Add util::tree::remove_child, and some tests. Add eq requirement for util::tree::WriteMethods

src/servo/dom/node.rs

@@ -158,6 +158,8 @@ impl NodeScope : tree::WriteMethods<Node> {
         tree::add_child(&self, node, child)
     }
 
+    pure fn eq(a: &Node, b: &Node) -> bool { a == b }
+
     fn with_tree_fields<R>(node: &Node, f: fn(&tree::Tree<Node>) -> R) -> R {
         self.write(node, |n| f(&n.tree))
     }

src/servo/layout/flow.rs

@@ -326,10 +326,11 @@ impl FlowTree : tree::ReadMethods<@FlowContext> {
 
 impl FlowTree : tree::WriteMethods<@FlowContext> {
     fn add_child(parent: @FlowContext, child: @FlowContext) {
-        assert !core::box::ptr_eq(parent, child);
         tree::add_child(&self, parent, child)
     }
 
+    pure fn eq(a: &@FlowContext, b: &@FlowContext) -> bool { core::box::ptr_eq(*a, *b) }
+
     fn with_tree_fields<R>(box: &@FlowContext, f: fn(&tree::Tree<@FlowContext>) -> R) -> R {
         f(&box.d().tree)
     }

src/servo/util/tree.rs

@@ -18,6 +18,7 @@ pub trait ReadMethods<T> {
 
 pub trait WriteMethods<T> {
     fn with_tree_fields<R>(&T, f: fn(&Tree<T>) -> R) -> R;
+    pure fn eq(&T, &T) -> bool;
 }
 
 pub fn each_child<T:Copy,O:ReadMethods<T>>(ops: &O, node: &T, f: fn(&T) -> bool) {
@@ -42,6 +43,7 @@ pub fn empty<T>() -> Tree<T> {
 }
 
 pub fn add_child<T:Copy,O:WriteMethods<T>>(ops: &O, parent: T, child: T) {
+    assert !ops.eq(&parent, &child);
 
     ops.with_tree_fields(&child, |child_tf| {
         match child_tf.parent {
@@ -58,7 +60,6 @@ pub fn add_child<T:Copy,O:WriteMethods<T>>(ops: &O, parent: T, child: T) {
                 parent_tf.first_child = Some(child);
               }
               Some(lc) => {
-                let lc = lc; // satisfy alias checker
                 ops.with_tree_fields(&lc, |lc_tf| {
                     assert lc_tf.next_sibling.is_none();
                     lc_tf.next_sibling = Some(child);
@@ -72,36 +73,90 @@ pub fn add_child<T:Copy,O:WriteMethods<T>>(ops: &O, parent: T, child: T) {
     });
 }
 
+pub fn remove_child<T:Copy,O:WriteMethods<T>>(ops: &O, parent: T, child: T) {
+    do ops.with_tree_fields(&child) |child_tf| {
+        match copy child_tf.parent {
+            None => { fail ~"Not a child"; }
+            Some(parent_n) => {
+                assert ops.eq(&parent, &parent_n);
+
+                // adjust parent fields
+                do ops.with_tree_fields(&parent) |parent_tf| {
+                    match copy parent_tf.first_child {
+                        None => { fail ~"parent had no first child??" },
+                        Some(first_child) if ops.eq(&child, &first_child) => {
+                            parent_tf.first_child = child_tf.next_sibling;
+                        },
+                        Some(_) => {}
+                    };
+                    
+                    match copy parent_tf.last_child {
+                        None => { fail ~"parent had no last child??" },
+                        Some(last_child) if ops.eq(&child, &last_child) => {
+                            parent_tf.last_child = child_tf.prev_sibling;
+                        },
+                        Some(_) => {}
+                    }
+                }
+            }
+        }
+
+        // adjust siblings
+        match child_tf.prev_sibling {
+            None => {},
+            Some(_) => {
+                do ops.with_tree_fields(&child_tf.prev_sibling.get()) |prev_tf| {
+                    prev_tf.next_sibling = child_tf.next_sibling;
+                }
+            }
+        }
+        match child_tf.next_sibling {
+            None => {},
+            Some(_) => {
+                do ops.with_tree_fields(&child_tf.next_sibling.get()) |next_tf| {
+                    next_tf.prev_sibling = child_tf.prev_sibling;
+                }
+            }
+        }
+
+        // clear child 
+        child_tf.parent = None;
+        child_tf.next_sibling = None;
+        child_tf.prev_sibling = None;
+    }
+}
+
 pub fn get_parent<T:Copy,O:ReadMethods<T>>(ops: &O, node: &T) -> Option<T> {
     ops.with_tree_fields(node, |tf| tf.parent)
 }
 
 #[cfg(test)]
 mod test {
-    enum dummy = @{
-        fields: Tree<dummy>,
+    enum dummy = {
+        fields: Tree<@dummy>,
         value: uint
     };
 
     enum dtree { dtree }
 
-    impl dtree : ReadMethods<dummy> {
-        fn with_tree_fields<R>(d: &dummy, f: fn(&Tree<dummy>) -> R) -> R {
+    impl dtree : ReadMethods<@dummy> {
+        fn with_tree_fields<R>(d: &@dummy, f: fn(&Tree<@dummy>) -> R) -> R {
             f(&d.fields)
         }
     }
 
-    impl dtree : WriteMethods<dummy> {
-        fn with_tree_fields<R>(d: &dummy, f: fn(&Tree<dummy>) -> R) -> R {
+    impl dtree : WriteMethods<@dummy> {
+        fn with_tree_fields<R>(d: &@dummy, f: fn(&Tree<@dummy>) -> R) -> R {
             f(&d.fields)
         }
+        pure fn eq(a: &@dummy, b: &@dummy) -> bool { core::box::ptr_eq(*a, *b) }
     }
 
-    fn new_dummy(v: uint) -> dummy {
-        dummy(@{fields: empty(), value: v})
+    fn new_dummy(v: uint) -> @dummy {
+        @dummy({fields: empty(), value: v})
     }
 
-    fn parent_with_3_children() -> {p: dummy, children: ~[dummy]} {
+    fn parent_with_3_children() -> {p: @dummy, children: ~[@dummy]} {
         let children = ~[new_dummy(0u),
                          new_dummy(1u),
                          new_dummy(2u)];
@@ -135,4 +190,54 @@ mod test {
         }
         assert i == 1u;
     }
+
+    #[test]
+    fn remove_first_child() {
+        let {p, children} = parent_with_3_children();
+        remove_child(&dtree, p, children[0]);
+
+        let mut i = 0;
+        for each_child(&dtree, &p) |_c| {
+            i += 1;
+        }
+        assert i == 2;
+    }
+
+    #[test]
+    fn remove_last_child() {
+        let {p, children} = parent_with_3_children();
+        remove_child(&dtree, p, children[2]);
+
+        let mut i = 0;
+        for each_child(&dtree, &p) |_c| {
+            i += 1;
+        }
+        assert i == 2;
+    }
+
+    #[test]
+    fn remove_middle_child() {
+        let {p, children} = parent_with_3_children();
+        remove_child(&dtree, p, children[1]);
+
+        let mut i = 0;
+        for each_child(&dtree, &p) |_c| {
+            i += 1;
+        }
+        assert i == 2;
+    }
+
+    #[test]
+    fn remove_all_child() {
+        let {p, children} = parent_with_3_children();
+        remove_child(&dtree, p, children[0]);
+        remove_child(&dtree, p, children[1]);
+        remove_child(&dtree, p, children[2]);
+
+        let mut i = 0;
+        for each_child(&dtree, &p) |_c| {
+            i += 1;
+        }
+        assert i == 0;
+    }
 }