script/event_loop/
document_loader.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
5//! Tracking of pending loads in a document.
6//!
7//! <https://html.spec.whatwg.org/multipage/#the-end>
8
9use std::collections::HashMap;
10
11use js::context::JSContext;
12use net_traits::ResourceThreads;
13use script_bindings::cell::DomRefCell;
14use script_bindings::script_runtime::{during_gc_collection, runtime_is_alive};
15use servo_url::ServoUrl;
16
17use crate::dom::bindings::root::Dom;
18use crate::dom::document::Document;
19
20#[derive(Clone, Debug, Eq, Hash, JSTraceable, MallocSizeOf, PartialEq)]
21pub(crate) enum LoadType {
22    Image(#[no_trace] ServoUrl),
23    Script(#[no_trace] ServoUrl),
24    Subframe(#[no_trace] ServoUrl),
25    Stylesheet(#[no_trace] ServoUrl),
26    PageSource(#[no_trace] ServoUrl),
27    Media,
28}
29
30/// Canary value ensuring that manually added blocking loads are always removed by the
31/// time that the owner is destroyed.
32#[derive(JSTraceable, MallocSizeOf)]
33#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
34pub(crate) struct LoadBlocker {
35    /// The document whose load event is blocked by this object existing.
36    doc: Dom<Document>,
37    /// The load that is blocking the document's load event.
38    load: Option<LoadType>,
39}
40
41impl LoadBlocker {
42    /// Mark the document's load event as blocked on this new load.
43    pub(crate) fn new(doc: &Document, load: LoadType) -> LoadBlocker {
44        doc.loader_mut().add_blocking_load(load.clone());
45        LoadBlocker {
46            doc: Dom::from_ref(doc),
47            load: Some(load),
48        }
49    }
50
51    /// Remove this load from the associated document's list of blocking loads.
52    pub(crate) fn terminate(cx: &mut JSContext, blocker: &DomRefCell<Option<LoadBlocker>>) {
53        let Some(load) = blocker
54            .safe_borrow_mut(cx.no_gc())
55            .as_mut()
56            .and_then(|blocker| blocker.load.take())
57        else {
58            return;
59        };
60
61        if let Some(blocker) = blocker.borrow().as_ref() {
62            blocker.doc.finish_load(load, cx);
63        }
64
65        *blocker.safe_borrow_mut(cx.no_gc()) = None;
66    }
67}
68
69impl Drop for LoadBlocker {
70    fn drop(&mut self) {
71        // We need to check here if the whole runtime is alive, otherwise
72        // we interact with a document that is also being dropped. That
73        // would panic, since we should no longer schedule a task for
74        // a dropped runtime. Therefore, we should only run the drop logic
75        // in case this element is dropped, but its containing document
76        // is still alive.
77        //
78        // This destructor can also run from during GC (see #46207), which can lead to
79        // accessing already freed memory if we run `finish_load_for_dropped_blocker`.
80        if runtime_is_alive() &&
81            !during_gc_collection() &&
82            let Some(load) = self.load.take()
83        {
84            self.doc.finish_load_for_dropped_blocker(load);
85        }
86    }
87}
88
89#[derive(JSTraceable, MallocSizeOf)]
90pub(crate) struct DocumentLoader {
91    #[no_trace]
92    resource_threads: ResourceThreads,
93    /// A map from [`LoadType`] to the number of blocking loads. When a particular [`LoadType`]
94    /// reaches zero, it is removed from the map and no longer blocks the load.
95    blocking_loads: HashMap<LoadType, u32>,
96    events_inhibited: bool,
97}
98
99impl DocumentLoader {
100    pub(crate) fn new(existing: &DocumentLoader) -> DocumentLoader {
101        DocumentLoader::new_with_threads(existing.resource_threads.clone(), None)
102    }
103
104    pub(crate) fn new_with_threads(
105        resource_threads: ResourceThreads,
106        initial_load: Option<ServoUrl>,
107    ) -> DocumentLoader {
108        debug!("Initial blocking load {:?}.", initial_load);
109
110        let initial_loads = initial_load
111            .into_iter()
112            .map(|url| (LoadType::PageSource(url), 1))
113            .collect();
114
115        DocumentLoader {
116            resource_threads,
117            blocking_loads: initial_loads,
118            events_inhibited: false,
119        }
120    }
121
122    /// Add a load to the list of blocking loads.
123    pub(crate) fn add_blocking_load(&mut self, load: LoadType) {
124        debug!(
125            "Adding blocking load {:?} ({}).",
126            load,
127            self.blocking_loads.len()
128        );
129        self.blocking_loads
130            .entry(load)
131            .and_modify(|load_number| *load_number += 1)
132            .or_insert(1);
133    }
134
135    /// Mark an in-progress network request complete.
136    pub(crate) fn finish_load(&mut self, load: &LoadType) {
137        debug!(
138            "Removing blocking load {:?} ({}).",
139            load,
140            self.blocking_loads.len()
141        );
142
143        let Some(entry) = self.blocking_loads.get_mut(load) else {
144            warn!("unknown completed load {load:?}");
145            return;
146        };
147
148        *entry = entry.saturating_sub(1);
149        if *entry == 0 {
150            self.blocking_loads.remove(load);
151        }
152    }
153
154    pub(crate) fn is_blocked(&self) -> bool {
155        // TODO: Ensure that we report blocked if parsing is still ongoing.
156        !self.blocking_loads.is_empty()
157    }
158
159    pub(crate) fn is_only_blocked_by_iframes(&self) -> bool {
160        self.blocking_loads
161            .keys()
162            .all(|load| matches!(*load, LoadType::Subframe(_)))
163    }
164
165    pub(crate) fn inhibit_events(&mut self) {
166        self.events_inhibited = true;
167    }
168
169    pub(crate) fn events_inhibited(&self) -> bool {
170        self.events_inhibited
171    }
172
173    pub(crate) fn resource_threads(&self) -> &ResourceThreads {
174        &self.resource_threads
175    }
176}
script/event_loop/document_loader.rs

script/event_loop/
document_loader.rs
