message: Clarify documentation of `window::frames`
diff: @@ -17,7 +17,11 @@ 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
  -/// framerate of the monitor of said window.
  +/// 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),
  