servo: first hack at block layout algorithm

Source-Repo: https://github.com/servo/servo
Source-Revision: 668f28dc15c32c2e27e13c2feec5e5b2e033efe6

servo/src/dom/rcu.rs

@@ -0,0 +1,6 @@
+enum handle<T> = @T;
+
+impl methods<T> for handle<T> {
+    fn get() -> @T { *self }
+}
+

servo/src/layout/base.rs

@@ -0,0 +1,96 @@
+import dom::rcu;
+import dom::rcu::methods;
+
+// FIXME--mut should be inherited
+type point<A> = { mut x: A, mut y: A };
+type size<A> = { mut width: A, mut height: A };
+type rect<A> = { mut origin: point<A>, mut size: size<A> };
+
+enum au = int;
+
+type tree_fields<T> = {
+    parent: option<T>,
+    first_child: option<T>,
+    last_child: option<T>,
+    prev_sibling: option<T>,
+    next_sibling: option<T>
+};
+
+enum box = @{
+    tree: tree_fields<box>,
+    node: node,
+    mut bounds: rect<au>
+};
+
+type node_data = {
+    tree: tree_fields<node>,
+    kind: node_kind,
+
+    // Points to the primary box.  Note that there may be multiple
+    // boxes per DOM node.
+    mut linfo: option<box>,
+};
+
+enum node_kind {
+    nk_div,
+    nk_img(size<au>)
+}
+
+enum node = rcu::handle<node_data>;
+
+iface tree {
+    fn tree_fields() -> tree_fields<self>;
+}
+
+impl of tree for box {
+    fn tree_fields() -> tree_fields<box> {
+        ret self.tree;
+    }
+}
+
+impl of tree for node {
+    fn tree_fields() -> tree_fields<node> {
+        ret (*self).get().tree;
+    }
+}
+
+fn each_child<T:copy tree>(
+    node: T, f: fn(T) -> bool) {
+
+    let mut p = node.tree_fields().first_child;
+    loop {
+        alt p {
+          none { ret; }
+          some(c) {
+            if !f(c) { ret; }
+            p = c.tree_fields().next_sibling;
+          }
+        }
+    }
+}
+
+fn reflow_block(root: box, available_width: au) {
+    // Root here is the root of the reflow, not necessarily the doc as
+    // a whole.
+
+    alt (*root.node).get().kind {
+      nk_img(size) {
+        root.bounds.size = size;
+        ret;
+      }
+
+      nk_div { /* fallthrough */ }
+    }
+
+    let mut current_height = 0;
+    for each_child(root) {|c|
+        let mut blk_available_width = available_width;
+        // FIXME subtract borders, margins, etc
+        c.bounds.origin = {x: au(0), y: au(current_height)};
+        reflow_block(c, blk_available_width);
+        current_height += *c.bounds.size.height;
+    }
+
+    root.bounds.size = {width: available_width, // FIXME
+                        height: au(current_height)};
+}