Merge remote-tracking branch 'origin/master' into feat/multi-window-support

# Conflicts:
#	examples/events/src/main.rs
#	glutin/src/application.rs
#	native/src/window.rs
#	winit/src/window.rs

native/src/window/event.rs

@@ -1,3 +1,5 @@
+use crate::time::Instant;
+
 use std::path::PathBuf;
 
 /// A window-related event.
@@ -19,6 +21,11 @@ pub enum Event {
         height: u32,
     },
 
+    /// A window redraw was requested.
+    ///
+    /// The [`Instant`] contains the current time.
+    RedrawRequested(Instant),
+
     /// The user has requested for the window to close.
     ///
     /// Usually, you will want to terminate the execution whenever this event

native/src/window/redraw_request.rs

@@ -0,0 +1,38 @@
+use crate::time::Instant;
+
+/// A request to redraw a window.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+pub enum RedrawRequest {
+    /// Redraw the next frame.
+    NextFrame,
+
+    /// Redraw at the given time.
+    At(Instant),
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::time::{Duration, Instant};
+
+    #[test]
+    fn ordering() {
+        let now = Instant::now();
+        let later = now + Duration::from_millis(10);
+
+        assert_eq!(RedrawRequest::NextFrame, RedrawRequest::NextFrame);
+        assert_eq!(RedrawRequest::At(now), RedrawRequest::At(now));
+
+        assert!(RedrawRequest::NextFrame < RedrawRequest::At(now));
+        assert!(RedrawRequest::At(now) > RedrawRequest::NextFrame);
+        assert!(RedrawRequest::At(now) < RedrawRequest::At(later));
+        assert!(RedrawRequest::At(later) > RedrawRequest::At(now));
+
+        assert!(RedrawRequest::NextFrame <= RedrawRequest::NextFrame);
+        assert!(RedrawRequest::NextFrame <= RedrawRequest::At(now));
+        assert!(RedrawRequest::At(now) >= RedrawRequest::NextFrame);
+        assert!(RedrawRequest::At(now) <= RedrawRequest::At(now));
+        assert!(RedrawRequest::At(now) <= RedrawRequest::At(later));
+        assert!(RedrawRequest::At(later) >= RedrawRequest::At(now));
+    }
+}