Index: sky/sdk/lib/framework/node.dart |
diff --git a/sky/sdk/lib/framework/node.dart b/sky/sdk/lib/framework/node.dart |
index 44c14fe5edfde4cd3f5c68e89b4a3382dedfd1f6..8e772a9d3be4b79a5da20c790d06046a567d92be 100644 |
--- a/sky/sdk/lib/framework/node.dart |
+++ b/sky/sdk/lib/framework/node.dart |
@@ -1,15 +1,33 @@ |
class AbstractNode { |
- // 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. |
+ // AbstractNode represents a node in a tree. |
+ // The AbstractNode protocol is as follows: |
+ // - 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). |
+ // - You can see the current parent by querying 'parent'. |
+ // - 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. |
+ // - Subclasses that have children must override 'attach()' and |
+ // 'detach()' as described below. |
+ // - 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. |
int _depth = 0; |
int get depth => _depth; |