[Gallery] Fix directory structure (#312)

gallery/lib/data/gallery_options.dart

@@ -0,0 +1,253 @@
+// Copyright 2019 The Flutter team. 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' show Platform;
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart' show timeDilation;
+import 'package:gallery/constants.dart';
+
+enum CustomTextDirection {
+  localeBased,
+  ltr,
+  rtl,
+}
+
+// See http://en.wikipedia.org/wiki/Right-to-left
+const List<String> rtlLanguages = <String>[
+  'ar', // Arabic
+  'fa', // Farsi
+  'he', // Hebrew
+  'ps', // Pashto
+  'ur', // Urdu
+];
+
+// Fake locale to represent the system Locale option.
+const systemLocaleOption = Locale('system');
+
+Locale _deviceLocale;
+Locale get deviceLocale => _deviceLocale;
+set deviceLocale(Locale locale) {
+  if (_deviceLocale == null) {
+    _deviceLocale = locale;
+  }
+}
+
+class GalleryOptions {
+  const GalleryOptions({
+    this.themeMode,
+    double textScaleFactor,
+    this.customTextDirection,
+    Locale locale,
+    this.timeDilation,
+    this.platform,
+  })  : _textScaleFactor = textScaleFactor,
+        _locale = locale;
+
+  final ThemeMode themeMode;
+  final double _textScaleFactor;
+  final CustomTextDirection customTextDirection;
+  final Locale _locale;
+  final double timeDilation;
+  final TargetPlatform platform;
+
+  // We use a sentinel value to indicate the system text scale option. By
+  // default, return the actual text scale factor, otherwise return the
+  // sentinel value.
+  double textScaleFactor(BuildContext context, {bool useSentinel = false}) {
+    if (_textScaleFactor == systemTextScaleFactorOption) {
+      return useSentinel
+          ? systemTextScaleFactorOption
+          : MediaQuery.of(context).textScaleFactor;
+    } else {
+      return _textScaleFactor;
+    }
+  }
+
+  Locale get locale =>
+      _locale ??
+      deviceLocale ??
+      // TODO: When deviceLocale can be obtained on macOS, this won't be necessary
+      // https://github.com/flutter/flutter/issues/45343
+      (!kIsWeb && Platform.isMacOS ? Locale('en', 'US') : null);
+
+  /// Returns the text direction based on the [CustomTextDirection] setting.
+  /// If the locale cannot be determined, returns null.
+  TextDirection textDirection() {
+    switch (customTextDirection) {
+      case CustomTextDirection.localeBased:
+        final String language = locale?.languageCode?.toLowerCase();
+        if (language == null) return null;
+        return rtlLanguages.contains(language)
+            ? TextDirection.rtl
+            : TextDirection.ltr;
+      case CustomTextDirection.rtl:
+        return TextDirection.rtl;
+      default:
+        return TextDirection.ltr;
+    }
+  }
+
+  GalleryOptions copyWith({
+    ThemeMode themeMode,
+    double textScaleFactor,
+    CustomTextDirection customTextDirection,
+    Locale locale,
+    double timeDilation,
+    TargetPlatform platform,
+  }) {
+    return GalleryOptions(
+      themeMode: themeMode ?? this.themeMode,
+      textScaleFactor: textScaleFactor ?? this._textScaleFactor,
+      customTextDirection: customTextDirection ?? this.customTextDirection,
+      locale: locale ?? this.locale,
+      timeDilation: timeDilation ?? this.timeDilation,
+      platform: platform ?? this.platform,
+    );
+  }
+
+  @override
+  bool operator ==(Object other) =>
+      other is GalleryOptions &&
+      themeMode == other.themeMode &&
+      _textScaleFactor == other._textScaleFactor &&
+      customTextDirection == other.customTextDirection &&
+      locale == other.locale &&
+      timeDilation == other.timeDilation &&
+      platform == other.platform;
+
+  @override
+  int get hashCode => hashValues(
+        themeMode,
+        _textScaleFactor,
+        customTextDirection,
+        locale,
+        timeDilation,
+        platform,
+      );
+
+  static GalleryOptions of(BuildContext context) {
+    final _ModelBindingScope scope =
+        context.dependOnInheritedWidgetOfExactType<_ModelBindingScope>();
+    return scope.modelBindingState.currentModel;
+  }
+
+  static void update(BuildContext context, GalleryOptions newModel) {
+    final _ModelBindingScope scope =
+        context.dependOnInheritedWidgetOfExactType<_ModelBindingScope>();
+    scope.modelBindingState.updateModel(newModel);
+  }
+}
+
+// Applies text GalleryOptions to a widget
+class ApplyTextOptions extends StatelessWidget {
+  const ApplyTextOptions({@required this.child});
+
+  final Widget child;
+
+  @override
+  Widget build(BuildContext context) {
+    final options = GalleryOptions.of(context);
+    final textDirection = options.textDirection();
+    final textScaleFactor = options.textScaleFactor(context);
+
+    Widget widget = MediaQuery(
+      data: MediaQuery.of(context).copyWith(
+        textScaleFactor: textScaleFactor,
+      ),
+      child: child,
+    );
+    return textDirection == null
+        ? widget
+        : Directionality(
+            textDirection: textDirection,
+            child: widget,
+          );
+  }
+}
+
+// Everything below is boilerplate except code relating to time dilation.
+// See https://medium.com/flutter/managing-flutter-application-state-with-inheritedwidgets-1140452befe1
+
+class _ModelBindingScope extends InheritedWidget {
+  _ModelBindingScope({
+    Key key,
+    @required this.modelBindingState,
+    Widget child,
+  })  : assert(modelBindingState != null),
+        super(key: key, child: child);
+
+  final _ModelBindingState modelBindingState;
+
+  @override
+  bool updateShouldNotify(_ModelBindingScope oldWidget) => true;
+}
+
+class ModelBinding extends StatefulWidget {
+  ModelBinding({
+    Key key,
+    this.initialModel = const GalleryOptions(),
+    this.child,
+  })  : assert(initialModel != null),
+        super(key: key);
+
+  final GalleryOptions initialModel;
+  final Widget child;
+
+  _ModelBindingState createState() => _ModelBindingState();
+}
+
+class _ModelBindingState extends State<ModelBinding> {
+  GalleryOptions currentModel;
+  Timer _timeDilationTimer;
+
+  @override
+  void initState() {
+    super.initState();
+    currentModel = widget.initialModel;
+  }
+
+  @override
+  void dispose() {
+    _timeDilationTimer?.cancel();
+    _timeDilationTimer = null;
+    super.dispose();
+  }
+
+  void handleTimeDilation(GalleryOptions newModel) {
+    if (currentModel.timeDilation != newModel.timeDilation) {
+      _timeDilationTimer?.cancel();
+      _timeDilationTimer = null;
+      if (newModel.timeDilation > 1) {
+        // We delay the time dilation change long enough that the user can see
+        // that UI has started reacting and then we slam on the brakes so that
+        // they see that the time is in fact now dilated.
+        _timeDilationTimer = Timer(const Duration(milliseconds: 150), () {
+          timeDilation = newModel.timeDilation;
+        });
+      } else {
+        timeDilation = newModel.timeDilation;
+      }
+    }
+  }
+
+  void updateModel(GalleryOptions newModel) {
+    if (newModel != currentModel) {
+      handleTimeDilation(newModel);
+      setState(() {
+        currentModel = newModel;
+      });
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return _ModelBindingScope(
+      modelBindingState: this,
+      child: widget.child,
+    );
+  }
+}