Add ergonomic wrappers for Flutter platform services (#3636)

These wrappers also give us a chance to document what these services do.

Fixes #3164

packages/flutter/lib/services.dart

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 /// System services exposed to Flutter apps.
-/// 
+///
 /// To use, import `package:flutter/services.dart`.
 ///
 /// For example, this library includes [fetch], which fetches data from the
@@ -18,8 +18,12 @@ export 'src/services/activity.dart';
 export 'src/services/app_messages.dart';
 export 'src/services/asset_bundle.dart';
 export 'src/services/binding.dart';
+export 'src/services/haptic_feedback.dart';
 export 'src/services/image_cache.dart';
 export 'src/services/image_decoder.dart';
 export 'src/services/image_resource.dart';
 export 'src/services/keyboard.dart';
+export 'src/services/path_provider.dart';
 export 'src/services/shell.dart';
+export 'src/services/system_chrome.dart';
+export 'src/services/system_sound.dart';

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

@@ -66,14 +66,14 @@ class _DatePickerState extends State<DatePicker> {
   _DatePickerMode _mode = _DatePickerMode.day;
 
   void _handleModeChanged(_DatePickerMode mode) {
-    userFeedback.performHapticFeedback(HapticFeedbackType.virtualKey);
+    HapticFeedback.vibrate();
     setState(() {
       _mode = mode;
     });
   }
 
   void _handleYearChanged(DateTime dateTime) {
-    userFeedback.performHapticFeedback(HapticFeedbackType.virtualKey);
+    HapticFeedback.vibrate();
     setState(() {
       _mode = _DatePickerMode.day;
     });
@@ -82,7 +82,7 @@ class _DatePickerState extends State<DatePicker> {
   }
 
   void _handleDayChanged(DateTime dateTime) {
-    userFeedback.performHapticFeedback(HapticFeedbackType.virtualKey);
+    HapticFeedback.vibrate();
     if (config.onChanged != null)
       config.onChanged(dateTime);
   }

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

@@ -4,7 +4,7 @@
 
 import 'dart:math' as math;
 
-import 'package:flutter/services.dart' show HapticFeedbackType, userFeedback;
+import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
 import 'colors.dart';
@@ -129,7 +129,7 @@ class _TimePickerState extends State<TimePicker> {
   _TimePickerMode _mode = _TimePickerMode.hour;
 
   void _handleModeChanged(_TimePickerMode mode) {
-    userFeedback.performHapticFeedback(HapticFeedbackType.virtualKey);
+    HapticFeedback.vibrate();
     setState(() {
       _mode = mode;
     });

packages/flutter/lib/src/services/activity.dart

@@ -3,13 +3,13 @@
 // found in the LICENSE file.
 
 import 'dart:ui';
-import 'dart:async';
 
 import 'package:sky_services/activity/activity.mojom.dart';
 
 import 'shell.dart';
 
-export 'package:sky_services/activity/activity.mojom.dart';
+export 'package:sky_services/activity/activity.mojom.dart' show Activity, Intent, ComponentName, StringExtra;
+
 
 // Dart wrapper around Activity mojo service available in Flutter on Android.
 //
@@ -21,7 +21,7 @@ export 'package:sky_services/activity/activity.mojom.dart';
 
 /// Open a document into a new task rooted at the activity launched by
 /// this Intent.
-/// 
+///
 /// See Android's Intent.FLAG_ACTIVITY_NEW_DOCUMENT.
 const int NEW_DOCUMENT = 0x00080000; // ignore: constant_identifier_names
 
@@ -44,24 +44,6 @@ ActivityProxy _initActivityProxy() {
 final ActivityProxy _activityProxy = _initActivityProxy();
 final Activity activity = _activityProxy.ptr;
 
-UserFeedbackProxy _initUserFeedbackProxy() {
-  UserFeedbackProxy proxy = new UserFeedbackProxy.unbound();
-  _activityProxy.ptr.getUserFeedback(proxy);
-  return proxy;
-}
-
-final UserFeedbackProxy _userFeedbackProxy = _initUserFeedbackProxy();
-final UserFeedback userFeedback = _userFeedbackProxy.ptr;
-
-PathServiceProxy _initPathServiceProxy() {
-  PathServiceProxy proxy = new PathServiceProxy.unbound();
-  shell.connectToService(null, proxy);
-  return proxy;
-}
-
-final PathServiceProxy _pathServiceProxy = _initPathServiceProxy();
-final PathService pathService = _pathServiceProxy.ptr;
-
 Color _cachedPrimaryColor;
 String _cachedLabel;
 
@@ -81,7 +63,3 @@ void updateTaskDescription({ String label, Color color }) {
 
   _activityProxy.ptr.setTaskDescription(description);
 }
-
-Future<String> getAppDataDir() async => (await _pathServiceProxy.ptr.getAppDataDir()).path;
-Future<String> getFilesDir() async => (await _pathServiceProxy.ptr.getFilesDir()).path;
-Future<String> getCacheDir() async => (await _pathServiceProxy.ptr.getCacheDir()).path;

packages/flutter/lib/src/services/app_messages.dart

@@ -5,30 +5,28 @@
 import 'dart:async';
 
 import 'package:mojo/core.dart' as core;
-import 'package:sky_services/flutter/platform/app_messages.mojom.dart';
+import 'package:sky_services/flutter/platform/app_messages.mojom.dart' as mojom;
 
 import 'shell.dart';
 
-// APIs for exchanging messages with the host application.
-
-ApplicationMessagesProxy _initHostAppMessagesProxy() {
-  ApplicationMessagesProxy proxy = new ApplicationMessagesProxy.unbound();
+mojom.ApplicationMessagesProxy _initHostAppMessagesProxy() {
+  mojom.ApplicationMessagesProxy proxy = new mojom.ApplicationMessagesProxy.unbound();
   shell.connectToViewAssociatedService(proxy);
   return proxy;
 }
 
-final ApplicationMessagesProxy _hostAppMessagesProxy = _initHostAppMessagesProxy();
+final mojom.ApplicationMessagesProxy _hostAppMessagesProxy = _initHostAppMessagesProxy();
 
 typedef Future<String> HostMessageCallback(String message);
 typedef Object _SendStringResponseFactory(String response);
 
-class _ApplicationMessagesImpl extends ApplicationMessages {
+class _ApplicationMessagesImpl extends mojom.ApplicationMessages {
   final Map<String, HostMessageCallback> handlers = <String, HostMessageCallback>{};
 
   _ApplicationMessagesImpl() {
-    shell.provideService(ApplicationMessages.serviceName,
+    shell.provideService(mojom.ApplicationMessages.serviceName,
       (core.MojoMessagePipeEndpoint endpoint) {
-        ApplicationMessagesStub stub = new ApplicationMessagesStub.fromEndpoint(endpoint);
+        mojom.ApplicationMessagesStub stub = new mojom.ApplicationMessagesStub.fromEndpoint(endpoint);
         stub.impl = this;
       }
     );
@@ -46,6 +44,8 @@ class _ApplicationMessagesImpl extends ApplicationMessages {
 
 final _ApplicationMessagesImpl _appMessages = new _ApplicationMessagesImpl();
 
+/// A service that can be implemented by the host application and the
+/// Flutter framework to exchange application-specific messages.
 class HostMessages {
   /// Send a message to the host application.
   static Future<String> sendToHost(String messageName, String message) async {

packages/flutter/lib/src/services/haptic_feedback.dart

@@ -0,0 +1,44 @@
+// Copyright 2016 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:async';
+
+import 'package:sky_services/flutter/platform/haptic_feedback.mojom.dart' as mojom;
+
+import 'shell.dart';
+
+mojom.HapticFeedbackProxy _initHapticFeedbackProxy() {
+  mojom.HapticFeedbackProxy proxy = new mojom.HapticFeedbackProxy.unbound();
+  shell.connectToViewAssociatedService(proxy);
+  return proxy;
+}
+
+final mojom.HapticFeedbackProxy _hapticFeedbackProxy = _initHapticFeedbackProxy();
+
+/// Allows access to the haptic feedback interface on the device. This API is
+/// intentionally terse since it invokes default platform behavior. It is not
+/// suitable for use if you require more flexible access to device sensors and
+/// peripherals.
+class HapticFeedback {
+  HapticFeedback._();
+
+  /// Provides haptic feedback to the user for a short duration.
+  ///
+  /// Platform Specific Notes:
+  ///
+  /// * _iOS_: Uses the platform "sound" for vibration (via
+  ///   AudioServicesPlaySystemSound)
+  /// * _Android_: Uses the platform haptic feedback API that simulates a short
+  ///   a short tap on a virtual keyboard.
+  ///
+  /// Return Value:
+  ///
+  ///   boolean indicating if the intent to provide haptic feedback to the user
+  ///   was successfully conveyed to the embedder. There may not be any actual
+  ///   feedback if the device does not have a vibrator or one is disabled in
+  ///   system settings.
+  static Future<bool> vibrate() async {
+    return (await _hapticFeedbackProxy.ptr.vibrate()).success;
+  }
+}

packages/flutter/lib/src/services/path_provider.dart

@@ -0,0 +1,49 @@
+// Copyright 2016 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:async';
+import 'dart:io';
+
+import 'package:sky_services/flutter/platform/path_provider.mojom.dart' as mojom;
+
+import 'shell.dart';
+
+mojom.PathProviderProxy _initPathProviderProxy() {
+  mojom.PathProviderProxy proxy = new mojom.PathProviderProxy.unbound();
+  shell.connectToViewAssociatedService(proxy);
+  return proxy;
+}
+
+final mojom.PathProviderProxy _pathProviderProxy = _initPathProviderProxy();
+
+/// Returns commonly used locations on the filesystem.
+class PathProvider {
+  PathProvider._();
+
+  /// Path to the temporary directory on the device. Files in this directory
+  /// may be cleared at any time. This does *not* return a new temporary
+  /// directory. Instead, the caller is responsible for creating
+  /// (and cleaning up) files or directories within this directory. This
+  /// directory is scoped to the calling application.
+  ///
+  /// Examples:
+  ///
+  ///  * _iOS_: `NSTemporaryDirectory()`
+  ///  * _Android_: `getCacheDir()` on the context.
+  static Future<Directory> getTemporaryDirectory() async {
+    return new Directory((await _pathProviderProxy.ptr.temporaryDirectory()).path);
+  }
+
+  /// Path to a directory where the application may place files that are private
+  /// to the application and will only be cleared when the application itself
+  /// is deleted.
+  ///
+  /// Examples:
+  ///
+  ///  * iOS: `NSDocumentsDirectory`
+  ///  * Android: The AppData directory.
+  static Future<Directory> getApplicationDocumentsDirectory() async {
+    return new Directory((await _pathProviderProxy.ptr.applicationDocumentsDirectory()).path);
+  }
+}

packages/flutter/lib/src/services/system_chrome.dart

@@ -0,0 +1,62 @@
+// Copyright 2016 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:async';
+
+import 'package:sky_services/flutter/platform/system_chrome.mojom.dart' as mojom;
+
+import 'shell.dart';
+
+export 'package:sky_services/flutter/platform/system_chrome.mojom.dart' show DeviceOrientation, SystemUIOverlay;
+
+mojom.SystemChromeProxy _initSystemChromeProxy() {
+  mojom.SystemChromeProxy proxy = new mojom.SystemChromeProxy.unbound();
+  shell.connectToViewAssociatedService(proxy);
+  return proxy;
+}
+
+final mojom.SystemChromeProxy _systemChromeProxy = _initSystemChromeProxy();
+
+/// Controls specific aspects of the embedder interface.
+class SystemChrome {
+  SystemChrome._();
+
+  /// Specifies the set of orientations the application interface can
+  /// be displayed in.
+  ///
+  /// Arguments:
+  ///
+  ///  * `device_orientation_mask`: A mask of `DeviceOrientation` enum values.
+  ///    The value 0 is synonymous with having all options enabled.
+  ///
+  /// Return Value:
+  ///
+  ///   boolean indicating if the orientation mask is valid and the changes
+  ///   could be conveyed successfully to the embedder.
+  static Future<bool> setPreferredOrientations(int deviceOrientationMask) async {
+    return (await _systemChromeProxy.ptr.setPreferredOrientations(deviceOrientationMask)).success;
+  }
+
+  /// Specifies the set of overlays visible on the embedder when the
+  /// application is running. The embedder may choose to ignore unsupported
+  /// overlays
+  ///
+  /// Arguments:
+  ///
+  ///  * `style`: A mask of `SystemUIOverlay` enum values that denotes the overlays
+  ///    to show.
+  ///
+  /// Return Value:
+  ///
+  ///   boolean indicating if the preference was conveyed successfully to the
+  ///   embedder.
+  ///
+  /// Platform Specific Notes:
+  ///
+  ///   If the overlay is unsupported on the platform, enabling or disabling
+  ///   that overlay is a no-op and always return true.
+  static Future<bool> setEnabledSystemUIOverlays(int overlaysMask) async {
+    return (await _systemChromeProxy.ptr.setEnabledSystemUiOverlays(overlaysMask)).success;
+  }
+}

packages/flutter/lib/src/services/system_sound.dart

@@ -0,0 +1,37 @@
+// Copyright 2016 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:async';
+
+import 'package:sky_services/flutter/platform/system_sound.mojom.dart' as mojom;
+
+import 'shell.dart';
+
+export 'package:sky_services/flutter/platform/system_sound.mojom.dart' show SystemSoundType;
+
+mojom.SystemSoundProxy _initSystemSoundProxy() {
+  mojom.SystemSoundProxy proxy = new mojom.SystemSoundProxy.unbound();
+  shell.connectToViewAssociatedService(proxy);
+  return proxy;
+}
+
+final mojom.SystemSoundProxy _systemChromeProxy = _initSystemSoundProxy();
+
+/// Allows easy access to the library of short system specific sounds for
+/// common tasks.
+class SystemSound {
+  SystemSound._();
+
+  /// Play the specified system sound. If that sound is not present on the
+  /// system, this method is a no-op and returns `true`.
+  ///
+  /// Return Value:
+  ///
+  ///   boolean indicating if the intent to play the specified sound was
+  ///   successfully conveyed to the embedder. No sound may actually play if the
+  ///   device is muted or the sound was not available on the platform.
+  static Future<bool> play(mojom.SystemSoundType type) async {
+    return (await _systemChromeProxy.ptr.play(type)).success;
+  }
+}

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

@@ -217,7 +217,7 @@ class LongPressDraggable<T> extends DraggableBase<T> {
       ..onStart = (Point position) {
         Drag result = onStart(position);
         if (result != null)
-          userFeedback.performHapticFeedback(HapticFeedbackType.virtualKey);
+          HapticFeedback.vibrate();
         return result;
       };
   }