de0e582940
<!-- Please describe your changes on the following line: --> @jdm @KiChjang First pass at using microtasks to await a stable state. I ran into all sorts of problems to get it to compile, I think it's mainly related to the fact that the microtasks are stored in a `Vec`, which meant the `Runnalbe.handler(self: Box<Self>)` couldn't be called while iterating over the Vec... It compiles now although I haven't run any tests. I'm assuming I'm missing something fundamental and was hoping my changes would highlight the problems I run into, and you had a better idea of how to implement this... Perhaps we shouldn't pass a `Runnable` to `await_stable_state` at all? --- <!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: --> - [ ] `./mach build -d` does not report any errors - [ ] `./mach test-tidy` does not report any errors - [ ] These changes fix #15375 (github issue number if applicable). <!-- Either: --> - [ ] There are tests for these changes OR - [ ] These changes do not require tests because _____ <!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.--> <!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. --> Source-Repo: https://github.com/servo/servo Source-Revision: f05491166f21879f74758b2f03bbc4c4a4c31eb8
98 lines
3.5 KiB
Rust
98 lines
3.5 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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//! Implementation of [microtasks](https://html.spec.whatwg.org/multipage/#microtask) and
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//! microtask queues. It is up to implementations of event loops to store a queue and
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//! perform checkpoints at appropriate times, as well as enqueue microtasks as required.
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use dom::bindings::callback::ExceptionHandling;
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use dom::bindings::cell::DOMRefCell;
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use dom::bindings::codegen::Bindings::PromiseBinding::PromiseJobCallback;
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use dom::bindings::js::Root;
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use dom::globalscope::GlobalScope;
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use dom::htmlmediaelement::MediaElementMicrotask;
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use dom::mutationobserver::MutationObserver;
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use msg::constellation_msg::PipelineId;
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use std::cell::Cell;
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use std::mem;
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use std::rc::Rc;
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/// A collection of microtasks in FIFO order.
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#[derive(JSTraceable, HeapSizeOf, Default)]
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pub struct MicrotaskQueue {
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/// The list of enqueued microtasks that will be invoked at the next microtask checkpoint.
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microtask_queue: DOMRefCell<Vec<Microtask>>,
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/// https://html.spec.whatwg.org/multipage/#performing-a-microtask-checkpoint
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performing_a_microtask_checkpoint: Cell<bool>,
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}
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#[derive(JSTraceable, HeapSizeOf)]
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pub enum Microtask {
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Promise(EnqueuedPromiseCallback),
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MediaElement(MediaElementMicrotask),
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NotifyMutationObservers,
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}
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pub trait MicrotaskRunnable {
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fn handler(&self) {}
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}
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/// A promise callback scheduled to run during the next microtask checkpoint (#4283).
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#[derive(JSTraceable, HeapSizeOf)]
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pub struct EnqueuedPromiseCallback {
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#[ignore_heap_size_of = "Rc has unclear ownership"]
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pub callback: Rc<PromiseJobCallback>,
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pub pipeline: PipelineId,
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}
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impl MicrotaskQueue {
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/// Add a new microtask to this queue. It will be invoked as part of the next
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/// microtask checkpoint.
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pub fn enqueue(&self, job: Microtask) {
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self.microtask_queue.borrow_mut().push(job);
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}
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/// https://html.spec.whatwg.org/multipage/#perform-a-microtask-checkpoint
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/// Perform a microtask checkpoint, executing all queued microtasks until the queue is empty.
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pub fn checkpoint<F>(&self, target_provider: F)
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where F: Fn(PipelineId) -> Option<Root<GlobalScope>>
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{
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if self.performing_a_microtask_checkpoint.get() {
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return;
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}
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// Step 1
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self.performing_a_microtask_checkpoint.set(true);
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// Steps 2-7
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while !self.microtask_queue.borrow().is_empty() {
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rooted_vec!(let mut pending_queue);
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mem::swap(
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&mut *pending_queue,
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&mut *self.microtask_queue.borrow_mut());
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for job in pending_queue.iter() {
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match *job {
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Microtask::Promise(ref job) => {
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if let Some(target) = target_provider(job.pipeline) {
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let _ = job.callback.Call_(&*target, ExceptionHandling::Report);
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}
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},
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Microtask::MediaElement(ref task) => {
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task.handler();
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}
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Microtask::NotifyMutationObservers => {
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MutationObserver::notify_mutation_observers();
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}
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}
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}
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}
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//TODO: Step 8 - notify about rejected promises
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// Step 9
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self.performing_a_microtask_checkpoint.set(false);
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}
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}
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