Move PaintListener to gfx_traits, Fixes #8834

Adding layers and msg dependency to gfx_traits.

components/gfx_traits/Cargo.toml

@@ -10,3 +10,10 @@ path = "lib.rs"
 [dependencies.azure]
 git = "https://github.com/servo/rust-azure"
 features = ["plugins"]
+
+[dependencies.layers]
+git = "https://github.com/servo/rust-layers"
+features = ["plugins"]
+
+[dependencies.msg]
+path = "../msg"

components/gfx_traits/lib.rs

@@ -4,6 +4,12 @@
 
 #![crate_name = "gfx_traits"]
 #![crate_type = "rlib"]
+
 extern crate azure;
+extern crate layers;
+extern crate msg;
 
 pub mod color;
+mod paint_listener;
+
+pub use paint_listener::PaintListener;

components/gfx_traits/paint_listener.rs

@@ -0,0 +1,34 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use layers::layers::{BufferRequest, LayerBufferSet};
+use layers::platform::surface::NativeDisplay;
+use msg::compositor_msg::{Epoch, FrameTreeId, LayerId, LayerProperties};
+use msg::constellation_msg::PipelineId;
+
+/// The interface used by the painter to acquire draw targets for each paint frame and
+/// submit them to be drawn to the display.
+pub trait PaintListener {
+    fn native_display(&mut self) -> Option<NativeDisplay>;
+
+    /// Informs the compositor of the layers for the given pipeline. The compositor responds by
+    /// creating and/or destroying paint layers as necessary.
+    fn initialize_layers_for_pipeline(&mut self,
+                                      pipeline_id: PipelineId,
+                                      properties: Vec<LayerProperties>,
+                                      epoch: Epoch);
+
+    /// Sends new buffers for the given layers to the compositor.
+    fn assign_painted_buffers(&mut self,
+                              pipeline_id: PipelineId,
+                              epoch: Epoch,
+                              replies: Vec<(LayerId, Box<LayerBufferSet>)>,
+                              frame_tree_id: FrameTreeId);
+
+    /// Inform the compositor that these buffer requests will be ignored.
+    fn ignore_buffer_requests(&mut self, buffer_requests: Vec<BufferRequest>);
+
+    // Notification that the paint task wants to exit.
+    fn notify_paint_task_exiting(&mut self, pipeline_id: PipelineId);
+}