Send mouse move events to the the previous layer when directing events to a new one for the first time. Resolves #7865.

components/compositing/compositor.rs

@@ -35,7 +35,7 @@ use msg::constellation_msg::{NavigationDirection, PipelineId, WindowSizeData};
 use pipeline::CompositionPipeline;
 use profile_traits::mem::{self, ReportKind, Reporter, ReporterRequest};
 use profile_traits::time::{self, ProfilerCategory, profile};
-use script_traits::CompositorEvent::TouchEvent;
+use script_traits::CompositorEvent::{MouseMoveEvent, TouchEvent};
 use script_traits::{ConstellationControlMsg, LayoutControlMsg, MouseButton};
 use script_traits::{TouchEventType, TouchId};
 use scrolling::ScrollingTimerProxy;
@@ -183,6 +183,9 @@ pub struct IOCompositor<Window: WindowMethods> {
     /// Pipeline IDs of subpages that the compositor has seen in a layer tree but which have not
     /// yet been painted.
     pending_subpages: HashSet<PipelineId>,
+
+    /// The id of the pipeline that was last sent a mouse move event, if any.
+    last_mouse_move_recipient: Option<PipelineId>,
 }
 
 /// The states of the touch input state machine.
@@ -352,6 +355,7 @@ impl<Window: WindowMethods> IOCompositor<Window> {
             ready_to_save_state: ReadyState::Unknown,
             surface_map: SurfaceMap::new(BUFFER_MAP_SIZE),
             pending_subpages: HashSet::new(),
+            last_mouse_move_recipient: None,
         }
     }
 
@@ -1169,8 +1173,24 @@ impl<Window: WindowMethods> IOCompositor<Window> {
         }
 
         match self.find_topmost_layer_at_point(cursor / self.scene.scale) {
-            Some(result) => result.layer.send_mouse_move_event(self, result.point),
-            None => {},
+            Some(result) => {
+                // In the case that the mouse was previously over a different layer,
+                // that layer must update its state.
+                if let Some(last_pipeline_id) = self.last_mouse_move_recipient {
+                    if last_pipeline_id != result.layer.pipeline_id() {
+                        if let Some(pipeline) = self.pipeline(last_pipeline_id) {
+                            let _ = pipeline.script_chan
+                                            .send(ConstellationControlMsg::SendEvent(
+                                                last_pipeline_id.clone(),
+                                                MouseMoveEvent(None)));
+                        }
+                    }
+                }
+
+                self.last_mouse_move_recipient = Some(result.layer.pipeline_id());
+                result.layer.send_mouse_move_event(self, result.point);
+            }
+            None => {}
         }
     }
 

components/compositing/compositor_layer.rs

@@ -385,7 +385,7 @@ impl CompositorLayer for Layer<CompositorData> {
                                      compositor: &IOCompositor<Window>,
                                      cursor: TypedPoint2D<LayerPixel, f32>)
                                      where Window: WindowMethods {
-        self.send_event(compositor, MouseMoveEvent(cursor.to_untyped()));
+        self.send_event(compositor, MouseMoveEvent(Some(cursor.to_untyped())));
     }
 
     fn send_event<Window>(&self,

components/script/dom/document.rs

@@ -668,10 +668,12 @@ impl Document {
 
     pub fn handle_mouse_move_event(&self,
                                js_runtime: *mut JSRuntime,
-                               point: Point2D<f32>,
+                               point: Option<Point2D<f32>>,
                                prev_mouse_over_targets: &mut RootedVec<JS<Element>>) {
         // Build a list of elements that are currently under the mouse.
-        let mouse_over_addresses = self.get_nodes_under_mouse(&point);
+        let mouse_over_addresses = point.as_ref()
+                                        .map(|point| self.get_nodes_under_mouse(point))
+                                        .unwrap_or(vec![]);
         let mut mouse_over_targets = mouse_over_addresses.iter().map(|node_address| {
             node::from_untrusted_node_address(js_runtime, *node_address)
                 .inclusive_ancestors()
@@ -690,7 +692,11 @@ impl Document {
 
                     let target = target_ref.upcast();
 
-                    self.fire_mouse_event(point, &target, "mouseout".to_owned());
+                    // FIXME: we should be dispatching this event but we lack an actual
+                    //        point to pass to it.
+                    if let Some(point) = point {
+                        self.fire_mouse_event(point, &target, "mouseout".to_owned());
+                    }
                 }
             }
         }
@@ -704,8 +710,9 @@ impl Document {
 
                 let target = target.upcast();
 
-                self.fire_mouse_event(point, target, "mouseover".to_owned());
-
+                if let Some(point) = point {
+                    self.fire_mouse_event(point, target, "mouseover".to_owned());
+                }
             }
         }
 
@@ -715,7 +722,9 @@ impl Document {
                 node::from_untrusted_node_address(js_runtime, mouse_over_addresses[0]);
 
             let target = top_most_node.upcast();
-            self.fire_mouse_event(point, target, "mousemove".to_owned());
+            if let Some(point) = point {
+                self.fire_mouse_event(point, target, "mousemove".to_owned());
+            }
         }
 
         // Store the current mouse over targets for next frame

components/script_traits/lib.rs

@@ -187,8 +187,8 @@ pub enum CompositorEvent {
     MouseDownEvent(MouseButton, Point2D<f32>),
     /// A mouse button was released on a point.
     MouseUpEvent(MouseButton, Point2D<f32>),
-    /// The mouse was moved over a point.
-    MouseMoveEvent(Point2D<f32>),
+    /// The mouse was moved over a point (or was moved out of the recognizable region).
+    MouseMoveEvent(Option<Point2D<f32>>),
     /// A touch event was generated with a touch ID and location.
     TouchEvent(TouchEventType, TouchId, Point2D<f32>),
     /// A key was pressed.