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

3 files changed, 65 insertions, 0 deletions

diff --git a/native/src/window.rs b/native/src/window.rs
index 96a5fe61..d3c8c96f 100644
--- a/native/src/window.rs
+++ b/native/src/window.rs
@@ -6,6 +6,7 @@ mod id;
 mod mode;
 mod position;
 mod settings;
+mod redraw_request;
 mod user_attention;
 
 pub use action::Action;
@@ -15,4 +16,23 @@ pub use id::Id;
 pub use mode::Mode;
 pub use position::Position;
 pub use settings::Settings;
+pub use redraw_request::RedrawRequest;
 pub use user_attention::UserAttention;
+
+use crate::subscription::{self, Subscription};
+use crate::time::Instant;
+
+/// Subscribes to the frames of the window of the running application.
+///
+/// The resulting [`Subscription`] will produce items at a rate equal to the
+/// refresh rate of the window. Note that this rate may be variable, as it is
+/// normally managed by the graphics driver and/or the OS.
+///
+/// In any case, this [`Subscription`] is useful to smoothly draw application-driven
+/// animations without missing any frames.
+pub fn frames() -> Subscription<Instant> {
+    subscription::raw_events(|event, _status| match event {
+        crate::Event::Window(Event::RedrawRequested(at)) => Some(at),
+        _ => None,
+    })
+}
diff --git a/native/src/window/event.rs b/native/src/window/event.rs
index 86321ac0..e2fb5e66 100644
--- a/native/src/window/event.rs
+++ b/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
diff --git a/native/src/window/redraw_request.rs b/native/src/window/redraw_request.rs
new file mode 100644
index 00000000..3b4f0fd3
--- /dev/null
+++ b/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));
+    }
+}