal barrier.
 const Color _kModalBarrierColor = Color(0x6604040F);
 
+// The duration of the transition used when a modal popup is shown.
+const Duration _kModalPopupTransitionDuration = Duration(milliseconds: 335);
+
 // Offset from offscreen to the right to fully on screen.
 final Tween<Offset> _kRightMiddleTween = new Tween<Offset>(
   begin: const Offset(1.0, 0.0),
@@ -715,6 +718,102 @@ class _CupertinoEdgeShadowPainter extends BoxPainter {
   }
 }
 
+class _CupertinoModalPopupRoute<T> extends PopupRoute<T> {
+  _CupertinoModalPopupRoute({
+    this.builder,
+    this.barrierLabel,
+    RouteSettings settings,
+  }) : super(settings: settings);
+
+  final WidgetBuilder builder;
+
+  @override
+  final String barrierLabel;
+
+  @override
+  Color get barrierColor => _kModalBarrierColor;
+
+  @override
+  bool get barrierDismissible => true;
+
+  @override
+  bool get semanticsDismissible => false;
+
+  @override
+  Duration get transitionDuration => _kModalPopupTransitionDuration;
+
+  Animation<double> _animation;
+
+  Tween<Offset> _offsetTween;
+
+  @override
+  Animation<double> createAnimation() {
+    assert(_animation == null);
+    _animation = new CurvedAnimation(
+      parent: super.createAnimation(),
+      curve: Curves.ease,
+      reverseCurve: Curves.ease.flipped,
+    );
+    _offsetTween = new Tween<Offset>(
+      begin: const Offset(0.0, 1.0),
+      end: const Offset(0.0, 0.0),
+    );
+    return _animation;
+  }
+
+  @override
+  Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
+    return builder(context);
+  }
+
+  @override
+  Widget buildTransitions(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, Widget child) {
+    return new Align(
+      alignment: Alignment.bottomCenter,
+      child: new FractionalTranslation(
+        translation: _offsetTween.evaluate(_animation),
+        child: child,
+      ),
+    );
+  }
+}
+
+/// Shows a modal iOS-style popup that slides up from the bottom of the screen.
+///
+/// Such a popup is an alternative to a menu or a dialog and prevents the user
+/// from interacting with the rest of the app.
+///
+/// The `context` argument is used to look up the [Navigator] for the popup.
+/// It is only used when the method is called. Its corresponding widget can be
+/// safely removed from the tree before the popup is closed.
+///
+/// The `builder` argument typically builds a [CupertinoActionSheet] widget.
+/// Content below the widget is dimmed with a [ModalBarrier]. The widget built
+/// by the `builder` does not share a context with the location that
+/// `showCupertinoModalPopup` is originally called from. Use a
+/// [StatefulBuilder] or a custom [StatefulWidget] if the widget needs to
+/// update dynamically.
+///
+/// Returns a `Future` that resolves to the value that was passed to
+/// [Navigator.pop] when the popup was closed.
+///
+/// See also:
+///
+///  * [ActionSheet], which is the widget usually returned by the `builder`
+///    argument to [showCupertinoModalPopup].
+///  * <https://developer.apple.com/design/human-interface-guidelines/ios/views/action-sheets/>
+Future<T> showCupertinoModalPopup<T>({
+  @required BuildContext context,
+  @required WidgetBuilder builder,
+}) {
+  return Navigator.of(context, rootNavigator: true).push(
+    new _CupertinoModalPopupRoute<T>(
+      builder: builder,
+      barrierLabel: 'Dismiss',
+    ),
+  );
+}
+
 Widget _buildCupertinoDialogTransitions(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, Widget child) {
   final CurvedAnimation fadeAnimation = new CurvedAnimation(
     parent: animation,

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

@@ -70,6 +70,7 @@ class BoxDecoration extends Decoration {
   ///   [BoxShape.circle].
   /// * If [boxShadow] is null, this decoration does not paint a shadow.
   /// * If [gradient] is null, this decoration does not paint gradients.
+  /// * If [backgroundBlendMode] is null, this decoration paints with [BlendMode.srcOver]
   ///
   /// The [shape] argument must not be null.
   const BoxDecoration({
@@ -79,13 +80,20 @@ class BoxDecoration extends Decoration {
     this.borderRadius,
     this.boxShadow,
     this.gradient,
+    this.backgroundBlendMode,
     this.shape = BoxShape.rectangle,
-  }) : assert(shape != null);
+  }) : assert(shape != null),
+       // TODO(mattcarroll): Use "backgroundBlendMode == null" when Dart #31140 is in.
+       assert(
+       identical(backgroundBlendMode, null) || color != null || gradient != null,
+       'backgroundBlendMode applies to BoxDecoration\'s background color or'
+           'gradient, but no color or gradient were provided.'
+       );
 
   @override
   bool debugAssertIsValid() {
     assert(shape != BoxShape.circle ||
-           borderRadius == null); // Can't have a border radius if you're a circle.
+          borderRadius == null); // Can't have a border radius if you're a circle.
     return super.debugAssertIsValid();
   }
 
@@ -136,6 +144,14 @@ class BoxDecoration extends Decoration {
   /// The [gradient] is drawn under the [image].
   final Gradient gradient;
 
+  /// The blend mode applied to the [color] or [gradient] background of the box.
+  ///
+  /// If no [backgroundBlendMode] is provided, then the default painting blend
+  /// mode is used.
+  ///
+  /// If no [color] or [gradient] is provided, then blend mode has no impact.
+  final BlendMode backgroundBlendMode;
+
   /// The shape to fill the background [color], [gradient], and [image] into and
   /// to cast as the [boxShadow].
   ///
@@ -332,6 +348,8 @@ class _BoxDecorationPainter extends BoxPainter {
     if (_cachedBackgroundPaint == null ||
         (_decoration.gradient != null && _rectForCachedBackgroundPaint != rect)) {
       final Paint paint = new Paint();
+      if (_decoration.backgroundBlendMode != null)
+        paint.blendMode = _decoration.backgroundBlendMode;
       if (_decoration.color != null)
         paint.color = _decoration.color;
       if (_decoration.gradient != null) {

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

@@ -33,6 +33,7 @@ class ModalBarrier extends StatelessWidget {
     this.color,
     this.dismissible = true,
     this.semanticsLabel,
+    this.barrierSemanticsDismissible = true,
   }) : super(key: key);
 
   /// If non-null, fill the barrier with this color.
@@ -51,6 +52,13 @@ class ModalBarrier extends StatelessWidget {
   ///    [ModalBarrier] built by [ModalRoute] pages.
   final bool dismissible;
 
+  /// Whether the modal barrier semantics are included in the semantics tree.
+  ///
+  /// See also:
+  ///  * [ModalRoute.semanticsDismissible], which controls this property for
+  ///    the [ModalBarrier] built by [ModalRoute] pages.
+  final bool barrierSemanticsDismissible;
+
   /// Semantics label used for the barrier if it is [dismissable].
   ///
   /// The semantics label is read out by accessibility tools (e.g. TalkBack
@@ -66,10 +74,12 @@ class ModalBarrier extends StatelessWidget {
   Widget build(BuildContext context) {
     assert(!dismissible || semanticsLabel == null || debugCheckHasDirectionality(context));
     final bool semanticsDismissible = dismissible && defaultTargetPlatform != TargetPlatform.android;
+    final bool modalBarrierSemanticsDismissible = barrierSemanticsDismissible ?? semanticsDismissible;
     return new BlockSemantics(
       child: new ExcludeSemantics(
-        // On Android, the back button is used to dismiss a modal.
-        excluding: !semanticsDismissible,
+        // On Android, the back button is used to dismiss a modal. On iOS, some
+        // modal barriers are not dismissible in accessibility mode.
+        excluding: !semanticsDismissible || !modalBarrierSemanticsDismissible,
         child: new GestureDetector(
           onTapDown: (TapDownDetails details) {
             if (dismissible)
@@ -117,6 +127,7 @@ class AnimatedModalBarrier extends AnimatedWidget {
     Animation<Color> color,
     this.dismissible = true,
     this.semanticsLabel,
+    this.barrierSemanticsDismissible,
   }) : super(key: key, listenable: color);
 
   /// If non-null, fill the barrier with this color.
@@ -145,12 +156,20 @@ class AnimatedModalBarrier extends AnimatedWidget {
   ///    [ModalBarrier] built by [ModalRoute] pages.
   final String semanticsLabel;
 
+  /// Whether the modal barrier semantics are included in the semantics tree.
+  ///
+  /// See also:
+  ///  * [ModalRoute.semanticsDismissible], which controls this property for
+  ///    the [ModalBarrier] built by [ModalRoute] pages.
+  final bool barrierSemanticsDismissible;
+
   @override
   Widget build(BuildContext context) {
     return new ModalBarrier(
       color: color?.value,
       dismissible: dismissible,
       semanticsLabel: semanticsLabel,
+      barrierSemanticsDismissible: barrierSemanticsDismissible,
     );
   }
 }

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

@@ -898,6 +898,21 @@ abstract class ModalRoute<T> extends TransitionRoute<T> with LocalHistoryRoute<T
   ///  * [ModalBarrier], the widget that implements this feature.
   bool get barrierDismissible;
 
+  /// Whether the semantics of the modal barrier are included in the
+  /// semantics tree.
+  ///
+  /// The modal barrier is the scrim that is rendered behind each route, which
+  /// generally prevents the user from interacting with the route below the
+  /// current route, and normally partially obscures such routes.
+  ///
+  /// If [semanticsDismissible] is true, then modal barrier semantics are
+  /// included in the semantics tree.
+  ///
+  /// If [semanticsDismissible] is false, then modal barrier semantics are
+  /// excluded from the the semantics tree and tapping on the modal barrier
+  /// has no effect.
+  bool get semanticsDismissible => true;
+
   /// The color to use for the modal barrier. If this is null, the barrier will
   /// be transparent.
   ///
@@ -1173,11 +1188,13 @@ abstract class ModalRoute<T> extends TransitionRoute<T> with LocalHistoryRoute<T
         color: color,
         dismissible: barrierDismissible, // changedInternalState is called if this updates
         semanticsLabel: barrierLabel, // changedInternalState is called if this updates
+        barrierSemanticsDismissible: semanticsDismissible,
       );
     } else {
       barrier = new ModalBarrier(
         dismissible: barrierDismissible, // changedInternalState is called if this updates
         semanticsLabel: barrierLabel, // changedInternalState is called if this updates
+        barrierSemanticsDismissible: semanticsDismissible,
       );
     }
     return new IgnorePointer(