layout: Expose whether the element was rendered in content_box_query …

…to script.

But don't change the API yet.

components/layout/query.rs

@@ -54,7 +54,7 @@ pub struct LayoutThreadData {
     pub stylist: Arc<Stylist>,
 
     /// A queued response for the union of the content boxes of a node.
-    pub content_box_response: Rect<Au>,
+    pub content_box_response: Option<Rect<Au>>,
 
     /// A queued response for the content boxes of a node.
     pub content_boxes_response: Vec<Rect<Au>>,
@@ -384,15 +384,12 @@ impl FragmentBorderBoxIterator for MarginRetrievingFragmentBorderBoxIterator {
 }
 
 pub fn process_content_box_request<N: LayoutNode>(
-        requested_node: N, layout_root: &mut Flow) -> Rect<Au> {
+        requested_node: N, layout_root: &mut Flow) -> Option<Rect<Au>> {
     // FIXME(pcwalton): This has not been updated to handle the stacking context relative
     // stuff. So the position is wrong in most cases.
     let mut iterator = UnioningFragmentBorderBoxIterator::new(requested_node.opaque());
     sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator);
-    match iterator.rect {
-        Some(rect) => rect,
-        None       => Rect::zero()
-    }
+    iterator.rect
 }
 
 pub fn process_content_boxes_request<N: LayoutNode>(requested_node: N, layout_root: &mut Flow)

components/layout_thread/lib.rs

@@ -464,7 +464,7 @@ impl LayoutThread {
                     constellation_chan: constellation_chan,
                     display_list: None,
                     stylist: stylist,
-                    content_box_response: Rect::zero(),
+                    content_box_response: None,
                     content_boxes_response: Vec::new(),
                     client_rect_response: Rect::zero(),
                     hit_test_response: (None, false),
@@ -1012,7 +1012,7 @@ impl LayoutThread {
                 debug!("layout: No root node: bailing");
                 match data.query_type {
                     ReflowQueryType::ContentBoxQuery(_) => {
-                        rw_data.content_box_response = Rect::zero();
+                        rw_data.content_box_response = None;
                     },
                     ReflowQueryType::ContentBoxesQuery(_) => {
                         rw_data.content_boxes_response = Vec::new();

components/script/dom/node.rs

@@ -524,8 +524,12 @@ impl Node {
         TrustedNodeAddress(&*self as *const Node as *const libc::c_void)
     }
 
+    /// Returns the rendered bounding content box if the element is rendered,
+    /// and none otherwise.
     pub fn bounding_content_box(&self) -> Rect<Au> {
-        window_from_node(self).content_box_query(self.to_trusted_node_address())
+        window_from_node(self)
+            .content_box_query(self.to_trusted_node_address())
+            .unwrap_or_else(Rect::zero)
     }
 
     pub fn content_boxes(&self) -> Vec<Rect<Au>> {

components/script/dom/window.rs

@@ -1216,11 +1216,11 @@ impl Window {
         &*self.layout_rpc
     }
 
-    pub fn content_box_query(&self, content_box_request: TrustedNodeAddress) -> Rect<Au> {
+    pub fn content_box_query(&self, content_box_request: TrustedNodeAddress) -> Option<Rect<Au>> {
         if !self.reflow(ReflowGoal::ForScriptQuery,
                         ReflowQueryType::ContentBoxQuery(content_box_request),
                         ReflowReason::Query) {
-            return Rect::zero();
+            return None;
         }
         let ContentBoxResponse(rect) = self.layout_rpc.content_box();
         rect

components/script_layout_interface/rpc.rs

@@ -43,7 +43,7 @@ pub trait LayoutRPC {
     fn text_index(&self) -> TextIndexResponse;
 }
 
-pub struct ContentBoxResponse(pub Rect<Au>);
+pub struct ContentBoxResponse(pub Option<Rect<Au>>);
 
 pub struct ContentBoxesResponse(pub Vec<Rect<Au>>);