servo/components/script/dom/bindings/reflector.rs
Josh Matthews 3a04f4195e
script: Return global objects for DOM objects in the relevant realm (#37120)
DomObject::global is a tricky API because it's used pervasively but has
subtle requirements that are not documented and not yet enforced by the
type system (#36116). The method returns the relevant global object for
a given DOM object, but that operation is only meaningful if there is an
active realm. We usually, but not always, have an active realm.

This change avoids a footgun by following the principle of least
surprise. Rather than making every single caller of `something.global()`
both prove that there is an active realm and think about which realm
they want active, we implement the obvious behaviour: always activate
the realm of the callee before obtaining the relevant global.
 
Testing: Existing WPT coverage is sufficient; this method is called all
over the codebase.
Fixes: #37070 #27037

Signed-off-by: Josh Matthews <josh@joshmatthews.net>
2025-05-25 03:21:05 +00:00

68 lines
2.4 KiB
Rust

/* 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/. */
//! The `Reflector` struct.
use js::rust::HandleObject;
use script_bindings::interfaces::GlobalScopeHelpers;
use crate::DomTypes;
use crate::dom::bindings::conversions::DerivedFrom;
use crate::dom::bindings::root::DomRoot;
use crate::dom::globalscope::GlobalScope;
use crate::realms::{InRealm, enter_realm};
use crate::script_runtime::CanGc;
/// Create the reflector for a new DOM object and yield ownership to the
/// reflector.
pub(crate) fn reflect_dom_object<D, T, U>(obj: Box<T>, global: &U, can_gc: CanGc) -> DomRoot<T>
where
D: DomTypes,
T: DomObject + DomObjectWrap<D>,
U: DerivedFrom<D::GlobalScope>,
{
let global_scope = global.upcast();
unsafe { T::WRAP(D::GlobalScope::get_cx(), global_scope, None, obj, can_gc) }
}
pub(crate) fn reflect_dom_object_with_proto<D, T, U>(
obj: Box<T>,
global: &U,
proto: Option<HandleObject>,
can_gc: CanGc,
) -> DomRoot<T>
where
D: DomTypes,
T: DomObject + DomObjectWrap<D>,
U: DerivedFrom<D::GlobalScope>,
{
let global_scope = global.upcast();
unsafe { T::WRAP(D::GlobalScope::get_cx(), global_scope, proto, obj, can_gc) }
}
pub(crate) trait DomGlobal {
/// Returns the [relevant global] in whatever realm is currently active.
///
/// [relevant global]: https://html.spec.whatwg.org/multipage/#concept-relevant-global
fn global_(&self, realm: InRealm) -> DomRoot<GlobalScope>;
/// Returns the [relevant global] in the same realm as the callee object.
/// If you know the callee's realm is already the current realm, it is
/// more efficient to call [DomGlobal::global_] instead.
///
/// [relevant global]: https://html.spec.whatwg.org/multipage/#concept-relevant-global
fn global(&self) -> DomRoot<GlobalScope>;
}
impl<T: DomGlobalGeneric<crate::DomTypeHolder>> DomGlobal for T {
fn global_(&self, realm: InRealm) -> DomRoot<GlobalScope> {
<Self as DomGlobalGeneric<crate::DomTypeHolder>>::global_(self, realm)
}
fn global(&self) -> DomRoot<GlobalScope> {
let realm = enter_realm(self);
<Self as DomGlobalGeneric<crate::DomTypeHolder>>::global_(self, InRealm::entered(&realm))
}
}
pub(crate) use script_bindings::reflector::*;