Add ANGLE rendering in Wrench

The `--angle` command-line parameter enables it on Windows,
when `--headless` is not also used. It panics on non-Windows.

servo-tidy.toml

@@ -19,7 +19,9 @@ packages = [
 ]
 
 # Files that are ignored for all tidy and lint checks.
-files = [ ]
+files = [
+    "./wrench/src/egl.rs",  # Copied from glutin
+]
 
 # Many directories are currently ignored while we tidy things up
 # gradually.

wrench/Cargo.toml

@@ -38,6 +38,7 @@ headless = [ "osmesa-sys", "osmesa-src" ]
 
 [target.'cfg(target_os = "windows")'.dependencies]
 dwrote = "0.4.1"
+mozangle = {version = "0.1.5", features = ["egl"]}
 
 [target.'cfg(any(target_os = "linux", target_os = "macos"))'.dependencies]
 font-loader = "0.6"

wrench/src/angle.rs

@@ -0,0 +1,72 @@
+/* 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 glutin;
+use glutin::{WindowBuilder, ContextBuilder, EventsLoop, Window, CreationError};
+
+#[cfg(not(windows))]
+pub enum Context {}
+
+#[cfg(windows)]
+pub use ::egl::Context;
+
+impl Context {
+    #[cfg(not(windows))]
+    pub fn with_window(
+        _: WindowBuilder,
+        _: ContextBuilder,
+        _: &EventsLoop,
+    ) -> Result<(Window, Self), CreationError> {
+        Err(CreationError::PlatformSpecific("ANGLE rendering is only supported on Windows".into()))
+    }
+
+    #[cfg(windows)]
+    pub fn with_window(
+        window_builder: WindowBuilder,
+        context_builder: ContextBuilder,
+        events_loop: &EventsLoop,
+    ) -> Result<(Window, Self), CreationError> {
+        use glutin::os::windows::WindowExt;
+
+        // FIXME: &context_builder.pf_reqs  https://github.com/tomaka/glutin/pull/1002
+        let pf_reqs = &glutin::PixelFormatRequirements::default();
+        let gl_attr = &context_builder.gl_attr.map_sharing(|_| unimplemented!());
+        let window = window_builder.build(events_loop)?;
+        Self::new(pf_reqs, gl_attr)
+            .and_then(|p| p.finish(window.get_hwnd() as _))
+            .map(|context| (window, context))
+    }
+}
+
+#[cfg(not(windows))]
+impl glutin::GlContext for Context {
+    unsafe fn make_current(&self) -> Result<(), glutin::ContextError> {
+        match *self {}
+    }
+
+    fn is_current(&self) -> bool {
+        match *self {}
+    }
+
+    fn get_proc_address(&self, _: &str) -> *const () {
+        match *self {}
+    }
+
+    fn swap_buffers(&self) -> Result<(), glutin::ContextError> {
+        match *self {}
+    }
+
+    fn get_api(&self) -> glutin::Api {
+        match *self {}
+    }
+
+    fn get_pixel_format(&self) -> glutin::PixelFormat {
+        match *self {}
+    }
+
+    fn resize(&self, _: u32, _: u32) {
+        match *self {}
+    }
+}
+

wrench/src/args.yaml

@@ -44,6 +44,9 @@ args:
       short: h
       long: headless
       help: Enable headless rendering
+  - angle:
+      long: angle
+      help: Enable ANGLE rendering (on Windows only)
   - dp_ratio:
       short: p
       long: device-pixel-ratio