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/compositing/Cargo.toml

@@ -52,6 +52,9 @@ git = "https://github.com/servo/rust-png"
 [dependencies.clipboard]
 git = "https://github.com/aweinstock314/rust-clipboard"
 
+[dependencies.ipc-channel]
+git = "https://github.com/pcwalton/ipc-channel"
+
 [dependencies]
 log = "*"
 num = "0.1.24"

components/compositing/compositor_task.rs

@@ -13,10 +13,11 @@ use windowing::{WindowEvent, WindowMethods};
 
 use euclid::point::Point2D;
 use euclid::rect::Rect;
+use ipc_channel::ipc::IpcReceiver;
 use layers::platform::surface::NativeDisplay;
 use layers::layers::{BufferRequest, LayerBuffer, LayerBufferSet};
 use msg::compositor_msg::{Epoch, LayerId, LayerProperties, FrameTreeId};
-use msg::compositor_msg::{PaintListener, ScriptListener};
+use msg::compositor_msg::{PaintListener, ScriptToCompositorMsg};
 use msg::constellation_msg::{AnimationState, ConstellationChan, PipelineId};
 use msg::constellation_msg::{Key, KeyState, KeyModifiers};
 use profile_traits::mem;
@@ -61,31 +62,28 @@ impl CompositorReceiver for Receiver<Msg> {
     }
 }
 
-/// Implementation of the abstract `ScriptListener` interface.
-impl ScriptListener for Box<CompositorProxy+'static+Send> {
-    fn scroll_fragment_point(&mut self,
-                             pipeline_id: PipelineId,
-                             layer_id: LayerId,
-                             point: Point2D<f32>) {
-        self.send(Msg::ScrollFragmentPoint(pipeline_id, layer_id, point));
-    }
+pub fn run_script_listener_thread(mut compositor_proxy: Box<CompositorProxy + 'static + Send>,
+                                  receiver: IpcReceiver<ScriptToCompositorMsg>) {
+    while let Ok(msg) = receiver.recv() {
+        match msg {
+            ScriptToCompositorMsg::ScrollFragmentPoint(pipeline_id, layer_id, point) => {
+                compositor_proxy.send(Msg::ScrollFragmentPoint(pipeline_id, layer_id, point));
+            }
 
-    fn close(&mut self) {
-        let (chan, port) = channel();
-        self.send(Msg::Exit(chan));
-        port.recv().unwrap();
-    }
+            ScriptToCompositorMsg::Exit => {
+                let (chan, port) = channel();
+                compositor_proxy.send(Msg::Exit(chan));
+                port.recv().unwrap();
+            }
 
-    fn dup(&mut self) -> Box<ScriptListener+'static> {
-        box self.clone_compositor_proxy() as Box<ScriptListener+'static>
-    }
+            ScriptToCompositorMsg::SetTitle(pipeline_id, title) => {
+                compositor_proxy.send(Msg::ChangePageTitle(pipeline_id, title))
+            }
 
-    fn set_title(&mut self, pipeline_id: PipelineId, title: Option<String>) {
-        self.send(Msg::ChangePageTitle(pipeline_id, title))
-    }
-
-    fn send_key_event(&mut self, key: Key, state: KeyState, modifiers: KeyModifiers) {
-        self.send(Msg::KeyEvent(key, state, modifiers));
+            ScriptToCompositorMsg::SendKeyEvent(key, key_state, key_modifiers) => {
+                compositor_proxy.send(Msg::KeyEvent(key, key_state, key_modifiers))
+            }
+        }
     }
 }
 

components/compositing/lib.rs

@@ -14,6 +14,7 @@ extern crate azure;
 extern crate devtools_traits;
 extern crate euclid;
 extern crate gfx;
+extern crate ipc_channel;
 extern crate layers;
 extern crate layout_traits;
 extern crate png;

components/compositing/pipeline.rs

@@ -7,13 +7,16 @@ use layout_traits::{LayoutControlMsg, LayoutTaskFactory, LayoutControlChan};
 use script_traits::{ScriptControlChan, ScriptTaskFactory};
 use script_traits::{NewLayoutInfo, ConstellationControlMsg};
 
+use compositor_task;
 use devtools_traits::DevtoolsControlChan;
 use euclid::rect::{TypedRect};
 use euclid::scale_factor::ScaleFactor;
 use gfx::paint_task::Msg as PaintMsg;
 use gfx::paint_task::{PaintChan, PaintTask};
 use gfx::font_cache_task::FontCacheTask;
+use ipc_channel::ipc;
 use layers::geometry::DevicePixel;
+use msg::compositor_msg::ScriptListener;
 use msg::constellation_msg::{ConstellationChan, Failure, FrameId, PipelineId, SubpageId};
 use msg::constellation_msg::{LoadData, WindowSizeData, PipelineExitType, MozBrowserEvent};
 use profile_traits::mem;
@@ -22,6 +25,7 @@ use net_traits::ResourceTask;
 use net_traits::image_cache_task::ImageCacheTask;
 use net_traits::storage_task::StorageTask;
 use std::sync::mpsc::{Receiver, channel};
+use std::thread;
 use url::Url;
 use util::geometry::{PagePx, ViewportPx};
 use util::opts;
@@ -91,6 +95,8 @@ impl Pipeline {
         let script_chan = match script_chan {
             None => {
                 let (script_chan, script_port) = channel();
+                let (script_to_compositor_chan, script_to_compositor_port) =
+                    ipc::channel().unwrap();
 
                 let window_size = window_rect.map(|rect| {
                     WindowSizeData {
@@ -100,10 +106,18 @@ impl Pipeline {
                     }
                 });
 
+                let compositor_proxy_for_script_listener_thread =
+                    compositor_proxy.clone_compositor_proxy();
+                thread::spawn(move || {
+                    compositor_task::run_script_listener_thread(
+                        compositor_proxy_for_script_listener_thread,
+                        script_to_compositor_port)
+                });
+
                 ScriptTaskFactory::create(None::<&mut STF>,
                                           id,
                                           parent_info,
-                                          compositor_proxy.clone_compositor_proxy(),
+                                          ScriptListener::new(script_to_compositor_chan),
                                           &layout_pair,
                                           ScriptControlChan(script_chan.clone()),
                                           script_port,