script: Stop trusting pointers to DOM nodes that layout provides.

Pointers to DOM nodes from layout could go stale if incremental reflow
does not correctly destroy dead nodes. Therefore, we ask the JavaScript
garbage collector to verify that each DOM node is indeed a valid pointer
before calling event handlers on it, and fail otherwise.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/components/script/layout_interface.rs b/src/components/script/layout_interface.rs
index 613e61a3429..b0b9ec479f4 100644
--- a/src/components/script/layout_interface.rs
+++ b/src/components/script/layout_interface.rs
@@ -14,8 +14,9 @@ use geom::rect::Rect;
 use geom::size::Size2D;
 use script_task::{ScriptChan};
 use servo_util::geometry::Au;
-use std::comm::{Chan, SharedChan};
 use std::cmp;
+use std::comm::{Chan, SharedChan};
+use std::libc::c_void;
 use style::Stylesheet;
 
 /// Asynchronous messages that script can send to layout.
@@ -58,9 +59,13 @@ pub enum LayoutQuery {
     HitTestQuery(AbstractNode, Point2D<f32>, Chan<Result<HitTestResponse, ()>>),
 }
 
+/// The address of a node. Layout sends these back. They must be validated via
+/// `from_untrusted_node_address` before they can be used, because we do not trust layout.
+pub type UntrustedNodeAddress = *c_void;
+
 pub struct ContentBoxResponse(Rect<Au>);
 pub struct ContentBoxesResponse(~[Rect<Au>]);
-pub struct HitTestResponse(AbstractNode);
+pub struct HitTestResponse(UntrustedNodeAddress);
 
 /// Determines which part of the 
 #[deriving(Eq, Ord)]