fonts: Remove web fonts when their stylsheet is removed (#32346)

This is the first part of ensuring that unused fonts do not leak. This
change makes it so that when a stylesheet is removed, the corresponding
web fonts are removed from the `FontContext`.

Note: WebRender assets are still leaked, which was the situation before
for all fonts. A followup change will fix this issue.

Fixes #15139.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Mukilan Thiyagarajan <mukilan@igalia.com>

10 files changed, 258 insertions, 57 deletions

diff --git a/components/gfx/font_cache_thread.rs b/components/gfx/font_cache_thread.rs
index 5be2ed7d492..bde22d4b515 100644
--- a/components/gfx/font_cache_thread.rs
+++ b/components/gfx/font_cache_thread.rs
@@ -484,6 +484,7 @@ impl FontSource for FontCacheThread {
                     identifier: serialized_font_template.identifier,
                     descriptor: serialized_font_template.descriptor.clone(),
                     data: font_data.map(Arc::new),
+                    stylesheet: None,
                 }))
             })
             .collect()
diff --git a/components/gfx/font_context.rs b/components/gfx/font_context.rs
index ef83d3e9de2..e27c4d0bef4 100644
--- a/components/gfx/font_context.rs
+++ b/components/gfx/font_context.rs
@@ -5,7 +5,6 @@
 use std::collections::HashMap;
 use std::default::Default;
 use std::hash::{BuildHasherDefault, Hash, Hasher};
-use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Arc;
 
 use app_units::Au;
@@ -24,7 +23,7 @@ use style::font_face::{FontFaceSourceFormat, FontFaceSourceFormatKeyword, Source
 use style::media_queries::Device;
 use style::properties::style_structs::Font as FontStyleStruct;
 use style::shared_lock::SharedRwLockReadGuard;
-use style::stylesheets::{Stylesheet, StylesheetInDocument};
+use style::stylesheets::{DocumentStyleSheet, StylesheetInDocument};
 use style::Atom;
 use url::Url;
 
@@ -51,7 +50,6 @@ pub struct FontContext<S: FontSource> {
     cache: CachingFontSource<S>,
     web_fonts: CrossThreadFontStore,
     webrender_font_store: CrossThreadWebRenderFontStore,
-    web_fonts_still_loading: AtomicUsize,
 }
 
 impl<S: FontSource> MallocSizeOf for FontContext<S> {
@@ -69,12 +67,11 @@ impl<S: FontSource> FontContext<S> {
             cache: CachingFontSource::new(font_source),
             web_fonts: Arc::new(RwLock::default()),
             webrender_font_store: Arc::new(RwLock::default()),
-            web_fonts_still_loading: Default::default(),
         }
     }
 
     pub fn web_fonts_still_loading(&self) -> usize {
-        self.web_fonts_still_loading.load(Ordering::SeqCst)
+        self.web_fonts.read().number_of_fonts_still_loading()
     }
 
     /// Handle the situation where a web font finishes loading, specifying if the load suceeded or failed.
@@ -83,7 +80,6 @@ impl<S: FontSource> FontContext<S> {
         finished_callback: &WebFontLoadFinishedCallback,
         succeeded: bool,
     ) {
-        self.web_fonts_still_loading.fetch_sub(1, Ordering::SeqCst);
         if succeeded {
             self.cache.invalidate_after_web_font_load();
         }
@@ -159,6 +155,8 @@ impl<S: FontSource> FontContext<S> {
             font_template, font_descriptor
         );
 
+        // TODO: Inserting `None` into the cache here is a bit bogus. Instead we should somehow
+        // mark this template as invalid so it isn't tried again.
         let font = self
             .create_font(
                 font_template,
@@ -229,29 +227,31 @@ impl<S: FontSource> FontContext<S> {
 
 #[derive(Clone)]
 pub struct WebFontDownloadState {
-    css_font_face_descriptors: Arc<CSSFontFaceDescriptors>,
+    pub css_font_face_descriptors: Arc<CSSFontFaceDescriptors>,
     remaining_sources: Vec<Source>,
     finished_callback: WebFontLoadFinishedCallback,
     core_resource_thread: CoreResourceThread,
     local_fonts: Arc<HashMap<Atom, Option<FontTemplateRef>>>,
+    pub stylesheet: DocumentStyleSheet,
 }
 
 pub trait FontContextWebFontMethods {
     fn add_all_web_fonts_from_stylesheet(
         &self,
-        stylesheet: &Stylesheet,
+        stylesheet: &DocumentStyleSheet,
         guard: &SharedRwLockReadGuard,
         device: &Device,
         finished_callback: WebFontLoadFinishedCallback,
         synchronous: bool,
     ) -> usize;
     fn process_next_web_font_source(&self, web_font_download_state: WebFontDownloadState);
+    fn remove_all_web_fonts_from_stylesheet(&self, stylesheet: &DocumentStyleSheet);
 }
 
 impl<S: FontSource + Send + 'static> FontContextWebFontMethods for Arc<FontContext<S>> {
     fn add_all_web_fonts_from_stylesheet(
         &self,
-        stylesheet: &Stylesheet,
+        stylesheet: &DocumentStyleSheet,
         guard: &SharedRwLockReadGuard,
         device: &Device,
         finished_callback: WebFontLoadFinishedCallback,
@@ -312,17 +312,20 @@ impl<S: FontSource + Send + 'static> FontContextWebFontMethods for Arc<FontConte
                 }
             }
 
+            number_loading += 1;
+            self.web_fonts
+                .write()
+                .handle_web_font_load_started_for_stylesheet(stylesheet);
+
             self.process_next_web_font_source(WebFontDownloadState {
                 css_font_face_descriptors: Arc::new(rule.into()),
                 remaining_sources: sources,
                 finished_callback: finished_callback.clone(),
                 core_resource_thread: self.resource_threads.lock().clone(),
                 local_fonts: Arc::new(local_fonts),
+                stylesheet: stylesheet.clone(),
             });
 
-            number_loading += 1;
-            self.web_fonts_still_loading.fetch_add(1, Ordering::SeqCst);
-
             // If the load is synchronous wait for it to be signalled.
             if let Some(ref synchronous_receiver) = synchronous_receiver {
                 synchronous_receiver.recv().unwrap();
@@ -334,6 +337,9 @@ impl<S: FontSource + Send + 'static> FontContextWebFontMethods for Arc<FontConte
 
     fn process_next_web_font_source(&self, mut state: WebFontDownloadState) {
         let Some(source) = state.remaining_sources.pop() else {
+            self.web_fonts
+                .write()
+                .handle_web_font_failed_to_load(&state);
             self.handle_web_font_load_finished(&state.finished_callback, false);
             return;
         };
@@ -354,23 +360,48 @@ impl<S: FontSource + Send + 'static> FontContextWebFontMethods for Arc<FontConte
                         FontTemplate::new_for_local_web_font(
                             local_template,
                             &state.css_font_face_descriptors,
+                            state.stylesheet.clone(),
                         )
                         .ok()
                     })
                 {
-                    this.web_fonts
+                    let not_cancelled = self
+                        .web_fonts
                         .write()
-                        .families
-                        .entry(web_font_family_name.clone())
-                        .or_default()
-                        .add_template(new_template);
-                    self.handle_web_font_load_finished(&state.finished_callback, true);
+                        .handle_web_font_loaded(&state, new_template);
+                    self.handle_web_font_load_finished(&state.finished_callback, not_cancelled);
                 } else {
                     this.process_next_web_font_source(state);
                 }
             },
         }
     }
+
+    fn remove_all_web_fonts_from_stylesheet(&self, stylesheet: &DocumentStyleSheet) {
+        let mut web_fonts = self.web_fonts.write();
+        let mut fonts = self.cache.fonts.write();
+        let mut font_groups = self.cache.resolved_font_groups.write();
+
+        // Cancel any currently in-progress web font loads.
+        web_fonts.handle_stylesheet_removed(stylesheet);
+
+        let mut removed_any = false;
+        for family in web_fonts.families.values_mut() {
+            removed_any |= family.remove_templates_for_stylesheet(stylesheet);
+        }
+        if !removed_any {
+            return;
+        };
+
+        fonts.retain(|_, font| match font {
+            Some(font) => font.template.borrow().stylesheet.as_ref() != Some(stylesheet),
+            _ => true,
+        });
+
+        // Removing this stylesheet modified the available fonts, so invalidate the cache
+        // of resolved font groups.
+        font_groups.clear();
+    }
 }
 
 struct RemoteWebFontDownloader<FCT: FontSource> {
@@ -437,6 +468,18 @@ impl<FCT: FontSource + Send + 'static> RemoteWebFontDownloader<FCT> {
     /// After a download finishes, try to process the downloaded data, returning true if
     /// the font is added successfully to the [`FontContext`] or false if it isn't.
     fn process_downloaded_font_and_signal_completion(&self, state: &WebFontDownloadState) -> bool {
+        if self
+            .font_context
+            .web_fonts
+            .read()
+            .font_load_cancelled_for_stylesheet(&state.stylesheet)
+        {
+            self.font_context
+                .handle_web_font_load_finished(&state.finished_callback, false);
+            // Returning true here prevents trying to load the next font on the source list.
+            return true;
+        }
+
         let font_data = std::mem::take(&mut *self.response_data.lock());
         trace!(
             "@font-face {} data={:?}",
@@ -459,21 +502,21 @@ impl<FCT: FontSource + Send + 'static> RemoteWebFontDownloader<FCT> {
             self.url.clone().into(),
             Arc::new(font_data),
             &state.css_font_face_descriptors,
+            Some(state.stylesheet.clone()),
         ) else {
             return false;
         };
 
-        let family_name = state.css_font_face_descriptors.family_name.clone();
-        self.font_context
+        let not_cancelled = self
+            .font_context
             .web_fonts
             .write()
-            .families
-            .entry(family_name.clone())
-            .or_default()
-            .add_template(new_template);
-
+            .handle_web_font_loaded(state, new_template);
         self.font_context
-            .handle_web_font_load_finished(&state.finished_callback, true);
+            .handle_web_font_load_finished(&state.finished_callback, not_cancelled);
+
+        // If the load was canceled above, then we still want to return true from this function in
+        // order to halt any attempt to load sources that come later on the source list.
         true
     }
 
diff --git a/components/gfx/font_store.rs b/components/gfx/font_store.rs
index 888a0ae0a1e..8abb74fc188 100644
--- a/components/gfx/font_store.rs
+++ b/components/gfx/font_store.rs
@@ -8,15 +8,18 @@ use std::sync::Arc;
 use app_units::Au;
 use atomic_refcell::AtomicRefCell;
 use parking_lot::RwLock;
+use style::stylesheets::DocumentStyleSheet;
 use webrender_api::{FontInstanceFlags, FontInstanceKey, FontKey};
 
 use crate::font::FontDescriptor;
 use crate::font_cache_thread::{FontIdentifier, FontSource, LowercaseString};
+use crate::font_context::WebFontDownloadState;
 use crate::font_template::{FontTemplate, FontTemplateRef, FontTemplateRefMethods};
 
 #[derive(Default)]
 pub struct FontStore {
     pub(crate) families: HashMap<LowercaseString, FontTemplates>,
+    web_fonts_loading: Vec<(DocumentStyleSheet, usize)>,
 }
 pub(crate) type CrossThreadFontStore = Arc<RwLock<FontStore>>;
 
@@ -24,6 +27,77 @@ impl FontStore {
     pub(crate) fn clear(&mut self) {
         self.families.clear();
     }
+
+    pub(crate) fn font_load_cancelled_for_stylesheet(
+        &self,
+        stylesheet: &DocumentStyleSheet,
+    ) -> bool {
+        !self
+            .web_fonts_loading
+            .iter()
+            .any(|(loading_stylesheet, _)| loading_stylesheet == stylesheet)
+    }
+
+    pub(crate) fn handle_stylesheet_removed(&mut self, stylesheet: &DocumentStyleSheet) {
+        self.web_fonts_loading
+            .retain(|(loading_stylesheet, _)| loading_stylesheet != stylesheet);
+    }
+
+    pub(crate) fn handle_web_font_load_started_for_stylesheet(
+        &mut self,
+        stylesheet: &DocumentStyleSheet,
+    ) {
+        if let Some((_, count)) = self
+            .web_fonts_loading
+            .iter_mut()
+            .find(|(loading_stylesheet, _)| loading_stylesheet == stylesheet)
+        {
+            *count += 1;
+        } else {
+            self.web_fonts_loading.push((stylesheet.clone(), 1))
+        }
+    }
+
+    fn remove_one_web_font_loading_for_stylesheet(&mut self, stylesheet: &DocumentStyleSheet) {
+        if let Some((_, count)) = self
+            .web_fonts_loading
+            .iter_mut()
+            .find(|(loading_stylesheet, _)| loading_stylesheet == stylesheet)
+        {
+            *count -= 1;
+        }
+        self.web_fonts_loading.retain(|(_, count)| *count != 0);
+    }
+
+    pub(crate) fn handle_web_font_failed_to_load(&mut self, state: &WebFontDownloadState) {
+        self.remove_one_web_font_loading_for_stylesheet(&state.stylesheet);
+    }
+
+    /// Handle a web font load finishing, adding the new font to the [`FontStore`]. If the web font
+    /// load was canceled (for instance, if the stylesheet was removed), then do nothing and return
+    /// false.
+    pub(crate) fn handle_web_font_loaded(
+        &mut self,
+        state: &WebFontDownloadState,
+        new_template: FontTemplate,
+    ) -> bool {
+        // Abort processing this web font if the originating stylesheet was removed.
+        if self.font_load_cancelled_for_stylesheet(&state.stylesheet) {
+            return false;
+        }
+
+        let family_name = state.css_font_face_descriptors.family_name.clone();
+        self.families
+            .entry(family_name)
+            .or_default()
+            .add_template(new_template);
+        self.remove_one_web_font_loading_for_stylesheet(&state.stylesheet);
+        true
+    }
+
+    pub(crate) fn number_of_fonts_still_loading(&self) -> usize {
+        self.web_fonts_loading.iter().map(|(_, count)| count).sum()
+    }
 }
 
 #[derive(Default)]
@@ -127,4 +201,14 @@ impl FontTemplates {
         self.templates
             .push(Arc::new(AtomicRefCell::new(new_template)));
     }
+
+    pub(crate) fn remove_templates_for_stylesheet(
+        &mut self,
+        stylesheet: &DocumentStyleSheet,
+    ) -> bool {
+        let length_before = self.templates.len();
+        self.templates
+            .retain(|template| template.borrow().stylesheet.as_ref() != Some(stylesheet));
+        length_before != self.templates.len()
+    }
 }
diff --git a/components/gfx/font_template.rs b/components/gfx/font_template.rs
index 3bc9f21acf0..bfa8bb49fb4 100644
--- a/components/gfx/font_template.rs
+++ b/components/gfx/font_template.rs
@@ -12,6 +12,7 @@ use serde::{Deserialize, Serialize};
 use servo_url::ServoUrl;
 use style::computed_values::font_stretch::T as FontStretch;
 use style::computed_values::font_style::T as FontStyle;
+use style::stylesheets::DocumentStyleSheet;
 use style::values::computed::font::FontWeight;
 
 use crate::font::{FontDescriptor, PlatformFontMethods};
@@ -132,9 +133,11 @@ pub struct FontTemplate {
     pub descriptor: FontTemplateDescriptor,
     /// The data to use for this [`FontTemplate`]. For web fonts, this is always filled, but
     /// for local fonts, this is loaded only lazily in layout.
-    ///
-    /// TODO: There is no mechanism for web fonts to unset their data!
     pub data: Option<Arc<Vec<u8>>>,
+    /// If this font is a web font, this is a reference to the stylesheet that
+    /// created it. This will be used to remove this font from caches, when the
+    /// stylesheet is removed.
+    pub stylesheet: Option<DocumentStyleSheet>,
 }
 
 impl malloc_size_of::MallocSizeOf for FontTemplate {
@@ -164,6 +167,7 @@ impl FontTemplate {
             identifier: FontIdentifier::Local(identifier),
             descriptor,
             data: None,
+            stylesheet: None,
         }
     }
 
@@ -172,6 +176,7 @@ impl FontTemplate {
         url: ServoUrl,
         data: Arc<Vec<u8>>,
         css_font_template_descriptors: &CSSFontFaceDescriptors,
+        stylesheet: Option<DocumentStyleSheet>,
     ) -> Result<FontTemplate, &'static str> {
         let identifier = FontIdentifier::Web(url.clone());
         let Ok(handle) = PlatformFont::new_from_data(identifier, data.clone(), 0, None) else {
@@ -185,6 +190,7 @@ impl FontTemplate {
             identifier: FontIdentifier::Web(url),
             descriptor,
             data: Some(data),
+            stylesheet,
         })
     }
 
@@ -194,11 +200,13 @@ impl FontTemplate {
     pub fn new_for_local_web_font(
         local_template: FontTemplateRef,
         css_font_template_descriptors: &CSSFontFaceDescriptors,
+        stylesheet: DocumentStyleSheet,
     ) -> Result<FontTemplate, &'static str> {
         let mut alias_template = local_template.borrow().clone();
         alias_template
             .descriptor
             .override_values_with_css_font_template_descriptors(css_font_template_descriptors);
+        alias_template.stylesheet = Some(stylesheet);
         Ok(alias_template)
     }
 
diff --git a/components/gfx/tests/font_context.rs b/components/gfx/tests/font_context.rs
index 06870f6f88c..dc61775db18 100644
--- a/components/gfx/tests/font_context.rs
+++ b/components/gfx/tests/font_context.rs
@@ -24,6 +24,7 @@ use servo_atoms::Atom;
 use servo_url::ServoUrl;
 use style::properties::longhands::font_variant_caps::computed_value::T as FontVariantCaps;
 use style::properties::style_structs::Font as FontStyleStruct;
+use style::stylesheets::Stylesheet;
 use style::values::computed::font::{
     FamilyName, FontFamily, FontFamilyList, FontFamilyNameSyntax, FontSize, FontStretch, FontStyle,
     FontWeight, SingleFontFamily,
@@ -85,6 +86,7 @@ impl MockFontCacheThread {
                 Self::url_for_font_name(name),
                 std::sync::Arc::new(data),
                 &CSSFontFaceDescriptors::new(name),
+                None,
             )
             .unwrap(),
         );
diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index f4efdc17c41..0192f58a4f4 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -273,7 +273,10 @@ impl Layout for LayoutThread {
 
     fn load_web_fonts_from_stylesheet(&self, stylesheet: ServoArc<Stylesheet>) {
         let guard = stylesheet.shared_lock.read();
-        self.load_all_web_fonts_from_stylesheet_with_guard(&stylesheet, &guard);
+        self.load_all_web_fonts_from_stylesheet_with_guard(
+            &DocumentStyleSheet(stylesheet.clone()),
+            &guard,
+        );
     }
 
     fn add_stylesheet(
@@ -282,24 +285,25 @@ impl Layout for LayoutThread {
         before_stylesheet: Option<ServoArc<Stylesheet>>,
     ) {
         let guard = stylesheet.shared_lock.read();
+        let stylesheet = DocumentStyleSheet(stylesheet.clone());
         self.load_all_web_fonts_from_stylesheet_with_guard(&stylesheet, &guard);
 
         match before_stylesheet {
             Some(insertion_point) => self.stylist.insert_stylesheet_before(
-                DocumentStyleSheet(stylesheet.clone()),
+                stylesheet,
                 DocumentStyleSheet(insertion_point),
                 &guard,
             ),
-            None => self
-                .stylist
-                .append_stylesheet(DocumentStyleSheet(stylesheet.clone()), &guard),
+            None => self.stylist.append_stylesheet(stylesheet, &guard),
         }
     }
 
     fn remove_stylesheet(&mut self, stylesheet: ServoArc<Stylesheet>) {
         let guard = stylesheet.shared_lock.read();
-        self.stylist
-            .remove_stylesheet(DocumentStyleSheet(stylesheet.clone()), &guard);
+        let stylesheet = DocumentStyleSheet(stylesheet.clone());
+        self.stylist.remove_stylesheet(stylesheet.clone(), &guard);
+        self.font_context
+            .remove_all_web_fonts_from_stylesheet(&stylesheet);
     }
 
     fn query_content_box(&self, node: OpaqueNode) -> Option<UntypedRect<Au>> {
@@ -668,7 +672,7 @@ impl LayoutThread {
 
     fn load_all_web_fonts_from_stylesheet_with_guard(
         &self,
-        stylesheet: &Stylesheet,
+        stylesheet: &DocumentStyleSheet,
         guard: &SharedRwLockReadGuard,
     ) {
         if !stylesheet.is_effective_for_device(self.stylist.device(), guard) {
@@ -982,10 +986,7 @@ impl LayoutThread {
             for stylesheet in &ua_stylesheets.user_or_user_agent_stylesheets {
                 self.stylist
                     .append_stylesheet(stylesheet.clone(), &ua_or_user_guard);
-                self.load_all_web_fonts_from_stylesheet_with_guard(
-                    &stylesheet.0,
-                    &ua_or_user_guard,
-                );
+                self.load_all_web_fonts_from_stylesheet_with_guard(&stylesheet, &ua_or_user_guard);
             }
 
             if self.stylist.quirks_mode() != QuirksMode::NoQuirks {
@@ -994,7 +995,7 @@ impl LayoutThread {
                     &ua_or_user_guard,
                 );
                 self.load_all_web_fonts_from_stylesheet_with_guard(
-                    &ua_stylesheets.quirks_mode_stylesheet.0,
+                    &ua_stylesheets.quirks_mode_stylesheet,
                     &ua_or_user_guard,
                 );
             }
diff --git a/components/layout_thread_2020/lib.rs b/components/layout_thread_2020/lib.rs
index b9cc25fbc7d..63af1c98349 100644
--- a/components/layout_thread_2020/lib.rs
+++ b/components/layout_thread_2020/lib.rs
@@ -249,7 +249,10 @@ impl Layout for LayoutThread {
 
     fn load_web_fonts_from_stylesheet(&self, stylesheet: ServoArc<Stylesheet>) {
         let guard = stylesheet.shared_lock.read();
-        self.load_all_web_fonts_from_stylesheet_with_guard(&stylesheet, &guard);
+        self.load_all_web_fonts_from_stylesheet_with_guard(
+            &DocumentStyleSheet(stylesheet.clone()),
+            &guard,
+        );
     }
 
     fn add_stylesheet(
@@ -258,25 +261,25 @@ impl Layout for LayoutThread {
         before_stylesheet: Option<ServoArc<Stylesheet>>,
     ) {
         let guard = stylesheet.shared_lock.read();
+        let stylesheet = DocumentStyleSheet(stylesheet.clone());
         self.load_all_web_fonts_from_stylesheet_with_guard(&stylesheet, &guard);
 
         match before_stylesheet {
             Some(insertion_point) => self.stylist.insert_stylesheet_before(
-                DocumentStyleSheet(stylesheet.clone()),
+                stylesheet,
                 DocumentStyleSheet(insertion_point),
                 &guard,
             ),
-            None => self
-                .stylist
-                .append_stylesheet(DocumentStyleSheet(stylesheet.clone()), &guard),
+            None => self.stylist.append_stylesheet(stylesheet, &guard),
         }
     }
 
     fn remove_stylesheet(&mut self, stylesheet: ServoArc<Stylesheet>) {
-        // TODO(mrobinson): This should also unload web fonts from the FontCacheThread.
         let guard = stylesheet.shared_lock.read();
-        self.stylist
-            .remove_stylesheet(DocumentStyleSheet(stylesheet.clone()), &guard);
+        let stylesheet = DocumentStyleSheet(stylesheet.clone());
+        self.stylist.remove_stylesheet(stylesheet.clone(), &guard);
+        self.font_context
+            .remove_all_web_fonts_from_stylesheet(&stylesheet);
     }
 
     fn query_content_box(&self, node: OpaqueNode) -> Option<UntypedRect<Au>> {
@@ -584,7 +587,7 @@ impl LayoutThread {
 
     fn load_all_web_fonts_from_stylesheet_with_guard(
         &self,
-        stylesheet: &Stylesheet,
+        stylesheet: &DocumentStyleSheet,
         guard: &SharedRwLockReadGuard,
     ) {
         if !stylesheet.is_effective_for_device(self.stylist.device(), guard) {
@@ -651,10 +654,7 @@ impl LayoutThread {
             for stylesheet in &ua_stylesheets.user_or_user_agent_stylesheets {
                 self.stylist
                     .append_stylesheet(stylesheet.clone(), &ua_or_user_guard);
-                self.load_all_web_fonts_from_stylesheet_with_guard(
-                    &stylesheet.0,
-                    &ua_or_user_guard,
-                );
+                self.load_all_web_fonts_from_stylesheet_with_guard(stylesheet, &ua_or_user_guard);
             }
 
             if self.stylist.quirks_mode() != QuirksMode::NoQuirks {
@@ -663,7 +663,7 @@ impl LayoutThread {
                     &ua_or_user_guard,
                 );
                 self.load_all_web_fonts_from_stylesheet_with_guard(
-                    &ua_stylesheets.quirks_mode_stylesheet.0,
+                    &ua_stylesheets.quirks_mode_stylesheet,
                     &ua_or_user_guard,
                 );
             }
diff --git a/tests/wpt/meta/MANIFEST.json b/tests/wpt/meta/MANIFEST.json
index 3fc382143d9..66ce446fe98 100644
--- a/tests/wpt/meta/MANIFEST.json
+++ b/tests/wpt/meta/MANIFEST.json
@@ -179113,7 +179113,20 @@
         {}
        ]
       ]
-     }
+     },
+     "web-font-no-longer-accessible-when-stylesheet-removed.html": [
+      "aac3e77a819019d349123fac2265531f3746f826",
+      [
+       null,
+       [
+        [
+         "/css/css-fonts/web-font-no-longer-accessible-when-stylesheet-removed-ref.html",
+         "=="
+        ]
+       ],
+       {}
+      ]
+     ]
     },
     "css-grid": {
      "abspos": {
@@ -403830,7 +403843,11 @@
        "4e88cace350e32711fc06220c2d14dcbd3ab3339",
        []
       ]
-     }
+     },
+     "web-font-no-longer-accessible-when-stylesheet-removed-ref.html": [
+      "363b88d7180a9471c647cd69b9c69678e2f88da6",
+      []
+     ]
     },
     "css-gcpm": {
      "META.yml": [
diff --git a/tests/wpt/tests/css/css-fonts/web-font-no-longer-accessible-when-stylesheet-removed-ref.html b/tests/wpt/tests/css/css-fonts/web-font-no-longer-accessible-when-stylesheet-removed-ref.html
new file mode 100644
index 00000000000..363b88d7180
--- /dev/null
+++ b/tests/wpt/tests/css/css-fonts/web-font-no-longer-accessible-when-stylesheet-removed-ref.html
@@ -0,0 +1,16 @@
+ <!DOCTYPE html>
+
+<html>
+    <head>
+        <title>CSS fonts: Web fonts from removed stylsheets should not be accessible</title>
+        <link rel="author" title="Martin Robinson" href="mrobinson@igalia.com">
+        <link rel="help" href="https://drafts.csswg.org/css-fonts/#font-face-rule">
+    </head>
+
+    <body>
+        <p>Test passes if the text below is not rendered with Ahem.</p>
+        <p>TEXT</p>
+    </body>
+
+</html>
+
diff --git a/tests/wpt/tests/css/css-fonts/web-font-no-longer-accessible-when-stylesheet-removed.html b/tests/wpt/tests/css/css-fonts/web-font-no-longer-accessible-when-stylesheet-removed.html
new file mode 100644
index 00000000000..aac3e77a819
--- /dev/null
+++ b/tests/wpt/tests/css/css-fonts/web-font-no-longer-accessible-when-stylesheet-removed.html
@@ -0,0 +1,29 @@
+ <!DOCTYPE html>
+
+<html>
+    <head>
+        <title>CSS fonts: Web fonts from removed stylsheets should not be accessible</title>
+        <link rel="author" title="Martin Robinson" href="mrobinson@igalia.com">
+        <link rel="match" href="web-font-no-longer-accessible-when-stylesheet-removed-ref.html">
+        <link rel="help" href="https://drafts.csswg.org/css-fonts/#font-face-rule">
+    </head>
+
+    <body>
+        <style id="web-font-stylesheet">
+        @font-face {
+            font-family: CustomFontFamily;
+            src: url(/fonts/Ahem.ttf);
+        }
+        </style>
+
+        <p>Test passes if the text below is not rendered with Ahem.</p>
+        <p style="font-family: CustomFontFamily;">TEXT</p>
+
+        <script>
+            let styleTag = document.getElementById("web-font-stylesheet");
+            styleTag.parentNode.removeChild(styleTag);
+        </script>
+    </body>
+
+</html>
+