Files
servo/components/script/dom/mutationobserver.rs
Narfinger 423800eec4 Script: Lazily transform the DOMString into Rust String instead of immediately. (#39509)
This implements LazyDOMString (from now on DOMString) as outlined in
https://github.com/servo/servo/issues/39479.
Constructing from a *mut JSString we keep the in a
RootedTraceableBox<Heap<*mut JSString>> and transform
the string into a rust string if necessary via the `make_rust_string`
method.
Methods used in script are implemented on this string. Currently we
transform the string at all times.
But in the future more efficient implementations are possible.

We implement the safety critical sections in a separate module
DOMStringInner which allows simple constructors, `make_rust_string` and
the `bytes` method.
This method returns the new type `EncodedBytes` which contains the
reference to the underlying string in either format.

Testing: WPT tests still seem to work, so this should test this
functionality.

---------

Signed-off-by: Narfinger <Narfinger@users.noreply.github.com>
2025-10-09 18:18:03 +00:00

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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
use std::cell::LazyCell;
use std::collections::HashMap;
use std::rc::Rc;
use dom_struct::dom_struct;
use html5ever::{LocalName, Namespace, ns};
use js::rust::HandleObject;
use crate::dom::bindings::cell::DomRefCell;
use crate::dom::bindings::codegen::Bindings::MutationObserverBinding::MutationObserver_Binding::MutationObserverMethods;
use crate::dom::bindings::codegen::Bindings::MutationObserverBinding::{
MutationCallback, MutationObserverInit,
};
use crate::dom::bindings::error::{Error, Fallible};
use crate::dom::bindings::reflector::{DomGlobal, Reflector, reflect_dom_object_with_proto};
use crate::dom::bindings::root::DomRoot;
use crate::dom::bindings::str::DOMString;
use crate::dom::mutationrecord::MutationRecord;
use crate::dom::node::{Node, ShadowIncluding};
use crate::dom::window::Window;
use crate::script_runtime::CanGc;
use crate::script_thread::ScriptThread;
#[dom_struct]
pub(crate) struct MutationObserver {
reflector_: Reflector,
#[ignore_malloc_size_of = "can't measure Rc values"]
callback: Rc<MutationCallback>,
record_queue: DomRefCell<Vec<DomRoot<MutationRecord>>>,
node_list: DomRefCell<Vec<DomRoot<Node>>>,
}
pub(crate) enum Mutation<'a> {
Attribute {
name: LocalName,
namespace: Namespace,
old_value: Option<DOMString>,
},
CharacterData {
old_value: String,
},
ChildList {
added: Option<&'a [&'a Node]>,
removed: Option<&'a [&'a Node]>,
prev: Option<&'a Node>,
next: Option<&'a Node>,
},
}
#[derive(JSTraceable, MallocSizeOf)]
pub(crate) struct RegisteredObserver {
pub(crate) observer: DomRoot<MutationObserver>,
options: ObserverOptions,
}
#[derive(JSTraceable, MallocSizeOf)]
pub(crate) struct ObserverOptions {
attribute_old_value: bool,
attributes: bool,
character_data: bool,
character_data_old_value: bool,
child_list: bool,
subtree: bool,
attribute_filter: Vec<DOMString>,
}
impl MutationObserver {
fn new_with_proto(
global: &Window,
proto: Option<HandleObject>,
callback: Rc<MutationCallback>,
can_gc: CanGc,
) -> DomRoot<MutationObserver> {
let boxed_observer = Box::new(MutationObserver::new_inherited(callback));
reflect_dom_object_with_proto(boxed_observer, global, proto, can_gc)
}
fn new_inherited(callback: Rc<MutationCallback>) -> MutationObserver {
MutationObserver {
reflector_: Reflector::new(),
callback,
record_queue: DomRefCell::new(vec![]),
node_list: DomRefCell::new(vec![]),
}
}
pub(crate) fn record_queue(&self) -> &DomRefCell<Vec<DomRoot<MutationRecord>>> {
&self.record_queue
}
pub(crate) fn callback(&self) -> &Rc<MutationCallback> {
&self.callback
}
/// <https://dom.spec.whatwg.org/#queueing-a-mutation-record>
pub(crate) fn queue_a_mutation_record<'a, F>(
target: &Node,
attr_type: LazyCell<Mutation<'a>, F>,
) where
F: FnOnce() -> Mutation<'a>,
{
if !target.global().as_window().get_exists_mut_observer() {
return;
}
// Step 1 Let interestedObservers be an empty map.
let mut interested_observers: HashMap<DomRoot<MutationObserver>, Option<DOMString>> =
HashMap::new();
// Step 2 Let nodes be the inclusive ancestors of target.
// Step 3 For each node in nodes ...
for node in target.inclusive_ancestors(ShadowIncluding::No) {
let registered = node.registered_mutation_observers();
if registered.is_none() {
continue;
}
// Step 3 ... and then for each registered of nodes registered observer list:
for registered in &*registered.unwrap() {
// 3.2 "1": node is not target and options["subtree"] is false
if &*node != target && !registered.options.subtree {
continue;
}
match *attr_type {
// 3.2 "2", "3"
Mutation::Attribute {
ref name,
ref namespace,
ref old_value,
} => {
// 3.1.2 "2": type is "attributes" and options["attributes"] either does not exist or is false
if !registered.options.attributes {
continue;
}
// 3.1.2 "3": type is "attributes", options["attributeFilter"] exists,
// and options["attributeFilter"] does not contain name or namespace is non-null
if !registered.options.attribute_filter.is_empty() {
if *namespace != ns!() {
continue;
}
if !registered
.options
.attribute_filter
.iter()
.any(|s| *s == **name)
{
continue;
}
}
// 3.2.1 Let mo be registereds observer.
let mo = registered.observer.clone();
// 3.2.2 If interestedObservers[mo] does not exist, then set interestedObservers[mo] to null.
if registered.options.attribute_old_value {
// 3.2.3 ... type is "attributes" and options["attributeOldValue"] is true ...
interested_observers.insert(mo, old_value.clone());
} else {
// 3.2.2 If interestedObservers[mo] does not exist, then set interestedObservers[mo] to null.
interested_observers.entry(mo).or_insert(None);
}
},
// 3.2 "4"
Mutation::CharacterData { ref old_value } => {
// 3.2 "4": type is "characterData" and options["characterData"] either does not exist or is false
if !registered.options.character_data {
continue;
}
// 3.2.1 Let mo be registereds observer.
let mo = registered.observer.clone();
if registered.options.character_data_old_value {
// 3.2.3 ... type is "characterData" and options["characterDataOldValue"] is true
interested_observers
.insert(mo, Some(DOMString::from(old_value.clone())));
} else {
// 3.2.2 If interestedObservers[mo] does not exist, then set interestedObservers[mo] to null.
interested_observers.entry(mo).or_insert(None);
}
},
// 3.2 "5"
Mutation::ChildList { .. } => {
// 3.2 "5": type is "childList" and options["childList"] is false
if !registered.options.child_list {
continue;
}
// 3.2.1 Let mo be registereds observer.
let mo = registered.observer.clone();
// 3.2.2 If interestedObservers[mo] does not exist, then set interestedObservers[mo] to null.
interested_observers.entry(mo).or_insert(None);
},
}
}
}
// Step 4 For each observer → mappedOldValue of interestedObservers:
for (observer, mapped_old_value) in interested_observers {
// Step 4.1 Let record be a new MutationRecord object ...
let record = match *attr_type {
Mutation::Attribute {
ref name,
ref namespace,
..
} => {
let namespace = if *namespace != ns!() {
Some(namespace)
} else {
None
};
MutationRecord::attribute_mutated(
target,
name,
namespace,
mapped_old_value,
CanGc::note(),
)
},
Mutation::CharacterData { .. } => {
MutationRecord::character_data_mutated(target, mapped_old_value, CanGc::note())
},
Mutation::ChildList {
ref added,
ref removed,
ref next,
ref prev,
} => MutationRecord::child_list_mutated(
target,
*added,
*removed,
*next,
*prev,
CanGc::note(),
),
};
// Step 4.2 Enqueue record to observers record queue.
observer.record_queue.borrow_mut().push(record);
// Step 4.3 Append observer to the surrounding agents pending mutation observers.
ScriptThread::mutation_observers().add_mutation_observer(&observer);
}
// Step 5 Queue a mutation observer microtask.
let mutation_observers = ScriptThread::mutation_observers();
mutation_observers.queue_mutation_observer_microtask(ScriptThread::microtask_queue());
}
}
impl MutationObserverMethods<crate::DomTypeHolder> for MutationObserver {
/// <https://dom.spec.whatwg.org/#dom-mutationobserver-mutationobserver>
fn Constructor(
global: &Window,
proto: Option<HandleObject>,
can_gc: CanGc,
callback: Rc<MutationCallback>,
) -> Fallible<DomRoot<MutationObserver>> {
global.set_exists_mut_observer();
let observer = MutationObserver::new_with_proto(global, proto, callback, can_gc);
ScriptThread::mutation_observers().add_mutation_observer(&observer);
Ok(observer)
}
/// <https://dom.spec.whatwg.org/#dom-mutationobserver-observe>
fn Observe(&self, target: &Node, options: &MutationObserverInit) -> Fallible<()> {
let attribute_filter = options.attributeFilter.clone().unwrap_or_default();
let attribute_old_value = options.attributeOldValue.unwrap_or(false);
let mut attributes = options.attributes.unwrap_or(false);
let mut character_data = options.characterData.unwrap_or(false);
let character_data_old_value = options.characterDataOldValue.unwrap_or(false);
let child_list = options.childList;
let subtree = options.subtree;
// Step 1
if (options.attributeOldValue.is_some() || options.attributeFilter.is_some()) &&
options.attributes.is_none()
{
attributes = true;
}
// Step 2
if options.characterDataOldValue.is_some() && options.characterData.is_none() {
character_data = true;
}
// Step 3
if !child_list && !attributes && !character_data {
return Err(Error::Type(
"One of childList, attributes, or characterData must be true".into(),
));
}
// Step 4
if attribute_old_value && !attributes {
return Err(Error::Type(
"attributeOldValue is true but attributes is false".into(),
));
}
// Step 5
if options.attributeFilter.is_some() && !attributes {
return Err(Error::Type(
"attributeFilter is present but attributes is false".into(),
));
}
// Step 6
if character_data_old_value && !character_data {
return Err(Error::Type(
"characterDataOldValue is true but characterData is false".into(),
));
}
// Step 7
let add_new_observer = {
let mut replaced = false;
for registered in &mut *target.registered_mutation_observers_mut() {
if !std::ptr::eq(&*registered.observer, self) {
continue;
}
// TODO: remove matching transient registered observers
registered.options.attribute_old_value = attribute_old_value;
registered.options.attributes = attributes;
registered.options.character_data = character_data;
registered.options.character_data_old_value = character_data_old_value;
registered.options.child_list = child_list;
registered.options.subtree = subtree;
registered
.options
.attribute_filter
.clone_from(&attribute_filter);
replaced = true;
}
!replaced
};
// Step 8
if add_new_observer {
target.add_mutation_observer(RegisteredObserver {
observer: DomRoot::from_ref(self),
options: ObserverOptions {
attributes,
attribute_old_value,
character_data,
character_data_old_value,
subtree,
attribute_filter,
child_list,
},
});
self.node_list.borrow_mut().push(DomRoot::from_ref(target));
}
Ok(())
}
/// <https://dom.spec.whatwg.org/#dom-mutationobserver-takerecords>
fn TakeRecords(&self) -> Vec<DomRoot<MutationRecord>> {
let records: Vec<DomRoot<MutationRecord>> = self.record_queue.borrow().clone();
self.record_queue.borrow_mut().clear();
records
}
/// <https://dom.spec.whatwg.org/#dom-mutationobserver-disconnect>
fn Disconnect(&self) {
// Step 1
let mut nodes = self.node_list.borrow_mut();
for node in nodes.drain(..) {
node.remove_mutation_observer(self);
}
// Step 2
self.record_queue.borrow_mut().clear();
}
}