diff --git a/packages/flutter/lib/src/rendering/node.dart b/packages/flutter/lib/src/rendering/node.dart index dd7433fe7ec..fed8f6c7648 100644 --- a/packages/flutter/lib/src/rendering/node.dart +++ b/packages/flutter/lib/src/rendering/node.dart @@ -4,54 +4,49 @@ import 'package:meta/meta.dart'; -/// An abstract node in a tree +/// An abstract node in a tree. /// /// AbstractNode has as notion of depth, attachment, and parent, but does not /// have a model for children. /// -/// * When a subclass is changing the parent of a child, it should -/// call either parent.adoptChild(child) or parent.dropChild(child) -/// as appropriate. Subclasses should expose an API for -/// manipulating the tree if you want to (e.g. a setter for a -/// 'child' property, or an 'add()' method to manipulate a list). +/// When a subclass is changing the parent of a child, it should call either +/// `parent.adoptChild(child)` or `parent.dropChild(child)` as appropriate. +/// Subclasses can expose an API for manipulating the tree if desired (e.g. a +/// setter for a `child` property, or an `add()` method to manipulate a list). /// -/// * You can see the current parent by querying 'parent'. +/// The current parent node is exposed by the [parent] property. /// -/// * You can see the current attachment state by querying -/// 'attached'. The root of any tree that is to be considered -/// attached should be manually attached by calling 'attach()'. -/// Other than that, don't call 'attach()' or 'detach()'. This is -/// all managed automatically assuming you call the 'adoptChild()' -/// and 'dropChild()' methods appropriately. +/// The current attachment state is exposed by [attached]. The root of any tree +/// that is to be considered attached should be manually attached by calling +/// [attach]. Other than that, the [attach] and [detach] methods should not be +/// called directly; attachment is managed automatically by the aforementioned +/// [adoptChild] and [dropChild] methods. /// -/// * Subclasses that have children must override 'attach()' and -/// 'detach()' as described below. +/// Subclasses that have children must override [attach] and [detach] as +/// described in the documentation for those methods. /// -/// * Nodes always have a 'depth' greater than their ancestors'. -/// There's no guarantee regarding depth between siblings. The -/// depth of a node is used to ensure that nodes are processed in -/// depth order. The 'depth' of a child can be more than one -/// greater than the 'depth' of the parent, because the 'depth' -/// values are never decreased: all that matters is that it's -/// greater than the parent. Consider a tree with a root node A, a -/// child B, and a grandchild C. Initially, A will have 'depth' 0, -/// B 'depth' 1, and C 'depth' 2. If C is moved to be a child of A, -/// sibling of B, then the numbers won't change. C's 'depth' will -/// still be 2. This is all managed automatically assuming you call -/// 'adoptChild()' and 'dropChild()' appropriately. +/// Nodes always have a [depth] greater than their ancestors'. There's no +/// guarantee regarding depth between siblings. The depth of a node is used to +/// ensure that nodes are processed in depth order. The [depth] of a child can +/// be more than one greater than the [depth] of the parent, because the [depth] +/// values are never decreased: all that matters is that it's greater than the +/// parent. Consider a tree with a root node A, a child B, and a grandchild C. +/// Initially, A will have [depth] 0, B [depth] 1, and C [depth] 2. If C is +/// moved to be a child of A, sibling of B, then the numbers won't change. C's +/// [depth] will still be 2. The [depth] is automatically maintained by the +/// [adoptChild] and [dropChild] methods. class AbstractNode { - - // AbstractNode represents a node in a tree. - // The AbstractNode protocol is described in README.md. - - int _depth = 0; /// The depth of this node in the tree. /// /// The depth of nodes in a tree monotonically increases as you traverse down /// the trees. int get depth => _depth; + int _depth = 0; - /// Call only from overrides of [redepthChildren] + /// Adjust the [depth] of the given [child] to be greated than this node's own + /// [depth]. + /// + /// Only call this method from overrides of [redepthChildren]. @protected void redepthChild(AbstractNode child) { assert(child.owner == owner); @@ -61,23 +56,27 @@ class AbstractNode { } } - /// Override this method in subclasses with child nodes to call - /// redepthChild(child) for each child. Do not call directly. + /// Adjust the [depth] of this node's children, if any. + /// + /// Override this method in subclasses with child nodes to call [redepthChild] + /// for each child. Do not call this method directly. void redepthChildren() { } - Object _owner; /// The owner for this node (null if unattached). + /// + /// The entire subtree that this node belongs to will have the same owner. Object get owner => _owner; + Object _owner; /// Whether this node is in a tree whose root is attached to something. bool get attached => _owner != null; /// Mark this node as attached to the given owner. /// - /// Typically called only from the parent's attach(), and to mark the root of - /// a tree attached. + /// Typically called only from the [parent]'s [attach] method, and by the + /// [owner] to mark the root of a tree as attached. /// - /// Subclasses with children should attach all their children to the same + /// Subclasses with children should [attach] all their children to the same /// [owner] whenever this method is called. @mustCallSuper void attach(@checked Object owner) { @@ -88,10 +87,10 @@ class AbstractNode { /// Mark this node as detached. /// - /// Typically called only from the parent's detach(), and to mark the root of - /// a tree detached. + /// Typically called only from the [parent]'s [detach], and by the [owner] to + /// mark the root of a tree as detached. /// - /// Subclasses with children should detach all their children whenever this + /// Subclasses with children should [detach] all their children whenever this /// method is called. @mustCallSuper void detach() { @@ -99,10 +98,12 @@ class AbstractNode { _owner = null; } - AbstractNode _parent; /// The parent of this node in the tree. AbstractNode get parent => _parent; + AbstractNode _parent; + /// Mark the given node as being a child of this node. + /// /// Subclasses should call this function when they acquire a new child. @protected @mustCallSuper @@ -122,6 +123,8 @@ class AbstractNode { redepthChild(child); } + /// Disconnect the given node from this node. + /// /// Subclasses should call this function when they lose a child. @protected @mustCallSuper