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|
use std::cell::RefCell;
use std::rc::Rc;
use std::sync::atomic::AtomicBool;
use std::sync::mpsc::Sender;
use std::sync::{Arc, Mutex, Weak};
use std::time::{Duration, Instant};
use atomic::Ordering;
use calloop::ping::{make_ping, Ping};
use calloop::timer::{TimeoutAction, Timer};
use calloop::LoopHandle;
use smithay::reexports::wayland_server::Client;
use smithay::wayland::compositor::{Blocker, BlockerState};
/// Default time limit, after which the transaction completes.
///
/// Serves to avoid hanging when a client fails to respond to a configure promptly.
const TIME_LIMIT: Duration = Duration::from_millis(300);
/// Transaction between Wayland clients.
///
/// How to use it:
/// 1. Create a transaction with [`Transaction::new()`].
/// 2. Clone it as many times as you need.
/// 3. Before adding the transaction as a commit blocker, remember to call
/// [`Transaction::add_notification()`] to receive a notification when the transaction completes.
/// 4. Before adding the transaction as a commit blocker, remember to call
/// [`Transaction::register_deadline_timer()`] to make sure the transaction completes when
/// reaching the deadline.
/// 5. In your surface pre-commit handler, if the transaction corresponding to that commit isn't
/// ready, get a blocker with [`Transaction::blocker()`] and add it to the surface.
#[derive(Debug, Clone)]
pub struct Transaction {
inner: Arc<Inner>,
deadline: Rc<RefCell<Deadline>>,
}
/// Blocker for a [`Transaction`].
#[derive(Debug)]
pub struct TransactionBlocker(Weak<Inner>);
#[derive(Debug)]
enum Deadline {
NotRegistered(Instant),
Registered { remove: Ping },
}
#[derive(Debug)]
struct Inner {
/// Whether the transaction is completed.
completed: AtomicBool,
/// Notifications to send out upon completing the transaction.
notifications: Mutex<Option<(Sender<Client>, Vec<Client>)>>,
}
impl Transaction {
/// Creates a new transaction.
#[allow(clippy::new_without_default)]
pub fn new() -> Self {
Self {
inner: Arc::new(Inner::new()),
deadline: Rc::new(RefCell::new(Deadline::NotRegistered(
Instant::now() + TIME_LIMIT,
))),
}
}
/// Gets a blocker for this transaction.
pub fn blocker(&self) -> TransactionBlocker {
trace!(transaction = ?Arc::as_ptr(&self.inner), "generating blocker");
TransactionBlocker(Arc::downgrade(&self.inner))
}
/// Adds a notification for when this transaction completes.
pub fn add_notification(&self, sender: Sender<Client>, client: Client) {
if self.is_completed() {
error!("tried to add notification to a completed transaction");
return;
}
let mut guard = self.inner.notifications.lock().unwrap();
guard.get_or_insert((sender, Vec::new())).1.push(client);
}
/// Registers this transaction's deadline timer on an event loop.
pub fn register_deadline_timer<T: 'static>(&self, event_loop: &LoopHandle<'static, T>) {
let mut cell = self.deadline.borrow_mut();
if let Deadline::NotRegistered(deadline) = *cell {
let timer = Timer::from_deadline(deadline);
let inner = Arc::downgrade(&self.inner);
let token = event_loop
.insert_source(timer, move |_, _, _| {
let _span = trace_span!("deadline timer", transaction = ?Weak::as_ptr(&inner))
.entered();
if let Some(inner) = inner.upgrade() {
trace!("deadline reached, completing transaction");
inner.complete();
} else {
// We should remove the timer automatically. But this callback can still
// just happen to run while the ping callback is scheduled, leading to this
// branch being legitimately taken.
trace!("transaction completed without removing the timer");
}
TimeoutAction::Drop
})
.unwrap();
// Add a ping source that will be used to remove the timer automatically.
let (ping, source) = make_ping().unwrap();
let loop_handle = event_loop.clone();
event_loop
.insert_source(source, move |_, _, _| {
loop_handle.remove(token);
})
.unwrap();
*cell = Deadline::Registered { remove: ping };
}
}
/// Returns whether this transaction has already completed.
pub fn is_completed(&self) -> bool {
self.inner.is_completed()
}
/// Returns whether this is the last instance of this transaction.
pub fn is_last(&self) -> bool {
Arc::strong_count(&self.inner) == 1
}
}
impl Drop for Transaction {
fn drop(&mut self) {
let _span = trace_span!("drop", transaction = ?Arc::as_ptr(&self.inner)).entered();
if self.is_last() {
// If this was the last transaction, complete it.
trace!("last transaction dropped, completing");
self.inner.complete();
// Also remove the timer.
if let Deadline::Registered { remove } = &*self.deadline.borrow() {
remove.ping();
};
}
}
}
impl TransactionBlocker {
pub fn completed() -> Self {
Self(Weak::new())
}
}
impl Blocker for TransactionBlocker {
fn state(&self) -> BlockerState {
if self.0.upgrade().map_or(true, |x| x.is_completed()) {
BlockerState::Released
} else {
BlockerState::Pending
}
}
}
impl Inner {
fn new() -> Self {
Self {
completed: AtomicBool::new(false),
notifications: Mutex::new(None),
}
}
fn is_completed(&self) -> bool {
self.completed.load(Ordering::Relaxed)
}
fn complete(&self) {
self.completed.store(true, Ordering::Relaxed);
let mut guard = self.notifications.lock().unwrap();
if let Some((sender, clients)) = guard.take() {
for client in clients {
if let Err(err) = sender.send(client) {
warn!("error sending blocker notification: {err:?}");
};
}
}
}
}
|
