packages/flutter/lib/src/widgets/debug.dart - external/github.com/flutter/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 'dart:collection';
 import 'dart:developer' show Timeline; // to disambiguate reference in dartdocs below

 import 'package:flutter/foundation.dart';

 import 'basic.dart';
 import 'framework.dart';
 import 'localizations.dart';
 import 'media_query.dart';
 import 'overlay.dart';
 import 'table.dart';

 // Any changes to this file should be reflected in the debugAssertAllWidgetVarsUnset()
 // function below.

 /// Log the dirty widgets that are built each frame.
 ///
 /// Combined with [debugPrintBuildScope] or [debugPrintBeginFrameBanner], this
 /// allows you to distinguish builds triggered by the initial mounting of a
 /// widget tree (e.g. in a call to [runApp]) from the regular builds triggered
 /// by the pipeline.
 ///
 /// Combined with [debugPrintScheduleBuildForStacks], this lets you watch a
 /// widget's dirty/clean lifecycle.
 ///
 /// To get similar information but showing it on the timeline available from the
 /// Observatory rather than getting it in the console (where it can be
 /// overwhelming), consider [debugProfileBuildsEnabled].
 ///
 /// See also:
 ///
 ///  * [WidgetsBinding.drawFrame], which pumps the build and rendering pipeline
 ///    to generate a frame.
 bool debugPrintRebuildDirtyWidgets = false;

 /// Signature for [debugOnRebuildDirtyWidget] implementations.
 typedef RebuildDirtyWidgetCallback = void Function(Element e, bool builtOnce);

 /// Callback invoked for every dirty widget built each frame.
 ///
 /// This callback is only invoked in debug builds.
 ///
 /// See also:
 ///
 ///  * [debugPrintRebuildDirtyWidgets], which does something similar but logs
 ///    to the console instead of invoking a callback.
 ///  * [debugOnProfilePaint], which does something similar for [RenderObject]
 ///    painting.
 ///  * [WidgetInspectorService], which uses the [debugOnRebuildDirtyWidget]
 ///    callback to generate aggregate profile statistics describing which widget
 ///    rebuilds occurred when the
 ///    `ext.flutter.inspector.trackRebuildDirtyWidgets` service extension is
 ///    enabled.
 RebuildDirtyWidgetCallback? debugOnRebuildDirtyWidget;

 /// Log all calls to [BuildOwner.buildScope].
 ///
 /// Combined with [debugPrintScheduleBuildForStacks], this allows you to track
 /// when a [State.setState] call gets serviced.
 ///
 /// Combined with [debugPrintRebuildDirtyWidgets] or
 /// [debugPrintBeginFrameBanner], this allows you to distinguish builds
 /// triggered by the initial mounting of a widget tree (e.g. in a call to
 /// [runApp]) from the regular builds triggered by the pipeline.
 ///
 /// See also:
 ///
 ///  * [WidgetsBinding.drawFrame], which pumps the build and rendering pipeline
 ///    to generate a frame.
 bool debugPrintBuildScope = false;

 /// Log the call stacks that mark widgets as needing to be rebuilt.
 ///
 /// This is called whenever [BuildOwner.scheduleBuildFor] adds an element to the
 /// dirty list. Typically this is as a result of [Element.markNeedsBuild] being
 /// called, which itself is usually a result of [State.setState] being called.
 ///
 /// To see when a widget is rebuilt, see [debugPrintRebuildDirtyWidgets].
 ///
 /// To see when the dirty list is flushed, see [debugPrintBuildScope].
 ///
 /// To see when a frame is scheduled, see [debugPrintScheduleFrameStacks].
 bool debugPrintScheduleBuildForStacks = false;

 /// Log when widgets with global keys are deactivated and log when they are
 /// reactivated (retaken).
 ///
 /// This can help track down framework bugs relating to the [GlobalKey] logic.
 bool debugPrintGlobalKeyedWidgetLifecycle = false;

 /// Adds [Timeline] events for every Widget built.
 ///
 /// For details on how to use [Timeline] events in the Dart Observatory to
 /// optimize your app, see https://flutter.dev/docs/testing/debugging#tracing-any-dart-code-performance
 /// and https://fuchsia.googlesource.com/topaz/+/master/shell/docs/performance.md
 ///
 /// See also:
 ///
 ///  * [debugPrintRebuildDirtyWidgets], which does something similar but
 ///    reporting the builds to the console.
 ///  * [debugProfileLayoutsEnabled], which does something similar for layout,
 ///    and [debugPrintLayouts], its console equivalent.
 ///  * [debugProfilePaintsEnabled], which does something similar for painting.
 bool debugProfileBuildsEnabled = false;

 /// Show banners for deprecated widgets.
 bool debugHighlightDeprecatedWidgets = false;

 Key? _firstNonUniqueKey(Iterable<Widget> widgets) {
   final Set<Key> keySet = HashSet<Key>();
   for (final Widget widget in widgets) {
     assert(widget != null);
     if (widget.key == null)
       continue;
     if (!keySet.add(widget.key!))
       return widget.key;
   }
   return null;
 }

 /// Asserts if the given child list contains any duplicate non-null keys.
 ///
 /// To invoke this function, use the following pattern, typically in the
 /// relevant Widget's constructor:
 ///
 /// ```dart
 /// assert(!debugChildrenHaveDuplicateKeys(this, children));
 /// ```
 ///
 /// For a version of this function that can be used in contexts where
 /// the list of items does not have a particular parent, see
 /// [debugItemsHaveDuplicateKeys].
 ///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugChildrenHaveDuplicateKeys(Widget parent, Iterable<Widget> children) {
   assert(() {
     final Key? nonUniqueKey = _firstNonUniqueKey(children);
     if (nonUniqueKey != null) {
       throw FlutterError(
         'Duplicate keys found.\n'
         'If multiple keyed nodes exist as children of another node, they must have unique keys.\n'
         '$parent has multiple children with key $nonUniqueKey.',
       );
     }
     return true;
   }());
   return false;
 }

 /// Asserts if the given list of items contains any duplicate non-null keys.
 ///
 /// To invoke this function, use the following pattern:
 ///
 /// ```dart
 /// assert(!debugItemsHaveDuplicateKeys(items));
 /// ```
 ///
 /// For a version of this function specifically intended for parents
 /// checking their children lists, see [debugChildrenHaveDuplicateKeys].
 ///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugItemsHaveDuplicateKeys(Iterable<Widget> items) {
   assert(() {
     final Key? nonUniqueKey = _firstNonUniqueKey(items);
     if (nonUniqueKey != null)
       throw FlutterError('Duplicate key found: $nonUniqueKey.');
     return true;
   }());
   return false;
 }

 /// Asserts that the given context has a [Table] ancestor.
 ///
 /// Used by [TableRowInkWell] to make sure that it is only used in an appropriate context.
 ///
 /// To invoke this function, use the following pattern, typically in the
 /// relevant Widget's build method:
 ///
 /// ```dart
 /// assert(debugCheckHasTable(context));
 /// ```
 ///
 /// This method can be expensive (it walks the element tree).
 ///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasTable(BuildContext context) {
   assert(() {
     if (context.widget is! Table && context.findAncestorWidgetOfExactType<Table>() == null) {
       throw FlutterError.fromParts(<DiagnosticsNode>[
         ErrorSummary('No Table widget found.'),
         ErrorDescription('${context.widget.runtimeType} widgets require a Table widget ancestor.'),
         context.describeWidget('The specific widget that could not find a Table ancestor was'),
         context.describeOwnershipChain('The ownership chain for the affected widget is'),
       ]);
     }
     return true;
   }());
   return true;
 }

 /// Asserts that the given context has a [MediaQuery] ancestor.
 ///
 /// Used by various widgets to make sure that they are only used in an
 /// appropriate context.
 ///
 /// To invoke this function, use the following pattern, typically in the
 /// relevant Widget's build method:
 ///
 /// ```dart
 /// assert(debugCheckHasMediaQuery(context));
 /// ```
 ///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasMediaQuery(BuildContext context) {
   assert(() {
     if (context.widget is! MediaQuery && context.getElementForInheritedWidgetOfExactType<MediaQuery>() == null) {
       throw FlutterError.fromParts(<DiagnosticsNode>[
         ErrorSummary('No MediaQuery widget ancestor found.'),
         ErrorDescription('${context.widget.runtimeType} widgets require a MediaQuery widget ancestor.'),
         context.describeWidget('The specific widget that could not find a MediaQuery ancestor was'),
         context.describeOwnershipChain('The ownership chain for the affected widget is'),
         ErrorHint(
           'No MediaQuery ancestor could be found starting from the context '
           'that was passed to MediaQuery.of(). This can happen because you '
           'have not added a WidgetsApp, CupertinoApp, or MaterialApp widget '
           '(those widgets introduce a MediaQuery), or it can happen if the '
           'context you use comes from a widget above those widgets.',
         ),
       ]);
     }
     return true;
   }());
   return true;
 }

 /// Asserts that the given context has a [Directionality] ancestor.
 ///
 /// Used by various widgets to make sure that they are only used in an
 /// appropriate context.
 ///
 /// To invoke this function, use the following pattern, typically in the
 /// relevant Widget's build method:
 ///
 /// ```dart
 /// assert(debugCheckHasDirectionality(context));
 /// ```
 ///
 /// To improve the error messages you can add some extra color using the
 /// named arguments.
 ///
 ///  * why: explain why the direction is needed, for example "to resolve
 ///    the 'alignment' argument". Should be an adverb phrase describing why.
 ///  * hint: explain why this might be happening, for example "The default
 ///    value of the 'alignment' argument of the $runtimeType widget is an
 ///    AlignmentDirectional value.". Should be a fully punctuated sentence.
 ///  * alternative: provide additional advice specific to the situation,
 ///    especially an alternative to providing a Directionality ancestor.
 ///    For example, "Alternatively, consider specifying the 'textDirection'
 ///    argument.". Should be a fully punctuated sentence.
 ///
 /// Each one can be null, in which case it is skipped (this is the default).
 /// If they are non-null, they are included in the order above, interspersed
 /// with the more generic advice regarding [Directionality].
 ///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasDirectionality(BuildContext context, { String? why, String? hint, String? alternative }) {
   assert(() {
     if (context.widget is! Directionality && context.getElementForInheritedWidgetOfExactType<Directionality>() == null) {
       why = why == null ? '' : ' $why';
       throw FlutterError.fromParts(<DiagnosticsNode>[
         ErrorSummary('No Directionality widget found.'),
         ErrorDescription('${context.widget.runtimeType} widgets require a Directionality widget ancestor$why.\n'),
         if (hint != null)
           ErrorHint(hint),
         context.describeWidget('The specific widget that could not find a Directionality ancestor was'),
         context.describeOwnershipChain('The ownership chain for the affected widget is'),
         ErrorHint(
           'Typically, the Directionality widget is introduced by the MaterialApp '
           'or WidgetsApp widget at the top of your application widget tree. It '
           'determines the ambient reading direction and is used, for example, to '
           'determine how to lay out text, how to interpret "start" and "end" '
           'values, and to resolve EdgeInsetsDirectional, '
           'AlignmentDirectional, and other *Directional objects.',
         ),
         if (alternative != null)
           ErrorHint(alternative),
       ]);
     }
     return true;
   }());
   return true;
 }

 /// Asserts that the `built` widget is not null.
 ///
 /// Used when the given `widget` calls a builder function to check that the
 /// function returned a non-null value, as typically required.
 ///
 /// Does nothing when asserts are disabled.
 void debugWidgetBuilderValue(Widget widget, Widget? built) {
   assert(() {
     if (built == null) {
       throw FlutterError.fromParts(<DiagnosticsNode>[
         ErrorSummary('A build function returned null.'),
         DiagnosticsProperty<Widget>('The offending widget is', widget, style: DiagnosticsTreeStyle.errorProperty),
         ErrorDescription('Build functions must never return null.'),
         ErrorHint(
           'To return an empty space that causes the building widget to fill available room, return "Container()". '
           'To return an empty space that takes as little room as possible, return "Container(width: 0.0, height: 0.0)".',
         ),
       ]);
     }
     if (widget == built) {
       throw FlutterError.fromParts(<DiagnosticsNode>[
         ErrorSummary('A build function returned context.widget.'),
         DiagnosticsProperty<Widget>('The offending widget is', widget, style: DiagnosticsTreeStyle.errorProperty),
         ErrorDescription(
           'Build functions must never return their BuildContext parameter\'s widget or a child that contains "context.widget". '
           'Doing so introduces a loop in the widget tree that can cause the app to crash.',
         ),
       ]);
     }
     return true;
   }());
 }

 /// Asserts that the given context has a [Localizations] ancestor that contains
 /// a [WidgetsLocalizations] delegate.
 ///
 /// To call this function, use the following pattern, typically in the
 /// relevant Widget's build method:
 ///
 /// ```dart
 /// assert(debugCheckHasWidgetsLocalizations(context));
 /// ```
 ///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasWidgetsLocalizations(BuildContext context) {
   assert(() {
     if (Localizations.of<WidgetsLocalizations>(context, WidgetsLocalizations) == null) {
       throw FlutterError.fromParts(<DiagnosticsNode>[
         ErrorSummary('No WidgetsLocalizations found.'),
         ErrorDescription(
           '${context.widget.runtimeType} widgets require WidgetsLocalizations '
           'to be provided by a Localizations widget ancestor.',
         ),
         ErrorDescription(
           'The widgets library uses Localizations to generate messages, '
           'labels, and abbreviations.',
         ),
         ErrorHint(
           'To introduce a WidgetsLocalizations, either use a '
           'WidgetsApp at the root of your application to include them '
           'automatically, or add a Localization widget with a '
           'WidgetsLocalizations delegate.',
         ),
         ...context.describeMissingAncestor(expectedAncestorType: WidgetsLocalizations),
       ]);
     }
     return true;
   }());
   return true;
 }

 /// Asserts that the given context has an [Overlay] ancestor.
 ///
 /// To call this function, use the following pattern, typically in the
 /// relevant Widget's build method:
 ///
 /// ```dart
 /// assert(debugCheckHasOverlay(context));
 /// ```
 ///
 /// This method can be expensive (it walks the element tree).
 ///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasOverlay(BuildContext context) {
   assert(() {
     if (context.widget is! Overlay && context.findAncestorWidgetOfExactType<Overlay>() == null) {
       throw FlutterError.fromParts(<DiagnosticsNode>[
         ErrorSummary('No Overlay widget found.'),
         ErrorDescription(
           '${context.widget.runtimeType} widgets require an Overlay '
           'widget ancestor.\n'
           'An overlay lets widgets float on top of other widget children.',
         ),
         ErrorHint(
           'To introduce an Overlay widget, you can either directly '
           'include one, or use a widget that contains an Overlay itself, '
           'such as a Navigator, WidgetApp, MaterialApp, or CupertinoApp.',
         ),
         ...context.describeMissingAncestor(expectedAncestorType: Overlay),
       ]);
     }
     return true;
   }());
   return true;
 }

 /// Returns true if none of the widget library debug variables have been changed.
 ///
 /// This function is used by the test framework to ensure that debug variables
 /// haven't been inadvertently changed.
 ///
 /// See [the widgets library](widgets/widgets-library.html) for a complete list.
 bool debugAssertAllWidgetVarsUnset(String reason) {
   assert(() {
     if (debugPrintRebuildDirtyWidgets ||
         debugPrintBuildScope ||
         debugPrintScheduleBuildForStacks ||
         debugPrintGlobalKeyedWidgetLifecycle ||
         debugProfileBuildsEnabled ||
         debugHighlightDeprecatedWidgets) {
       throw FlutterError(reason);
     }
     return true;
   }());
   return true;
 }
	// 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:collection';
	import 'dart:developer' show Timeline; // to disambiguate reference in dartdocs below

	import 'package:flutter/foundation.dart';

	import 'basic.dart';
	import 'framework.dart';
	import 'localizations.dart';
	import 'media_query.dart';
	import 'overlay.dart';
	import 'table.dart';

	// Any changes to this file should be reflected in the debugAssertAllWidgetVarsUnset()
	// function below.

	/// Log the dirty widgets that are built each frame.
	///
	/// Combined with [debugPrintBuildScope] or [debugPrintBeginFrameBanner], this
	/// allows you to distinguish builds triggered by the initial mounting of a
	/// widget tree (e.g. in a call to [runApp]) from the regular builds triggered
	/// by the pipeline.
	///
	/// Combined with [debugPrintScheduleBuildForStacks], this lets you watch a
	/// widget's dirty/clean lifecycle.
	///
	/// To get similar information but showing it on the timeline available from the
	/// Observatory rather than getting it in the console (where it can be
	/// overwhelming), consider [debugProfileBuildsEnabled].
	///
	/// See also:
	///
	/// * [WidgetsBinding.drawFrame], which pumps the build and rendering pipeline
	/// to generate a frame.
	bool debugPrintRebuildDirtyWidgets = false;

	/// Signature for [debugOnRebuildDirtyWidget] implementations.
	typedef RebuildDirtyWidgetCallback = void Function(Element e, bool builtOnce);

	/// Callback invoked for every dirty widget built each frame.
	///
	/// This callback is only invoked in debug builds.
	///
	/// See also:
	///
	/// * [debugPrintRebuildDirtyWidgets], which does something similar but logs
	/// to the console instead of invoking a callback.
	/// * [debugOnProfilePaint], which does something similar for [RenderObject]
	/// painting.
	/// * [WidgetInspectorService], which uses the [debugOnRebuildDirtyWidget]
	/// callback to generate aggregate profile statistics describing which widget
	/// rebuilds occurred when the
	/// `ext.flutter.inspector.trackRebuildDirtyWidgets` service extension is
	/// enabled.
	RebuildDirtyWidgetCallback? debugOnRebuildDirtyWidget;

	/// Log all calls to [BuildOwner.buildScope].
	///
	/// Combined with [debugPrintScheduleBuildForStacks], this allows you to track
	/// when a [State.setState] call gets serviced.
	///
	/// Combined with [debugPrintRebuildDirtyWidgets] or
	/// [debugPrintBeginFrameBanner], this allows you to distinguish builds
	/// triggered by the initial mounting of a widget tree (e.g. in a call to
	/// [runApp]) from the regular builds triggered by the pipeline.
	///
	/// See also:
	///
	/// * [WidgetsBinding.drawFrame], which pumps the build and rendering pipeline
	/// to generate a frame.
	bool debugPrintBuildScope = false;

	/// Log the call stacks that mark widgets as needing to be rebuilt.
	///
	/// This is called whenever [BuildOwner.scheduleBuildFor] adds an element to the
	/// dirty list. Typically this is as a result of [Element.markNeedsBuild] being
	/// called, which itself is usually a result of [State.setState] being called.
	///
	/// To see when a widget is rebuilt, see [debugPrintRebuildDirtyWidgets].
	///
	/// To see when the dirty list is flushed, see [debugPrintBuildScope].
	///
	/// To see when a frame is scheduled, see [debugPrintScheduleFrameStacks].
	bool debugPrintScheduleBuildForStacks = false;

	/// Log when widgets with global keys are deactivated and log when they are
	/// reactivated (retaken).
	///
	/// This can help track down framework bugs relating to the [GlobalKey] logic.
	bool debugPrintGlobalKeyedWidgetLifecycle = false;

	/// Adds [Timeline] events for every Widget built.
	///
	/// For details on how to use [Timeline] events in the Dart Observatory to
	/// optimize your app, see https://flutter.dev/docs/testing/debugging#tracing-any-dart-code-performance
	/// and https://fuchsia.googlesource.com/topaz/+/master/shell/docs/performance.md
	///
	/// See also:
	///
	/// * [debugPrintRebuildDirtyWidgets], which does something similar but
	/// reporting the builds to the console.
	/// * [debugProfileLayoutsEnabled], which does something similar for layout,
	/// and [debugPrintLayouts], its console equivalent.
	/// * [debugProfilePaintsEnabled], which does something similar for painting.
	bool debugProfileBuildsEnabled = false;

	/// Show banners for deprecated widgets.
	bool debugHighlightDeprecatedWidgets = false;

	Key? _firstNonUniqueKey(Iterable<Widget> widgets) {
	final Set<Key> keySet = HashSet<Key>();
	for (final Widget widget in widgets) {
	assert(widget != null);
	if (widget.key == null)
	continue;
	if (!keySet.add(widget.key!))
	return widget.key;
	}
	return null;
	}

	/// Asserts if the given child list contains any duplicate non-null keys.
	///
	/// To invoke this function, use the following pattern, typically in the
	/// relevant Widget's constructor:
	///
	/// ```dart
	/// assert(!debugChildrenHaveDuplicateKeys(this, children));
	/// ```
	///
	/// For a version of this function that can be used in contexts where
	/// the list of items does not have a particular parent, see
	/// [debugItemsHaveDuplicateKeys].
	///
	/// Does nothing if asserts are disabled. Always returns true.
	bool debugChildrenHaveDuplicateKeys(Widget parent, Iterable<Widget> children) {
	assert(() {
	final Key? nonUniqueKey = _firstNonUniqueKey(children);
	if (nonUniqueKey != null) {
	throw FlutterError(
	'Duplicate keys found.\n'
	'If multiple keyed nodes exist as children of another node, they must have unique keys.\n'
	'$parent has multiple children with key $nonUniqueKey.',
	);
	}
	return true;
	}());
	return false;
	}

	/// Asserts if the given list of items contains any duplicate non-null keys.
	///
	/// To invoke this function, use the following pattern:
	///
	/// ```dart
	/// assert(!debugItemsHaveDuplicateKeys(items));
	/// ```
	///
	/// For a version of this function specifically intended for parents
	/// checking their children lists, see [debugChildrenHaveDuplicateKeys].
	///
	/// Does nothing if asserts are disabled. Always returns true.
	bool debugItemsHaveDuplicateKeys(Iterable<Widget> items) {
	assert(() {
	final Key? nonUniqueKey = _firstNonUniqueKey(items);
	if (nonUniqueKey != null)
	throw FlutterError('Duplicate key found: $nonUniqueKey.');
	return true;
	}());
	return false;
	}

	/// Asserts that the given context has a [Table] ancestor.
	///
	/// Used by [TableRowInkWell] to make sure that it is only used in an appropriate context.
	///
	/// To invoke this function, use the following pattern, typically in the
	/// relevant Widget's build method:
	///
	/// ```dart
	/// assert(debugCheckHasTable(context));
	/// ```
	///
	/// This method can be expensive (it walks the element tree).
	///
	/// Does nothing if asserts are disabled. Always returns true.
	bool debugCheckHasTable(BuildContext context) {
	assert(() {
	if (context.widget is! Table && context.findAncestorWidgetOfExactType<Table>() == null) {
	throw FlutterError.fromParts(<DiagnosticsNode>[
	ErrorSummary('No Table widget found.'),
	ErrorDescription('${context.widget.runtimeType} widgets require a Table widget ancestor.'),
	context.describeWidget('The specific widget that could not find a Table ancestor was'),
	context.describeOwnershipChain('The ownership chain for the affected widget is'),
	]);
	}
	return true;
	}());
	return true;
	}

	/// Asserts that the given context has a [MediaQuery] ancestor.
	///
	/// Used by various widgets to make sure that they are only used in an
	/// appropriate context.
	///
	/// To invoke this function, use the following pattern, typically in the
	/// relevant Widget's build method:
	///
	/// ```dart
	/// assert(debugCheckHasMediaQuery(context));
	/// ```
	///
	/// Does nothing if asserts are disabled. Always returns true.
	bool debugCheckHasMediaQuery(BuildContext context) {
	assert(() {
	if (context.widget is! MediaQuery && context.getElementForInheritedWidgetOfExactType<MediaQuery>() == null) {
	throw FlutterError.fromParts(<DiagnosticsNode>[
	ErrorSummary('No MediaQuery widget ancestor found.'),
	ErrorDescription('${context.widget.runtimeType} widgets require a MediaQuery widget ancestor.'),
	context.describeWidget('The specific widget that could not find a MediaQuery ancestor was'),
	context.describeOwnershipChain('The ownership chain for the affected widget is'),
	ErrorHint(
	'No MediaQuery ancestor could be found starting from the context '
	'that was passed to MediaQuery.of(). This can happen because you '
	'have not added a WidgetsApp, CupertinoApp, or MaterialApp widget '
	'(those widgets introduce a MediaQuery), or it can happen if the '
	'context you use comes from a widget above those widgets.',
	),
	]);
	}
	return true;
	}());
	return true;
	}

	/// Asserts that the given context has a [Directionality] ancestor.
	///
	/// Used by various widgets to make sure that they are only used in an
	/// appropriate context.
	///
	/// To invoke this function, use the following pattern, typically in the
	/// relevant Widget's build method:
	///
	/// ```dart
	/// assert(debugCheckHasDirectionality(context));
	/// ```
	///
	/// To improve the error messages you can add some extra color using the
	/// named arguments.
	///
	/// * why: explain why the direction is needed, for example "to resolve
	/// the 'alignment' argument". Should be an adverb phrase describing why.
	/// * hint: explain why this might be happening, for example "The default
	/// value of the 'alignment' argument of the $runtimeType widget is an
	/// AlignmentDirectional value.". Should be a fully punctuated sentence.
	/// * alternative: provide additional advice specific to the situation,
	/// especially an alternative to providing a Directionality ancestor.
	/// For example, "Alternatively, consider specifying the 'textDirection'
	/// argument.". Should be a fully punctuated sentence.
	///
	/// Each one can be null, in which case it is skipped (this is the default).
	/// If they are non-null, they are included in the order above, interspersed
	/// with the more generic advice regarding [Directionality].
	///
	/// Does nothing if asserts are disabled. Always returns true.
	bool debugCheckHasDirectionality(BuildContext context, { String? why, String? hint, String? alternative }) {
	assert(() {
	if (context.widget is! Directionality && context.getElementForInheritedWidgetOfExactType<Directionality>() == null) {
	why = why == null ? '' : ' $why';
	throw FlutterError.fromParts(<DiagnosticsNode>[
	ErrorSummary('No Directionality widget found.'),
	ErrorDescription('${context.widget.runtimeType} widgets require a Directionality widget ancestor$why.\n'),
	if (hint != null)
	ErrorHint(hint),
	context.describeWidget('The specific widget that could not find a Directionality ancestor was'),
	context.describeOwnershipChain('The ownership chain for the affected widget is'),
	ErrorHint(
	'Typically, the Directionality widget is introduced by the MaterialApp '
	'or WidgetsApp widget at the top of your application widget tree. It '
	'determines the ambient reading direction and is used, for example, to '
	'determine how to lay out text, how to interpret "start" and "end" '
	'values, and to resolve EdgeInsetsDirectional, '
	'AlignmentDirectional, and other *Directional objects.',
	),
	if (alternative != null)
	ErrorHint(alternative),
	]);
	}
	return true;
	}());
	return true;
	}

	/// Asserts that the `built` widget is not null.
	///
	/// Used when the given `widget` calls a builder function to check that the
	/// function returned a non-null value, as typically required.
	///
	/// Does nothing when asserts are disabled.
	void debugWidgetBuilderValue(Widget widget, Widget? built) {
	assert(() {
	if (built == null) {
	throw FlutterError.fromParts(<DiagnosticsNode>[
	ErrorSummary('A build function returned null.'),
	DiagnosticsProperty<Widget>('The offending widget is', widget, style: DiagnosticsTreeStyle.errorProperty),
	ErrorDescription('Build functions must never return null.'),
	ErrorHint(
	'To return an empty space that causes the building widget to fill available room, return "Container()". '
	'To return an empty space that takes as little room as possible, return "Container(width: 0.0, height: 0.0)".',
	),
	]);
	}
	if (widget == built) {
	throw FlutterError.fromParts(<DiagnosticsNode>[
	ErrorSummary('A build function returned context.widget.'),
	DiagnosticsProperty<Widget>('The offending widget is', widget, style: DiagnosticsTreeStyle.errorProperty),
	ErrorDescription(
	'Build functions must never return their BuildContext parameter\'s widget or a child that contains "context.widget". '
	'Doing so introduces a loop in the widget tree that can cause the app to crash.',
	),
	]);
	}
	return true;
	}());
	}

	/// Asserts that the given context has a [Localizations] ancestor that contains
	/// a [WidgetsLocalizations] delegate.
	///
	/// To call this function, use the following pattern, typically in the
	/// relevant Widget's build method:
	///
	/// ```dart
	/// assert(debugCheckHasWidgetsLocalizations(context));
	/// ```
	///
	/// Does nothing if asserts are disabled. Always returns true.
	bool debugCheckHasWidgetsLocalizations(BuildContext context) {
	assert(() {
	if (Localizations.of<WidgetsLocalizations>(context, WidgetsLocalizations) == null) {
	throw FlutterError.fromParts(<DiagnosticsNode>[
	ErrorSummary('No WidgetsLocalizations found.'),
	ErrorDescription(
	'${context.widget.runtimeType} widgets require WidgetsLocalizations '
	'to be provided by a Localizations widget ancestor.',
	),
	ErrorDescription(
	'The widgets library uses Localizations to generate messages, '
	'labels, and abbreviations.',
	),
	ErrorHint(
	'To introduce a WidgetsLocalizations, either use a '
	'WidgetsApp at the root of your application to include them '
	'automatically, or add a Localization widget with a '
	'WidgetsLocalizations delegate.',
	),
	...context.describeMissingAncestor(expectedAncestorType: WidgetsLocalizations),
	]);
	}
	return true;
	}());
	return true;
	}

	/// Asserts that the given context has an [Overlay] ancestor.
	///
	/// To call this function, use the following pattern, typically in the
	/// relevant Widget's build method:
	///
	/// ```dart
	/// assert(debugCheckHasOverlay(context));
	/// ```
	///
	/// This method can be expensive (it walks the element tree).
	///
	/// Does nothing if asserts are disabled. Always returns true.
	bool debugCheckHasOverlay(BuildContext context) {
	assert(() {
	if (context.widget is! Overlay && context.findAncestorWidgetOfExactType<Overlay>() == null) {
	throw FlutterError.fromParts(<DiagnosticsNode>[
	ErrorSummary('No Overlay widget found.'),
	ErrorDescription(
	'${context.widget.runtimeType} widgets require an Overlay '
	'widget ancestor.\n'
	'An overlay lets widgets float on top of other widget children.',
	),
	ErrorHint(
	'To introduce an Overlay widget, you can either directly '
	'include one, or use a widget that contains an Overlay itself, '
	'such as a Navigator, WidgetApp, MaterialApp, or CupertinoApp.',
	),
	...context.describeMissingAncestor(expectedAncestorType: Overlay),
	]);
	}
	return true;
	}());
	return true;
	}

	/// Returns true if none of the widget library debug variables have been changed.
	///
	/// This function is used by the test framework to ensure that debug variables
	/// haven't been inadvertently changed.
	///
	/// See [the widgets library](widgets/widgets-library.html) for a complete list.
	bool debugAssertAllWidgetVarsUnset(String reason) {
	assert(() {
	if (debugPrintRebuildDirtyWidgets \|\|
	debugPrintBuildScope \|\|
	debugPrintScheduleBuildForStacks \|\|
	debugPrintGlobalKeyedWidgetLifecycle \|\|
	debugProfileBuildsEnabled \|\|
	debugHighlightDeprecatedWidgets) {
	throw FlutterError(reason);
	}
	return true;
	}());
	return true;
	}