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|
use crate::futures::futures::{
channel::mpsc,
stream,
task::{Context, Poll},
Future, Sink, StreamExt,
};
use std::pin::Pin;
/// An event loop proxy with backpressure that implements `Sink`.
#[derive(Debug)]
pub struct Proxy<Message: 'static> {
raw: winit::event_loop::EventLoopProxy<Message>,
sender: mpsc::Sender<Message>,
notifier: mpsc::Sender<usize>,
}
impl<Message: 'static> Clone for Proxy<Message> {
fn clone(&self) -> Self {
Self {
raw: self.raw.clone(),
sender: self.sender.clone(),
notifier: self.notifier.clone(),
}
}
}
impl<Message: 'static> Proxy<Message> {
const MAX_SIZE: usize = 100;
/// Creates a new [`Proxy`] from an `EventLoopProxy`.
pub fn new(
raw: winit::event_loop::EventLoopProxy<Message>,
) -> (Self, impl Future<Output = ()>) {
let (notifier, processed) = mpsc::channel(Self::MAX_SIZE);
let (sender, receiver) = mpsc::channel(Self::MAX_SIZE);
let proxy = raw.clone();
let worker = async move {
enum Item<T> {
MessageProduced(T),
BatchProcessed(usize),
}
let mut receiver = receiver.map(Item::MessageProduced);
let mut processed = processed.map(Item::BatchProcessed);
let mut count = 0;
loop {
if count < Self::MAX_SIZE {
let mut stream =
stream::select(receiver.by_ref(), processed.by_ref());
match stream.select_next_some().await {
Item::MessageProduced(message) => {
let _ = proxy.send_event(message);
count += 1;
}
Item::BatchProcessed(amount) => {
count = count.saturating_sub(amount);
}
}
} else if let Item::BatchProcessed(amount) =
processed.select_next_some().await
{
count = count.saturating_sub(amount);
}
}
};
(
Self {
raw,
sender,
notifier,
},
worker,
)
}
/// Sends a `Message` to the event loop.
///
/// Note: This skips the backpressure mechanism with an unbounded
/// channel. Use sparingly!
pub fn send(&mut self, message: Message)
where
Message: std::fmt::Debug,
{
self.raw
.send_event(message)
.expect("Send message to event loop");
}
/// Frees an amount of slots for additional messages to be queued in
/// this [`Proxy`].
pub fn free_slots(&mut self, amount: usize) {
let _ = self.notifier.start_send(amount);
}
}
impl<Message: 'static> Sink<Message> for Proxy<Message> {
type Error = mpsc::SendError;
fn poll_ready(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Result<(), Self::Error>> {
self.sender.poll_ready(cx)
}
fn start_send(
mut self: Pin<&mut Self>,
message: Message,
) -> Result<(), Self::Error> {
self.sender.start_send(message)
}
fn poll_flush(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Result<(), Self::Error>> {
match self.sender.poll_ready(cx) {
Poll::Ready(Err(ref e)) if e.is_disconnected() => {
// If the receiver disconnected, we consider the sink to be flushed.
Poll::Ready(Ok(()))
}
x => x,
}
}
fn poll_close(
mut self: Pin<&mut Self>,
_cx: &mut Context<'_>,
) -> Poll<Result<(), Self::Error>> {
self.sender.disconnect();
Poll::Ready(Ok(()))
}
}
|
