Combine some access to the thread local variable for script thread. (#38752)

This combines some access to the thread local variable for script
thread.

- We introduce a new UserInteractingScriptGuard which on drop handles
  the resetting of was_interacting to the previous value. Sometimes
throughout the code `ScriptThread::is_user_interacting` was reset to the
previous value while sometimes just set to false. This should
remove this footgun.
- This also reduces the amount of thread local access for
MutationObservers and task queue.

Testing: WPT tests should cover this.
Fixes: This addresses part of
https://github.com/servo/servo/issues/37969 but there is probably still
stuff to be done.

---------

Signed-off-by: Narfinger <Narfinger@users.noreply.github.com>
Signed-off-by: Josh Matthews <josh@joshmatthews.net>
Co-authored-by: Josh Matthews <josh@joshmatthews.net>

components/script/dom/html/htmlslotelement.rs

@@ -28,7 +28,6 @@ use crate::dom::document::Document;
 use crate::dom::element::{AttributeMutation, Element};
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::html::htmlelement::HTMLElement;
-use crate::dom::mutationobserver::MutationObserver;
 use crate::dom::node::{BindContext, Node, NodeDamage, NodeTraits, ShadowIncluding, UnbindContext};
 use crate::dom::virtualmethods::VirtualMethods;
 use crate::script_runtime::CanGc;
@@ -357,7 +356,8 @@ impl HTMLSlotElement {
         ScriptThread::add_signal_slot(self);
 
         // Step 2. Queue a mutation observer microtask.
-        MutationObserver::queue_mutation_observer_microtask();
+        let mutation_observers = ScriptThread::mutation_observers();
+        mutation_observers.queue_mutation_observer_microtask(ScriptThread::microtask_queue());
     }
 
     pub(crate) fn remove_from_signal_slots(&self) {

components/script/dom/mutationobserver.rs

@@ -9,22 +9,18 @@ use dom_struct::dom_struct;
 use html5ever::{LocalName, Namespace, ns};
 use js::rust::HandleObject;
 
-use crate::dom::bindings::callback::ExceptionHandling;
 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::inheritance::Castable;
 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::eventtarget::EventTarget;
 use crate::dom::mutationrecord::MutationRecord;
 use crate::dom::node::{Node, ShadowIncluding};
 use crate::dom::window::Window;
-use crate::microtask::Microtask;
 use crate::script_runtime::CanGc;
 use crate::script_thread::ScriptThread;
 
@@ -91,59 +87,12 @@ impl MutationObserver {
         }
     }
 
-    /// <https://dom.spec.whatwg.org/#queue-a-mutation-observer-compound-microtask>
-    pub(crate) fn queue_mutation_observer_microtask() {
-        // Step 1. If the surrounding agent’s mutation observer microtask queued is true, then return.
-        if ScriptThread::is_mutation_observer_microtask_queued() {
-            return;
-        }
-
-        // Step 2. Set the surrounding agent’s mutation observer microtask queued to true.
-        ScriptThread::set_mutation_observer_microtask_queued(true);
-
-        // Step 3. Queue a microtask to notify mutation observers.
-        ScriptThread::enqueue_microtask(Microtask::NotifyMutationObservers);
+    pub(crate) fn record_queue(&self) -> &DomRefCell<Vec<DomRoot<MutationRecord>>> {
+        &self.record_queue
     }
 
-    /// <https://dom.spec.whatwg.org/#notify-mutation-observers>
-    pub(crate) fn notify_mutation_observers(can_gc: CanGc) {
-        // Step 1. Set the surrounding agent’s mutation observer microtask queued to false.
-        ScriptThread::set_mutation_observer_microtask_queued(false);
-
-        // Step 2. Let notifySet be a clone of the surrounding agent’s pending mutation observers.
-        // TODO Step 3. Empty the surrounding agent’s pending mutation observers.
-        let notify_list = ScriptThread::get_mutation_observers();
-
-        // Step 4. Let signalSet be a clone of the surrounding agent’s signal slots.
-        // Step 5. Empty the surrounding agent’s signal slots.
-        let signal_set = ScriptThread::take_signal_slots();
-
-        // Step 6. For each mo of notifySet:
-        for mo in &notify_list {
-            // Step 6.1 Let records be a clone of mo’s record queue.
-            let queue: Vec<DomRoot<MutationRecord>> = mo.record_queue.borrow().clone();
-
-            // Step 6.2 Empty mo’s record queue.
-            mo.record_queue.borrow_mut().clear();
-
-            // TODO Step 6.3 For each node of mo’s node list, remove all transient registered observers
-            // whose observer is mo from node’s registered observer list.
-
-            // Step 6.4 If records is not empty, then invoke mo’s callback with « records,
-            // mo » and "report", and with callback this value mo.
-            if !queue.is_empty() {
-                let _ = mo
-                    .callback
-                    .Call_(&**mo, queue, mo, ExceptionHandling::Report, can_gc);
-            }
-        }
-
-        // Step 6. For each slot of signalSet, fire an event named slotchange,
-        // with its bubbles attribute set to true, at slot.
-        for slot in signal_set {
-            slot.upcast::<EventTarget>()
-                .fire_event(atom!("slotchange"), can_gc);
-        }
+    pub(crate) fn callback(&self) -> &Rc<MutationCallback> {
+        &self.callback
     }
 
     /// <https://dom.spec.whatwg.org/#queueing-a-mutation-record>
@@ -286,7 +235,8 @@ impl MutationObserver {
         }
 
         // Step 5
-        MutationObserver::queue_mutation_observer_microtask();
+        let mutation_observers = ScriptThread::mutation_observers();
+        mutation_observers.queue_mutation_observer_microtask(ScriptThread::microtask_queue());
     }
 }
 
@@ -300,7 +250,7 @@ impl MutationObserverMethods<crate::DomTypeHolder> for MutationObserver {
     ) -> Fallible<DomRoot<MutationObserver>> {
         global.set_exists_mut_observer();
         let observer = MutationObserver::new_with_proto(global, proto, callback, can_gc);
-        ScriptThread::add_mutation_observer(&observer);
+        ScriptThread::mutation_observers().add_mutation_observer(&observer);
         Ok(observer)
     }
 

components/script/dom/webxr/xrsystem.rs

@@ -323,10 +323,8 @@ impl XRSystem {
                 task!(fire_sessionavailable_event: move || {
                     // The sessionavailable event indicates user intent to enter an XR session
                     let xr = xr.root();
-                    let interacting = ScriptThread::is_user_interacting();
-                    ScriptThread::set_user_interacting(true);
-                    xr.upcast::<EventTarget>().fire_bubbling_event(atom!("sessionavailable"), CanGc::note());
-                    ScriptThread::set_user_interacting(interacting);
+                        let _guard = ScriptThread::user_interacting_guard();
+                        xr.upcast::<EventTarget>().fire_bubbling_event(atom!("sessionavailable"), CanGc::note());
                 })
             );
     }

components/script/dom/webxr/xrtest.rs

@@ -15,6 +15,7 @@ use js::jsval::JSVal;
 use profile_traits::ipc;
 use webxr_api::{self, Error as XRError, MockDeviceInit, MockDeviceMsg};
 
+use crate::ScriptThread;
 use crate::dom::bindings::callback::ExceptionHandling;
 use crate::dom::bindings::cell::DomRefCell;
 use crate::dom::bindings::codegen::Bindings::FunctionBinding::Function;
@@ -27,7 +28,6 @@ use crate::dom::fakexrdevice::{FakeXRDevice, get_origin, get_views, get_world};
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::promise::Promise;
 use crate::script_runtime::CanGc;
-use crate::script_thread::ScriptThread;
 
 #[dom_struct]
 pub(crate) struct XRTest {
@@ -181,7 +181,7 @@ impl XRTestMethods<crate::DomTypeHolder> for XRTest {
 
     /// <https://github.com/immersive-web/webxr-test-api/blob/master/explainer.md>
     fn SimulateUserActivation(&self, f: Rc<Function>, can_gc: CanGc) {
-        ScriptThread::set_user_interacting(true);
+        let _guard = ScriptThread::user_interacting_guard();
         rooted!(in(*GlobalScope::get_cx()) let mut value: JSVal);
         let _ = f.Call__(
             vec![],
@@ -189,7 +189,6 @@ impl XRTestMethods<crate::DomTypeHolder> for XRTest {
             ExceptionHandling::Rethrow,
             can_gc,
         );
-        ScriptThread::set_user_interacting(false);
     }
 
     /// <https://github.com/immersive-web/webxr-test-api/blob/master/explainer.md>