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// 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.
class AbstractNode {
// AbstractNode represents a node in a tree.
// The AbstractNode protocol is described in README.md.
int _depth = 0;
int get depth => _depth;
void redepthChild(AbstractNode child) { // internal, do not call
assert(child._attached == _attached);
if (child._depth <= _depth) {
child._depth = _depth + 1;
child.redepthChildren();
}
}
void redepthChildren() { // internal, do not call
// override this in subclasses with child nodes
// simply call redepthChild(child) for each child
}
bool _attached = false;
bool get attached => _attached;
void attach() {
// override this in subclasses with child nodes
// simply call attach() for each child then call your superclass
_attached = true;
attachChildren();
}
attachChildren() { } // workaround for lack of inter-class mixins in Dart
void detach() {
// override this in subclasses with child nodes
// simply call detach() for each child then call your superclass
_attached = false;
detachChildren();
}
detachChildren() { } // workaround for lack of inter-class mixins in Dart
AbstractNode _parent;
AbstractNode get parent => _parent;
void adoptChild(AbstractNode child) { // only for use by subclasses
assert(child != null);
assert(child._parent == null);
child._parent = this;
if (attached)
child.attach();
redepthChild(child);
}
void dropChild(AbstractNode child) { // only for use by subclasses
assert(child != null);
assert(child._parent == this);
assert(child.attached == attached);
child._parent = null;
if (attached)
child.detach();
}
}