packages/flutter/lib/src/widgets/media_query.dart - mirrors/flutter - Git at Google

 // Copyright 2015 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:ui' as ui;

 import 'package:flutter/foundation.dart';

 import 'basic.dart';
 import 'framework.dart';

 /// Whether in portrait or landscape.
 enum Orientation {
   /// Taller than wide.
   portrait,

   /// Wider than tall.
   landscape
 }

 /// Information about a piece of media (e.g., a window).
 ///
 /// For example, the [MediaQueryData.size] property contains the width and
 /// height of the current window.
 ///
 /// To obtain the current [MediaQueryData] for a given [BuildContext], use the
 /// [MediaQuery.of] function. For example, to obtain the size of the current
 /// window, use `MediaQuery.of(context).size`.
 ///
 /// If no [MediaQuery] is in scope then the [MediaQuery.of] method will throw an
 /// exception, unless the `nullOk` argument is set to true, in which case it
 /// returns null.
 @immutable
 class MediaQueryData {
   /// Creates data for a media query with explicit values.
   ///
   /// Consider using [MediaQueryData.fromWindow] to create data based on a
   /// [Window].
   const MediaQueryData({
     this.size = Size.zero,
     this.devicePixelRatio = 1.0,
     this.textScaleFactor = 1.0,
     this.padding = EdgeInsets.zero,
     this.viewInsets = EdgeInsets.zero,
     this.alwaysUse24HourFormat = false,
   });

   /// Creates data for a media query based on the given window.
   ///
   /// If you use this, you should ensure that you also register for
   /// notifications so that you can update your [MediaQueryData] when the
   /// window's metrics change. For example, see
   /// [WidgetsBindingObserver.didChangeMetrics] or [Window.onMetricsChanged].
   MediaQueryData.fromWindow(ui.Window window)
     : size = window.physicalSize / window.devicePixelRatio,
       devicePixelRatio = window.devicePixelRatio,
       textScaleFactor = window.textScaleFactor,
       padding = new EdgeInsets.fromWindowPadding(window.padding, window.devicePixelRatio),
       viewInsets = new EdgeInsets.fromWindowPadding(window.viewInsets, window.devicePixelRatio),
       alwaysUse24HourFormat = window.alwaysUse24HourFormat;

   /// The size of the media in logical pixel (e.g, the size of the screen).
   ///
   /// Logical pixels are roughly the same visual size across devices. Physical
   /// pixels are the size of the actual hardware pixels on the device. The
   /// number of physical pixels per logical pixel is described by the
   /// [devicePixelRatio].
   final Size size;

   /// The number of device pixels for each logical pixel. This number might not
   /// be a power of two. Indeed, it might not even be an integer. For example,
   /// the Nexus 6 has a device pixel ratio of 3.5.
   final double devicePixelRatio;

   /// The number of font pixels for each logical pixel.
   ///
   /// For example, if the text scale factor is 1.5, text will be 50% larger than
   /// the specified font size.
   ///
   /// See also:
   ///
   ///  * [MediaQuery.textScaleFactorOf], a convenience method which returns the
   ///    textScaleFactor defined for a [BuildContext].
   final double textScaleFactor;

   /// The number of physical pixels on each side of the display rectangle into
   /// which the application can render, but over which the operating system
   /// will likely place system UI, such as the keyboard, that fully obscures
   /// any content.
   final EdgeInsets viewInsets;

   /// The number of physical pixels on each side of the display rectangle into
   /// which the application can render, but which may be partially obscured by
   /// system UI (such as the system notification area), or or physical
   /// intrusions in the display (e.g. overscan regions on television screens or
   /// phone sensor housings).
   ///
   /// If you consumed this padding (e.g. by building a widget that envelops or
   /// accounts for this padding in its layout in such a way that children are
   /// no longer exposed to this padding), you should remove this padding
   /// for subsequent descendants in the widget tree by inserting a new
   /// [MediaQuery] widget using the [MediaQuery.removePadding] factory.
   ///
   /// See also:
   ///
   ///  * [SafeArea], a widget that consumes this padding with a [Padding] widget
   ///    and automatically removes it from the [MediaQuery] for its child.
   final EdgeInsets padding;

   /// Whether to use 24-hour format when formatting time.
   ///
   /// The behavior of this flag is different across platforms:
   ///
   /// - On Android this flag is reported directly from the user settings called
   ///   "Use 24-hour format". It applies to any locale used by the application,
   ///   whether it is the system-wide locale, or the custom locale set by the
   ///   application.
   /// - On iOS this flag is set to true when the user setting called "24-Hour
   ///   Time" is set or the system-wide locale's default uses 24-hour
   ///   formatting.
   final bool alwaysUse24HourFormat;

   /// The orientation of the media (e.g., whether the device is in landscape or portrait mode).
   Orientation get orientation {
     return size.width > size.height ? Orientation.landscape : Orientation.portrait;
   }

   /// Creates a copy of this media query data but with the given fields replaced
   /// with the new values.
   MediaQueryData copyWith({
     Size size,
     double devicePixelRatio,
     double textScaleFactor,
     EdgeInsets padding,
     EdgeInsets viewInsets,
     bool alwaysUse24HourFormat,
   }) {
     return new MediaQueryData(
       size: size ?? this.size,
       devicePixelRatio: devicePixelRatio ?? this.devicePixelRatio,
       textScaleFactor: textScaleFactor ?? this.textScaleFactor,
       padding: padding ?? this.padding,
       viewInsets: viewInsets ?? this.viewInsets,
       alwaysUse24HourFormat: alwaysUse24HourFormat ?? this.alwaysUse24HourFormat,
     );
   }

   /// Creates a copy of this media query data but with the given [padding]s
   /// replaced with zero.
   ///
   /// The `removeLeft`, `removeTop`, `removeRight`, and `removeBottom` arguments
   /// must not be null. If all four are false (the default) then this
   /// [MediaQueryData] is returned unmodified.
   ///
   /// See also:
   ///
   ///  * [new MediaQuery.removePadding], which uses this method to remove padding
   ///    from the ambient [MediaQuery].
   ///  * [SafeArea], which both removes the padding from the [MediaQuery] and
   ///    adds a [Padding] widget.
   ///  * [removeViewInsets], the same thing but for [viewInsets].
   MediaQueryData removePadding({
     bool removeLeft = false,
     bool removeTop = false,
     bool removeRight = false,
     bool removeBottom = false,
   }) {
     if (!(removeLeft || removeTop || removeRight || removeBottom))
       return this;
     return new MediaQueryData(
       size: size,
       devicePixelRatio: devicePixelRatio,
       textScaleFactor: textScaleFactor,
       padding: padding.copyWith(
         left: removeLeft ? 0.0 : null,
         top: removeTop ? 0.0 : null,
         right: removeRight ? 0.0 : null,
         bottom: removeBottom ? 0.0 : null,
       ),
       viewInsets: viewInsets,
       alwaysUse24HourFormat: alwaysUse24HourFormat,
     );
   }

   /// Creates a copy of this media query data but with the given [viewInsets]
   /// replaced with zero.
   ///
   /// The `removeLeft`, `removeTop`, `removeRight`, and `removeBottom` arguments
   /// must not be null. If all four are false (the default) then this
   /// [MediaQueryData] is returned unmodified.
   ///
   /// See also:
   ///
   ///  * [new MediaQuery.removeViewInsets], which uses this method to remove
   ///    padding from the ambient [MediaQuery].
   ///  * [removePadding], the same thing but for [padding].
   MediaQueryData removeViewInsets({
     bool removeLeft = false,
     bool removeTop = false,
     bool removeRight = false,
     bool removeBottom = false,
   }) {
     if (!(removeLeft || removeTop || removeRight || removeBottom))
       return this;
     return new MediaQueryData(
       size: size,
       devicePixelRatio: devicePixelRatio,
       textScaleFactor: textScaleFactor,
       padding: padding,
       viewInsets: viewInsets.copyWith(
         left: removeLeft ? 0.0 : null,
         top: removeTop ? 0.0 : null,
         right: removeRight ? 0.0 : null,
         bottom: removeBottom ? 0.0 : null,
       ),
       alwaysUse24HourFormat: alwaysUse24HourFormat,
     );
   }

   @override
   bool operator ==(Object other) {
     if (other.runtimeType != runtimeType)
       return false;
     final MediaQueryData typedOther = other;
     return typedOther.size == size
         && typedOther.devicePixelRatio == devicePixelRatio
         && typedOther.textScaleFactor == textScaleFactor
         && typedOther.padding == padding
         && typedOther.viewInsets == viewInsets
         && typedOther.alwaysUse24HourFormat == alwaysUse24HourFormat;
   }

   @override
   int get hashCode => hashValues(size, devicePixelRatio, textScaleFactor, padding, viewInsets, alwaysUse24HourFormat);

   @override
   String toString() {
     return '$runtimeType('
              'size: $size, '
              'devicePixelRatio: $devicePixelRatio, '
              'textScaleFactor: $textScaleFactor, '
              'padding: $padding, '
              'viewInsets: $viewInsets, '
              'alwaysUse24HourFormat: $alwaysUse24HourFormat'
            ')';
   }
 }

 /// Establishes a subtree in which media queries resolve to the given data.
 ///
 /// For example, to learn the size of the current media (e.g., the window
 /// containing your app), you can read the [MediaQueryData.size] property from
 /// the [MediaQueryData] returned by [MediaQuery.of]:
 /// `MediaQuery.of(context).size`.
 ///
 /// Querying the current media using [MediaQuery.of] will cause your widget to
 /// rebuild automatically whenever the [MediaQueryData] changes (e.g., if the
 /// user rotates their device).
 ///
 /// If no [MediaQuery] is in scope then the [MediaQuery.of] method will throw an
 /// exception, unless the `nullOk` argument is set to true, in which case it
 /// returns null.
 ///
 /// See also:
 ///
 ///  * [WidgetsApp] and [MaterialApp], which introduce a [MediaQuery] and keep
 ///    it up to date with the current screen metrics as they change.
 ///  * [MediaQueryData], the data structure that represents the metrics.
 class MediaQuery extends InheritedWidget {
   /// Creates a widget that provides [MediaQueryData] to its descendants.
   ///
   /// The [data] and [child] arguments must not be null.
   const MediaQuery({
     Key key,
     @required this.data,
     @required Widget child,
   }) : assert(child != null),
        assert(data != null),
        super(key: key, child: child);

   /// Creates a new [MediaQuery] that inherits from the ambient [MediaQuery] from
   /// the given context, but removes the specified paddings.
   ///
   /// This should be inserted into the widget tree when the [MediaQuery] padding
   /// is consumed by a widget in such a way that the padding is no longer
   /// exposed to the widget's descendants or siblings.
   ///
   /// The [context] argument is required, must not be null, and must have a
   /// [MediaQuery] in scope.
   ///
   /// The `removeLeft`, `removeTop`, `removeRight`, and `removeBottom` arguments
   /// must not be null. If all four are false (the default) then the returned
   /// [MediaQuery] reuses the ambient [MediaQueryData] unmodified, which is not
   /// particularly useful.
   ///
   /// The [child] argument is required and must not be null.
   ///
   /// See also:
   ///
   ///  * [SafeArea], which both removes the padding from the [MediaQuery] and
   ///    adds a [Padding] widget.
   ///  * [MediaQueryData.padding], the affected property of the [MediaQueryData].
   ///  * [new removeViewInsets], the same thing but for removing view insets.
   factory MediaQuery.removePadding({
     Key key,
     @required BuildContext context,
     bool removeLeft = false,
     bool removeTop = false,
     bool removeRight = false,
     bool removeBottom = false,
     @required Widget child,
   }) {
     return new MediaQuery(
       key: key,
       data: MediaQuery.of(context).removePadding(
         removeLeft: removeLeft,
         removeTop: removeTop,
         removeRight: removeRight,
         removeBottom: removeBottom,
       ),
       child: child,
     );
   }

   /// Creates a new [MediaQuery] that inherits from the ambient [MediaQuery] from
   /// the given context, but removes the specified view insets.
   ///
   /// This should be inserted into the widget tree when the [MediaQuery] view
   /// insets are consumed by a widget in such a way that the view insets are no
   /// longer exposed to the widget's descendants or siblings.
   ///
   /// The [context] argument is required, must not be null, and must have a
   /// [MediaQuery] in scope.
   ///
   /// The `removeLeft`, `removeTop`, `removeRight`, and `removeBottom` arguments
   /// must not be null. If all four are false (the default) then the returned
   /// [MediaQuery] reuses the ambient [MediaQueryData] unmodified, which is not
   /// particularly useful.
   ///
   /// The [child] argument is required and must not be null.
   ///
   /// See also:
   ///
   ///  * [MediaQueryData.viewInsets], the affected property of the [MediaQueryData].
   ///  * [new removePadding], the same thing but for removing paddings.
   factory MediaQuery.removeViewInsets({
     Key key,
     @required BuildContext context,
     bool removeLeft = false,
     bool removeTop = false,
     bool removeRight = false,
     bool removeBottom = false,
     @required Widget child,
   }) {
     return new MediaQuery(
       key: key,
       data: MediaQuery.of(context).removeViewInsets(
         removeLeft: removeLeft,
         removeTop: removeTop,
         removeRight: removeRight,
         removeBottom: removeBottom,
       ),
       child: child,
     );
   }

   /// Contains information about the current media.
   ///
   /// For example, the [MediaQueryData.size] property contains the width and
   /// height of the current window.
   final MediaQueryData data;

   /// The data from the closest instance of this class that encloses the given
   /// context.
   ///
   /// You can use this function to query the size an orientation of the screen.
   /// When that information changes, your widget will be scheduled to be rebuilt,
   /// keeping your widget up-to-date.
   ///
   /// Typical usage is as follows:
   ///
   /// ```dart
   /// MediaQueryData media = MediaQuery.of(context);
   /// ```
   ///
   /// If there is no [MediaQuery] in scope, then this will throw an exception.
   /// To return null if there is no [MediaQuery], then pass `nullOk: true`.
   ///
   /// If you use this from a widget (e.g. in its build function), consider
   /// calling [debugCheckHasMediaQuery].
   static MediaQueryData of(BuildContext context, { bool nullOk = false }) {
     assert(context != null);
     assert(nullOk != null);
     final MediaQuery query = context.inheritFromWidgetOfExactType(MediaQuery);
     if (query != null)
       return query.data;
     if (nullOk)
       return null;
     throw new FlutterError(
       'MediaQuery.of() called with a context that does not contain a MediaQuery.\n'
       'No MediaQuery ancestor could be found starting from the context that was passed '
       'to MediaQuery.of(). This can happen because you do not have a WidgetsApp or '
       'MaterialApp widget (those widgets introduce a MediaQuery), or it can happen '
       'if the context you use comes from a widget above those widgets.\n'
       'The context used was:\n'
       '  $context'
     );
   }

   /// Returns textScaleFactor for the nearest MediaQuery ancestor or 1.0, if
   /// no such ancestor exists.
   static double textScaleFactorOf(BuildContext context) {
     return MediaQuery.of(context, nullOk: true)?.textScaleFactor ?? 1.0;
   }

   @override
   bool updateShouldNotify(MediaQuery oldWidget) => data != oldWidget.data;

   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties.add(new DiagnosticsProperty<MediaQueryData>('data', data, showName: false));
   }
 }
	// Copyright 2015 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:ui' as ui;

	import 'package:flutter/foundation.dart';

	import 'basic.dart';
	import 'framework.dart';

	/// Whether in portrait or landscape.
	enum Orientation {
	/// Taller than wide.
	portrait,

	/// Wider than tall.
	landscape
	}

	/// Information about a piece of media (e.g., a window).
	///
	/// For example, the [MediaQueryData.size] property contains the width and
	/// height of the current window.
	///
	/// To obtain the current [MediaQueryData] for a given [BuildContext], use the
	/// [MediaQuery.of] function. For example, to obtain the size of the current
	/// window, use `MediaQuery.of(context).size`.
	///
	/// If no [MediaQuery] is in scope then the [MediaQuery.of] method will throw an
	/// exception, unless the `nullOk` argument is set to true, in which case it
	/// returns null.
	@immutable
	class MediaQueryData {
	/// Creates data for a media query with explicit values.
	///
	/// Consider using [MediaQueryData.fromWindow] to create data based on a
	/// [Window].
	const MediaQueryData({
	this.size = Size.zero,
	this.devicePixelRatio = 1.0,
	this.textScaleFactor = 1.0,
	this.padding = EdgeInsets.zero,
	this.viewInsets = EdgeInsets.zero,
	this.alwaysUse24HourFormat = false,
	});

	/// Creates data for a media query based on the given window.
	///
	/// If you use this, you should ensure that you also register for
	/// notifications so that you can update your [MediaQueryData] when the
	/// window's metrics change. For example, see
	/// [WidgetsBindingObserver.didChangeMetrics] or [Window.onMetricsChanged].
	MediaQueryData.fromWindow(ui.Window window)
	: size = window.physicalSize / window.devicePixelRatio,
	devicePixelRatio = window.devicePixelRatio,
	textScaleFactor = window.textScaleFactor,
	padding = new EdgeInsets.fromWindowPadding(window.padding, window.devicePixelRatio),
	viewInsets = new EdgeInsets.fromWindowPadding(window.viewInsets, window.devicePixelRatio),
	alwaysUse24HourFormat = window.alwaysUse24HourFormat;

	/// The size of the media in logical pixel (e.g, the size of the screen).
	///
	/// Logical pixels are roughly the same visual size across devices. Physical
	/// pixels are the size of the actual hardware pixels on the device. The
	/// number of physical pixels per logical pixel is described by the
	/// [devicePixelRatio].
	final Size size;

	/// The number of device pixels for each logical pixel. This number might not
	/// be a power of two. Indeed, it might not even be an integer. For example,
	/// the Nexus 6 has a device pixel ratio of 3.5.
	final double devicePixelRatio;

	/// The number of font pixels for each logical pixel.
	///
	/// For example, if the text scale factor is 1.5, text will be 50% larger than
	/// the specified font size.
	///
	/// See also:
	///
	/// * [MediaQuery.textScaleFactorOf], a convenience method which returns the
	/// textScaleFactor defined for a [BuildContext].
	final double textScaleFactor;

	/// The number of physical pixels on each side of the display rectangle into
	/// which the application can render, but over which the operating system
	/// will likely place system UI, such as the keyboard, that fully obscures
	/// any content.
	final EdgeInsets viewInsets;

	/// The number of physical pixels on each side of the display rectangle into
	/// which the application can render, but which may be partially obscured by
	/// system UI (such as the system notification area), or or physical
	/// intrusions in the display (e.g. overscan regions on television screens or
	/// phone sensor housings).
	///
	/// If you consumed this padding (e.g. by building a widget that envelops or
	/// accounts for this padding in its layout in such a way that children are
	/// no longer exposed to this padding), you should remove this padding
	/// for subsequent descendants in the widget tree by inserting a new
	/// [MediaQuery] widget using the [MediaQuery.removePadding] factory.
	///
	/// See also:
	///
	/// * [SafeArea], a widget that consumes this padding with a [Padding] widget
	/// and automatically removes it from the [MediaQuery] for its child.
	final EdgeInsets padding;

	/// Whether to use 24-hour format when formatting time.
	///
	/// The behavior of this flag is different across platforms:
	///
	/// - On Android this flag is reported directly from the user settings called
	/// "Use 24-hour format". It applies to any locale used by the application,
	/// whether it is the system-wide locale, or the custom locale set by the
	/// application.
	/// - On iOS this flag is set to true when the user setting called "24-Hour
	/// Time" is set or the system-wide locale's default uses 24-hour
	/// formatting.
	final bool alwaysUse24HourFormat;

	/// The orientation of the media (e.g., whether the device is in landscape or portrait mode).
	Orientation get orientation {
	return size.width > size.height ? Orientation.landscape : Orientation.portrait;
	}

	/// Creates a copy of this media query data but with the given fields replaced
	/// with the new values.
	MediaQueryData copyWith({
	Size size,
	double devicePixelRatio,
	double textScaleFactor,
	EdgeInsets padding,
	EdgeInsets viewInsets,
	bool alwaysUse24HourFormat,
	}) {
	return new MediaQueryData(
	size: size ?? this.size,
	devicePixelRatio: devicePixelRatio ?? this.devicePixelRatio,
	textScaleFactor: textScaleFactor ?? this.textScaleFactor,
	padding: padding ?? this.padding,
	viewInsets: viewInsets ?? this.viewInsets,
	alwaysUse24HourFormat: alwaysUse24HourFormat ?? this.alwaysUse24HourFormat,
	);
	}

	/// Creates a copy of this media query data but with the given [padding]s
	/// replaced with zero.
	///
	/// The `removeLeft`, `removeTop`, `removeRight`, and `removeBottom` arguments
	/// must not be null. If all four are false (the default) then this
	/// [MediaQueryData] is returned unmodified.
	///
	/// See also:
	///
	/// * [new MediaQuery.removePadding], which uses this method to remove padding
	/// from the ambient [MediaQuery].
	/// * [SafeArea], which both removes the padding from the [MediaQuery] and
	/// adds a [Padding] widget.
	/// * [removeViewInsets], the same thing but for [viewInsets].
	MediaQueryData removePadding({
	bool removeLeft = false,
	bool removeTop = false,
	bool removeRight = false,
	bool removeBottom = false,
	}) {
	if (!(removeLeft \|\| removeTop \|\| removeRight \|\| removeBottom))
	return this;
	return new MediaQueryData(
	size: size,
	devicePixelRatio: devicePixelRatio,
	textScaleFactor: textScaleFactor,
	padding: padding.copyWith(
	left: removeLeft ? 0.0 : null,
	top: removeTop ? 0.0 : null,
	right: removeRight ? 0.0 : null,
	bottom: removeBottom ? 0.0 : null,
	),
	viewInsets: viewInsets,
	alwaysUse24HourFormat: alwaysUse24HourFormat,
	);
	}

	/// Creates a copy of this media query data but with the given [viewInsets]
	/// replaced with zero.
	///
	/// The `removeLeft`, `removeTop`, `removeRight`, and `removeBottom` arguments
	/// must not be null. If all four are false (the default) then this
	/// [MediaQueryData] is returned unmodified.
	///
	/// See also:
	///
	/// * [new MediaQuery.removeViewInsets], which uses this method to remove
	/// padding from the ambient [MediaQuery].
	/// * [removePadding], the same thing but for [padding].
	MediaQueryData removeViewInsets({
	bool removeLeft = false,
	bool removeTop = false,
	bool removeRight = false,
	bool removeBottom = false,
	}) {
	if (!(removeLeft \|\| removeTop \|\| removeRight \|\| removeBottom))
	return this;
	return new MediaQueryData(
	size: size,
	devicePixelRatio: devicePixelRatio,
	textScaleFactor: textScaleFactor,
	padding: padding,
	viewInsets: viewInsets.copyWith(
	left: removeLeft ? 0.0 : null,
	top: removeTop ? 0.0 : null,
	right: removeRight ? 0.0 : null,
	bottom: removeBottom ? 0.0 : null,
	),
	alwaysUse24HourFormat: alwaysUse24HourFormat,
	);
	}

	@override
	bool operator ==(Object other) {
	if (other.runtimeType != runtimeType)
	return false;
	final MediaQueryData typedOther = other;
	return typedOther.size == size
	&& typedOther.devicePixelRatio == devicePixelRatio
	&& typedOther.textScaleFactor == textScaleFactor
	&& typedOther.padding == padding
	&& typedOther.viewInsets == viewInsets
	&& typedOther.alwaysUse24HourFormat == alwaysUse24HourFormat;
	}

	@override
	int get hashCode => hashValues(size, devicePixelRatio, textScaleFactor, padding, viewInsets, alwaysUse24HourFormat);

	@override
	String toString() {
	return '$runtimeType('
	'size: $size, '
	'devicePixelRatio: $devicePixelRatio, '
	'textScaleFactor: $textScaleFactor, '
	'padding: $padding, '
	'viewInsets: $viewInsets, '
	'alwaysUse24HourFormat: $alwaysUse24HourFormat'
	')';
	}
	}

	/// Establishes a subtree in which media queries resolve to the given data.
	///
	/// For example, to learn the size of the current media (e.g., the window
	/// containing your app), you can read the [MediaQueryData.size] property from
	/// the [MediaQueryData] returned by [MediaQuery.of]:
	/// `MediaQuery.of(context).size`.
	///
	/// Querying the current media using [MediaQuery.of] will cause your widget to
	/// rebuild automatically whenever the [MediaQueryData] changes (e.g., if the
	/// user rotates their device).
	///
	/// If no [MediaQuery] is in scope then the [MediaQuery.of] method will throw an
	/// exception, unless the `nullOk` argument is set to true, in which case it
	/// returns null.
	///
	/// See also:
	///
	/// * [WidgetsApp] and [MaterialApp], which introduce a [MediaQuery] and keep
	/// it up to date with the current screen metrics as they change.
	/// * [MediaQueryData], the data structure that represents the metrics.
	class MediaQuery extends InheritedWidget {
	/// Creates a widget that provides [MediaQueryData] to its descendants.
	///
	/// The [data] and [child] arguments must not be null.
	const MediaQuery({
	Key key,
	@required this.data,
	@required Widget child,
	}) : assert(child != null),
	assert(data != null),
	super(key: key, child: child);

	/// Creates a new [MediaQuery] that inherits from the ambient [MediaQuery] from
	/// the given context, but removes the specified paddings.
	///
	/// This should be inserted into the widget tree when the [MediaQuery] padding
	/// is consumed by a widget in such a way that the padding is no longer
	/// exposed to the widget's descendants or siblings.
	///
	/// The [context] argument is required, must not be null, and must have a
	/// [MediaQuery] in scope.
	///
	/// The `removeLeft`, `removeTop`, `removeRight`, and `removeBottom` arguments
	/// must not be null. If all four are false (the default) then the returned
	/// [MediaQuery] reuses the ambient [MediaQueryData] unmodified, which is not
	/// particularly useful.
	///
	/// The [child] argument is required and must not be null.
	///
	/// See also:
	///
	/// * [SafeArea], which both removes the padding from the [MediaQuery] and
	/// adds a [Padding] widget.
	/// * [MediaQueryData.padding], the affected property of the [MediaQueryData].
	/// * [new removeViewInsets], the same thing but for removing view insets.
	factory MediaQuery.removePadding({
	Key key,
	@required BuildContext context,
	bool removeLeft = false,
	bool removeTop = false,
	bool removeRight = false,
	bool removeBottom = false,
	@required Widget child,
	}) {
	return new MediaQuery(
	key: key,
	data: MediaQuery.of(context).removePadding(
	removeLeft: removeLeft,
	removeTop: removeTop,
	removeRight: removeRight,
	removeBottom: removeBottom,
	),
	child: child,
	);
	}

	/// Creates a new [MediaQuery] that inherits from the ambient [MediaQuery] from
	/// the given context, but removes the specified view insets.
	///
	/// This should be inserted into the widget tree when the [MediaQuery] view
	/// insets are consumed by a widget in such a way that the view insets are no
	/// longer exposed to the widget's descendants or siblings.
	///
	/// The [context] argument is required, must not be null, and must have a
	/// [MediaQuery] in scope.
	///
	/// The `removeLeft`, `removeTop`, `removeRight`, and `removeBottom` arguments
	/// must not be null. If all four are false (the default) then the returned
	/// [MediaQuery] reuses the ambient [MediaQueryData] unmodified, which is not
	/// particularly useful.
	///
	/// The [child] argument is required and must not be null.
	///
	/// See also:
	///
	/// * [MediaQueryData.viewInsets], the affected property of the [MediaQueryData].
	/// * [new removePadding], the same thing but for removing paddings.
	factory MediaQuery.removeViewInsets({
	Key key,
	@required BuildContext context,
	bool removeLeft = false,
	bool removeTop = false,
	bool removeRight = false,
	bool removeBottom = false,
	@required Widget child,
	}) {
	return new MediaQuery(
	key: key,
	data: MediaQuery.of(context).removeViewInsets(
	removeLeft: removeLeft,
	removeTop: removeTop,
	removeRight: removeRight,
	removeBottom: removeBottom,
	),
	child: child,
	);
	}

	/// Contains information about the current media.
	///
	/// For example, the [MediaQueryData.size] property contains the width and
	/// height of the current window.
	final MediaQueryData data;

	/// The data from the closest instance of this class that encloses the given
	/// context.
	///
	/// You can use this function to query the size an orientation of the screen.
	/// When that information changes, your widget will be scheduled to be rebuilt,
	/// keeping your widget up-to-date.
	///
	/// Typical usage is as follows:
	///
	/// ```dart
	/// MediaQueryData media = MediaQuery.of(context);
	/// ```
	///
	/// If there is no [MediaQuery] in scope, then this will throw an exception.
	/// To return null if there is no [MediaQuery], then pass `nullOk: true`.
	///
	/// If you use this from a widget (e.g. in its build function), consider
	/// calling [debugCheckHasMediaQuery].
	static MediaQueryData of(BuildContext context, { bool nullOk = false }) {
	assert(context != null);
	assert(nullOk != null);
	final MediaQuery query = context.inheritFromWidgetOfExactType(MediaQuery);
	if (query != null)
	return query.data;
	if (nullOk)
	return null;
	throw new FlutterError(
	'MediaQuery.of() called with a context that does not contain a MediaQuery.\n'
	'No MediaQuery ancestor could be found starting from the context that was passed '
	'to MediaQuery.of(). This can happen because you do not have a WidgetsApp or '
	'MaterialApp widget (those widgets introduce a MediaQuery), or it can happen '
	'if the context you use comes from a widget above those widgets.\n'
	'The context used was:\n'
	' $context'
	);
	}

	/// Returns textScaleFactor for the nearest MediaQuery ancestor or 1.0, if
	/// no such ancestor exists.
	static double textScaleFactorOf(BuildContext context) {
	return MediaQuery.of(context, nullOk: true)?.textScaleFactor ?? 1.0;
	}

	@override
	bool updateShouldNotify(MediaQuery oldWidget) => data != oldWidget.data;

	@override
	void debugFillProperties(DiagnosticPropertiesBuilder properties) {
	super.debugFillProperties(properties);
	properties.add(new DiagnosticsProperty<MediaQueryData>('data', data, showName: false));
	}
	}