examples/flutter_gallery/lib/gallery/options.dart - mirrors/flutter - Git at Google

 // Copyright 2014 The Flutter 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 'package:flutter/material.dart';

 import 'about.dart';
 import 'scales.dart';

 class GalleryOptions {
   GalleryOptions({
     this.themeMode,
     this.textScaleFactor,
     this.visualDensity,
     this.textDirection = TextDirection.ltr,
     this.timeDilation = 1.0,
     this.platform,
     this.showOffscreenLayersCheckerboard = false,
     this.showRasterCacheImagesCheckerboard = false,
     this.showPerformanceOverlay = false,
   });

   final ThemeMode themeMode;
   final GalleryTextScaleValue textScaleFactor;
   final GalleryVisualDensityValue visualDensity;
   final TextDirection textDirection;
   final double timeDilation;
   final TargetPlatform platform;
   final bool showPerformanceOverlay;
   final bool showRasterCacheImagesCheckerboard;
   final bool showOffscreenLayersCheckerboard;

   GalleryOptions copyWith({
     ThemeMode themeMode,
     GalleryTextScaleValue textScaleFactor,
     GalleryVisualDensityValue visualDensity,
     TextDirection textDirection,
     double timeDilation,
     TargetPlatform platform,
     bool showPerformanceOverlay,
     bool showRasterCacheImagesCheckerboard,
     bool showOffscreenLayersCheckerboard,
   }) {
     return GalleryOptions(
       themeMode: themeMode ?? this.themeMode,
       textScaleFactor: textScaleFactor ?? this.textScaleFactor,
       visualDensity: visualDensity ?? this.visualDensity,
       textDirection: textDirection ?? this.textDirection,
       timeDilation: timeDilation ?? this.timeDilation,
       platform: platform ?? this.platform,
       showPerformanceOverlay: showPerformanceOverlay ?? this.showPerformanceOverlay,
       showOffscreenLayersCheckerboard: showOffscreenLayersCheckerboard ?? this.showOffscreenLayersCheckerboard,
       showRasterCacheImagesCheckerboard: showRasterCacheImagesCheckerboard ?? this.showRasterCacheImagesCheckerboard,
     );
   }

   @override
   bool operator ==(Object other) {
     if (other.runtimeType != runtimeType)
       return false;
     return other is GalleryOptions
         && other.themeMode == themeMode
         && other.textScaleFactor == textScaleFactor
         && other.visualDensity == visualDensity
         && other.textDirection == textDirection
         && other.platform == platform
         && other.showPerformanceOverlay == showPerformanceOverlay
         && other.showRasterCacheImagesCheckerboard == showRasterCacheImagesCheckerboard
         && other.showOffscreenLayersCheckerboard == showRasterCacheImagesCheckerboard;
   }

   @override
   int get hashCode => hashValues(
     themeMode,
     textScaleFactor,
     visualDensity,
     textDirection,
     timeDilation,
     platform,
     showPerformanceOverlay,
     showRasterCacheImagesCheckerboard,
     showOffscreenLayersCheckerboard,
   );

   @override
   String toString() {
     return '$runtimeType($themeMode)';
   }
 }

 const double _kItemHeight = 48.0;
 const EdgeInsetsDirectional _kItemPadding = EdgeInsetsDirectional.only(start: 56.0);

 class _OptionsItem extends StatelessWidget {
   const _OptionsItem({ Key key, this.child }) : super(key: key);

   final Widget child;

   @override
   Widget build(BuildContext context) {
     final double textScaleFactor = MediaQuery.textScaleFactorOf(context);

     return MergeSemantics(
       child: Container(
         constraints: BoxConstraints(minHeight: _kItemHeight * textScaleFactor),
         padding: _kItemPadding,
         alignment: AlignmentDirectional.centerStart,
         child: DefaultTextStyle(
           style: DefaultTextStyle.of(context).style,
           maxLines: 2,
           overflow: TextOverflow.fade,
           child: IconTheme(
             data: Theme.of(context).primaryIconTheme,
             child: child,
           ),
         ),
       ),
     );
   }
 }

 class _BooleanItem extends StatelessWidget {
   const _BooleanItem(this.title, this.value, this.onChanged, { this.switchKey });

   final String title;
   final bool value;
   final ValueChanged<bool> onChanged;
   // [switchKey] is used for accessing the switch from driver tests.
   final Key switchKey;

   @override
   Widget build(BuildContext context) {
     final bool isDark = Theme.of(context).brightness == Brightness.dark;
     return _OptionsItem(
       child: Row(
         children: <Widget>[
           Expanded(child: Text(title)),
           Switch(
             key: switchKey,
             value: value,
             onChanged: onChanged,
             activeColor: const Color(0xFF39CEFD),
             activeTrackColor: isDark ? Colors.white30 : Colors.black26,
           ),
         ],
       ),
     );
   }
 }

 class _ActionItem extends StatelessWidget {
   const _ActionItem(this.text, this.onTap);

   final String text;
   final VoidCallback onTap;

   @override
   Widget build(BuildContext context) {
     return _OptionsItem(
       child: _FlatButton(
         onPressed: onTap,
         child: Text(text),
       ),
     );
   }
 }

 class _FlatButton extends StatelessWidget {
   const _FlatButton({ Key key, this.onPressed, this.child }) : super(key: key);

   final VoidCallback onPressed;
   final Widget child;

   @override
   Widget build(BuildContext context) {
     return FlatButton(
       padding: EdgeInsets.zero,
       onPressed: onPressed,
       child: DefaultTextStyle(
         style: Theme.of(context).primaryTextTheme.subtitle1,
         child: child,
       ),
     );
   }
 }

 class _Heading extends StatelessWidget {
   const _Heading(this.text);

   final String text;

   @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
     return _OptionsItem(
       child: DefaultTextStyle(
         style: theme.textTheme.headline6.copyWith(
           fontFamily: 'GoogleSans',
           color: theme.colorScheme.onPrimary,
           fontWeight: FontWeight.w700,
         ),
         child: Semantics(
           child: Text(text),
           header: true,
         ),
       ),
     );
   }
 }

 class _ThemeModeItem extends StatelessWidget {
   const _ThemeModeItem(this.options, this.onOptionsChanged);

   final GalleryOptions options;
   final ValueChanged<GalleryOptions> onOptionsChanged;

   static final Map<ThemeMode, String> modeLabels = <ThemeMode, String>{
     ThemeMode.system: 'System Default',
     ThemeMode.light: 'Light',
     ThemeMode.dark: 'Dark',
   };

   @override
   Widget build(BuildContext context) {
     return _OptionsItem(
       child: Row(
         children: <Widget>[
           Expanded(
             child: Column(
               crossAxisAlignment: CrossAxisAlignment.start,
               children: <Widget>[
                 const Text('Theme'),
                 Text(
                   '${modeLabels[options.themeMode]}',
                   style: Theme.of(context).primaryTextTheme.bodyText2,
                 ),
               ],
             ),
           ),
           PopupMenuButton<ThemeMode>(
             padding: const EdgeInsetsDirectional.only(end: 16.0),
             icon: const Icon(Icons.arrow_drop_down),
             initialValue: options.themeMode,
             itemBuilder: (BuildContext context) {
               return ThemeMode.values.map<PopupMenuItem<ThemeMode>>((ThemeMode mode) {
                 return PopupMenuItem<ThemeMode>(
                   value: mode,
                   child: Text(modeLabels[mode]),
                 );
               }).toList();
             },
             onSelected: (ThemeMode mode) {
               onOptionsChanged(
                 options.copyWith(themeMode: mode),
               );
             },
           ),
         ],
       ),
     );
   }
 }

 class _TextScaleFactorItem extends StatelessWidget {
   const _TextScaleFactorItem(this.options, this.onOptionsChanged);

   final GalleryOptions options;
   final ValueChanged<GalleryOptions> onOptionsChanged;

   @override
   Widget build(BuildContext context) {
     return _OptionsItem(
       child: Row(
         children: <Widget>[
           Expanded(
             child: Column(
               crossAxisAlignment: CrossAxisAlignment.start,
               children: <Widget>[
                 const Text('Text size'),
                 Text(
                   '${options.textScaleFactor.label}',
                   style: Theme.of(context).primaryTextTheme.bodyText2,
                 ),
               ],
             ),
           ),
           PopupMenuButton<GalleryTextScaleValue>(
             padding: const EdgeInsetsDirectional.only(end: 16.0),
             icon: const Icon(Icons.arrow_drop_down),
             itemBuilder: (BuildContext context) {
               return kAllGalleryTextScaleValues.map<PopupMenuItem<GalleryTextScaleValue>>((GalleryTextScaleValue scaleValue) {
                 return PopupMenuItem<GalleryTextScaleValue>(
                   value: scaleValue,
                   child: Text(scaleValue.label),
                 );
               }).toList();
             },
             onSelected: (GalleryTextScaleValue scaleValue) {
               onOptionsChanged(
                 options.copyWith(textScaleFactor: scaleValue),
               );
             },
           ),
         ],
       ),
     );
   }
 }

 class _VisualDensityItem extends StatelessWidget {
   const _VisualDensityItem(this.options, this.onOptionsChanged);

   final GalleryOptions options;
   final ValueChanged<GalleryOptions> onOptionsChanged;

   @override
   Widget build(BuildContext context) {
     return _OptionsItem(
       child: Row(
         children: <Widget>[
           Expanded(
             child: Column(
               crossAxisAlignment: CrossAxisAlignment.start,
               children: <Widget>[
                 const Text('Visual density'),
                 Text(
                   '${options.visualDensity.label}',
                   style: Theme.of(context).primaryTextTheme.bodyText2,
                 ),
               ],
             ),
           ),
           PopupMenuButton<GalleryVisualDensityValue>(
             padding: const EdgeInsetsDirectional.only(end: 16.0),
             icon: const Icon(Icons.arrow_drop_down),
             itemBuilder: (BuildContext context) {
               return kAllGalleryVisualDensityValues.map<PopupMenuItem<GalleryVisualDensityValue>>((GalleryVisualDensityValue densityValue) {
                 return PopupMenuItem<GalleryVisualDensityValue>(
                   value: densityValue,
                   child: Text(densityValue.label),
                 );
               }).toList();
             },
             onSelected: (GalleryVisualDensityValue densityValue) {
               onOptionsChanged(
                 options.copyWith(visualDensity: densityValue),
               );
             },
           ),
         ],
       ),
     );
   }
 }

 class _TextDirectionItem extends StatelessWidget {
   const _TextDirectionItem(this.options, this.onOptionsChanged);

   final GalleryOptions options;
   final ValueChanged<GalleryOptions> onOptionsChanged;

   @override
   Widget build(BuildContext context) {
     return _BooleanItem(
       'Force RTL',
       options.textDirection == TextDirection.rtl,
       (bool value) {
         onOptionsChanged(
           options.copyWith(
             textDirection: value ? TextDirection.rtl : TextDirection.ltr,
           ),
         );
       },
       switchKey: const Key('text_direction'),
     );
   }
 }

 class _TimeDilationItem extends StatelessWidget {
   const _TimeDilationItem(this.options, this.onOptionsChanged);

   final GalleryOptions options;
   final ValueChanged<GalleryOptions> onOptionsChanged;

   @override
   Widget build(BuildContext context) {
     return _BooleanItem(
       'Slow motion',
       options.timeDilation != 1.0,
       (bool value) {
         onOptionsChanged(
           options.copyWith(
             timeDilation: value ? 20.0 : 1.0,
           ),
         );
       },
       switchKey: const Key('slow_motion'),
     );
   }
 }

 class _PlatformItem extends StatelessWidget {
   const _PlatformItem(this.options, this.onOptionsChanged);

   final GalleryOptions options;
   final ValueChanged<GalleryOptions> onOptionsChanged;

   String _platformLabel(TargetPlatform platform) {
     switch(platform) {
       case TargetPlatform.android:
         return 'Mountain View';
       case TargetPlatform.fuchsia:
         return 'Fuchsia';
       case TargetPlatform.iOS:
         return 'Cupertino';
       case TargetPlatform.macOS:
         return 'Material Desktop (macOS)';
     }
     assert(false);
     return null;
   }

   @override
   Widget build(BuildContext context) {
     return _OptionsItem(
       child: Row(
         children: <Widget>[
           Expanded(
             child: Column(
               crossAxisAlignment: CrossAxisAlignment.start,
               children: <Widget>[
                 const Text('Platform mechanics'),
                  Text(
                    '${_platformLabel(options.platform)}',
                    style: Theme.of(context).primaryTextTheme.bodyText2,
                  ),
               ],
             ),
           ),
           PopupMenuButton<TargetPlatform>(
             padding: const EdgeInsetsDirectional.only(end: 16.0),
             icon: const Icon(Icons.arrow_drop_down),
             itemBuilder: (BuildContext context) {
               return TargetPlatform.values.map((TargetPlatform platform) {
                 return PopupMenuItem<TargetPlatform>(
                   value: platform,
                   child: Text(_platformLabel(platform)),
                 );
               }).toList();
             },
             onSelected: (TargetPlatform platform) {
               onOptionsChanged(
                 options.copyWith(platform: platform),
               );
             },
           ),
         ],
       ),
     );
   }
 }

 class GalleryOptionsPage extends StatelessWidget {
   const GalleryOptionsPage({
     Key key,
     this.options,
     this.onOptionsChanged,
     this.onSendFeedback,
   }) : super(key: key);

   final GalleryOptions options;
   final ValueChanged<GalleryOptions> onOptionsChanged;
   final VoidCallback onSendFeedback;

   List<Widget> _enabledDiagnosticItems() {
     // Boolean showFoo options with a value of null: don't display
     // the showFoo option at all.
     if (options.showOffscreenLayersCheckerboard == null &&
         options.showRasterCacheImagesCheckerboard == null &&
         options.showPerformanceOverlay == null)
       return const <Widget>[];

     return <Widget>[
       const Divider(),
       const _Heading('Diagnostics'),
       if (options.showOffscreenLayersCheckerboard != null)
         _BooleanItem(
           'Highlight offscreen layers',
           options.showOffscreenLayersCheckerboard,
           (bool value) {
             onOptionsChanged(options.copyWith(showOffscreenLayersCheckerboard: value));
           },
         ),
       if (options.showRasterCacheImagesCheckerboard != null)
         _BooleanItem(
           'Highlight raster cache images',
           options.showRasterCacheImagesCheckerboard,
           (bool value) {
             onOptionsChanged(options.copyWith(showRasterCacheImagesCheckerboard: value));
           },
         ),
       if (options.showPerformanceOverlay != null)
         _BooleanItem(
           'Show performance overlay',
           options.showPerformanceOverlay,
           (bool value) {
             onOptionsChanged(options.copyWith(showPerformanceOverlay: value));
           },
         ),
     ];
   }

   @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);

     return DefaultTextStyle(
       style: theme.primaryTextTheme.subtitle1,
       child: ListView(
         padding: const EdgeInsets.only(bottom: 124.0),
         children: <Widget>[
           const _Heading('Display'),
           _ThemeModeItem(options, onOptionsChanged),
           _TextScaleFactorItem(options, onOptionsChanged),
           _VisualDensityItem(options, onOptionsChanged),
           _TextDirectionItem(options, onOptionsChanged),
           _TimeDilationItem(options, onOptionsChanged),
           const Divider(),
           const ExcludeSemantics(child: _Heading('Platform mechanics')),
           _PlatformItem(options, onOptionsChanged),
           ..._enabledDiagnosticItems(),
           const Divider(),
           const _Heading('Flutter gallery'),
           _ActionItem('About Flutter Gallery', () {
             showGalleryAboutDialog(context);
           }),
           _ActionItem('Send feedback', onSendFeedback),
         ],
       ),
     );
   }
 }
	// Copyright 2014 The Flutter 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 'package:flutter/material.dart';

	import 'about.dart';
	import 'scales.dart';

	class GalleryOptions {
	GalleryOptions({
	this.themeMode,
	this.textScaleFactor,
	this.visualDensity,
	this.textDirection = TextDirection.ltr,
	this.timeDilation = 1.0,
	this.platform,
	this.showOffscreenLayersCheckerboard = false,
	this.showRasterCacheImagesCheckerboard = false,
	this.showPerformanceOverlay = false,
	});

	final ThemeMode themeMode;
	final GalleryTextScaleValue textScaleFactor;
	final GalleryVisualDensityValue visualDensity;
	final TextDirection textDirection;
	final double timeDilation;
	final TargetPlatform platform;
	final bool showPerformanceOverlay;
	final bool showRasterCacheImagesCheckerboard;
	final bool showOffscreenLayersCheckerboard;

	GalleryOptions copyWith({
	ThemeMode themeMode,
	GalleryTextScaleValue textScaleFactor,
	GalleryVisualDensityValue visualDensity,
	TextDirection textDirection,
	double timeDilation,
	TargetPlatform platform,
	bool showPerformanceOverlay,
	bool showRasterCacheImagesCheckerboard,
	bool showOffscreenLayersCheckerboard,
	}) {
	return GalleryOptions(
	themeMode: themeMode ?? this.themeMode,
	textScaleFactor: textScaleFactor ?? this.textScaleFactor,
	visualDensity: visualDensity ?? this.visualDensity,
	textDirection: textDirection ?? this.textDirection,
	timeDilation: timeDilation ?? this.timeDilation,
	platform: platform ?? this.platform,
	showPerformanceOverlay: showPerformanceOverlay ?? this.showPerformanceOverlay,
	showOffscreenLayersCheckerboard: showOffscreenLayersCheckerboard ?? this.showOffscreenLayersCheckerboard,
	showRasterCacheImagesCheckerboard: showRasterCacheImagesCheckerboard ?? this.showRasterCacheImagesCheckerboard,
	);
	}

	@override
	bool operator ==(Object other) {
	if (other.runtimeType != runtimeType)
	return false;
	return other is GalleryOptions
	&& other.themeMode == themeMode
	&& other.textScaleFactor == textScaleFactor
	&& other.visualDensity == visualDensity
	&& other.textDirection == textDirection
	&& other.platform == platform
	&& other.showPerformanceOverlay == showPerformanceOverlay
	&& other.showRasterCacheImagesCheckerboard == showRasterCacheImagesCheckerboard
	&& other.showOffscreenLayersCheckerboard == showRasterCacheImagesCheckerboard;
	}

	@override
	int get hashCode => hashValues(
	themeMode,
	textScaleFactor,
	visualDensity,
	textDirection,
	timeDilation,
	platform,
	showPerformanceOverlay,
	showRasterCacheImagesCheckerboard,
	showOffscreenLayersCheckerboard,
	);

	@override
	String toString() {
	return '$runtimeType($themeMode)';
	}
	}

	const double _kItemHeight = 48.0;
	const EdgeInsetsDirectional _kItemPadding = EdgeInsetsDirectional.only(start: 56.0);

	class _OptionsItem extends StatelessWidget {
	const _OptionsItem({ Key key, this.child }) : super(key: key);

	final Widget child;

	@override
	Widget build(BuildContext context) {
	final double textScaleFactor = MediaQuery.textScaleFactorOf(context);

	return MergeSemantics(
	child: Container(
	constraints: BoxConstraints(minHeight: _kItemHeight * textScaleFactor),
	padding: _kItemPadding,
	alignment: AlignmentDirectional.centerStart,
	child: DefaultTextStyle(
	style: DefaultTextStyle.of(context).style,
	maxLines: 2,
	overflow: TextOverflow.fade,
	child: IconTheme(
	data: Theme.of(context).primaryIconTheme,
	child: child,
	),
	),
	),
	);
	}
	}

	class _BooleanItem extends StatelessWidget {
	const _BooleanItem(this.title, this.value, this.onChanged, { this.switchKey });

	final String title;
	final bool value;
	final ValueChanged<bool> onChanged;
	// [switchKey] is used for accessing the switch from driver tests.
	final Key switchKey;

	@override
	Widget build(BuildContext context) {
	final bool isDark = Theme.of(context).brightness == Brightness.dark;
	return _OptionsItem(
	child: Row(
	children: <Widget>[
	Expanded(child: Text(title)),
	Switch(
	key: switchKey,
	value: value,
	onChanged: onChanged,
	activeColor: const Color(0xFF39CEFD),
	activeTrackColor: isDark ? Colors.white30 : Colors.black26,
	),
	],
	),
	);
	}
	}

	class _ActionItem extends StatelessWidget {
	const _ActionItem(this.text, this.onTap);

	final String text;
	final VoidCallback onTap;

	@override
	Widget build(BuildContext context) {
	return _OptionsItem(
	child: _FlatButton(
	onPressed: onTap,
	child: Text(text),
	),
	);
	}
	}

	class _FlatButton extends StatelessWidget {
	const _FlatButton({ Key key, this.onPressed, this.child }) : super(key: key);

	final VoidCallback onPressed;
	final Widget child;

	@override
	Widget build(BuildContext context) {
	return FlatButton(
	padding: EdgeInsets.zero,
	onPressed: onPressed,
	child: DefaultTextStyle(
	style: Theme.of(context).primaryTextTheme.subtitle1,
	child: child,
	),
	);
	}
	}

	class _Heading extends StatelessWidget {
	const _Heading(this.text);

	final String text;

	@override
	Widget build(BuildContext context) {
	final ThemeData theme = Theme.of(context);
	return _OptionsItem(
	child: DefaultTextStyle(
	style: theme.textTheme.headline6.copyWith(
	fontFamily: 'GoogleSans',
	color: theme.colorScheme.onPrimary,
	fontWeight: FontWeight.w700,
	),
	child: Semantics(
	child: Text(text),
	header: true,
	),
	),
	);
	}
	}

	class _ThemeModeItem extends StatelessWidget {
	const _ThemeModeItem(this.options, this.onOptionsChanged);

	final GalleryOptions options;
	final ValueChanged<GalleryOptions> onOptionsChanged;

	static final Map<ThemeMode, String> modeLabels = <ThemeMode, String>{
	ThemeMode.system: 'System Default',
	ThemeMode.light: 'Light',
	ThemeMode.dark: 'Dark',
	};

	@override
	Widget build(BuildContext context) {
	return _OptionsItem(
	child: Row(
	children: <Widget>[
	Expanded(
	child: Column(
	crossAxisAlignment: CrossAxisAlignment.start,
	children: <Widget>[
	const Text('Theme'),
	Text(
	'${modeLabels[options.themeMode]}',
	style: Theme.of(context).primaryTextTheme.bodyText2,
	),
	],
	),
	),
	PopupMenuButton<ThemeMode>(
	padding: const EdgeInsetsDirectional.only(end: 16.0),
	icon: const Icon(Icons.arrow_drop_down),
	initialValue: options.themeMode,
	itemBuilder: (BuildContext context) {
	return ThemeMode.values.map<PopupMenuItem<ThemeMode>>((ThemeMode mode) {
	return PopupMenuItem<ThemeMode>(
	value: mode,
	child: Text(modeLabels[mode]),
	);
	}).toList();
	},
	onSelected: (ThemeMode mode) {
	onOptionsChanged(
	options.copyWith(themeMode: mode),
	);
	},
	),
	],
	),
	);
	}
	}

	class _TextScaleFactorItem extends StatelessWidget {
	const _TextScaleFactorItem(this.options, this.onOptionsChanged);

	final GalleryOptions options;
	final ValueChanged<GalleryOptions> onOptionsChanged;

	@override
	Widget build(BuildContext context) {
	return _OptionsItem(
	child: Row(
	children: <Widget>[
	Expanded(
	child: Column(
	crossAxisAlignment: CrossAxisAlignment.start,
	children: <Widget>[
	const Text('Text size'),
	Text(
	'${options.textScaleFactor.label}',
	style: Theme.of(context).primaryTextTheme.bodyText2,
	),
	],
	),
	),
	PopupMenuButton<GalleryTextScaleValue>(
	padding: const EdgeInsetsDirectional.only(end: 16.0),
	icon: const Icon(Icons.arrow_drop_down),
	itemBuilder: (BuildContext context) {
	return kAllGalleryTextScaleValues.map<PopupMenuItem<GalleryTextScaleValue>>((GalleryTextScaleValue scaleValue) {
	return PopupMenuItem<GalleryTextScaleValue>(
	value: scaleValue,
	child: Text(scaleValue.label),
	);
	}).toList();
	},
	onSelected: (GalleryTextScaleValue scaleValue) {
	onOptionsChanged(
	options.copyWith(textScaleFactor: scaleValue),
	);
	},
	),
	],
	),
	);
	}
	}

	class _VisualDensityItem extends StatelessWidget {
	const _VisualDensityItem(this.options, this.onOptionsChanged);

	final GalleryOptions options;
	final ValueChanged<GalleryOptions> onOptionsChanged;

	@override
	Widget build(BuildContext context) {
	return _OptionsItem(
	child: Row(
	children: <Widget>[
	Expanded(
	child: Column(
	crossAxisAlignment: CrossAxisAlignment.start,
	children: <Widget>[
	const Text('Visual density'),
	Text(
	'${options.visualDensity.label}',
	style: Theme.of(context).primaryTextTheme.bodyText2,
	),
	],
	),
	),
	PopupMenuButton<GalleryVisualDensityValue>(
	padding: const EdgeInsetsDirectional.only(end: 16.0),
	icon: const Icon(Icons.arrow_drop_down),
	itemBuilder: (BuildContext context) {
	return kAllGalleryVisualDensityValues.map<PopupMenuItem<GalleryVisualDensityValue>>((GalleryVisualDensityValue densityValue) {
	return PopupMenuItem<GalleryVisualDensityValue>(
	value: densityValue,
	child: Text(densityValue.label),
	);
	}).toList();
	},
	onSelected: (GalleryVisualDensityValue densityValue) {
	onOptionsChanged(
	options.copyWith(visualDensity: densityValue),
	);
	},
	),
	],
	),
	);
	}
	}

	class _TextDirectionItem extends StatelessWidget {
	const _TextDirectionItem(this.options, this.onOptionsChanged);

	final GalleryOptions options;
	final ValueChanged<GalleryOptions> onOptionsChanged;

	@override
	Widget build(BuildContext context) {
	return _BooleanItem(
	'Force RTL',
	options.textDirection == TextDirection.rtl,
	(bool value) {
	onOptionsChanged(
	options.copyWith(
	textDirection: value ? TextDirection.rtl : TextDirection.ltr,
	),
	);
	},
	switchKey: const Key('text_direction'),
	);
	}
	}

	class _TimeDilationItem extends StatelessWidget {
	const _TimeDilationItem(this.options, this.onOptionsChanged);

	final GalleryOptions options;
	final ValueChanged<GalleryOptions> onOptionsChanged;

	@override
	Widget build(BuildContext context) {
	return _BooleanItem(
	'Slow motion',
	options.timeDilation != 1.0,
	(bool value) {
	onOptionsChanged(
	options.copyWith(
	timeDilation: value ? 20.0 : 1.0,
	),
	);
	},
	switchKey: const Key('slow_motion'),
	);
	}
	}

	class _PlatformItem extends StatelessWidget {
	const _PlatformItem(this.options, this.onOptionsChanged);

	final GalleryOptions options;
	final ValueChanged<GalleryOptions> onOptionsChanged;

	String _platformLabel(TargetPlatform platform) {
	switch(platform) {
	case TargetPlatform.android:
	return 'Mountain View';
	case TargetPlatform.fuchsia:
	return 'Fuchsia';
	case TargetPlatform.iOS:
	return 'Cupertino';
	case TargetPlatform.macOS:
	return 'Material Desktop (macOS)';
	}
	assert(false);
	return null;
	}

	@override
	Widget build(BuildContext context) {
	return _OptionsItem(
	child: Row(
	children: <Widget>[
	Expanded(
	child: Column(
	crossAxisAlignment: CrossAxisAlignment.start,
	children: <Widget>[
	const Text('Platform mechanics'),
	Text(
	'${_platformLabel(options.platform)}',
	style: Theme.of(context).primaryTextTheme.bodyText2,
	),
	],
	),
	),
	PopupMenuButton<TargetPlatform>(
	padding: const EdgeInsetsDirectional.only(end: 16.0),
	icon: const Icon(Icons.arrow_drop_down),
	itemBuilder: (BuildContext context) {
	return TargetPlatform.values.map((TargetPlatform platform) {
	return PopupMenuItem<TargetPlatform>(
	value: platform,
	child: Text(_platformLabel(platform)),
	);
	}).toList();
	},
	onSelected: (TargetPlatform platform) {
	onOptionsChanged(
	options.copyWith(platform: platform),
	);
	},
	),
	],
	),
	);
	}
	}

	class GalleryOptionsPage extends StatelessWidget {
	const GalleryOptionsPage({
	Key key,
	this.options,
	this.onOptionsChanged,
	this.onSendFeedback,
	}) : super(key: key);

	final GalleryOptions options;
	final ValueChanged<GalleryOptions> onOptionsChanged;
	final VoidCallback onSendFeedback;

	List<Widget> _enabledDiagnosticItems() {
	// Boolean showFoo options with a value of null: don't display
	// the showFoo option at all.
	if (options.showOffscreenLayersCheckerboard == null &&
	options.showRasterCacheImagesCheckerboard == null &&
	options.showPerformanceOverlay == null)
	return const <Widget>[];

	return <Widget>[
	const Divider(),
	const _Heading('Diagnostics'),
	if (options.showOffscreenLayersCheckerboard != null)
	_BooleanItem(
	'Highlight offscreen layers',
	options.showOffscreenLayersCheckerboard,
	(bool value) {
	onOptionsChanged(options.copyWith(showOffscreenLayersCheckerboard: value));
	},
	),
	if (options.showRasterCacheImagesCheckerboard != null)
	_BooleanItem(
	'Highlight raster cache images',
	options.showRasterCacheImagesCheckerboard,
	(bool value) {
	onOptionsChanged(options.copyWith(showRasterCacheImagesCheckerboard: value));
	},
	),
	if (options.showPerformanceOverlay != null)
	_BooleanItem(
	'Show performance overlay',
	options.showPerformanceOverlay,
	(bool value) {
	onOptionsChanged(options.copyWith(showPerformanceOverlay: value));
	},
	),
	];
	}

	@override
	Widget build(BuildContext context) {
	final ThemeData theme = Theme.of(context);

	return DefaultTextStyle(
	style: theme.primaryTextTheme.subtitle1,
	child: ListView(
	padding: const EdgeInsets.only(bottom: 124.0),
	children: <Widget>[
	const _Heading('Display'),
	_ThemeModeItem(options, onOptionsChanged),
	_TextScaleFactorItem(options, onOptionsChanged),
	_VisualDensityItem(options, onOptionsChanged),
	_TextDirectionItem(options, onOptionsChanged),
	_TimeDilationItem(options, onOptionsChanged),
	const Divider(),
	const ExcludeSemantics(child: _Heading('Platform mechanics')),
	_PlatformItem(options, onOptionsChanged),
	..._enabledDiagnosticItems(),
	const Divider(),
	const _Heading('Flutter gallery'),
	_ActionItem('About Flutter Gallery', () {
	showGalleryAboutDialog(context);
	}),
	_ActionItem('Send feedback', onSendFeedback),
	],
	),
	);
	}
	}