media_query.dart

// 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 'dart:math' as math;
import 'dart:ui' as ui;
import 'dart:ui' show Brightness;

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.
///
/// ## Insets and Padding
///
/// ![A diagram of padding, viewInsets, and viewPadding in correlation with each
/// other](https://flutter.github.io/assets-for-api-docs/assets/widgets/media_query.png)
///
/// This diagram illustrates how [padding] relates to [viewPadding] and
/// [viewInsets], shown here in its simplest configuration, as the difference
/// between the two. In cases when the viewInsets exceed the viewPadding, like
/// when a software keyboard is shown below, padding goes to zero rather than a
/// negative value. Therefore, padding is calculated by taking
/// `max(0.0, viewPadding - viewInsets)`.
///
/// {@animation 300 300 https://flutter.github.io/assets-for-api-docs/assets/widgets/window_padding.mp4}
///
/// In this diagram, the black areas represent system UI that the app cannot
/// draw over. The red area represents view padding that the application may not
/// be able to detect gestures in and may not want to draw in. The grey area
/// represents the system keyboard, which can cover over the bottom view padding
/// when visible.
///
/// MediaQueryData includes three [EdgeInsets] values:
/// [padding], [viewPadding], and [viewInsets]. These values reflect the
/// configuration of the device and are used and optionally consumed by widgets
/// that position content within these insets. The padding value defines areas
/// that might not be completely visible, like the display "notch" on the iPhone
/// X. The viewInsets value defines areas that aren't visible at all, typically
/// because they're obscured by the device's keyboard. Similar to viewInsets,
/// viewPadding does not differentiate padding in areas that may be obscured.
/// For example, by using the viewPadding property, padding would defer to the
/// iPhone "safe area" regardless of whether a keyboard is showing.
///
/// The viewInsets and viewPadding are independent values, they're
/// measured from the edges of the MediaQuery widget's bounds. Together they
/// inform the [padding] property. The bounds of the top level MediaQuery
/// created by [WidgetsApp] are the same as the window that contains the app.
///
/// Widgets whose layouts consume space defined by [viewInsets], [viewPadding],
/// or [padding] should enclose their children in secondary MediaQuery
/// widgets that reduce those properties by the same amount.
/// The [removePadding], [removeViewPadding], and [removeViewInsets] methods are
/// useful for this.
///
/// See also:
///
///  * [Scaffold], [SafeArea], [CupertinoTabScaffold], and
///    [CupertinoPageScaffold], all of which are informed by [padding],
///    [viewPadding], and [viewInsets].
@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.platformBrightness = Brightness.light,
    this.padding = EdgeInsets.zero,
    this.viewInsets = EdgeInsets.zero,
    this.systemGestureInsets = EdgeInsets.zero,
    this.viewPadding = EdgeInsets.zero,
    this.physicalDepth = double.maxFinite,
    this.alwaysUse24HourFormat = false,
    this.accessibleNavigation = false,
    this.invertColors = false,
    this.highContrast = false,
    this.disableAnimations = false,
    this.boldText = 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,
      platformBrightness = window.platformBrightness,
      padding = EdgeInsets.fromWindowPadding(window.padding, window.devicePixelRatio),
      viewPadding = EdgeInsets.fromWindowPadding(window.viewPadding, window.devicePixelRatio),
      viewInsets = EdgeInsets.fromWindowPadding(window.viewInsets, window.devicePixelRatio),
      systemGestureInsets = EdgeInsets.fromWindowPadding(window.systemGestureInsets, window.devicePixelRatio),
      physicalDepth = window.physicalDepth,
      accessibleNavigation = window.accessibilityFeatures.accessibleNavigation,
      invertColors = window.accessibilityFeatures.invertColors,
      disableAnimations = window.accessibilityFeatures.disableAnimations,
      boldText = window.accessibilityFeatures.boldText,
      highContrast = false,
      alwaysUse24HourFormat = window.alwaysUse24HourFormat;

  /// The size of the media in logical pixels (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 current brightness mode of the host platform.
  ///
  /// For example, starting in Android Pie, battery saver mode asks all apps to
  /// render in a "dark mode".
  ///
  /// Not all platforms necessarily support a concept of brightness mode. Those
  /// platforms will report [Brightness.light] in this property.
  final Brightness platformBrightness;

  /// The parts of the display that are completely obscured by system UI,
  /// typically by the device's keyboard.
  ///
  /// When a mobile device's keyboard is visible `viewInsets.bottom`
  /// corresponds to the top of the keyboard.
  ///
  /// This value is independent of the [padding] and [viewPadding]. viewPadding
  /// is measured from the edges of the [MediaQuery] widget's bounds. Padding is
  /// calculated based on the viewPadding and viewInsets. The bounds of the top
  /// level MediaQuery created by [WidgetsApp] are the same as the window
  /// (often the mobile device screen) that contains the app.
  ///
  /// See also:
  ///
  ///  * [ui.window], which provides some additional detail about this property
  ///    and how it relates to [padding] and [viewPadding].
  final EdgeInsets viewInsets;

  /// The parts of the display that are partially obscured by system UI,
  /// typically by the hardware display "notches" or the system status bar.
  ///
  /// 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.
  ///
  /// Padding is derived from the values of viewInsets and viewPadding.
  ///
  /// See also:
  ///
  ///  * [ui.window], which provides some additional detail about this
  ///    property and how it relates to [viewInsets] and [viewPadding].
  ///  * [SafeArea], a widget that consumes this padding with a [Padding] widget
  ///    and automatically removes it from the [MediaQuery] for its child.
  final EdgeInsets padding;

  /// The parts of the display that are partially obscured by system UI,
  /// typically by the hardware display "notches" or the system status bar.
  ///
  /// This value remains the same regardless of whether the system is reporting
  /// other obstructions in the same physical area of the screen. For example, a
  /// software keyboard on the bottom of the screen that may cover and consume
  /// the same area that requires bottom padding will not affect this value.
  ///
  /// This value is independent of the [padding] and [viewInsets]: their values
  /// are measured from the edges of the [MediaQuery] widget's bounds. The
  /// bounds of the top level MediaQuery created by [WidgetsApp] are the
  /// same as the window that contains the app. On mobile devices, this will
  /// typically be the full screen.
  ///
  /// See also:
  ///
  ///  * [ui.window], which provides some additional detail about this
  ///    property and how it relates to [padding] and [viewInsets].
  final EdgeInsets viewPadding;

  /// The areas along the edges of the display where the system consumes
  /// certain input events and blocks delivery of those events to the app.
  ///
  /// Starting with Android Q, simple swipe gestures that start within the
  /// [systemGestureInsets] areas are used by the system for page navigation
  /// and may not be delivered to the app. Taps and swipe gestures that begin
  /// with a long-press are delivered to the app, but simple press-drag-release
  /// swipe gestures which begin within the area defined by [systemGestureInsets]
  /// may not be.
  ///
  /// Apps should avoid locating gesture detectors within the system gesture
  /// insets area. Apps should feel free to put visual elements within
  /// this area.
  ///
  /// This property is currently only expected to be set to a non-default value
  /// on Android starting with version Q.
  ///
  /// {@tool sample --template=stateful_widget_material}
  ///
  /// For apps that might be deployed on Android Q devices with full gesture
  /// navigation enabled, use [MediaQuery.systemGestureInsets] with [Padding]
  /// to avoid having the left and right edges of the [Slider] from appearing
  /// within the area reserved for system gesture navigation.
  ///
  /// By default, [Slider]s expand to fill the available width. So, we pad the
  /// left and right sides.
  ///
  /// ```dart
  /// double _currentValue = 0.2;
  ///
  /// @override
  /// Widget build(BuildContext context) {
  ///   EdgeInsets systemGestureInsets = MediaQuery.of(context).systemGestureInsets;
  ///   return Scaffold(
  ///     appBar: AppBar(title: Text('Pad Slider to avoid systemGestureInsets')),
  ///     body: Padding(
  ///       padding: EdgeInsets.only( // only left and right padding are needed here
  ///         left: systemGestureInsets.left,
  ///         right: systemGestureInsets.right,
  ///       ),
  ///       child: Slider(
  ///         value: _currentValue.toDouble(),
  ///         onChanged: (double newValue) {
  ///           setState(() {
  ///             _currentValue = newValue;
  ///           });
  ///         },
  ///       ),
  ///     ),
  ///   );
  /// }
  /// ```
  /// {@end-tool}
  final EdgeInsets systemGestureInsets;

  /// The physical depth is the maximum elevation that the Window allows.
  ///
  /// Physical layers drawn at or above this elevation will have their elevation
  /// clamped to this value. This can happen if the physical layer itself has
  /// an elevation larger than the available depth, or if some ancestor of the
  /// layer causes it to have a cumulative elevation that is larger than the
  /// available depth.
  ///
  /// The default value is [double.maxFinite], which is used for platforms that
  /// do not specify a maximum elevation. This property is currently only
  /// expected to be set to a non-default value on Fuchsia.
  final double physicalDepth;

  /// 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;

  /// Whether the user is using an accessibility service like TalkBack or
  /// VoiceOver to interact with the application.
  ///
  /// When this setting is true, features such as timeouts should be disabled or
  /// have minimum durations increased.
  ///
  /// See also:
  ///
  ///  * [Window.AccessibilityFeatures], where the setting originates.
  final bool accessibleNavigation;

  /// Whether the device is inverting the colors of the platform.
  ///
  /// This flag is currently only updated on iOS devices.
  ///
  /// See also:
  ///
  ///  * [Window.AccessibilityFeatures], where the setting originates.
  final bool invertColors;

  /// Whether the user requested a high contrast between foreground and background
  /// content on iOS, via Settings -> Accessibility -> Increase Contrast.
  ///
  /// This flag is currently only updated on iOS devices that are running iOS 13
  /// or above.
  final bool highContrast;

  /// Whether the platform is requesting that animations be disabled or reduced
  /// as much as possible.
  ///
  /// See also:
  ///
  ///  * [Window.AccessibilityFeatures], where the setting originates.
  final bool disableAnimations;

  /// Whether the platform is requesting that text be drawn with a bold font
  /// weight.
  ///
  /// See also:
  ///
  ///  * [Window.AccessibilityFeatures], where the setting originates.
  final bool boldText;

  /// 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,
    Brightness platformBrightness,
    EdgeInsets padding,
    EdgeInsets viewPadding,
    EdgeInsets viewInsets,
    EdgeInsets systemGestureInsets,
    double physicalDepth,
    bool alwaysUse24HourFormat,
    bool highContrast,
    bool disableAnimations,
    bool invertColors,
    bool accessibleNavigation,
    bool boldText,
  }) {
    return MediaQueryData(
      size: size ?? this.size,
      devicePixelRatio: devicePixelRatio ?? this.devicePixelRatio,
      textScaleFactor: textScaleFactor ?? this.textScaleFactor,
      platformBrightness: platformBrightness ?? this.platformBrightness,
      padding: padding ?? this.padding,
      viewPadding: viewPadding ?? this.viewPadding,
      viewInsets: viewInsets ?? this.viewInsets,
      systemGestureInsets: systemGestureInsets ?? this.systemGestureInsets,
      physicalDepth: physicalDepth ?? this.physicalDepth,
      alwaysUse24HourFormat: alwaysUse24HourFormat ?? this.alwaysUse24HourFormat,
      invertColors: invertColors ?? this.invertColors,
      highContrast: highContrast ?? this.highContrast,
      disableAnimations: disableAnimations ?? this.disableAnimations,
      accessibleNavigation: accessibleNavigation ?? this.accessibleNavigation,
      boldText: boldText ?? this.boldText,
    );
  }

  /// 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:
  ///
  ///  * [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].
  ///  * [removeViewPadding], the same thing but for [viewPadding].
  MediaQueryData removePadding({
    bool removeLeft = false,
    bool removeTop = false,
    bool removeRight = false,
    bool removeBottom = false,
  }) {
    if (!(removeLeft || removeTop || removeRight || removeBottom))
      return this;
    return MediaQueryData(
      size: size,
      devicePixelRatio: devicePixelRatio,
      textScaleFactor: textScaleFactor,
      platformBrightness: platformBrightness,
      padding: padding.copyWith(
        left: removeLeft ? 0.0 : null,
        top: removeTop ? 0.0 : null,
        right: removeRight ? 0.0 : null,
        bottom: removeBottom ? 0.0 : null,
      ),
      viewPadding: viewPadding.copyWith(
        left: removeLeft ? math.max(0.0, viewPadding.left - padding.left) : null,
        top: removeTop ? math.max(0.0, viewPadding.top - padding.top) : null,
        right: removeRight ? math.max(0.0, viewPadding.right - padding.right) : null,
        bottom: removeBottom ? math.max(0.0, viewPadding.bottom - padding.bottom) : null,
      ),
      viewInsets: viewInsets,
      alwaysUse24HourFormat: alwaysUse24HourFormat,
      highContrast: highContrast,
      disableAnimations: disableAnimations,
      invertColors: invertColors,
      accessibleNavigation: accessibleNavigation,
      boldText: boldText,
    );
  }

  /// 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:
  ///
  ///  * [MediaQuery.removeViewInsets], which uses this method to remove
  ///    [viewInsets] from the ambient [MediaQuery].
  ///  * [removePadding], the same thing but for [padding].
  ///  * [removeViewPadding], the same thing but for [viewPadding].
  MediaQueryData removeViewInsets({
    bool removeLeft = false,
    bool removeTop = false,
    bool removeRight = false,
    bool removeBottom = false,
  }) {
    if (!(removeLeft || removeTop || removeRight || removeBottom))
      return this;
    return MediaQueryData(
      size: size,
      devicePixelRatio: devicePixelRatio,
      textScaleFactor: textScaleFactor,
      platformBrightness: platformBrightness,
      padding: padding,
      viewPadding: viewPadding.copyWith(
        left: removeLeft ? math.max(0.0, viewPadding.left - viewInsets.left) : null,
        top: removeTop ? math.max(0.0, viewPadding.top - viewInsets.top) : null,
        right: removeRight ? math.max(0.0, viewPadding.right - viewInsets.right) : null,
        bottom: removeBottom ? math.max(0.0, viewPadding.bottom - viewInsets.bottom) : null,
      ),
      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,
      highContrast: highContrast,
      disableAnimations: disableAnimations,
      invertColors: invertColors,
      accessibleNavigation: accessibleNavigation,
      boldText: boldText,
    );
  }

  /// Creates a copy of this media query data but with the given [viewPadding]
  /// 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:
  ///
  ///  * [MediaQuery.removeViewPadding], which uses this method to remove
  ///    [viewPadding] from the ambient [MediaQuery].
  ///  * [removePadding], the same thing but for [padding].
  ///  * [removeViewInsets], the same thing but for [viewInsets].
  MediaQueryData removeViewPadding({
    bool removeLeft = false,
    bool removeTop = false,
    bool removeRight = false,
    bool removeBottom = false,
  }) {
    if (!(removeLeft || removeTop || removeRight || removeBottom))
      return this;
    return MediaQueryData(
      size: size,
      devicePixelRatio: devicePixelRatio,
      textScaleFactor: textScaleFactor,
      platformBrightness: platformBrightness,
      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,
      viewPadding: viewPadding.copyWith(
        left: removeLeft ? 0.0 : null,
        top: removeTop ? 0.0 : null,
        right: removeRight ? 0.0 : null,
        bottom: removeBottom ? 0.0 : null,
      ),
      alwaysUse24HourFormat: alwaysUse24HourFormat,
      highContrast: highContrast,
      disableAnimations: disableAnimations,
      invertColors: invertColors,
      accessibleNavigation: accessibleNavigation,
      boldText: boldText,
    );
  }

  @override
  bool operator ==(Object other) {
    if (other.runtimeType != runtimeType)
      return false;
    return other is MediaQueryData
        && other.size == size
        && other.devicePixelRatio == devicePixelRatio
        && other.textScaleFactor == textScaleFactor
        && other.platformBrightness == platformBrightness
        && other.padding == padding
        && other.viewPadding == viewPadding
        && other.viewInsets == viewInsets
        && other.physicalDepth == physicalDepth
        && other.alwaysUse24HourFormat == alwaysUse24HourFormat
        && other.highContrast == highContrast
        && other.disableAnimations == disableAnimations
        && other.invertColors == invertColors
        && other.accessibleNavigation == accessibleNavigation
        && other.boldText == boldText;
  }

  @override
  int get hashCode {
    return hashValues(
      size,
      devicePixelRatio,
      textScaleFactor,
      platformBrightness,
      padding,
      viewPadding,
      viewInsets,
      physicalDepth,
      alwaysUse24HourFormat,
      highContrast,
      disableAnimations,
      invertColors,
      accessibleNavigation,
      boldText,
    );
  }

  @override
  String toString() {
    final List<String> properties = <String>[
      'size: $size',
      'devicePixelRatio: ${devicePixelRatio.toStringAsFixed(1)}',
      'textScaleFactor: ${textScaleFactor.toStringAsFixed(1)}',
      'platformBrightness: $platformBrightness',
      'padding: $padding',
      'viewPadding: $viewPadding',
      'viewInsets: $viewInsets',
      'physicalDepth: $physicalDepth',
      'alwaysUse24HourFormat: $alwaysUse24HourFormat',
      'accessibleNavigation: $accessibleNavigation',
      'highContrast: $highContrast',
      'disableAnimations: $disableAnimations',
      'invertColors: $invertColors',
      'boldText: $boldText',
    ];
    return '${objectRuntimeType(this, 'MediaQueryData')}(${properties.join(', ')})';
  }
}

/// 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.
///
/// {@youtube 560 315 https://www.youtube.com/watch?v=A3WrA4zAaPw}
///
/// 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 padding.
  ///
  /// 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].
  ///  * [removeViewInsets], the same thing but for [MediaQueryData.viewInsets].
  ///  * [removeViewPadding], the same thing but for
  ///    [MediaQueryData.viewPadding].
  factory MediaQuery.removePadding({
    Key key,
    @required BuildContext context,
    bool removeLeft = false,
    bool removeTop = false,
    bool removeRight = false,
    bool removeBottom = false,
    @required Widget child,
  }) {
    return 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].
  ///  * [removePadding], the same thing but for [MediaQueryData.padding].
  ///  * [removeViewPadding], the same thing but for
  ///    [MediaQueryData.viewPadding].
  factory MediaQuery.removeViewInsets({
    Key key,
    @required BuildContext context,
    bool removeLeft = false,
    bool removeTop = false,
    bool removeRight = false,
    bool removeBottom = false,
    @required Widget child,
  }) {
    return MediaQuery(
      key: key,
      data: MediaQuery.of(context).removeViewInsets(
        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 padding.
  ///
  /// This should be inserted into the widget tree when the [MediaQuery] view
  /// padding is consumed by a widget in such a way that the view 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:
  ///
  ///  * [MediaQueryData.viewPadding], the affected property of the
  ///    [MediaQueryData].
  ///  * [removePadding], the same thing but for [MediaQueryData.padding].
  ///  * [removeViewInsets], the same thing but for [MediaQueryData.viewInsets].
  factory MediaQuery.removeViewPadding({
    Key key,
    @required BuildContext context,
    bool removeLeft = false,
    bool removeTop = false,
    bool removeRight = false,
    bool removeBottom = false,
    @required Widget child,
  }) {
    return MediaQuery(
      key: key,
      data: MediaQuery.of(context).removeViewPadding(
        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.dependOnInheritedWidgetOfExactType<MediaQuery>();
    if (query != null)
      return query.data;
    if (nullOk)
      return null;
    throw FlutterError.fromParts(<DiagnosticsNode>[
      ErrorSummary('MediaQuery.of() called with a context that does not contain a MediaQuery.'),
      ErrorDescription(
        '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.'
      ),
      context.describeElement('The context used was')
    ]);
  }

  /// 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;
  }

  /// Returns platformBrightness for the nearest MediaQuery ancestor or
  /// [Brightness.light], if no such ancestor exists.
  ///
  /// Use of this method will cause the given [context] to rebuild any time that
  /// any property of the ancestor [MediaQuery] changes.
  static Brightness platformBrightnessOf(BuildContext context) {
    return MediaQuery.of(context, nullOk: true)?.platformBrightness ?? Brightness.light;
  }

  /// Returns the boldText accessibility setting for the nearest MediaQuery
  /// ancestor, or false if no such ancestor exists.
  static bool boldTextOverride(BuildContext context) {
    return MediaQuery.of(context, nullOk: true)?.boldText ?? false;
  }

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

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