script/dom/workers/
abstractworkerglobalscope.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5use crossbeam_channel::{Receiver, select};
6use devtools_traits::DevtoolScriptControlMsg;
7use rustc_hash::FxHashSet;
8use script_bindings::reflector::DomObject;
9
10use crate::dom::bindings::conversions::DerivedFrom;
11use crate::dom::dedicatedworkerglobalscope::AutoWorkerReset;
12use crate::dom::globalscope::GlobalScope;
13use crate::dom::worker::TrustedWorkerAddress;
14use crate::dom::workerglobalscope::WorkerGlobalScope;
15use crate::realms::enter_auto_realm;
16use crate::task_queue::{QueuedTaskConversion, TaskQueue};
17
18pub(crate) trait WorkerEventLoopMethods {
19    type WorkerMsg: QueuedTaskConversion + Send;
20    type ControlMsg;
21    type Event;
22    fn task_queue(&self) -> &TaskQueue<Self::WorkerMsg>;
23    fn handle_event(&self, event: Self::Event, cx: &mut js::context::JSContext) -> bool;
24    fn handle_worker_post_event(
25        &self,
26        worker: &TrustedWorkerAddress,
27    ) -> Option<AutoWorkerReset<'_>>;
28    fn from_control_msg(msg: Self::ControlMsg) -> Self::Event;
29    fn from_worker_msg(msg: Self::WorkerMsg) -> Self::Event;
30    fn from_devtools_msg(msg: DevtoolScriptControlMsg) -> Self::Event;
31    fn from_timer_msg() -> Self::Event;
32    fn control_receiver(&self) -> &Receiver<Self::ControlMsg>;
33}
34
35// https://html.spec.whatwg.org/multipage/#worker-event-loop
36pub(crate) fn run_worker_event_loop<T, WorkerMsg, Event>(
37    worker_scope: &T,
38    worker: Option<&TrustedWorkerAddress>,
39    cx: &mut js::context::JSContext,
40) where
41    WorkerMsg: QueuedTaskConversion + Send,
42    T: WorkerEventLoopMethods<WorkerMsg = WorkerMsg, Event = Event>
43        + DerivedFrom<WorkerGlobalScope>
44        + DerivedFrom<GlobalScope>
45        + DomObject,
46{
47    let scope = worker_scope.upcast::<WorkerGlobalScope>();
48    let task_queue = worker_scope.task_queue();
49
50    let never = crossbeam_channel::never();
51    let devtools_receiver = scope.devtools_receiver().unwrap_or(&never);
52
53    let event = select! {
54        recv(worker_scope.control_receiver()) -> msg => match msg {
55            Ok(msg) => Some(T::from_control_msg(msg)),
56            Err(_) => None,
57        },
58        recv(task_queue.select()) -> msg => match msg {
59            Ok(msg) => {
60                task_queue.take_tasks(msg, &FxHashSet::default());
61                task_queue.recv().ok().map(T::from_worker_msg)
62            },
63            Err(_) => None,
64        },
65        recv(devtools_receiver) -> msg => match msg {
66            Ok(msg) => msg.ok().map(T::from_devtools_msg),
67            Err(_) => None,
68        },
69        recv(scope.timer_scheduler().wait_channel()) -> _ => Some(T::from_timer_msg()),
70    };
71
72    // Worker channels can be closed during teardown (for example, after an
73    // explicit close/exit Sharedworker path). Treat that as a clean shutdown signal rather
74    // than panicking on RecvError.
75    let Some(event) = event else {
76        return;
77    };
78
79    scope.timer_scheduler().dispatch_completed_timers();
80
81    let mut sequential = vec![event];
82
83    // https://html.spec.whatwg.org/multipage/#worker-event-loop
84    // Once the WorkerGlobalScope's closing flag is set to true,
85    // the event loop's task queues must discard any further tasks
86    // that would be added to them
87    // (tasks already on the queue are unaffected except where otherwise specified).
88    while !scope.is_closing() {
89        // Batch all events that are ready.
90        // The task queue will throttle non-priority tasks if necessary.
91        match task_queue.take_tasks_and_recv(&FxHashSet::default()) {
92            Err(_) => match devtools_receiver.try_recv() {
93                Ok(message) => sequential.push(T::from_devtools_msg(message.unwrap())),
94                Err(_) => break,
95            },
96            Ok(ev) => sequential.push(T::from_worker_msg(ev)),
97        }
98    }
99
100    // Step 3
101    for event in sequential {
102        let mut realm = enter_auto_realm(cx, worker_scope);
103        let cx = &mut realm.current_realm();
104        if !worker_scope.handle_event(event, cx) {
105            // Shutdown
106            return;
107        }
108        // Step 6
109        let _ar = match worker {
110            Some(worker) => worker_scope.handle_worker_post_event(worker),
111            None => None,
112        };
113        scope.perform_a_microtask_checkpoint(cx);
114    }
115    worker_scope
116        .upcast::<GlobalScope>()
117        .perform_a_dom_garbage_collection_checkpoint();
118}
script/dom/workers/abstractworkerglobalscope.rs

script/dom/workers/
abstractworkerglobalscope.rs
