1 files changed, 99 insertions, 0 deletions
diff --git a/components/compositing/headless.rs b/components/compositing/headless.rs
new file mode 100644
index 00000000000..d8d56e64d00
--- /dev/null
+++ b/components/compositing/headless.rs
@@ -0,0 +1,99 @@
+/* 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 compositor_task::{Msg, Exit, ChangeReadyState, SetIds};
+use compositor_task::{GetGraphicsMetadata, CreateOrUpdateRootLayer, CreateOrUpdateDescendantLayer};
+use compositor_task::{SetLayerClipRect, Paint, ScrollFragmentPoint, LoadComplete};
+use compositor_task::{ShutdownComplete, ChangeRenderState, RenderMsgDiscarded};
+
+use geom::scale_factor::ScaleFactor;
+use geom::size::TypedSize2D;
+use servo_msg::constellation_msg::{ConstellationChan, ExitMsg, ResizedWindowMsg, WindowSizeData};
+use servo_util::memory::MemoryProfilerChan;
+use servo_util::memory;
+use servo_util::time::TimeProfilerChan;
+use servo_util::time;
+
+/// Starts the compositor, which listens for messages on the specified port.
+///
+/// This is the null compositor which doesn't draw anything to the screen.
+/// It's intended for headless testing.
+pub struct NullCompositor {
+    /// The port on which we receive messages.
+    pub port: Receiver<Msg>,
+}
+
+impl NullCompositor {
+    fn new(port: Receiver<Msg>) -> NullCompositor {
+        NullCompositor {
+            port: port,
+        }
+    }
+
+    pub fn create(port: Receiver<Msg>,
+                  constellation_chan: ConstellationChan,
+                  time_profiler_chan: TimeProfilerChan,
+                  memory_profiler_chan: MemoryProfilerChan) {
+        let compositor = NullCompositor::new(port);
+
+        // Tell the constellation about the initial fake size.
+        {
+            let ConstellationChan(ref chan) = constellation_chan;
+            chan.send(ResizedWindowMsg(WindowSizeData {
+                initial_viewport: TypedSize2D(640_f32, 480_f32),
+                visible_viewport: TypedSize2D(640_f32, 480_f32),
+                device_pixel_ratio: ScaleFactor(1.0),
+            }));
+        }
+        compositor.handle_message(constellation_chan);
+
+        // Drain compositor port, sometimes messages contain channels that are blocking
+        // another task from finishing (i.e. SetIds)
+        loop {
+            match compositor.port.try_recv() {
+                Err(_) => break,
+                Ok(_) => {},
+            }
+        }
+
+        time_profiler_chan.send(time::ExitMsg);
+        memory_profiler_chan.send(memory::ExitMsg);
+    }
+
+    fn handle_message(&self, constellation_chan: ConstellationChan) {
+        loop {
+            match self.port.recv() {
+                Exit(chan) => {
+                    debug!("shutting down the constellation");
+                    let ConstellationChan(ref con_chan) = constellation_chan;
+                    con_chan.send(ExitMsg);
+                    chan.send(());
+                }
+
+                ShutdownComplete => {
+                    debug!("constellation completed shutdown");
+                    break
+                }
+
+                GetGraphicsMetadata(chan) => {
+                    chan.send(None);
+                }
+
+                SetIds(_, response_chan, _) => {
+                    response_chan.send(());
+                }
+
+                // Explicitly list ignored messages so that when we add a new one,
+                // we'll notice and think about whether it needs a response, like
+                // SetIds.
+
+                CreateOrUpdateRootLayer(..) |
+                CreateOrUpdateDescendantLayer(..) |
+                SetLayerClipRect(..) | Paint(..) |
+                ChangeReadyState(..) | ChangeRenderState(..) | ScrollFragmentPoint(..) |
+                LoadComplete(..) | RenderMsgDiscarded(..) => ()
+            }
+        }
+    }
+}