If a mouse event is targeting an iframe, forward it to the iframe's inner window

Fixes #8759.

This adds a slow path for cases where the compositor's layer-based hit testing
is incorrect.  To optimize for this case, we could instead replace the
layer hit testing with display-list hit testing done in the paint task.

2 files changed, 39 insertions, 4 deletions

diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 0887cd8b1e3..0e790188320 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -5,12 +5,15 @@
 use document_loader::{DocumentLoader, LoadType};
 use dom::attr::{Attr, AttrValue};
 use dom::bindings::cell::DOMRefCell;
+use dom::bindings::codegen::Bindings::DOMRectBinding::DOMRectMethods;
 use dom::bindings::codegen::Bindings::DocumentBinding;
 use dom::bindings::codegen::Bindings::DocumentBinding::{DocumentMethods, DocumentReadyState};
+use dom::bindings::codegen::Bindings::ElementBinding::ElementMethods;
 use dom::bindings::codegen::Bindings::EventBinding::EventMethods;
 use dom::bindings::codegen::Bindings::EventHandlerBinding::EventHandlerNonNull;
 use dom::bindings::codegen::Bindings::EventHandlerBinding::OnErrorEventHandlerNonNull;
 use dom::bindings::codegen::Bindings::EventTargetBinding::EventTargetMethods;
+use dom::bindings::codegen::Bindings::HTMLIFrameElementBinding::HTMLIFrameElementMethods;
 use dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
 use dom::bindings::codegen::Bindings::NodeFilterBinding::NodeFilter;
 use dom::bindings::codegen::Bindings::PerformanceBinding::PerformanceMethods;
@@ -604,7 +607,7 @@ impl Document {
 
     pub fn handle_mouse_event(&self,
                               js_runtime: *mut JSRuntime,
-                              _button: MouseButton,
+                              button: MouseButton,
                               client_point: Point2D<f32>,
                               mouse_event_type: MouseEventType) {
         let mouse_event_type_string = match mouse_event_type {
@@ -635,6 +638,21 @@ impl Document {
             },
         };
 
+        // If the target is an iframe, forward the event to the child document.
+        if let Some(iframe) = el.downcast::<HTMLIFrameElement>() {
+            if let Some(pipeline_id) = iframe.pipeline_id() {
+                let rect = iframe.upcast::<Element>().GetBoundingClientRect();
+                let child_origin = Point2D::new(rect.X() as f32, rect.Y() as f32);
+                let child_point = client_point - child_origin;
+
+                let event = ConstellationMsg::ForwardMouseButtonEvent(pipeline_id,
+                                                                      mouse_event_type,
+                                                                      button, child_point);
+                self.window.constellation_chan().0.send(event).unwrap();
+            }
+            return;
+        }
+
         let node = el.upcast::<Node>();
         debug!("{} on {:?}", mouse_event_type_string, node.debug_str());
         // Prevent click event if form control element is disabled.
@@ -767,11 +785,23 @@ impl Document {
         if mouse_over_addresses.len() > 0 {
             let top_most_node = node::from_untrusted_node_address(js_runtime,
                                                                   mouse_over_addresses[0]);
+            let client_point = client_point.unwrap(); // Must succeed because hit test succeeded.
 
-            let target = top_most_node.upcast();
-            if let Some(client_point) = client_point {
-                self.fire_mouse_event(client_point, target, "mousemove".to_owned());
+            // If the target is an iframe, forward the event to the child document.
+            if let Some(iframe) = top_most_node.downcast::<HTMLIFrameElement>() {
+                if let Some(pipeline_id) = iframe.pipeline_id() {
+                    let rect = iframe.upcast::<Element>().GetBoundingClientRect();
+                    let child_origin = Point2D::new(rect.X() as f32, rect.Y() as f32);
+                    let child_point = client_point - child_origin;
+
+                    let event = ConstellationMsg::ForwardMouseMoveEvent(pipeline_id, child_point);
+                    self.window.constellation_chan().0.send(event).unwrap();
+                }
+                return;
             }
+
+            let target = top_most_node.upcast();
+            self.fire_mouse_event(client_point, target, "mousemove".to_owned());
         }
 
         // Store the current mouse over targets for next frame
diff --git a/components/script/dom/htmliframeelement.rs b/components/script/dom/htmliframeelement.rs
index 78400b6d49a..fe07d28a198 100644
--- a/components/script/dom/htmliframeelement.rs
+++ b/components/script/dom/htmliframeelement.rs
@@ -186,6 +186,11 @@ impl HTMLIFrameElement {
     }
 
     #[inline]
+    pub fn pipeline_id(&self) -> Option<PipelineId> {
+        self.pipeline_id.get()
+    }
+
+    #[inline]
     pub fn subpage_id(&self) -> Option<SubpageId> {
         self.subpage_id.get()
     }