LookupBoundary (#116429)

* LookupBoundary simplified

* tests

* doc and impl complete

* doc fixes

* add more tests

* review

* empty

packages/flutter/lib/src/widgets/framework.dart

@@ -2020,6 +2020,13 @@ class _InactiveElements {
 /// this callback.
 typedef ElementVisitor = void Function(Element element);
 
+/// Signature for the callback to [BuildContext.visitAncestorElements].
+///
+/// The argument is the ancestor being visited.
+///
+/// Return false to stop the walk.
+typedef ConditionalElementVisitor = bool Function(Element element);
+
 /// A handle to the location of a widget in the widget tree.
 ///
 /// This class presents a set of methods that can be used from
@@ -2221,7 +2228,7 @@ abstract class BuildContext {
   ///
   /// All of the qualifications about when [dependOnInheritedWidgetOfExactType] can
   /// be called apply to this method as well.
-  InheritedWidget dependOnInheritedElement(InheritedElement ancestor, { Object aspect });
+  InheritedWidget dependOnInheritedElement(InheritedElement ancestor, { Object? aspect });
 
   /// Obtains the nearest widget of the given type `T`, which must be the type of a
   /// concrete [InheritedWidget] subclass, and registers this build context with
@@ -2229,6 +2236,7 @@ abstract class BuildContext {
   /// type is introduced, or the widget goes away), this build context is
   /// rebuilt so that it can obtain new values from that widget.
   ///
+  /// {@template flutter.widgets.BuildContext.dependOnInheritedWidgetOfExactType}
   /// This is typically called implicitly from `of()` static methods, e.g.
   /// [Theme.of].
   ///
@@ -2262,6 +2270,7 @@ abstract class BuildContext {
   /// [InheritedWidget] subclasses that supports partial updates, like
   /// [InheritedModel]. It specifies what "aspect" of the inherited
   /// widget this context depends on.
+  /// {@endtemplate}
   T? dependOnInheritedWidgetOfExactType<T extends InheritedWidget>({ Object? aspect });
 
   /// Obtains the element corresponding to the nearest widget of the given type `T`,
@@ -2269,6 +2278,7 @@ abstract class BuildContext {
   ///
   /// Returns null if no such element is found.
   ///
+  /// {@template flutter.widgets.BuildContext.getElementForInheritedWidgetOfExactType}
   /// Calling this method is O(1) with a small constant factor.
   ///
   /// This method does not establish a relationship with the target in the way
@@ -2280,11 +2290,13 @@ abstract class BuildContext {
   /// [dependOnInheritedWidgetOfExactType] in [State.didChangeDependencies]. It is
   /// safe to use this method from [State.deactivate], which is called whenever
   /// the widget is removed from the tree.
+  /// {@endtemplate}
   InheritedElement? getElementForInheritedWidgetOfExactType<T extends InheritedWidget>();
 
   /// Returns the nearest ancestor widget of the given type `T`, which must be the
   /// type of a concrete [Widget] subclass.
   ///
+  /// {@template flutter.widgets.BuildContext.findAncestorWidgetOfExactType}
   /// In general, [dependOnInheritedWidgetOfExactType] is more useful, since
   /// inherited widgets will trigger consumers to rebuild when they change. This
   /// method is appropriate when used in interaction event handlers (e.g.
@@ -2306,11 +2318,13 @@ abstract class BuildContext {
   ///
   /// Returns null if a widget of the requested type does not appear in the
   /// ancestors of this context.
+  /// {@endtemplate}
   T? findAncestorWidgetOfExactType<T extends Widget>();
 
   /// Returns the [State] object of the nearest ancestor [StatefulWidget] widget
   /// that is an instance of the given type `T`.
   ///
+  /// {@template flutter.widgets.BuildContext.findAncestorStateOfType}
   /// This should not be used from build methods, because the build context will
   /// not be rebuilt if the value that would be returned by this method changes.
   /// In general, [dependOnInheritedWidgetOfExactType] is more appropriate for such
@@ -2332,6 +2346,7 @@ abstract class BuildContext {
   /// because the widget tree is no longer stable at that time. To refer to
   /// an ancestor from one of those methods, save a reference to the ancestor
   /// by calling [findAncestorStateOfType] in [State.didChangeDependencies].
+  /// {@endtemplate}
   ///
   /// {@tool snippet}
   ///
@@ -2344,17 +2359,20 @@ abstract class BuildContext {
   /// Returns the [State] object of the furthest ancestor [StatefulWidget] widget
   /// that is an instance of the given type `T`.
   ///
+  /// {@template flutter.widgets.BuildContext.findRootAncestorStateOfType}
   /// Functions the same way as [findAncestorStateOfType] but keeps visiting subsequent
   /// ancestors until there are none of the type instance of `T` remaining.
   /// Then returns the last one found.
   ///
   /// This operation is O(N) as well though N is the entire widget tree rather than
   /// a subtree.
+  /// {@endtemplate}
   T? findRootAncestorStateOfType<T extends State>();
 
   /// Returns the [RenderObject] object of the nearest ancestor [RenderObjectWidget] widget
   /// that is an instance of the given type `T`.
   ///
+  /// {@template flutter.widgets.BuildContext.findAncestorRenderObjectOfType}
   /// This should not be used from build methods, because the build context will
   /// not be rebuilt if the value that would be returned by this method changes.
   /// In general, [dependOnInheritedWidgetOfExactType] is more appropriate for such
@@ -2371,13 +2389,16 @@ abstract class BuildContext {
   /// because the widget tree is no longer stable at that time. To refer to
   /// an ancestor from one of those methods, save a reference to the ancestor
   /// by calling [findAncestorRenderObjectOfType] in [State.didChangeDependencies].
+  /// {@endtemplate}
   T? findAncestorRenderObjectOfType<T extends RenderObject>();
 
   /// Walks the ancestor chain, starting with the parent of this build context's
-  /// widget, invoking the argument for each ancestor. The callback is given a
-  /// reference to the ancestor widget's corresponding [Element] object. The
-  /// walk stops when it reaches the root widget or when the callback returns
-  /// false. The callback must not return null.
+  /// widget, invoking the argument for each ancestor.
+  ///
+  /// {@template flutter.widgets.BuildContext.visitAncestorElements}
+  /// The callback is given a reference to the ancestor widget's corresponding
+  /// [Element] object. The walk stops when it reaches the root widget or when
+  /// the callback returns false. The callback must not return null.
   ///
   /// This is useful for inspecting the widget tree.
   ///
@@ -2387,10 +2408,12 @@ abstract class BuildContext {
   /// because the element tree is no longer stable at that time. To refer to
   /// an ancestor from one of those methods, save a reference to the ancestor
   /// by calling [visitAncestorElements] in [State.didChangeDependencies].
-  void visitAncestorElements(bool Function(Element element) visitor);
+  /// {@endtemplate}
+  void visitAncestorElements(ConditionalElementVisitor visitor);
 
   /// Walks the children of this widget.
   ///
+  /// {@template flutter.widgets.BuildContext.visitChildElements}
   /// This is useful for applying changes to children after they are built
   /// without waiting for the next frame, especially if the children are known,
   /// and especially if there is exactly one child (as is always the case for
@@ -2408,6 +2431,7 @@ abstract class BuildContext {
   /// significantly cheaper to use an [InheritedWidget] and have the descendants
   /// pull data down, than it is to use [visitChildElements] recursively to push
   /// data down to them.
+  /// {@endtemplate}
   void visitChildElements(ElementVisitor visitor);
 
   /// Start bubbling this notification at the given build context.
@@ -4452,7 +4476,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
   }
 
   @override
-  void visitAncestorElements(bool Function(Element element) visitor) {
+  void visitAncestorElements(ConditionalElementVisitor visitor) {
     assert(_debugCheckStateIsActiveForAncestorLookup());
     Element? ancestor = _parent;
     while (ancestor != null && visitor(ancestor)) {

packages/flutter/lib/widgets.dart

@@ -72,6 +72,7 @@ export 'src/widgets/keyboard_listener.dart';
 export 'src/widgets/layout_builder.dart';
 export 'src/widgets/list_wheel_scroll_view.dart';
 export 'src/widgets/localizations.dart';
+export 'src/widgets/lookup_boundary.dart';
 export 'src/widgets/magnifier.dart';
 export 'src/widgets/media_query.dart';
 export 'src/widgets/modal_barrier.dart';