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use super::*;
use std::{pin::Pin, task::Poll};
/// See [`Var::wait_update`].
pub(crate) struct WaitUpdateFut<'a> {
var: &'a AnyVar,
update_id: VarUpdateId,
}
impl<'a> WaitUpdateFut<'a> {
pub(super) fn new(var: &'a AnyVar) -> Self {
Self {
update_id: var.last_update(),
var,
}
}
fn poll_impl(&mut self, cx: &mut std::task::Context<'_>) -> Poll<VarUpdateId> {
let update_id = self.var.last_update();
if update_id != self.update_id {
// has changed since init or last poll
self.update_id = update_id;
Poll::Ready(update_id)
} else {
// has not changed since init or last poll, register hook
let waker = cx.waker().clone();
let handle = self.var.hook(move |_| {
waker.wake_by_ref();
false
});
// check if changed in parallel while was registering hook
let update_id = self.var.last_update();
if update_id != self.update_id {
// changed in parallel
// the hook will be dropped (handle not perm), it may wake in parallel too, but poll checks again.
self.update_id = update_id;
Poll::Ready(update_id)
} else {
// really not ready yet
handle.perm();
Poll::Pending
}
}
}
}
impl Future for WaitUpdateFut<'_> {
type Output = VarUpdateId;
fn poll(mut self: Pin<&mut Self>, cx: &mut std::task::Context<'_>) -> Poll<Self::Output> {
self.poll_impl(cx)
}
}
/// See [`Var::wait_animation`].
pub(crate) struct WaitIsNotAnimatingFut<'a> {
var: &'a AnyVar,
observed_animation_start: bool,
}
impl<'a> WaitIsNotAnimatingFut<'a> {
pub(super) fn new(var: &'a AnyVar) -> Self {
Self {
observed_animation_start: var.is_animating(),
var,
}
}
}
impl Future for WaitIsNotAnimatingFut<'_> {
type Output = ();
fn poll(mut self: Pin<&mut Self>, cx: &mut std::task::Context<'_>) -> Poll<()> {
if !self.var.capabilities().contains(VarCapability::NEW) {
// var cannot have new value, ready to avoid deadlock.
self.observed_animation_start = false;
return Poll::Ready(());
}
if self.observed_animation_start {
// already observed `is_animating` in a previous poll.
if self.var.is_animating() {
// still animating, but received poll so an animation was overridden and stopped.
// try hook with new animation.
while self.var.capabilities().contains(VarCapability::NEW) {
let waker = cx.waker().clone();
let r = self.var.hook_animation_stop(move || {
waker.wake_by_ref();
});
if r.is_dummy() {
// failed to hook with new animation too.
if self.var.is_animating() {
// but has yet another animation, try again.
continue;
} else {
// observed `is_animating` changing to `false`.
self.observed_animation_start = false;
return Poll::Ready(());
}
} else {
r.perm();
// new animation hook setup ok, break loop.
return Poll::Pending;
}
}
// var no longer has the `NEW` capability.
self.observed_animation_start = false;
Poll::Ready(())
} else {
// now observed change to `false`.
self.observed_animation_start = false;
Poll::Ready(())
}
} else {
// have not observed `is_animating` yet.
// hook with normal var updates, `is_animating && is_new` is always `true`.
let waker = cx.waker().clone();
let start_hook = self.var.hook(move |_| {
waker.wake_by_ref();
false
});
if self.var.is_animating() {
// observed `is_animating` already, changed in other thread during the `hook` setup.
self.observed_animation_start = true;
while self.var.capabilities().contains(VarCapability::NEW) {
// hook with animation stop.
let waker = cx.waker().clone();
let r = self.var.hook_animation_stop(Box::new(move || {
waker.wake_by_ref();
}));
if r.is_dummy() {
// failed to hook, animation already stopped during hook setup.
if self.var.is_animating() {
// but var is still animating, reason a new animation replaced the previous one (that stopped).
// continue to hook with new animation.
continue;
} else {
// we have observed `is_animating` changing to `false` in one poll call.
self.observed_animation_start = false;
return Poll::Ready(());
}
} else {
r.perm();
// animation hook setup ok, break loop.
return Poll::Pending;
}
}
// var no longer has the `NEW` capability.
self.observed_animation_start = false;
Poll::Ready(())
} else {
// updates hook ok.
start_hook.perm();
Poll::Pending
}
}
}
}