compositor: Unify the cross process and in-process API (#36543)

Because there used to be two traits exposing messages to the compositor,
there were two kinds of messages that could be sent:

1. In-process messages from the `Constellation`
2. Cross-process messages from other parts of Servo

Now these two types of messages can be unified into one type.

This is a reland of #36443, which caused regressions due to the fact
that messages to the compositor were no longer triggering the event loop
waker. This version of the PR splits out just the bits that unify the
two APIs, leaving the cleanup of routes in the constellation for another
PR.

Testing: This is covered by existing WPT tests.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

7 files changed, 87 insertions, 183 deletions

diff --git a/components/compositing/compositor.rs b/components/compositing/compositor.rs
index f4ecd82cbc1..461a5a819d5 100644
--- a/components/compositing/compositor.rs
+++ b/components/compositing/compositor.rs
@@ -19,11 +19,10 @@ use bitflags::bitflags;
 use compositing_traits::display_list::{CompositorDisplayListInfo, HitTestInfo, ScrollTree};
 use compositing_traits::rendering_context::RenderingContext;
 use compositing_traits::{
-    CompositionPipeline, CompositorMsg, CompositorReceiver, CrossProcessCompositorMessage,
-    ImageUpdate, RendererWebView, SendableFrameTree,
+    CompositionPipeline, CompositorMsg, ImageUpdate, RendererWebView, SendableFrameTree,
 };
 use constellation_traits::{AnimationTickType, EmbedderToConstellationMessage, PaintMetricEvent};
-use crossbeam_channel::Sender;
+use crossbeam_channel::{Receiver, Sender};
 use dpi::PhysicalSize;
 use embedder_traits::{
     AnimationState, CompositorHitTestResult, Cursor, InputEvent, MouseButtonEvent, MouseMoveEvent,
@@ -90,7 +89,7 @@ pub struct ServoRenderer {
     shutdown_state: Rc<Cell<ShutdownState>>,
 
     /// The port on which we receive messages.
-    compositor_receiver: CompositorReceiver,
+    compositor_receiver: Receiver<CompositorMsg>,
 
     /// The channel on which messages can be sent to the constellation.
     pub(crate) constellation_sender: Sender<EmbedderToConstellationMessage>,
@@ -467,8 +466,8 @@ impl IOCompositor {
             .global
             .borrow_mut()
             .compositor_receiver
-            .try_recv_compositor_msg()
-            .is_some()
+            .try_recv()
+            .is_ok()
         {}
 
         // Tell the profiler, memory profiler, and scrolling timer to shut down.
@@ -630,33 +629,14 @@ impl IOCompositor {
                 webview.dispatch_input_event(InputEvent::MouseMove(MouseMoveEvent { point }));
             },
 
-            CompositorMsg::CrossProcess(cross_proces_message) => {
-                self.handle_cross_process_message(cross_proces_message);
-            },
-        }
-    }
-
-    /// Accept messages from content processes that need to be relayed to the WebRender
-    /// instance in the parent process.
-    #[cfg_attr(
-        feature = "tracing",
-        tracing::instrument(skip_all, fields(servo_profiling = true), level = "trace")
-    )]
-    fn handle_cross_process_message(&mut self, msg: CrossProcessCompositorMessage) {
-        match msg {
-            CrossProcessCompositorMessage::SendInitialTransaction(pipeline) => {
+            CompositorMsg::SendInitialTransaction(pipeline) => {
                 let mut txn = Transaction::new();
                 txn.set_display_list(WebRenderEpoch(0), (pipeline, Default::default()));
                 self.generate_frame(&mut txn, RenderReasons::SCENE);
                 self.global.borrow_mut().send_transaction(txn);
             },
 
-            CrossProcessCompositorMessage::SendScrollNode(
-                webview_id,
-                pipeline_id,
-                point,
-                external_scroll_id,
-            ) => {
+            CompositorMsg::SendScrollNode(webview_id, pipeline_id, point, external_scroll_id) => {
                 let Some(webview) = self.webviews.get_mut(webview_id) else {
                     return;
                 };
@@ -690,7 +670,7 @@ impl IOCompositor {
                 self.global.borrow_mut().send_transaction(txn);
             },
 
-            CrossProcessCompositorMessage::SendDisplayList {
+            CompositorMsg::SendDisplayList {
                 webview_id,
                 display_list_descriptor,
                 display_list_receiver,
@@ -779,7 +759,7 @@ impl IOCompositor {
                 self.global.borrow_mut().send_transaction(transaction);
             },
 
-            CrossProcessCompositorMessage::HitTest(pipeline, point, flags, sender) => {
+            CompositorMsg::HitTest(pipeline, point, flags, sender) => {
                 // When a display list is sent to WebRender, it starts scene building in a
                 // separate thread and then that display list is available for hit testing.
                 // Without flushing scene building, any hit test we do might be done against
@@ -805,11 +785,11 @@ impl IOCompositor {
                 let _ = sender.send(result);
             },
 
-            CrossProcessCompositorMessage::GenerateImageKey(sender) => {
+            CompositorMsg::GenerateImageKey(sender) => {
                 let _ = sender.send(self.global.borrow().webrender_api.generate_image_key());
             },
 
-            CrossProcessCompositorMessage::UpdateImages(updates) => {
+            CompositorMsg::UpdateImages(updates) => {
                 let mut txn = Transaction::new();
                 for update in updates {
                     match update {
@@ -825,26 +805,21 @@ impl IOCompositor {
                 self.global.borrow_mut().send_transaction(txn);
             },
 
-            CrossProcessCompositorMessage::AddFont(font_key, data, index) => {
+            CompositorMsg::AddFont(font_key, data, index) => {
                 self.add_font(font_key, index, data);
             },
 
-            CrossProcessCompositorMessage::AddSystemFont(font_key, native_handle) => {
+            CompositorMsg::AddSystemFont(font_key, native_handle) => {
                 let mut transaction = Transaction::new();
                 transaction.add_native_font(font_key, native_handle);
                 self.global.borrow_mut().send_transaction(transaction);
             },
 
-            CrossProcessCompositorMessage::AddFontInstance(
-                font_instance_key,
-                font_key,
-                size,
-                flags,
-            ) => {
+            CompositorMsg::AddFontInstance(font_instance_key, font_key, size, flags) => {
                 self.add_font_instance(font_instance_key, font_key, size, flags);
             },
 
-            CrossProcessCompositorMessage::RemoveFonts(keys, instance_keys) => {
+            CompositorMsg::RemoveFonts(keys, instance_keys) => {
                 let mut transaction = Transaction::new();
 
                 for instance in instance_keys.into_iter() {
@@ -857,13 +832,13 @@ impl IOCompositor {
                 self.global.borrow_mut().send_transaction(transaction);
             },
 
-            CrossProcessCompositorMessage::AddImage(key, desc, data) => {
+            CompositorMsg::AddImage(key, desc, data) => {
                 let mut txn = Transaction::new();
                 txn.add_image(key, desc, data.into(), None);
                 self.global.borrow_mut().send_transaction(txn);
             },
 
-            CrossProcessCompositorMessage::GenerateFontKeys(
+            CompositorMsg::GenerateFontKeys(
                 number_of_font_keys,
                 number_of_font_instance_keys,
                 result_sender,
@@ -881,7 +856,7 @@ impl IOCompositor {
                     .collect();
                 let _ = result_sender.send((font_keys, font_instance_keys));
             },
-            CrossProcessCompositorMessage::GetClientWindowRect(webview_id, response_sender) => {
+            CompositorMsg::GetClientWindowRect(webview_id, response_sender) => {
                 let client_window_rect = self
                     .webviews
                     .get(webview_id)
@@ -891,7 +866,7 @@ impl IOCompositor {
                     warn!("Sending response to get client window failed ({error:?}).");
                 }
             },
-            CrossProcessCompositorMessage::GetScreenSize(webview_id, response_sender) => {
+            CompositorMsg::GetScreenSize(webview_id, response_sender) => {
                 let screen_size = self
                     .webviews
                     .get(webview_id)
@@ -901,7 +876,7 @@ impl IOCompositor {
                     warn!("Sending response to get screen size failed ({error:?}).");
                 }
             },
-            CrossProcessCompositorMessage::GetAvailableScreenSize(webview_id, response_sender) => {
+            CompositorMsg::GetAvailableScreenSize(webview_id, response_sender) => {
                 let available_screen_size = self
                     .webviews
                     .get(webview_id)
@@ -935,16 +910,14 @@ impl IOCompositor {
                 }
                 let _ = sender.send(());
             },
-            CompositorMsg::CrossProcess(CrossProcessCompositorMessage::GenerateImageKey(
-                sender,
-            )) => {
+            CompositorMsg::GenerateImageKey(sender) => {
                 let _ = sender.send(self.global.borrow().webrender_api.generate_image_key());
             },
-            CompositorMsg::CrossProcess(CrossProcessCompositorMessage::GenerateFontKeys(
+            CompositorMsg::GenerateFontKeys(
                 number_of_font_keys,
                 number_of_font_instance_keys,
                 result_sender,
-            )) => {
+            ) => {
                 let font_keys = (0..number_of_font_keys)
                     .map(|_| self.global.borrow().webrender_api.generate_font_key())
                     .collect();
@@ -958,26 +931,17 @@ impl IOCompositor {
                     .collect();
                 let _ = result_sender.send((font_keys, font_instance_keys));
             },
-            CompositorMsg::CrossProcess(CrossProcessCompositorMessage::GetClientWindowRect(
-                _,
-                response_sender,
-            )) => {
+            CompositorMsg::GetClientWindowRect(_, response_sender) => {
                 if let Err(error) = response_sender.send(Default::default()) {
                     warn!("Sending response to get client window failed ({error:?}).");
                 }
             },
-            CompositorMsg::CrossProcess(CrossProcessCompositorMessage::GetScreenSize(
-                _,
-                response_sender,
-            )) => {
+            CompositorMsg::GetScreenSize(_, response_sender) => {
                 if let Err(error) = response_sender.send(Default::default()) {
                     warn!("Sending response to get client window failed ({error:?}).");
                 }
             },
-            CompositorMsg::CrossProcess(CrossProcessCompositorMessage::GetAvailableScreenSize(
-                _,
-                response_sender,
-            )) => {
+            CompositorMsg::GetAvailableScreenSize(_, response_sender) => {
                 if let Err(error) = response_sender.send(Default::default()) {
                     warn!("Sending response to get client window failed ({error:?}).");
                 }
@@ -1600,12 +1564,7 @@ impl IOCompositor {
         // Check for new messages coming from the other threads in the system.
         let mut compositor_messages = vec![];
         let mut found_recomposite_msg = false;
-        while let Some(msg) = self
-            .global
-            .borrow_mut()
-            .compositor_receiver
-            .try_recv_compositor_msg()
-        {
+        while let Ok(msg) = self.global.borrow_mut().compositor_receiver.try_recv() {
             match msg {
                 CompositorMsg::NewWebRenderFrameReady(..) if found_recomposite_msg => {
                     // Only take one of duplicate NewWebRendeFrameReady messages, but do subtract
diff --git a/components/compositing/lib.rs b/components/compositing/lib.rs
index 2e09fd0b1ab..8631b63076a 100644
--- a/components/compositing/lib.rs
+++ b/components/compositing/lib.rs
@@ -8,9 +8,9 @@ use std::cell::Cell;
 use std::rc::Rc;
 
 use compositing_traits::rendering_context::RenderingContext;
-use compositing_traits::{CompositorProxy, CompositorReceiver};
+use compositing_traits::{CompositorMsg, CompositorProxy};
 use constellation_traits::EmbedderToConstellationMessage;
-use crossbeam_channel::Sender;
+use crossbeam_channel::{Receiver, Sender};
 use embedder_traits::ShutdownState;
 use profile_traits::{mem, time};
 use webrender::RenderApi;
@@ -32,7 +32,7 @@ pub struct InitialCompositorState {
     /// A channel to the compositor.
     pub sender: CompositorProxy,
     /// A port on which messages inbound to the compositor can be received.
-    pub receiver: CompositorReceiver,
+    pub receiver: Receiver<CompositorMsg>,
     /// A channel to the constellation.
     pub constellation_chan: Sender<EmbedderToConstellationMessage>,
     /// A channel to the time profiler thread.
diff --git a/components/compositing/tracing.rs b/components/compositing/tracing.rs
index 907c931aebe..0373d0f1d1a 100644
--- a/components/compositing/tracing.rs
+++ b/components/compositing/tracing.rs
@@ -42,7 +42,21 @@ mod from_constellation {
                 Self::LoadComplete(..) => target!("LoadComplete"),
                 Self::WebDriverMouseButtonEvent(..) => target!("WebDriverMouseButtonEvent"),
                 Self::WebDriverMouseMoveEvent(..) => target!("WebDriverMouseMoveEvent"),
-                Self::CrossProcess(_) => target!("CrossProcess"),
+                Self::SendInitialTransaction(..) => target!("SendInitialTransaction"),
+                Self::SendScrollNode(..) => target!("SendScrollNode"),
+                Self::SendDisplayList { .. } => target!("SendDisplayList"),
+                Self::HitTest(..) => target!("HitTest"),
+                Self::GenerateImageKey(..) => target!("GenerateImageKey"),
+                Self::AddImage(..) => target!("AddImage"),
+                Self::UpdateImages(..) => target!("UpdateImages"),
+                Self::GenerateFontKeys(..) => target!("GenerateFontKeys"),
+                Self::AddFont(..) => target!("AddFont"),
+                Self::AddSystemFont(..) => target!("AddSystemFont"),
+                Self::AddFontInstance(..) => target!("AddFontInstance"),
+                Self::RemoveFonts(..) => target!("RemoveFonts"),
+                Self::GetClientWindowRect(..) => target!("GetClientWindowRect"),
+                Self::GetScreenSize(..) => target!("GetScreenSize"),
+                Self::GetAvailableScreenSize(..) => target!("GetAvailableScreenSize"),
             }
         }
     }
diff --git a/components/script/dom/screen.rs b/components/script/dom/screen.rs
index 4d76b20d626..061b2da3eca 100644
--- a/components/script/dom/screen.rs
+++ b/components/script/dom/screen.rs
@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use compositing_traits::CrossProcessCompositorMessage;
+use compositing_traits::CompositorMsg;
 use dom_struct::dom_struct;
 use euclid::Size2D;
 use profile_traits::ipc;
@@ -41,7 +41,7 @@ impl Screen {
         self.window
             .compositor_api()
             .sender()
-            .send(CrossProcessCompositorMessage::GetScreenSize(
+            .send(CompositorMsg::GetScreenSize(
                 self.window.webview_id(),
                 sender,
             ))
@@ -57,7 +57,7 @@ impl Screen {
         self.window
             .compositor_api()
             .sender()
-            .send(CrossProcessCompositorMessage::GetAvailableScreenSize(
+            .send(CompositorMsg::GetAvailableScreenSize(
                 self.window.webview_id(),
                 sender,
             ))
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 90e498b9dba..ce3b5ff6e8c 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -1884,10 +1884,7 @@ impl Window {
         let (sender, receiver) =
             ProfiledIpc::channel::<DeviceIndependentIntRect>(timer_profile_chan).unwrap();
         let _ = self.compositor_api.sender().send(
-            compositing_traits::CrossProcessCompositorMessage::GetClientWindowRect(
-                self.webview_id(),
-                sender,
-            ),
+            compositing_traits::CompositorMsg::GetClientWindowRect(self.webview_id(), sender),
         );
         let rect = receiver.recv().unwrap_or_default();
         (
diff --git a/components/servo/lib.rs b/components/servo/lib.rs
index 68008775c42..87b95330021 100644
--- a/components/servo/lib.rs
+++ b/components/servo/lib.rs
@@ -48,8 +48,8 @@ pub use compositing_traits::rendering_context::{
     OffscreenRenderingContext, RenderingContext, SoftwareRenderingContext, WindowRenderingContext,
 };
 use compositing_traits::{
-    CompositorMsg, CompositorProxy, CompositorReceiver, CrossProcessCompositorApi,
-    WebrenderExternalImageHandlers, WebrenderExternalImageRegistry, WebrenderImageHandlerType,
+    CompositorMsg, CompositorProxy, CrossProcessCompositorApi, WebrenderExternalImageHandlers,
+    WebrenderExternalImageRegistry, WebrenderImageHandlerType,
 };
 #[cfg(all(
     not(target_os = "windows"),
@@ -992,7 +992,7 @@ fn create_embedder_channel(
 
 fn create_compositor_channel(
     event_loop_waker: Box<dyn EventLoopWaker>,
-) -> (CompositorProxy, CompositorReceiver) {
+) -> (CompositorProxy, Receiver<CompositorMsg>) {
     let (sender, receiver) = unbounded();
 
     let (compositor_ipc_sender, compositor_ipc_receiver) =
@@ -1009,13 +1009,11 @@ fn create_compositor_channel(
     ROUTER.add_typed_route(
         compositor_ipc_receiver,
         Box::new(move |message| {
-            compositor_proxy_clone.send(CompositorMsg::CrossProcess(
-                message.expect("Could not convert Compositor message"),
-            ));
+            compositor_proxy_clone.send(message.expect("Could not convert Compositor message"));
         }),
     );
 
-    (compositor_proxy, CompositorReceiver { receiver })
+    (compositor_proxy, receiver)
 }
 
 #[allow(clippy::too_many_arguments)]
diff --git a/components/shared/compositing/lib.rs b/components/shared/compositing/lib.rs
index acc14e3de29..3a5e188c5d6 100644
--- a/components/shared/compositing/lib.rs
+++ b/components/shared/compositing/lib.rs
@@ -7,7 +7,7 @@
 use std::fmt::{Debug, Error, Formatter};
 
 use base::id::{PipelineId, WebViewId};
-use crossbeam_channel::{Receiver, Sender};
+use crossbeam_channel::Sender;
 use embedder_traits::{
     AnimationState, EventLoopWaker, MouseButton, MouseButtonAction, TouchEventResult,
 };
@@ -22,7 +22,6 @@ use webrender_api::DocumentId;
 pub mod display_list;
 pub mod rendering_context;
 
-use core::fmt;
 use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
 
@@ -60,22 +59,8 @@ impl CompositorProxy {
     }
 }
 
-/// The port that the compositor receives messages on.
-pub struct CompositorReceiver {
-    pub receiver: Receiver<CompositorMsg>,
-}
-
-impl CompositorReceiver {
-    pub fn try_recv_compositor_msg(&mut self) -> Option<CompositorMsg> {
-        self.receiver.try_recv().ok()
-    }
-    pub fn recv_compositor_msg(&mut self) -> CompositorMsg {
-        self.receiver.recv().unwrap()
-    }
-}
-
 /// Messages from (or via) the constellation thread to the compositor.
-#[derive(IntoStaticStr)]
+#[derive(Deserialize, IntoStaticStr, Serialize)]
 pub enum CompositorMsg {
     /// Alerts the compositor that the given pipeline has changed whether it is running animations.
     ChangeRunningAnimationsState(WebViewId, PipelineId, AnimationState),
@@ -112,32 +97,6 @@ pub enum CompositorMsg {
     /// WebDriver mouse move event
     WebDriverMouseMoveEvent(WebViewId, f32, f32),
 
-    /// Messages forwarded to the compositor by the constellation from other crates. These
-    /// messages are mainly passed on from the compositor to WebRender.
-    CrossProcess(CrossProcessCompositorMessage),
-}
-
-pub struct SendableFrameTree {
-    pub pipeline: CompositionPipeline,
-    pub children: Vec<SendableFrameTree>,
-}
-
-/// The subset of the pipeline that is needed for layer composition.
-#[derive(Clone)]
-pub struct CompositionPipeline {
-    pub id: PipelineId,
-    pub webview_id: WebViewId,
-}
-
-impl Debug for CompositorMsg {
-    fn fmt(&self, formatter: &mut Formatter) -> Result<(), Error> {
-        let string: &'static str = self.into();
-        write!(formatter, "{string}")
-    }
-}
-
-#[derive(Deserialize, Serialize)]
-pub enum CrossProcessCompositorMessage {
     /// Inform WebRender of the existence of this pipeline.
     SendInitialTransaction(WebRenderPipelineId),
     /// Perform a scroll operation.
@@ -197,31 +156,29 @@ pub enum CrossProcessCompositorMessage {
     GetAvailableScreenSize(WebViewId, IpcSender<DeviceIndependentIntSize>),
 }
 
-impl fmt::Debug for CrossProcessCompositorMessage {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Self::AddImage(..) => f.write_str("AddImage"),
-            Self::GenerateFontKeys(..) => f.write_str("GenerateFontKeys"),
-            Self::AddSystemFont(..) => f.write_str("AddSystemFont"),
-            Self::SendInitialTransaction(..) => f.write_str("SendInitialTransaction"),
-            Self::SendScrollNode(..) => f.write_str("SendScrollNode"),
-            Self::SendDisplayList { .. } => f.write_str("SendDisplayList"),
-            Self::HitTest(..) => f.write_str("HitTest"),
-            Self::GenerateImageKey(..) => f.write_str("GenerateImageKey"),
-            Self::UpdateImages(..) => f.write_str("UpdateImages"),
-            Self::RemoveFonts(..) => f.write_str("RemoveFonts"),
-            Self::AddFontInstance(..) => f.write_str("AddFontInstance"),
-            Self::AddFont(..) => f.write_str("AddFont"),
-            Self::GetClientWindowRect(..) => f.write_str("GetClientWindowRect"),
-            Self::GetScreenSize(..) => f.write_str("GetScreenSize"),
-            Self::GetAvailableScreenSize(..) => f.write_str("GetAvailableScreenSize"),
-        }
+impl Debug for CompositorMsg {
+    fn fmt(&self, formatter: &mut Formatter) -> Result<(), Error> {
+        let string: &'static str = self.into();
+        write!(formatter, "{string}")
     }
 }
 
+#[derive(Deserialize, Serialize)]
+pub struct SendableFrameTree {
+    pub pipeline: CompositionPipeline,
+    pub children: Vec<SendableFrameTree>,
+}
+
+/// The subset of the pipeline that is needed for layer composition.
+#[derive(Clone, Deserialize, Serialize)]
+pub struct CompositionPipeline {
+    pub id: PipelineId,
+    pub webview_id: WebViewId,
+}
+
 /// A mechanism to send messages from ScriptThread to the parent process' WebRender instance.
 #[derive(Clone, Deserialize, Serialize)]
-pub struct CrossProcessCompositorApi(pub IpcSender<CrossProcessCompositorMessage>);
+pub struct CrossProcessCompositorApi(pub IpcSender<CompositorMsg>);
 
 impl CrossProcessCompositorApi {
     /// Create a new [`CrossProcessCompositorApi`] struct that does not have a listener on the other
@@ -232,18 +189,13 @@ impl CrossProcessCompositorApi {
     }
 
     /// Get the sender for this proxy.
-    pub fn sender(&self) -> &IpcSender<CrossProcessCompositorMessage> {
+    pub fn sender(&self) -> &IpcSender<CompositorMsg> {
         &self.0
     }
 
     /// Inform WebRender of the existence of this pipeline.
     pub fn send_initial_transaction(&self, pipeline: WebRenderPipelineId) {
-        if let Err(e) = self
-            .0
-            .send(CrossProcessCompositorMessage::SendInitialTransaction(
-                pipeline,
-            ))
-        {
+        if let Err(e) = self.0.send(CompositorMsg::SendInitialTransaction(pipeline)) {
             warn!("Error sending initial transaction: {}", e);
         }
     }
@@ -256,7 +208,7 @@ impl CrossProcessCompositorApi {
         point: LayoutPoint,
         scroll_id: ExternalScrollId,
     ) {
-        if let Err(e) = self.0.send(CrossProcessCompositorMessage::SendScrollNode(
+        if let Err(e) = self.0.send(CompositorMsg::SendScrollNode(
             webview_id,
             pipeline_id,
             point,
@@ -275,7 +227,7 @@ impl CrossProcessCompositorApi {
     ) {
         let (display_list_data, display_list_descriptor) = list.into_data();
         let (display_list_sender, display_list_receiver) = ipc::bytes_channel().unwrap();
-        if let Err(e) = self.0.send(CrossProcessCompositorMessage::SendDisplayList {
+        if let Err(e) = self.0.send(CompositorMsg::SendDisplayList {
             webview_id,
             display_list_descriptor,
             display_list_receiver,
@@ -310,9 +262,7 @@ impl CrossProcessCompositorApi {
     ) -> Vec<CompositorHitTestResult> {
         let (sender, receiver) = ipc::channel().unwrap();
         self.0
-            .send(CrossProcessCompositorMessage::HitTest(
-                pipeline, point, flags, sender,
-            ))
+            .send(CompositorMsg::HitTest(pipeline, point, flags, sender))
             .expect("error sending hit test");
         receiver.recv().expect("error receiving hit test result")
     }
@@ -320,9 +270,7 @@ impl CrossProcessCompositorApi {
     /// Create a new image key. Blocks until the key is available.
     pub fn generate_image_key(&self) -> Option<ImageKey> {
         let (sender, receiver) = ipc::channel().unwrap();
-        self.0
-            .send(CrossProcessCompositorMessage::GenerateImageKey(sender))
-            .ok()?;
+        self.0.send(CompositorMsg::GenerateImageKey(sender)).ok()?;
         receiver.recv().ok()
     }
 
@@ -332,19 +280,14 @@ impl CrossProcessCompositorApi {
         descriptor: ImageDescriptor,
         data: SerializableImageData,
     ) {
-        if let Err(e) = self.0.send(CrossProcessCompositorMessage::AddImage(
-            key, descriptor, data,
-        )) {
+        if let Err(e) = self.0.send(CompositorMsg::AddImage(key, descriptor, data)) {
             warn!("Error sending image update: {}", e);
         }
     }
 
     /// Perform an image resource update operation.
     pub fn update_images(&self, updates: Vec<ImageUpdate>) {
-        if let Err(e) = self
-            .0
-            .send(CrossProcessCompositorMessage::UpdateImages(updates))
-        {
+        if let Err(e) = self.0.send(CompositorMsg::UpdateImages(updates)) {
             warn!("error sending image updates: {}", e);
         }
     }
@@ -357,10 +300,7 @@ impl CrossProcessCompositorApi {
         if keys.is_empty() && instance_keys.is_empty() {
             return;
         }
-        let _ = self.0.send(CrossProcessCompositorMessage::RemoveFonts(
-            keys,
-            instance_keys,
-        ));
+        let _ = self.0.send(CompositorMsg::RemoveFonts(keys, instance_keys));
     }
 
     pub fn add_font_instance(
@@ -370,7 +310,7 @@ impl CrossProcessCompositorApi {
         size: f32,
         flags: FontInstanceFlags,
     ) {
-        let _x = self.0.send(CrossProcessCompositorMessage::AddFontInstance(
+        let _x = self.0.send(CompositorMsg::AddFontInstance(
             font_instance_key,
             font_key,
             size,
@@ -379,15 +319,11 @@ impl CrossProcessCompositorApi {
     }
 
     pub fn add_font(&self, font_key: FontKey, data: Arc<IpcSharedMemory>, index: u32) {
-        let _ = self.0.send(CrossProcessCompositorMessage::AddFont(
-            font_key, data, index,
-        ));
+        let _ = self.0.send(CompositorMsg::AddFont(font_key, data, index));
     }
 
     pub fn add_system_font(&self, font_key: FontKey, handle: NativeFontHandle) {
-        let _ = self.0.send(CrossProcessCompositorMessage::AddSystemFont(
-            font_key, handle,
-        ));
+        let _ = self.0.send(CompositorMsg::AddSystemFont(font_key, handle));
     }
 
     pub fn fetch_font_keys(
@@ -396,7 +332,7 @@ impl CrossProcessCompositorApi {
         number_of_font_instance_keys: usize,
     ) -> (Vec<FontKey>, Vec<FontInstanceKey>) {
         let (sender, receiver) = ipc_channel::ipc::channel().expect("Could not create IPC channel");
-        let _ = self.0.send(CrossProcessCompositorMessage::GenerateFontKeys(
+        let _ = self.0.send(CompositorMsg::GenerateFontKeys(
             number_of_font_keys,
             number_of_font_instance_keys,
             sender,