canvas: Move to shared memory for images and canvas backing stores.

The idea here is to land this before making images and canvas IPC-safe,
because this will shake out bugs relating to the shared memory. There
are currently test timeouts that are preventing multiprocess images and
canvas from landing, and I believe those are due to the inefficiency of
sending large amounts of data in the unoptimized builds we test with. By
moving to shared memory, this should drastically reduce the number of
copies and `serde` serialization.

Under the hood, this uses Mach OOL messages on Mac and temporary
memory-mapped files on Linux.

components/canvas/Cargo.toml

@@ -27,6 +27,9 @@ path = "../gfx_traits"
 git = "https://github.com/ecoal95/rust-offscreen-rendering-context"
 features = ["texture_surface"]
 
+[dependencies.ipc-channel]
+git = "https://github.com/pcwalton/ipc-channel"
+
 [dependencies]
 log = "0.3"
 cssparser = "0.3.1"

components/canvas/canvas_paint_task.rs

@@ -13,6 +13,7 @@ use euclid::rect::Rect;
 use euclid::size::Size2D;
 use layers::platform::surface::NativeSurface;
 use gfx_traits::color;
+use ipc_channel::ipc::IpcSharedMemory;
 use num::ToPrimitive;
 use util::opts;
 use util::task::spawn_named;
@@ -515,9 +516,9 @@ impl<'a> CanvasPaintTask<'a> {
         self.drawtarget = CanvasPaintTask::create(size);
     }
 
-    fn send_pixel_contents(&mut self, chan: Sender<Vec<u8>>) {
+    fn send_pixel_contents(&mut self, chan: Sender<IpcSharedMemory>) {
         self.drawtarget.snapshot().get_data_surface().with_data(|element| {
-            chan.send(element.to_vec()).unwrap();
+            chan.send(IpcSharedMemory::from_bytes(element)).unwrap();
         })
     }
 

components/canvas/lib.rs

@@ -18,6 +18,7 @@ extern crate gleam;
 extern crate num;
 extern crate layers;
 extern crate offscreen_gl_context;
+extern crate ipc_channel;
 
 #[macro_use]
 extern crate log;

components/canvas/webgl_paint_task.rs

@@ -16,6 +16,7 @@ use std::sync::mpsc::{channel, Sender};
 use util::vec::byte_swap;
 use layers::platform::surface::NativeSurface;
 use offscreen_gl_context::{GLContext, GLContextAttributes, ColorAttachmentType};
+use ipc_channel::ipc::IpcSharedMemory;
 
 pub struct WebGLPaintTask {
     size: Size2D<i32>,
@@ -440,9 +441,11 @@ impl WebGLPaintTask {
         gl::viewport(x, y, width, height);
     }
 
-    fn send_pixel_contents(&mut self, chan: Sender<Vec<u8>>) {
+    fn send_pixel_contents(&mut self, chan: Sender<IpcSharedMemory>) {
         // FIXME(#5652, dmarcos) Instead of a readback strategy we have
-        // to layerize the canvas
+        // to layerize the canvas.
+        // TODO(pcwalton): We'd save a copy if we had an `IpcSharedMemoryBuilder` abstraction that
+        // allowed you to mutate in-place before freezing the object for sending.
         let width = self.size.width as usize;
         let height = self.size.height as usize;
         let mut pixels = gl::read_pixels(0, 0,
@@ -461,7 +464,7 @@ impl WebGLPaintTask {
 
         // rgba -> bgra
         byte_swap(&mut pixels);
-        chan.send(pixels).unwrap();
+        chan.send(IpcSharedMemory::from_bytes(&pixels[..])).unwrap();
     }
 
     fn send_native_surface(&self, _: Sender<NativeSurface>) {

components/canvas_traits/Cargo.toml

@@ -19,6 +19,9 @@ git = "https://github.com/servo/rust-layers"
 [dependencies.offscreen_gl_context]
 git = "https://github.com/ecoal95/rust-offscreen-rendering-context"
 
+[dependencies.ipc-channel]
+git = "https://github.com/pcwalton/ipc-channel"
+
 [dependencies]
 cssparser = "0.3.1"
 euclid = "0.1"

components/canvas_traits/lib.rs

@@ -11,6 +11,7 @@ extern crate azure;
 extern crate euclid;
 extern crate cssparser;
 extern crate gfx_traits;
+extern crate ipc_channel;
 extern crate layers;
 extern crate offscreen_gl_context;
 
@@ -29,6 +30,7 @@ use std::sync::mpsc::{Sender};
 use layers::platform::surface::NativeSurface;
 use offscreen_gl_context::GLContextAttributes;
 use core::nonzero::NonZero;
+use ipc_channel::ipc::IpcSharedMemory;
 
 #[derive(Clone)]
 pub enum CanvasMsg {
@@ -41,7 +43,7 @@ pub enum CanvasMsg {
 pub enum CanvasCommonMsg {
     Close,
     Recreate(Size2D<i32>),
-    SendPixelContents(Sender<Vec<u8>>),
+    SendPixelContents(Sender<IpcSharedMemory>),
     SendNativeSurface(Sender<NativeSurface>),
 }
 

components/layout/display_list_builder.rs

@@ -32,6 +32,7 @@ use gfx::display_list::{GradientStop, ImageDisplayItem, LineDisplayItem};
 use gfx::display_list::{OpaqueNode, SolidColorDisplayItem};
 use gfx::display_list::{StackingContext, TextDisplayItem, TextOrientation};
 use gfx::paint_task::{PaintLayer, THREAD_TINT_COLORS};
+use ipc_channel::ipc::IpcSharedMemory;
 use msg::compositor_msg::{ScrollPolicy, LayerId};
 use msg::constellation_msg::ConstellationChan;
 use msg::constellation_msg::Msg as ConstellationMsg;
@@ -1098,14 +1099,14 @@ impl FragmentDisplayListBuilding for Fragment {
                     .computed_inline_size.map_or(0, |w| w.to_px() as usize);
                 let height = canvas_fragment_info.replaced_image_fragment_info
                     .computed_block_size.map_or(0, |h| h.to_px() as usize);
-                let (sender, receiver) = channel::<Vec<u8>>();
+                let (sender, receiver) = channel::<IpcSharedMemory>();
                 let canvas_data = match canvas_fragment_info.renderer {
                     Some(ref renderer) =>  {
                         renderer.lock().unwrap().send(CanvasMsg::Common(
                                 CanvasCommonMsg::SendPixelContents(sender))).unwrap();
                         receiver.recv().unwrap()
                     },
-                    None => vec![0xFFu8; width * height * 4],
+                    None => IpcSharedMemory::from_byte(0xFFu8, width * height * 4),
                 };
                 display_list.content.push_back(DisplayItem::ImageClass(box ImageDisplayItem{
                     base: BaseDisplayItem::new(stacking_relative_content_box,

components/net_traits/Cargo.toml

@@ -24,6 +24,9 @@ git = "https://github.com/servo/rust-stb-image"
 version = "0.6"
 features = [ "serde-serialization" ]
 
+[dependencies.ipc-channel]
+git = "https://github.com/pcwalton/ipc-channel"
+
 [dependencies]
 log = "0.3"
 url = "0.2.36"

components/net_traits/image/base.rs

@@ -2,6 +2,7 @@
  * 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 ipc_channel::ipc::IpcSharedMemory;
 use png;
 use stb_image::image as stb_image2;
 use std::mem;
@@ -23,7 +24,7 @@ pub struct Image {
     pub width: u32,
     pub height: u32,
     pub format: PixelFormat,
-    pub bytes: Vec<u8>,
+    pub bytes: IpcSharedMemory,
 }
 
 // TODO(pcwalton): Speed up with SIMD, or better yet, find some way to not do this.
@@ -66,7 +67,7 @@ pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
                 };
 
                 let bytes = mem::replace(bytes, Vec::new());
-
+                let bytes = IpcSharedMemory::from_bytes(&bytes[..]);
                 let image = Image {
                     width: png_image.width,
                     height: png_image.height,
@@ -96,7 +97,7 @@ pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
                     width: image.width as u32,
                     height: image.height as u32,
                     format: PixelFormat::RGBA8,
-                    bytes: image.data,
+                    bytes: IpcSharedMemory::from_bytes(&image.data[..]),
                 })
             }
             stb_image2::LoadResult::ImageF32(_image) => {

components/net_traits/lib.rs

@@ -12,6 +12,7 @@
 
 extern crate euclid;
 extern crate hyper;
+extern crate ipc_channel;
 #[macro_use]
 extern crate log;
 extern crate png;