Implement vsync for x11 and add vsync example

examples/vsync.rs

@@ -0,0 +1,46 @@
+#[cfg(target_os = "android")]
+#[macro_use]
+extern crate android_glue;
+
+extern crate clock_ticks;
+extern crate glutin;
+
+mod support;
+
+#[cfg(target_os = "android")]
+android_start!(main);
+
+#[cfg(not(feature = "window"))]
+fn main() { println!("This example requires glutin to be compiled with the `window` feature"); }
+
+#[cfg(feature = "window")]
+fn resize_callback(width: u32, height: u32) {
+    println!("Window resized to {}x{}", width, height);
+}
+
+#[cfg(feature = "window")]
+fn main() {
+    println!("Vsync example. This example may panic if your driver or your system forces \
+              you out of vsync. This is intended when `build_strict` is used.");
+
+    let mut window = glutin::WindowBuilder::new().with_vsync().build_strict().unwrap();
+    window.set_window_resize_callback(Some(resize_callback as fn(u32, u32)));
+    unsafe { window.make_current() };
+
+    let context = support::load(&window);
+
+    while !window.is_closed() {
+        let before = clock_ticks::precise_time_ns();
+
+        context.draw_frame((0.0, 1.0, 0.0, 1.0));
+        window.swap_buffers();
+
+        for ev in window.poll_events() {
+            println!("{:?}", ev);
+        }
+
+        let after = clock_ticks::precise_time_ns();
+        println!("Vsync example - Time of previous frame: {}ms",
+                 (after - before) as f32 / 1000000.0);
+    }
+}