Add debug option to disable vsync for profiling.

components/util/opts.rs

@@ -188,6 +188,9 @@ pub struct Opts {
 
     /// Do not use native titlebar
     pub no_native_titlebar: bool,
+
+    /// Enable vsync in the compositor
+    pub enable_vsync: bool,
 }
 
 fn print_usage(app: &str, opts: &Options) {
@@ -277,6 +280,9 @@ pub struct DebugOptions {
 
     /// Load web fonts synchronously to avoid non-deterministic network-driven reflows.
     pub load_webfonts_synchronously: bool,
+
+    /// Disable vsync in the compositor
+    pub disable_vsync: bool,
 }
 
 
@@ -312,6 +318,7 @@ impl DebugOptions {
                 "replace-surrogates" => debug_options.replace_surrogates = true,
                 "gc-profile" => debug_options.gc_profile = true,
                 "load-webfonts-synchronously" => debug_options.load_webfonts_synchronously = true,
+                "disable-vsync" => debug_options.disable_vsync = true,
                 "" => {},
                 _ => return Err(option)
             };
@@ -358,6 +365,8 @@ pub fn print_debug_usage(app: &str) -> ! {
     print_option("gc-profile", "Log GC passes and their durations.");
     print_option("load-webfonts-synchronously",
                  "Load web fonts synchronously to avoid non-deterministic network-driven reflows");
+    print_option("disable-vsync",
+                 "Disable vsync mode in the compositor to allow profiling at more than monitor refresh rate");
 
     println!("");
 
@@ -488,6 +497,7 @@ pub fn default_opts() -> Opts {
         convert_mouse_to_touch: false,
         exit_after_load: false,
         no_native_titlebar: false,
+        enable_vsync: true,
     }
 }
 
@@ -722,6 +732,7 @@ pub fn from_cmdline_args(args: &[String]) -> ArgumentParsingResult {
         convert_mouse_to_touch: debug_options.convert_mouse_to_touch,
         exit_after_load: opt_match.opt_present("x"),
         no_native_titlebar: opt_match.opt_present("b"),
+        enable_vsync: !debug_options.disable_vsync,
     };
 
     set_defaults(opts);

ports/glutin/window.rs

@@ -86,17 +86,21 @@ impl Window {
     pub fn new(is_foreground: bool,
                window_size: TypedSize2D<DevicePixel, u32>,
                parent: Option<glutin::WindowID>) -> Rc<Window> {
-        let mut glutin_window = glutin::WindowBuilder::new()
-                            .with_title("Servo".to_string())
-                            .with_decorations(!opts::get().no_native_titlebar)
-                            .with_vsync()
-                            .with_dimensions(window_size.to_untyped().width, window_size.to_untyped().height)
-                            .with_gl(Window::gl_version())
-                            .with_visibility(is_foreground)
-                            .with_parent(parent)
-                            .with_multitouch()
-                            .build()
-                            .unwrap();
+        let width = window_size.to_untyped().width;
+        let height = window_size.to_untyped().height;
+        let mut builder = glutin::WindowBuilder::new().with_title("Servo".to_string())
+                                                      .with_decorations(!opts::get().no_native_titlebar)
+                                                      .with_dimensions(width, height)
+                                                      .with_gl(Window::gl_version())
+                                                      .with_visibility(is_foreground)
+                                                      .with_parent(parent)
+                                                      .with_multitouch();
+
+        if opts::get().enable_vsync {
+            builder = builder.with_vsync();
+        }
+
+        let mut glutin_window = builder.build().unwrap();
 
         unsafe { glutin_window.make_current().expect("Failed to make context current!") }