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63d5c73dd1
This gets things off the ground barely enough to show some pixels. These are not pixels that are actually part of the stock app, but it's a start. R=abarth@chromium.org Review URL: https://codereview.chromium.org/1157033006
65 lines
2.2 KiB
Dart
65 lines
2.2 KiB
Dart
class AbstractNode {
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// Nodes always have a 'depth' greater than their ancestors'.
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// There's no guarantee regarding depth between siblings. The depth
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// of a node is used to ensure that nodes are processed in depth
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// order. The 'depth' of a child can be more than one greater than
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// the 'depth' of the parent, because the 'depth' values are never
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// decreased: all that matters is that it's greater than the parent.
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// Consider a tree with a root node A, a child B, and a grandchild
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// C. Initially, A will have 'depth' 0, B 'depth' 1, and C 'depth'
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// 2. If C is moved to be a child of A, sibling of B, then the
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// numbers won't change. C's 'depth' will still be 2.
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int _depth = 0;
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int get depth => _depth;
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void redepthChild(AbstractNode child) { // internal, do not call
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assert(child._attached == _attached);
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if (child._depth <= _depth) {
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child._depth = _depth + 1;
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child.redepthChildren();
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}
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}
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void redepthChildren() { // internal, do not call
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// override this in subclasses with child nodes
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// simply call redepthChild(child) for each child
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}
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bool _attached = false;
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bool get attached => _attached;
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void attach() {
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// override this in subclasses with child nodes
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// simply call attach() for each child then call your superclass
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_attached = true;
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attachChildren();
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}
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attachChildren() { } // workaround for lack of inter-class mixins in Dart
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void detach() {
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// override this in subclasses with child nodes
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// simply call detach() for each child then call your superclass
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_attached = false;
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detachChildren();
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}
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detachChildren() { } // workaround for lack of inter-class mixins in Dart
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AbstractNode _parent;
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AbstractNode get parent => _parent;
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void adoptChild(AbstractNode child) { // only for use by subclasses
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assert(child != null);
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assert(child._parent == null);
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child._parent = this;
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if (attached)
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child.attach();
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redepthChild(child);
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}
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void dropChild(AbstractNode child) { // only for use by subclasses
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assert(child != null);
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assert(child._parent == this);
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assert(child.attached == attached);
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child._parent = null;
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if (attached)
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child.detach();
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}
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}
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