Auto merge of #17068 - gterzian:remove_compositorproxy, r=asajeffrey

Separate waking the event loop, from communicating with Compositor

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@paulrouget first step of #15934, Glutin only for now, please take a look...

If this makes sense, I will also update the code for ports other than Glutin...

One question: one do I add the `warn!` macro to `servolib`? Also perhaps we would also want to add `box`, since I had to switch to using `Box::new`...

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- [ ] These changes fix #__ (github issue number if applicable).

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components/compositing/compositor.rs

@@ -103,7 +103,7 @@ pub struct IOCompositor<Window: WindowMethods> {
     window: Rc<Window>,
 
     /// The port on which we receive messages.
-    port: Box<CompositorReceiver>,
+    port: CompositorReceiver,
 
     /// The root pipeline.
     root_pipeline: Option<CompositionPipeline>,
@@ -133,7 +133,7 @@ pub struct IOCompositor<Window: WindowMethods> {
     /// The device pixel ratio for this window.
     scale_factor: ScaleFactor<f32, DeviceIndependentPixel, DevicePixel>,
 
-    channel_to_self: Box<CompositorProxy + Send>,
+    channel_to_self: CompositorProxy,
 
     /// A handle to the delayed composition timer.
     delayed_composition_timer: DelayedCompositionTimerProxy,
@@ -312,11 +312,11 @@ fn initialize_png(gl: &gl::Gl, width: usize, height: usize) -> RenderTargetInfo
 }
 
 struct RenderNotifier {
-    compositor_proxy: Box<CompositorProxy>,
+    compositor_proxy: CompositorProxy,
 }
 
 impl RenderNotifier {
-    fn new(compositor_proxy: Box<CompositorProxy>,
+    fn new(compositor_proxy: CompositorProxy,
            _: Sender<ConstellationMsg>) -> RenderNotifier {
         RenderNotifier {
             compositor_proxy: compositor_proxy,
@@ -336,7 +336,7 @@ impl webrender_traits::RenderNotifier for RenderNotifier {
 
 // Used to dispatch functions from webrender to the main thread's event loop.
 struct CompositorThreadDispatcher {
-    compositor_proxy: Box<CompositorProxy>
+    compositor_proxy: CompositorProxy
 }
 
 impl webrender_traits::RenderDispatcher for CompositorThreadDispatcher {

components/compositing/compositor_thread.rs

@@ -22,32 +22,46 @@ use style_traits::viewport::ViewportConstraints;
 use webrender;
 use webrender_traits;
 
-/// Sends messages to the compositor. This is a trait supplied by the port because the method used
-/// to communicate with the compositor may have to kick OS event loops awake, communicate cross-
-/// process, and so forth.
-pub trait CompositorProxy : 'static + Send {
-    /// Sends a message to the compositor.
-    fn send(&self, msg: Msg);
-    /// Clones the compositor proxy.
-    fn clone_compositor_proxy(&self) -> Box<CompositorProxy + 'static + Send>;
+
+/// Used to wake up the event loop, provided by the servo port/embedder.
+pub trait EventLoopWaker : 'static + Send {
+    fn clone(&self) -> Box<EventLoopWaker + Send>;
+    fn wake(&self);
 }
 
-/// The port that the compositor receives messages on. As above, this is a trait supplied by the
-/// Servo port.
-pub trait CompositorReceiver : 'static {
-    /// Receives the next message inbound for the compositor. This must not block.
-    fn try_recv_compositor_msg(&mut self) -> Option<Msg>;
-    /// Synchronously waits for, and returns, the next message inbound for the compositor.
-    fn recv_compositor_msg(&mut self) -> Msg;
+/// Sends messages to the compositor.
+pub struct CompositorProxy {
+    pub sender: Sender<Msg>,
+    pub event_loop_waker: Box<EventLoopWaker>,
 }
 
-/// A convenience implementation of `CompositorReceiver` for a plain old Rust `Receiver`.
-impl CompositorReceiver for Receiver<Msg> {
-    fn try_recv_compositor_msg(&mut self) -> Option<Msg> {
-        self.try_recv().ok()
+impl CompositorProxy {
+    pub fn send(&self, msg: Msg) {
+        // Send a message and kick the OS event loop awake.
+        if let Err(err) = self.sender.send(msg) {
+            warn!("Failed to send response ({}).", err);
+        }
+        self.event_loop_waker.wake();
     }
-    fn recv_compositor_msg(&mut self) -> Msg {
-        self.recv().unwrap()
+    pub fn clone_compositor_proxy(&self) -> CompositorProxy {
+        CompositorProxy {
+            sender: self.sender.clone(),
+            event_loop_waker: self.event_loop_waker.clone(),
+        }
+    }
+}
+
+/// The port that the compositor receives messages on.
+pub struct CompositorReceiver {
+    pub receiver: Receiver<Msg>
+}
+
+impl CompositorReceiver {
+    pub fn try_recv_compositor_msg(&mut self) -> Option<Msg> {
+        self.receiver.try_recv().ok()
+    }
+    pub fn recv_compositor_msg(&mut self) -> Msg {
+        self.receiver.recv().unwrap()
     }
 }
 
@@ -55,7 +69,7 @@ pub trait RenderListener {
     fn recomposite(&mut self, reason: CompositingReason);
 }
 
-impl RenderListener for Box<CompositorProxy + 'static> {
+impl RenderListener for CompositorProxy {
     fn recomposite(&mut self, reason: CompositingReason) {
         self.send(Msg::Recomposite(reason));
     }
@@ -173,9 +187,9 @@ impl Debug for Msg {
 /// Data used to construct a compositor.
 pub struct InitialCompositorState {
     /// A channel to the compositor.
-    pub sender: Box<CompositorProxy + Send>,
+    pub sender: CompositorProxy,
     /// A port on which messages inbound to the compositor can be received.
-    pub receiver: Box<CompositorReceiver>,
+    pub receiver: CompositorReceiver,
     /// A channel to the constellation.
     pub constellation_chan: Sender<ConstellationMsg>,
     /// A channel to the time profiler thread.

components/compositing/delayed_composition.rs

@@ -23,7 +23,7 @@ pub struct DelayedCompositionTimerProxy {
 }
 
 struct DelayedCompositionTimer {
-    compositor_proxy: Box<CompositorProxy>,
+    compositor_proxy: CompositorProxy,
     receiver: Receiver<ToDelayedCompositionTimerMsg>,
 }
 
@@ -33,7 +33,7 @@ enum ToDelayedCompositionTimerMsg {
 }
 
 impl DelayedCompositionTimerProxy {
-    pub fn new(compositor_proxy: Box<CompositorProxy + Send>) -> DelayedCompositionTimerProxy {
+    pub fn new(compositor_proxy: CompositorProxy) -> DelayedCompositionTimerProxy {
         let (to_timer_sender, to_timer_receiver) = channel();
         Builder::new().spawn(move || {
             let mut timer = DelayedCompositionTimer {

components/compositing/windowing.rs

@@ -4,7 +4,7 @@
 
 //! Abstract windowing methods. The concrete implementations of these can be found in `platform/`.
 
-use compositor_thread::{CompositorProxy, CompositorReceiver};
+use compositor_thread::EventLoopWaker;
 use euclid::{Point2D, Size2D};
 use euclid::point::TypedPoint2D;
 use euclid::rect::TypedRect;
@@ -144,12 +144,8 @@ pub trait WindowMethods {
     /// Returns the scale factor of the system (device pixels / device independent pixels).
     fn hidpi_factor(&self) -> ScaleFactor<f32, DeviceIndependentPixel, DevicePixel>;
 
-    /// Creates a channel to the compositor. The dummy parameter is needed because we don't have
-    /// UFCS in Rust yet.
-    ///
-    /// This is part of the windowing system because its implementation often involves OS-specific
-    /// magic to wake the up window's event loop.
-    fn create_compositor_channel(&self) -> (Box<CompositorProxy + Send>, Box<CompositorReceiver>);
+    /// Returns a thread-safe object to wake up the window's event loop.
+    fn create_event_loop_waker(&self) -> Box<EventLoopWaker>;
 
     /// Requests that the window system prepare a composite. Typically this will involve making
     /// some type of platform-specific graphics context current. Returns true if the composite may