compositing: Move messages that go over the ScriptListener to go over

an IPC channel instead.

Because this used a boxed trait object to invoke messages across a
process boundary, and boxed trait objects are not supported across IPC,
we spawn a helper thread inside the compositor to perform the marshaling
for us.

components/msg/compositor_msg.rs

@@ -7,6 +7,7 @@ use constellation_msg::{Key, KeyState, KeyModifiers};
 use euclid::point::Point2D;
 use euclid::rect::Rect;
 use euclid::Matrix4;
+use ipc_channel::ipc::IpcSender;
 use layers::platform::surface::NativeDisplay;
 use layers::layers::{BufferRequest, LayerBufferSet};
 use std::fmt::{Formatter, Debug};
@@ -35,7 +36,7 @@ impl FrameTreeId {
     }
 }
 
-#[derive(Clone, PartialEq, Eq, Copy, Hash)]
+#[derive(Clone, PartialEq, Eq, Copy, Hash, Deserialize, Serialize)]
 pub struct LayerId(pub usize, pub u32);
 
 impl Debug for LayerId {
@@ -115,16 +116,47 @@ pub trait PaintListener {
     fn notify_paint_task_exiting(&mut self, pipeline_id: PipelineId);
 }
 
+#[derive(Deserialize, Serialize)]
+pub enum ScriptToCompositorMsg {
+    ScrollFragmentPoint(PipelineId, LayerId, Point2D<f32>),
+    SetTitle(PipelineId, Option<String>),
+    SendKeyEvent(Key, KeyState, KeyModifiers),
+    Exit,
+}
+
 /// The interface used by the script task to tell the compositor to update its ready state,
 /// which is used in displaying the appropriate message in the window's title.
-pub trait ScriptListener {
-    fn scroll_fragment_point(&mut self,
-                             pipeline_id: PipelineId,
-                             layer_id: LayerId,
-                             point: Point2D<f32>);
-    /// Informs the compositor that the title of the page with the given pipeline ID has changed.
-    fn set_title(&mut self, pipeline_id: PipelineId, new_title: Option<String>);
-    fn close(&mut self);
-    fn dup(&mut self) -> Box<ScriptListener+'static>;
-    fn send_key_event(&mut self, key: Key, state: KeyState, modifiers: KeyModifiers);
+#[derive(Clone)]
+pub struct ScriptListener(IpcSender<ScriptToCompositorMsg>);
+
+impl ScriptListener {
+    pub fn new(sender: IpcSender<ScriptToCompositorMsg>) -> ScriptListener {
+        ScriptListener(sender)
+    }
+
+    pub fn scroll_fragment_point(&mut self,
+                                 pipeline_id: PipelineId,
+                                 layer_id: LayerId,
+                                 point: Point2D<f32>) {
+        self.0
+            .send(ScriptToCompositorMsg::ScrollFragmentPoint(pipeline_id, layer_id, point))
+            .unwrap()
+    }
+
+    pub fn close(&mut self) {
+        self.0.send(ScriptToCompositorMsg::Exit).unwrap()
+    }
+
+    pub fn dup(&mut self) -> ScriptListener {
+        self.clone()
+    }
+
+    pub fn set_title(&mut self, pipeline_id: PipelineId, title: Option<String>) {
+        self.0.send(ScriptToCompositorMsg::SetTitle(pipeline_id, title)).unwrap()
+    }
+
+    pub fn send_key_event(&mut self, key: Key, state: KeyState, modifiers: KeyModifiers) {
+        self.0.send(ScriptToCompositorMsg::SendKeyEvent(key, state, modifiers)).unwrap()
+    }
 }
+