From b05ef16d817af85d175d60422591d90fe3ec4218 Mon Sep 17 00:00:00 2001
From: Pierre Krieger <pierre.krieger1708@gmail.com>
Date: Fri, 23 Jan 2015 09:31:05 +0100
Subject: [PATCH] Implement vsync for x11 and add vsync example

---
 Cargo.toml            |  3 +++
 build.rs              |  2 ++
 examples/vsync.rs     | 46 ++++++++++++++++++++++++++++++++++++++++++
 src/x11/window/mod.rs | 47 +++++++++++++++++++++++++++++++++++++++++--
 4 files changed, 96 insertions(+), 2 deletions(-)
 create mode 100644 examples/vsync.rs

diff --git a/Cargo.toml b/Cargo.toml
index b7a148c9..a277291d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,6 +23,9 @@ gl_common = "*"
 gl_generator = "*"
 khronos_api = "*"
 
+[dev-dependencies]
+clock_ticks = "*"
+
 [target.arm-linux-androideabi.dependencies.android_glue]
 git = "https://github.com/tomaka/android-rs-glue"
 
diff --git a/build.rs b/build.rs
index f49b47f1..15a0f6da 100644
--- a/build.rs
+++ b/build.rs
@@ -39,6 +39,8 @@ fn main() {
                                         khronos_api::GLX_XML,
                                         vec![
                                             "GLX_ARB_create_context".to_string(),
+                                            "GLX_EXT_swap_control".to_string(),
+                                            "GLX_SGI_swap_control".to_string()
                                         ],
                                         "1.4", "core", &mut file).unwrap();
     }
diff --git a/examples/vsync.rs b/examples/vsync.rs
new file mode 100644
index 00000000..ec9ea79f
--- /dev/null
+++ b/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);
+    }
+}
diff --git a/src/x11/window/mod.rs b/src/x11/window/mod.rs
index f4c296a1..d3c5163d 100644
--- a/src/x11/window/mod.rs
+++ b/src/x11/window/mod.rs
@@ -298,7 +298,7 @@ impl Window {
 
 
         // creating GL context
-        let context = unsafe {
+        let (context, extra_functions) = unsafe {
             let mut attributes = Vec::new();
 
             if builder.gl_version.is_some() {
@@ -345,9 +345,52 @@ impl Window {
                 return Err(OsError(format!("GL context creation failed")));
             }
 
-            context
+            (context, extra_functions)
         };
 
+        // vsync
+        if builder.vsync {
+            unsafe { ffi::glx::MakeCurrent(display, window, context) };
+
+            if extra_functions.SwapIntervalEXT.is_loaded() {
+                // this should be the most common extension
+                unsafe {
+                    extra_functions.SwapIntervalEXT(display as *mut _, window, 1);
+                }
+
+                // checking that it worked
+                if builder.strict {
+                    let mut swap = unsafe { mem::uninitialized() };
+                    unsafe {
+                        ffi::glx::QueryDrawable(display, window,
+                                                ffi::glx_extra::SWAP_INTERVAL_EXT as i32,
+                                                &mut swap);
+                    }
+
+                    if swap != 1 {
+                        return Err(OsError(format!("Couldn't setup vsync: expected \
+                                                    interval `1` but got `{}`", swap)));
+                    }
+                }
+
+            // GLX_MESA_swap_control is not official
+            /*} else if extra_functions.SwapIntervalMESA.is_loaded() {
+                unsafe {
+                    extra_functions.SwapIntervalMESA(1);
+                }*/
+
+            } else if extra_functions.SwapIntervalSGI.is_loaded() {
+                unsafe {
+                    extra_functions.SwapIntervalSGI(1);
+                }
+
+            } else if builder.strict {
+                return Err(OsError(format!("Couldn't find any available vsync extension")));
+            }
+
+            unsafe { ffi::glx::MakeCurrent(display, 0, ptr::null()) };
+        }
+
         // creating the window object
         let window = Window {
             x: Arc::new(XWindow {