script: add skeleton implementation of `FontFace` API (#35262)

This patch implements the `FontFace` interface, but with some caveats

1. The interface is only exposed on `Window`. Support for Workers will
   be handled in the future.
2. The concept of `css-connected` `FontFace` is not implemented, so
   `@font-face` rules in stylesheets will not be represented in the DOM.
3. The constructor only supports using `url()` strings as source
   and `ArrayBuffer` and `ArrayBufferView` are not supported yet.

A skeleton implementation of the `load` method of `FontFaceSet` is also
implemented in this patch. The intention is to support some web pages
that don't load without this method.

Signed-off-by: Mukilan Thiyagarajan <mukilan@igalia.com>

52 files changed, 1157 insertions, 548 deletions

diff --git a/components/config/prefs.rs b/components/config/prefs.rs
index a6dffb72b43..8a3c8595f1d 100644
--- a/components/config/prefs.rs
+++ b/components/config/prefs.rs
@@ -81,6 +81,7 @@ pub struct Preferences {
     pub dom_customelements_enabled: bool,
     pub dom_document_dblclick_timeout: i64,
     pub dom_document_dblclick_dist: i64,
+    pub dom_fontface_enabled: bool,
     pub dom_forcetouch_enabled: bool,
     pub dom_fullscreen_test: bool,
     pub dom_gamepad_enabled: bool,
@@ -245,6 +246,7 @@ impl Preferences {
             dom_customelements_enabled: true,
             dom_document_dblclick_dist: 1,
             dom_document_dblclick_timeout: 300,
+            dom_fontface_enabled: false,
             dom_forcetouch_enabled: false,
             dom_fullscreen_test: false,
             dom_gamepad_enabled: true,
diff --git a/components/fonts/font_context.rs b/components/fonts/font_context.rs
index 212fb587f84..df8c7785658 100644
--- a/components/fonts/font_context.rs
+++ b/components/fonts/font_context.rs
@@ -11,7 +11,7 @@ use std::sync::Arc;
 use app_units::Au;
 use base::id::WebViewId;
 use fnv::FnvHasher;
-use fonts_traits::WebFontLoadFinishedCallback;
+use fonts_traits::StylesheetWebFontLoadFinishedCallback;
 use log::{debug, trace};
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
 use malloc_size_of_derive::MallocSizeOf;
@@ -21,7 +21,9 @@ use parking_lot::{Mutex, RwLock};
 use servo_arc::Arc as ServoArc;
 use servo_url::ServoUrl;
 use style::computed_values::font_variant_caps::T as FontVariantCaps;
-use style::font_face::{FontFaceSourceFormat, FontFaceSourceFormatKeyword, Source, UrlSource};
+use style::font_face::{
+    FontFaceSourceFormat, FontFaceSourceFormatKeyword, Source, SourceList, UrlSource,
+};
 use style::media_queries::Device;
 use style::properties::style_structs::Font as FontStyleStruct;
 use style::shared_lock::SharedRwLockReadGuard;
@@ -133,18 +135,6 @@ impl FontContext {
         }
     }
 
-    /// Handle the situation where a web font finishes loading, specifying if the load suceeded or failed.
-    fn handle_web_font_load_finished(
-        &self,
-        finished_callback: &WebFontLoadFinishedCallback,
-        succeeded: bool,
-    ) {
-        if succeeded {
-            self.invalidate_font_groups_after_web_font_load();
-        }
-        finished_callback(succeeded);
-    }
-
     /// Returns a `FontGroup` representing fonts which can be used for layout, given the `style`.
     /// Font groups are cached, so subsequent calls with the same `style` will return a reference
     /// to an existing `FontGroup`.
@@ -355,17 +345,138 @@ impl FontContext {
     fn invalidate_font_groups_after_web_font_load(&self) {
         self.resolved_font_groups.write().clear();
     }
+
+    pub fn is_supported_web_font_source(source: &&Source) -> bool {
+        let url_source = match source {
+            Source::Url(ref url_source) => url_source,
+            Source::Local(_) => return true,
+        };
+        let format_hint = match url_source.format_hint {
+            Some(ref format_hint) => format_hint,
+            None => return true,
+        };
+
+        if matches!(
+            format_hint,
+            FontFaceSourceFormat::Keyword(
+                FontFaceSourceFormatKeyword::Truetype |
+                    FontFaceSourceFormatKeyword::Opentype |
+                    FontFaceSourceFormatKeyword::Woff |
+                    FontFaceSourceFormatKeyword::Woff2
+            )
+        ) {
+            return true;
+        }
+
+        if let FontFaceSourceFormat::String(string) = format_hint {
+            return string == "truetype" ||
+                string == "opentype" ||
+                string == "woff" ||
+                string == "woff2";
+        }
+
+        false
+    }
 }
 
-#[derive(Clone)]
 pub(crate) struct WebFontDownloadState {
-    webview_id: WebViewId,
-    pub(crate) css_font_face_descriptors: Arc<CSSFontFaceDescriptors>,
+    webview_id: Option<WebViewId>,
+    css_font_face_descriptors: CSSFontFaceDescriptors,
     remaining_sources: Vec<Source>,
-    finished_callback: WebFontLoadFinishedCallback,
     core_resource_thread: CoreResourceThread,
-    local_fonts: Arc<HashMap<Atom, Option<FontTemplateRef>>>,
-    pub(crate) stylesheet: DocumentStyleSheet,
+    local_fonts: HashMap<Atom, Option<FontTemplateRef>>,
+    font_context: Arc<FontContext>,
+    initiator: WebFontLoadInitiator,
+}
+
+impl WebFontDownloadState {
+    fn new(
+        webview_id: Option<WebViewId>,
+        font_context: Arc<FontContext>,
+        css_font_face_descriptors: CSSFontFaceDescriptors,
+        initiator: WebFontLoadInitiator,
+        sources: Vec<Source>,
+        local_fonts: HashMap<Atom, Option<FontTemplateRef>>,
+    ) -> WebFontDownloadState {
+        match initiator {
+            WebFontLoadInitiator::Stylesheet(ref stylesheet, _) => {
+                font_context
+                    .web_fonts
+                    .write()
+                    .handle_web_font_load_started_for_stylesheet(stylesheet);
+            },
+            WebFontLoadInitiator::Script(_) => {
+                font_context
+                    .web_fonts
+                    .write()
+                    .handle_web_font_load_started_for_script();
+            },
+        };
+        let core_resource_thread = font_context.resource_threads.lock().clone();
+        WebFontDownloadState {
+            webview_id,
+            css_font_face_descriptors,
+            remaining_sources: sources,
+            core_resource_thread,
+            local_fonts,
+            font_context,
+            initiator,
+        }
+    }
+
+    fn handle_web_font_load_success(self, new_template: FontTemplate) {
+        let family_name = self.css_font_face_descriptors.family_name.clone();
+        match self.initiator {
+            WebFontLoadInitiator::Stylesheet(ref stylesheet, ref callback) => {
+                let not_cancelled = self
+                    .font_context
+                    .web_fonts
+                    .write()
+                    .handle_web_font_loaded_for_stylesheet(stylesheet, family_name, new_template);
+                self.font_context
+                    .invalidate_font_groups_after_web_font_load();
+                callback(not_cancelled);
+            },
+            WebFontLoadInitiator::Script(callback) => {
+                self.font_context
+                    .web_fonts
+                    .write()
+                    .handle_web_font_load_finished_for_script();
+                callback(family_name, Some(new_template));
+            },
+        }
+    }
+
+    fn handle_web_font_load_failure(self) {
+        let family_name = self.css_font_face_descriptors.family_name.clone();
+        match self.initiator {
+            WebFontLoadInitiator::Stylesheet(ref stylesheet, ref callback) => {
+                self.font_context
+                    .web_fonts
+                    .write()
+                    .handle_web_font_load_failed_for_stylesheet(stylesheet);
+                callback(false);
+            },
+            WebFontLoadInitiator::Script(callback) => {
+                self.font_context
+                    .web_fonts
+                    .write()
+                    .handle_web_font_load_finished_for_script();
+                callback(family_name, None);
+            },
+        }
+    }
+
+    fn font_load_cancelled(&self) -> bool {
+        match self.initiator {
+            WebFontLoadInitiator::Stylesheet(ref stylesheet, _) => self
+                .font_context
+                .web_fonts
+                .read()
+                .font_load_cancelled_for_stylesheet(stylesheet),
+            WebFontLoadInitiator::Script(_) => false,
+        }
+    }
 }
 
 pub trait FontContextWebFontMethods {
@@ -375,8 +486,20 @@ pub trait FontContextWebFontMethods {
         stylesheet: &DocumentStyleSheet,
         guard: &SharedRwLockReadGuard,
         device: &Device,
-        finished_callback: WebFontLoadFinishedCallback,
+        finished_callback: StylesheetWebFontLoadFinishedCallback,
     ) -> usize;
+    fn load_web_font_for_script(
+        &self,
+        webview_id: Option<WebViewId>,
+        source_list: SourceList,
+        descriptors: CSSFontFaceDescriptors,
+        finished_callback: ScriptWebFontLoadFinishedCallback,
+    );
+    fn add_template_to_font_context(
+        &self,
+        family_name: LowercaseFontFamilyName,
+        font_template: FontTemplate,
+    );
     fn remove_all_web_fonts_from_stylesheet(&self, stylesheet: &DocumentStyleSheet);
     fn collect_unused_webrender_resources(&self, all: bool)
         -> (Vec<FontKey>, Vec<FontInstanceKey>);
@@ -389,7 +512,7 @@ impl FontContextWebFontMethods for Arc<FontContext> {
         stylesheet: &DocumentStyleSheet,
         guard: &SharedRwLockReadGuard,
         device: &Device,
-        finished_callback: WebFontLoadFinishedCallback,
+        finished_callback: StylesheetWebFontLoadFinishedCallback,
     ) -> usize {
         let mut number_loading = 0;
         for rule in stylesheet.effective_rules(device, guard) {
@@ -402,57 +525,17 @@ impl FontContextWebFontMethods for Arc<FontContext> {
                 continue;
             };
 
-            let sources: Vec<Source> = font_face
-                .sources()
-                .0
-                .iter()
-                .rev()
-                .filter(is_supported_web_font_source)
-                .cloned()
-                .collect();
-            if sources.is_empty() {
-                continue;
-            }
-
-            // Fetch all local fonts first, beacause if we try to fetch them later on during the process of
-            // loading the list of web font `src`s we may be running in the context of the router thread, which
-            // means we won't be able to seend IPC messages to the FontCacheThread.
-            //
-            // TODO: This is completely wrong. The specification says that `local()` font-family should match
-            // against full PostScript names, but this is matching against font family names. This works...
-            // sometimes.
-            let mut local_fonts = HashMap::new();
-            for source in sources.iter() {
-                if let Source::Local(family_name) = source {
-                    local_fonts
-                        .entry(family_name.name.clone())
-                        .or_insert_with(|| {
-                            let family = SingleFontFamily::FamilyName(FamilyName {
-                                name: family_name.name.clone(),
-                                syntax: FontFamilyNameSyntax::Quoted,
-                            });
-                            self.system_font_service_proxy
-                                .find_matching_font_templates(None, &family)
-                                .first()
-                                .cloned()
-                        });
-                }
-            }
+            let css_font_face_descriptors = rule.into();
+            let completion_handler =
+                WebFontLoadInitiator::Stylesheet(stylesheet.clone(), finished_callback.clone());
 
             number_loading += 1;
-            self.web_fonts
-                .write()
-                .handle_web_font_load_started_for_stylesheet(stylesheet);
-
-            self.process_next_web_font_source(WebFontDownloadState {
-                webview_id,
-                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(),
-            });
+            self.start_loading_one_web_font(
+                Some(webview_id),
+                font_face.sources(),
+                css_font_face_descriptors,
+                completion_handler,
+            );
         }
 
         number_loading
@@ -553,15 +636,84 @@ impl FontContextWebFontMethods for Arc<FontContext> {
             removed_instance_keys.into_iter().collect(),
         )
     }
+
+    fn load_web_font_for_script(
+        &self,
+        webview_id: Option<WebViewId>,
+        sources: SourceList,
+        descriptors: CSSFontFaceDescriptors,
+        finished_callback: ScriptWebFontLoadFinishedCallback,
+    ) {
+        let completion_handler = WebFontLoadInitiator::Script(finished_callback);
+        self.start_loading_one_web_font(webview_id, &sources, descriptors, completion_handler);
+    }
+
+    fn add_template_to_font_context(
+        &self,
+        family_name: LowercaseFontFamilyName,
+        new_template: FontTemplate,
+    ) {
+        self.web_fonts
+            .write()
+            .add_new_template(family_name, new_template);
+        self.invalidate_font_groups_after_web_font_load();
+    }
 }
 
 impl FontContext {
+    fn start_loading_one_web_font(
+        self: &Arc<FontContext>,
+        webview_id: Option<WebViewId>,
+        source_list: &SourceList,
+        css_font_face_descriptors: CSSFontFaceDescriptors,
+        completion_handler: WebFontLoadInitiator,
+    ) {
+        let sources: Vec<Source> = source_list
+            .0
+            .iter()
+            .rev()
+            .filter(Self::is_supported_web_font_source)
+            .cloned()
+            .collect();
+
+        // Fetch all local fonts first, beacause if we try to fetch them later on during the process of
+        // loading the list of web font `src`s we may be running in the context of the router thread, which
+        // means we won't be able to seend IPC messages to the FontCacheThread.
+        //
+        // TODO: This is completely wrong. The specification says that `local()` font-family should match
+        // against full PostScript names, but this is matching against font family names. This works...
+        // sometimes.
+        let mut local_fonts = HashMap::new();
+        for source in sources.iter() {
+            if let Source::Local(family_name) = source {
+                local_fonts
+                    .entry(family_name.name.clone())
+                    .or_insert_with(|| {
+                        let family = SingleFontFamily::FamilyName(FamilyName {
+                            name: family_name.name.clone(),
+                            syntax: FontFamilyNameSyntax::Quoted,
+                        });
+                        self.system_font_service_proxy
+                            .find_matching_font_templates(None, &family)
+                            .first()
+                            .cloned()
+                    });
+            }
+        }
+
+        self.process_next_web_font_source(WebFontDownloadState::new(
+            webview_id,
+            self.clone(),
+            css_font_face_descriptors,
+            completion_handler,
+            sources,
+            local_fonts,
+        ));
+    }
+
     fn process_next_web_font_source(self: &Arc<FontContext>, 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);
+            state.handle_web_font_load_failure();
             return;
         };
 
@@ -581,17 +733,13 @@ impl FontContext {
                         let template = FontTemplate::new_for_local_web_font(
                             local_template.clone(),
                             &state.css_font_face_descriptors,
-                            state.stylesheet.clone(),
+                            state.initiator.stylesheet().cloned(),
                         )
                         .ok()?;
                         Some(template)
                     })
                 {
-                    let not_cancelled = self
-                        .web_fonts
-                        .write()
-                        .handle_web_font_loaded(&state, new_template);
-                    self.handle_web_font_load_finished(&state.finished_callback, not_cancelled);
+                    state.handle_web_font_load_success(new_template);
                 } else {
                     this.process_next_web_font_source(state);
                 }
@@ -600,12 +748,29 @@ impl FontContext {
     }
 }
 
+pub type ScriptWebFontLoadFinishedCallback =
+    Box<dyn FnOnce(LowercaseFontFamilyName, Option<FontTemplate>) + Send>;
+
+pub(crate) enum WebFontLoadInitiator {
+    Stylesheet(DocumentStyleSheet, StylesheetWebFontLoadFinishedCallback),
+    Script(ScriptWebFontLoadFinishedCallback),
+}
+
+impl WebFontLoadInitiator {
+    pub(crate) fn stylesheet(&self) -> Option<&DocumentStyleSheet> {
+        match self {
+            Self::Stylesheet(stylesheet, _) => Some(stylesheet),
+            Self::Script(_) => None,
+        }
+    }
+}
+
 struct RemoteWebFontDownloader {
-    font_context: Arc<FontContext>,
+    state: Option<WebFontDownloadState>,
     url: ServoArc<Url>,
     web_font_family_name: LowercaseFontFamilyName,
-    response_valid: Mutex<bool>,
-    response_data: Mutex<Vec<u8>>,
+    response_valid: bool,
+    response_data: Vec<u8>,
 }
 
 enum DownloaderResponseResult {
@@ -628,23 +793,21 @@ impl RemoteWebFontDownloader {
         };
 
         // FIXME: This shouldn't use NoReferrer, but the current documents url
-        let request = RequestBuilder::new(
-            Some(state.webview_id),
-            url.clone().into(),
-            Referrer::NoReferrer,
-        )
-        .destination(Destination::Font);
+        let request =
+            RequestBuilder::new(state.webview_id, url.clone().into(), Referrer::NoReferrer)
+                .destination(Destination::Font);
+
+        let core_resource_thread_clone = state.core_resource_thread.clone();
 
         debug!("Loading @font-face {} from {}", web_font_family_name, url);
-        let downloader = Self {
-            font_context,
+        let mut downloader = Self {
             url,
             web_font_family_name,
-            response_valid: Mutex::new(false),
-            response_data: Mutex::default(),
+            response_valid: false,
+            response_data: Vec::new(),
+            state: Some(state),
         };
 
-        let core_resource_thread_clone = state.core_resource_thread.clone();
         fetch_async(
             &core_resource_thread_clone,
             request,
@@ -653,40 +816,42 @@ impl RemoteWebFontDownloader {
                 match downloader.handle_web_font_fetch_message(response_message) {
                     DownloaderResponseResult::InProcess => {},
                     DownloaderResponseResult::Finished => {
-                        if !downloader.process_downloaded_font_and_signal_completion(&state) {
-                            downloader
-                                .font_context
-                                .process_next_web_font_source(state.clone())
+                        if !downloader.process_downloaded_font_and_signal_completion() {
+                            font_context.process_next_web_font_source(downloader.take_state())
                         }
                     },
-                    DownloaderResponseResult::Failure => downloader
-                        .font_context
-                        .process_next_web_font_source(state.clone()),
+                    DownloaderResponseResult::Failure => {
+                        font_context.process_next_web_font_source(downloader.take_state())
+                    },
                 }
             }),
         )
     }
 
+    fn take_state(&mut self) -> WebFontDownloadState {
+        self.state
+            .take()
+            .expect("must be non-None until download either succeeds or fails")
+    }
+
     /// 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);
+    fn process_downloaded_font_and_signal_completion(&mut self) -> bool {
+        let state = self
+            .state
+            .as_ref()
+            .expect("must be non-None until processing is completed");
+        if state.font_load_cancelled() {
+            self.take_state().handle_web_font_load_failure();
             // 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());
+        let font_data = std::mem::take(&mut self.response_data);
         trace!(
-            "@font-face {} data={:?}",
+            "Downloaded @font-face {} ({} bytes)",
             self.web_font_family_name,
-            font_data
+            font_data.len()
         );
 
         let font_data = match fontsan::process(&font_data) {
@@ -705,6 +870,8 @@ impl RemoteWebFontDownloader {
         let Ok(handle) = PlatformFont::new_from_data(identifier, &font_data, None) else {
             return false;
         };
+
+        let state = self.take_state();
         let mut descriptor = handle.descriptor();
         descriptor
             .override_values_with_css_font_template_descriptors(&state.css_font_face_descriptors);
@@ -712,20 +879,16 @@ impl RemoteWebFontDownloader {
         let new_template = FontTemplate::new(
             FontIdentifier::Web(url),
             descriptor,
-            Some(state.stylesheet.clone()),
+            state.initiator.stylesheet().cloned(),
         );
-        self.font_context
+
+        state
+            .font_context
             .font_data
             .write()
             .insert(new_template.identifier.clone(), font_data);
 
-        let not_cancelled = self
-            .font_context
-            .web_fonts
-            .write()
-            .handle_web_font_loaded(state, new_template);
-        self.font_context
-            .handle_web_font_load_finished(&state.finished_callback, not_cancelled);
+        state.handle_web_font_load_success(new_template);
 
         // 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.
@@ -733,7 +896,7 @@ impl RemoteWebFontDownloader {
     }
 
     fn handle_web_font_fetch_message(
-        &self,
+        &mut self,
         response_message: FetchResponseMsg,
     ) -> DownloaderResponseResult {
         match response_message {
@@ -746,7 +909,7 @@ impl RemoteWebFontDownloader {
                     self.web_font_family_name,
                     meta_result.is_ok()
                 );
-                *self.response_valid.lock() = meta_result.is_ok();
+                self.response_valid = meta_result.is_ok();
                 DownloaderResponseResult::InProcess
             },
             FetchResponseMsg::ProcessResponseChunk(_, new_bytes) => {
@@ -755,8 +918,8 @@ impl RemoteWebFontDownloader {
                     self.web_font_family_name,
                     new_bytes
                 );
-                if *self.response_valid.lock() {
-                    self.response_data.lock().extend(new_bytes)
+                if self.response_valid {
+                    self.response_data.extend(new_bytes)
                 }
                 DownloaderResponseResult::InProcess
             },
@@ -766,7 +929,7 @@ impl RemoteWebFontDownloader {
                     self.web_font_family_name,
                     response
                 );
-                if response.is_err() || !*self.response_valid.lock() {
+                if response.is_err() || !self.response_valid {
                     return DownloaderResponseResult::Failure;
                 }
                 DownloaderResponseResult::Finished
@@ -804,35 +967,3 @@ impl Hash for FontGroupCacheKey {
         self.style.hash.hash(hasher)
     }
 }
-
-fn is_supported_web_font_source(source: &&Source) -> bool {
-    let url_source = match source {
-        Source::Url(ref url_source) => url_source,
-        Source::Local(_) => return true,
-    };
-    let format_hint = match url_source.format_hint {
-        Some(ref format_hint) => format_hint,
-        None => return true,
-    };
-
-    if matches!(
-        format_hint,
-        FontFaceSourceFormat::Keyword(
-            FontFaceSourceFormatKeyword::Truetype |
-                FontFaceSourceFormatKeyword::Opentype |
-                FontFaceSourceFormatKeyword::Woff |
-                FontFaceSourceFormatKeyword::Woff2
-        )
-    ) {
-        return true;
-    }
-
-    if let FontFaceSourceFormat::String(string) = format_hint {
-        return string == "truetype" ||
-            string == "opentype" ||
-            string == "woff" ||
-            string == "woff2";
-    }
-
-    false
-}
diff --git a/components/fonts/font_store.rs b/components/fonts/font_store.rs
index 5791319bb14..826be947672 100644
--- a/components/fonts/font_store.rs
+++ b/components/fonts/font_store.rs
@@ -12,14 +12,14 @@ use style::stylesheets::DocumentStyleSheet;
 use style::values::computed::{FontStyle, FontWeight};
 
 use crate::font::FontDescriptor;
-use crate::font_context::WebFontDownloadState;
 use crate::font_template::{FontTemplate, FontTemplateRef, FontTemplateRefMethods, IsOblique};
 use crate::system_font_service::{FontIdentifier, LowercaseFontFamilyName};
 
 #[derive(Default)]
 pub struct FontStore {
     pub(crate) families: HashMap<LowercaseFontFamilyName, FontTemplates>,
-    web_fonts_loading: Vec<(DocumentStyleSheet, usize)>,
+    web_fonts_loading_for_stylesheets: Vec<(DocumentStyleSheet, usize)>,
+    web_fonts_loading_for_script: usize,
 }
 pub(crate) type CrossThreadFontStore = Arc<RwLock<FontStore>>;
 
@@ -33,13 +33,13 @@ impl FontStore {
         stylesheet: &DocumentStyleSheet,
     ) -> bool {
         !self
-            .web_fonts_loading
+            .web_fonts_loading_for_stylesheets
             .iter()
             .any(|(loading_stylesheet, _)| loading_stylesheet == stylesheet)
     }
 
     pub(crate) fn handle_stylesheet_removed(&mut self, stylesheet: &DocumentStyleSheet) {
-        self.web_fonts_loading
+        self.web_fonts_loading_for_stylesheets
             .retain(|(loading_stylesheet, _)| loading_stylesheet != stylesheet);
     }
 
@@ -48,54 +48,82 @@ impl FontStore {
         stylesheet: &DocumentStyleSheet,
     ) {
         if let Some((_, count)) = self
-            .web_fonts_loading
+            .web_fonts_loading_for_stylesheets
             .iter_mut()
             .find(|(loading_stylesheet, _)| loading_stylesheet == stylesheet)
         {
             *count += 1;
         } else {
-            self.web_fonts_loading.push((stylesheet.clone(), 1))
+            self.web_fonts_loading_for_stylesheets
+                .push((stylesheet.clone(), 1))
         }
     }
 
     fn remove_one_web_font_loading_for_stylesheet(&mut self, stylesheet: &DocumentStyleSheet) {
         if let Some((_, count)) = self
-            .web_fonts_loading
+            .web_fonts_loading_for_stylesheets
             .iter_mut()
             .find(|(loading_stylesheet, _)| loading_stylesheet == stylesheet)
         {
             *count -= 1;
         }
-        self.web_fonts_loading.retain(|(_, count)| *count != 0);
+        self.web_fonts_loading_for_stylesheets
+            .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);
+    pub(crate) fn handle_web_font_load_failed_for_stylesheet(
+        &mut self,
+        stylesheet: &DocumentStyleSheet,
+    ) {
+        self.remove_one_web_font_loading_for_stylesheet(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(
+    pub(crate) fn handle_web_font_loaded_for_stylesheet(
         &mut self,
-        state: &WebFontDownloadState,
+        stylesheet: &DocumentStyleSheet,
+        family_name: LowercaseFontFamilyName,
         new_template: FontTemplate,
     ) -> bool {
         // Abort processing this web font if the originating stylesheet was removed.
-        if self.font_load_cancelled_for_stylesheet(&state.stylesheet) {
+        if self.font_load_cancelled_for_stylesheet(stylesheet) {
             return false;
         }
-        let family_name = state.css_font_face_descriptors.family_name.clone();
+
+        self.add_new_template(family_name, new_template);
+
+        self.remove_one_web_font_loading_for_stylesheet(stylesheet);
+
+        true
+    }
+
+    pub(crate) fn add_new_template(
+        &mut self,
+        family_name: LowercaseFontFamilyName,
+        new_template: FontTemplate,
+    ) {
         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 handle_web_font_load_started_for_script(&mut self) {
+        self.web_fonts_loading_for_script += 1;
+    }
+
+    pub(crate) fn handle_web_font_load_finished_for_script(&mut self) {
+        self.web_fonts_loading_for_script -= 1;
     }
 
     pub(crate) fn number_of_fonts_still_loading(&self) -> usize {
-        self.web_fonts_loading.iter().map(|(_, count)| count).sum()
+        self.web_fonts_loading_for_script +
+            self.web_fonts_loading_for_stylesheets
+                .iter()
+                .map(|(_, count)| count)
+                .sum::<usize>()
     }
 }
 
diff --git a/components/fonts/font_template.rs b/components/fonts/font_template.rs
index d7733f66274..4c2e32bd3ea 100644
--- a/components/fonts/font_template.rs
+++ b/components/fonts/font_template.rs
@@ -177,13 +177,13 @@ impl FontTemplate {
     pub fn new_for_local_web_font(
         local_template: FontTemplateRef,
         css_font_template_descriptors: &CSSFontFaceDescriptors,
-        stylesheet: DocumentStyleSheet,
+        stylesheet: Option<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);
+        alias_template.stylesheet = stylesheet;
         Ok(alias_template)
     }
 
diff --git a/components/fonts/system_font_service.rs b/components/fonts/system_font_service.rs
index b29eca6b86c..e50b3144f54 100644
--- a/components/fonts/system_font_service.rs
+++ b/components/fonts/system_font_service.rs
@@ -565,7 +565,7 @@ impl SystemFontServiceProxy {
     }
 }
 
-#[derive(Clone, Debug, Default, Deserialize, Eq, Hash, PartialEq, Serialize)]
+#[derive(Clone, Debug, Default, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize)]
 pub struct LowercaseFontFamilyName {
     inner: String,
 }
diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 987d8ad1839..8c275230b23 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -24,7 +24,7 @@ use fnv::FnvHashMap;
 use fonts::{
     get_and_reset_text_shaping_performance_counter, FontContext, FontContextWebFontMethods,
 };
-use fonts_traits::WebFontLoadFinishedCallback;
+use fonts_traits::StylesheetWebFontLoadFinishedCallback;
 use fxhash::{FxHashMap, FxHashSet};
 use ipc_channel::ipc::IpcSender;
 use layout::construct::ConstructionResult;
@@ -627,7 +627,7 @@ impl LayoutThread {
             stylesheet,
             guard,
             self.stylist.device(),
-            Arc::new(web_font_finished_loading_callback) as WebFontLoadFinishedCallback,
+            Arc::new(web_font_finished_loading_callback) as StylesheetWebFontLoadFinishedCallback,
         );
     }
 
diff --git a/components/layout_thread_2020/lib.rs b/components/layout_thread_2020/lib.rs
index 03f47d5904c..a591226b946 100644
--- a/components/layout_thread_2020/lib.rs
+++ b/components/layout_thread_2020/lib.rs
@@ -23,7 +23,7 @@ use euclid::default::{Point2D as UntypedPoint2D, Rect as UntypedRect, Size2D as
 use euclid::{Point2D, Scale, Size2D, Vector2D};
 use fnv::FnvHashMap;
 use fonts::{FontContext, FontContextWebFontMethods};
-use fonts_traits::WebFontLoadFinishedCallback;
+use fonts_traits::StylesheetWebFontLoadFinishedCallback;
 use fxhash::FxHashMap;
 use ipc_channel::ipc::IpcSender;
 use layout::context::LayoutContext;
@@ -602,7 +602,7 @@ impl LayoutThread {
             stylesheet,
             guard,
             self.stylist.device(),
-            Arc::new(web_font_finished_loading_callback) as WebFontLoadFinishedCallback,
+            Arc::new(web_font_finished_loading_callback) as StylesheetWebFontLoadFinishedCallback,
         );
     }
 
diff --git a/components/malloc_size_of/lib.rs b/components/malloc_size_of/lib.rs
index ec633a49f9b..50d4ce30718 100644
--- a/components/malloc_size_of/lib.rs
+++ b/components/malloc_size_of/lib.rs
@@ -711,6 +711,7 @@ malloc_size_of_is_0!(std::sync::atomic::AtomicUsize);
 malloc_size_of_is_0!(std::time::Duration);
 malloc_size_of_is_0!(std::time::Instant);
 malloc_size_of_is_0!(std::time::SystemTime);
+malloc_size_of_is_0!(style::font_face::SourceList);
 
 macro_rules! malloc_size_of_is_webrender_malloc_size_of(
     ($($ty:ty),+) => (
diff --git a/components/profile/time.rs b/components/profile/time.rs
index 73a48efa764..c6afff4e7b5 100644
--- a/components/profile/time.rs
+++ b/components/profile/time.rs
@@ -104,6 +104,7 @@ impl Formattable for ProfilerCategory {
             ProfilerCategory::ScriptDocumentEvent => "Script Document Event",
             ProfilerCategory::ScriptEvaluate => "Script JS Evaluate",
             ProfilerCategory::ScriptFileRead => "Script File Read",
+            ProfilerCategory::ScriptFontLoading => "Script Font Loading",
             ProfilerCategory::ScriptHistoryEvent => "Script History Event",
             ProfilerCategory::ScriptImageCacheMsg => "Script Image Cache Msg",
             ProfilerCategory::ScriptInputEvent => "Script Input Event",
diff --git a/components/script/dom/eventsource.rs b/components/script/dom/eventsource.rs
index ba4c1dca9dc..bbec13d0d83 100644
--- a/components/script/dom/eventsource.rs
+++ b/components/script/dom/eventsource.rs
@@ -594,7 +594,7 @@ impl EventSourceMethods<crate::DomTypeHolder> for EventSource {
             last_event_id: String::new(),
             resource_timing: ResourceFetchTiming::new(ResourceTimingType::Resource),
         };
-        let listener = NetworkListener {
+        let mut listener = NetworkListener {
             context: Arc::new(Mutex::new(context)),
             task_source: global.task_manager().networking_task_source().into(),
         };
diff --git a/components/script/dom/fontface.rs b/components/script/dom/fontface.rs
new file mode 100644
index 00000000000..9fb753600fa
--- /dev/null
+++ b/components/script/dom/fontface.rs
@@ -0,0 +1,577 @@
+/* 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::{Cell, RefCell};
+use std::rc::Rc;
+
+use cssparser::{Parser, ParserInput};
+use dom_struct::dom_struct;
+use fonts::{FontContext, FontContextWebFontMethods, FontTemplate, LowercaseFontFamilyName};
+use js::rust::HandleObject;
+use style::error_reporting::ParseErrorReporter;
+use style::font_face::SourceList;
+use style::parser::ParserContext;
+use style::stylesheets::{CssRuleType, FontFaceRule, Origin, UrlExtraData};
+use style_traits::{ParsingMode, ToCss};
+
+use super::bindings::cell::DomRefCell;
+use super::bindings::codegen::UnionTypes::StringOrArrayBufferViewOrArrayBuffer;
+use super::bindings::error::{Error, ErrorResult, Fallible};
+use super::bindings::refcounted::Trusted;
+use super::bindings::reflector::DomGlobal;
+use super::bindings::root::MutNullableDom;
+use super::types::FontFaceSet;
+use crate::dom::bindings::codegen::Bindings::FontFaceBinding::{
+    FontFaceDescriptors, FontFaceLoadStatus, FontFaceMethods,
+};
+use crate::dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
+use crate::dom::bindings::codegen::UnionTypes;
+use crate::dom::bindings::reflector::{reflect_dom_object_with_proto, Reflector};
+use crate::dom::bindings::root::DomRoot;
+use crate::dom::bindings::str::DOMString;
+use crate::dom::globalscope::GlobalScope;
+use crate::dom::promise::Promise;
+use crate::dom::window::Window;
+use crate::script_runtime::CanGc;
+
+/// <https://drafts.csswg.org/css-font-loading/#fontface-interface>
+#[dom_struct]
+pub struct FontFace {
+    reflector: Reflector,
+    status: Cell<FontFaceLoadStatus>,
+    family_name: DomRefCell<DOMString>,
+    descriptors: DomRefCell<FontFaceDescriptors>,
+
+    /// A reference to the [`FontFaceSet`] that this `FontFace` is a member of, if it has been
+    /// added to one. `None` otherwise. The spec suggests that a `FontFace` can be a member of
+    /// multiple `FontFaceSet`s, but this doesn't seem to be the case in practice, as the
+    /// `FontFaceSet` constructor is not exposed on the global scope.
+    font_face_set: MutNullableDom<FontFaceSet>,
+
+    /// This holds the [`FontTemplate`] resulting from loading this `FontFace`, to be used when the
+    /// `FontFace` is added to the global `FontFaceSet` and thus the `[FontContext]`.
+    //
+    // TODO: This could potentially share the `FontTemplateRef` created by `FontContext`, rather
+    // than having its own copy of the template.
+    #[no_trace = "Does not contain managed objects"]
+    template: RefCell<Option<(LowercaseFontFamilyName, FontTemplate)>>,
+
+    #[no_trace = "Does not contain managed objects"]
+    /// <https://drafts.csswg.org/css-font-loading/#m-fontface-urls-slot>
+    urls: DomRefCell<Option<SourceList>>,
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-fontstatuspromise-slot>
+    #[ignore_malloc_size_of = "Rc"]
+    font_status_promise: Rc<Promise>,
+}
+
+/// Given the various font face descriptors, construct the equivalent `@font-face` css rule as a
+/// string and parse it using `style` crate. Returns `Err(Error::Syntax)` if parsing fails.
+///
+/// Due to lack of support in the `style` crate, parsing the whole `@font-face` rule is much easier
+/// to implement than parsing each declaration on its own.
+fn parse_font_face_descriptors(
+    global: &GlobalScope,
+    family_name: &DOMString,
+    sources: Option<&str>,
+    input_descriptors: &FontFaceDescriptors,
+) -> Fallible<FontFaceRule> {
+    let window = global.as_window(); // TODO: Support calling FontFace APIs from Worker
+    let quirks_mode = window.Document().quirks_mode();
+    let url_data = UrlExtraData(window.get_url().get_arc());
+    let error_reporter = FontFaceErrorReporter {
+        not_encountered_error: Cell::new(true),
+    };
+    let parser_context = ParserContext::new(
+        Origin::Author,
+        &url_data,
+        Some(CssRuleType::FontFace),
+        ParsingMode::DEFAULT,
+        quirks_mode,
+        /* namespaces = */ Default::default(),
+        Some(&error_reporter as &dyn ParseErrorReporter),
+        None,
+    );
+
+    let FontFaceDescriptors {
+        ref ascentOverride,
+        ref descentOverride,
+        ref display,
+        ref featureSettings,
+        ref lineGapOverride,
+        ref stretch,
+        ref style,
+        ref unicodeRange,
+        ref variationSettings,
+        ref weight,
+    } = input_descriptors;
+
+    let _ = variationSettings; // TODO: Stylo doesn't parse font-variation-settings yet.
+    let maybe_sources = sources.map_or_else(String::new, |sources| format!("src: {sources};"));
+    let font_face_rule = format!(
+        r"
+        ascent-override: {ascentOverride};
+        descent-override: {descentOverride};
+        font-display: {display};
+        font-family: {family_name};
+        font-feature-settings: {featureSettings};
+        font-stretch: {stretch};
+        font-style: {style};
+        font-weight: {weight};
+        line-gap-override: {lineGapOverride};
+        unicode-range: {unicodeRange};
+        {maybe_sources}
+    "
+    );
+
+    // TODO: Should this be the source location in the script that invoked the font face API?
+    let location = cssparser::SourceLocation { line: 0, column: 0 };
+    let mut input = ParserInput::new(&font_face_rule);
+    let mut parser = Parser::new(&mut input);
+    let mut parsed_font_face_rule =
+        style::font_face::parse_font_face_block(&parser_context, &mut parser, location);
+
+    if let Some(ref mut sources) = parsed_font_face_rule.sources {
+        let supported_sources: Vec<_> = sources
+            .0
+            .iter()
+            .rev()
+            .filter(FontContext::is_supported_web_font_source)
+            .cloned()
+            .collect();
+        if supported_sources.is_empty() {
+            error_reporter.not_encountered_error.set(false);
+        } else {
+            sources.0 = supported_sources;
+        }
+    }
+
+    if error_reporter.not_encountered_error.get() {
+        Ok(parsed_font_face_rule)
+    } else {
+        Err(Error::Syntax)
+    }
+}
+
+fn serialize_parsed_descriptors(font_face_rule: &FontFaceRule) -> FontFaceDescriptors {
+    FontFaceDescriptors {
+        ascentOverride: font_face_rule.ascent_override.to_css_string().into(),
+        descentOverride: font_face_rule.descent_override.to_css_string().into(),
+        display: font_face_rule.display.to_css_string().into(),
+        featureSettings: font_face_rule.feature_settings.to_css_string().into(),
+        lineGapOverride: font_face_rule.line_gap_override.to_css_string().into(),
+        stretch: font_face_rule.stretch.to_css_string().into(),
+        style: font_face_rule.style.to_css_string().into(),
+        unicodeRange: font_face_rule.unicode_range.to_css_string().into(),
+        variationSettings: font_face_rule.variation_settings.to_css_string().into(),
+        weight: font_face_rule.weight.to_css_string().into(),
+    }
+}
+
+struct FontFaceErrorReporter {
+    not_encountered_error: Cell<bool>,
+}
+
+impl ParseErrorReporter for FontFaceErrorReporter {
+    fn report_error(
+        &self,
+        _url: &UrlExtraData,
+        _location: cssparser::SourceLocation,
+        _error: style::error_reporting::ContextualParseError,
+    ) {
+        self.not_encountered_error.set(false);
+    }
+}
+
+impl FontFace {
+    /// Construct a [`FontFace`] to be used in the case of failure in parsing the
+    /// font face descriptors.
+    fn new_failed_font_face(global: &GlobalScope, can_gc: CanGc) -> Self {
+        let font_status_promise = Promise::new(global, can_gc);
+        // If any of them fail to parse correctly, reject font face’s [[FontStatusPromise]] with a
+        // DOMException named "SyntaxError"
+        font_status_promise.reject_error(Error::Syntax);
+
+        // set font face’s corresponding attributes to the empty string, and set font face’s status
+        // attribute to "error"
+        Self {
+            reflector: Reflector::new(),
+            font_face_set: MutNullableDom::default(),
+            font_status_promise,
+            family_name: DomRefCell::default(),
+            urls: DomRefCell::default(),
+            descriptors: DomRefCell::new(FontFaceDescriptors {
+                ascentOverride: DOMString::new(),
+                descentOverride: DOMString::new(),
+                display: DOMString::new(),
+                featureSettings: DOMString::new(),
+                lineGapOverride: DOMString::new(),
+                stretch: DOMString::new(),
+                style: DOMString::new(),
+                unicodeRange: DOMString::new(),
+                variationSettings: DOMString::new(),
+                weight: DOMString::new(),
+            }),
+            status: Cell::new(FontFaceLoadStatus::Error),
+            template: RefCell::default(),
+        }
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#font-face-constructor>
+    fn new_inherited(
+        global: &GlobalScope,
+        family_name: DOMString,
+        source: StringOrArrayBufferViewOrArrayBuffer,
+        descriptors: &FontFaceDescriptors,
+        can_gc: CanGc,
+    ) -> Self {
+        // TODO: Add support for ArrayBuffer and ArrayBufferView sources.
+        let StringOrArrayBufferViewOrArrayBuffer::String(ref source_string) = source else {
+            return Self::new_failed_font_face(global, can_gc);
+        };
+
+        // Step 1. Parse the family argument, and the members of the descriptors argument,
+        // according to the grammars of the corresponding descriptors of the CSS @font-face rule If
+        // the source argument is a CSSOMString, parse it according to the grammar of the CSS src
+        // descriptor of the @font-face rule.
+        let parse_result =
+            parse_font_face_descriptors(global, &family_name, Some(source_string), descriptors);
+
+        let Ok(ref parsed_font_face_rule) = parse_result else {
+            // If any of them fail to parse correctly, reject font face’s
+            // [[FontStatusPromise]] with a DOMException named "SyntaxError", set font face’s
+            // corresponding attributes to the empty string, and set font face’s status attribute
+            // to "error".
+            return Self::new_failed_font_face(global, can_gc);
+        };
+
+        // Set its internal [[FontStatusPromise]] slot to a fresh pending Promise object.
+        let font_status_promise = Promise::new(global, can_gc);
+
+        let sources = parsed_font_face_rule
+            .sources
+            .clone()
+            .expect("Sources should be non-None after validation");
+
+        // Let font face be a fresh FontFace object.
+        Self {
+            reflector: Reflector::new(),
+
+            // Set font face’s status attribute to "unloaded".
+            status: Cell::new(FontFaceLoadStatus::Unloaded),
+
+            // Set font face’s corresponding attributes to the serialization of the parsed values.
+            descriptors: DomRefCell::new(serialize_parsed_descriptors(parsed_font_face_rule)),
+
+            font_face_set: MutNullableDom::default(),
+            family_name: DomRefCell::new(family_name.clone()),
+            urls: DomRefCell::new(Some(sources)),
+            template: RefCell::default(),
+            font_status_promise,
+        }
+    }
+
+    pub(crate) fn new(
+        global: &GlobalScope,
+        proto: Option<HandleObject>,
+        font_family: DOMString,
+        source: StringOrArrayBufferViewOrArrayBuffer,
+        descriptors: &FontFaceDescriptors,
+        can_gc: CanGc,
+    ) -> DomRoot<Self> {
+        reflect_dom_object_with_proto(
+            Box::new(Self::new_inherited(
+                global,
+                font_family,
+                source,
+                descriptors,
+                can_gc,
+            )),
+            global,
+            proto,
+            can_gc,
+        )
+    }
+
+    pub(super) fn set_associated_font_face_set(&self, font_face_set: &FontFaceSet) {
+        self.font_face_set.set(Some(font_face_set));
+    }
+
+    pub(super) fn loaded(&self) -> bool {
+        self.status.get() == FontFaceLoadStatus::Loaded
+    }
+
+    pub(super) fn template(&self) -> Option<(LowercaseFontFamilyName, FontTemplate)> {
+        self.template.borrow().clone()
+    }
+
+    /// Implements the body of the setter for the descriptor attributes of the [`FontFace`] interface.
+    ///
+    /// <https://drafts.csswg.org/css-font-loading/#fontface-interface>:
+    /// On setting, parse the string according to the grammar for the corresponding @font-face
+    /// descriptor. If it does not match the grammar, throw a SyntaxError; otherwise, set the attribute
+    /// to the serialization of the parsed value.
+    fn validate_and_set_descriptors(&self, new_descriptors: FontFaceDescriptors) -> ErrorResult {
+        let global = self.global();
+        let parsed_font_face_rule = parse_font_face_descriptors(
+            &global,
+            &self.family_name.borrow(),
+            None,
+            &new_descriptors,
+        )?;
+
+        *self.descriptors.borrow_mut() = serialize_parsed_descriptors(&parsed_font_face_rule);
+        Ok(())
+    }
+}
+
+impl FontFaceMethods<crate::DomTypeHolder> for FontFace {
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-family>
+    fn Family(&self) -> DOMString {
+        self.family_name.borrow().clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-family>
+    fn SetFamily(&self, family_name: DOMString) -> ErrorResult {
+        let descriptors = self.descriptors.borrow();
+        let global = self.global();
+        let _ = parse_font_face_descriptors(&global, &family_name, None, &descriptors)?;
+        *self.family_name.borrow_mut() = family_name;
+        Ok(())
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-style>
+    fn Style(&self) -> DOMString {
+        self.descriptors.borrow().style.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-style>
+    fn SetStyle(&self, value: DOMString) -> ErrorResult {
+        let mut new_descriptors = self.descriptors.borrow().clone();
+        new_descriptors.style = value;
+        self.validate_and_set_descriptors(new_descriptors)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-weight>
+    fn Weight(&self) -> DOMString {
+        self.descriptors.borrow().weight.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-weight>
+    fn SetWeight(&self, value: DOMString) -> ErrorResult {
+        let mut new_descriptors = self.descriptors.borrow().clone();
+        new_descriptors.weight = value;
+        self.validate_and_set_descriptors(new_descriptors)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-stretch>
+    fn Stretch(&self) -> DOMString {
+        self.descriptors.borrow().stretch.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-stretch>
+    fn SetStretch(&self, value: DOMString) -> ErrorResult {
+        let mut new_descriptors = self.descriptors.borrow().clone();
+        new_descriptors.stretch = value;
+        self.validate_and_set_descriptors(new_descriptors)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-unicoderange>
+    fn UnicodeRange(&self) -> DOMString {
+        self.descriptors.borrow().unicodeRange.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-unicoderange>
+    fn SetUnicodeRange(&self, value: DOMString) -> ErrorResult {
+        let mut new_descriptors = self.descriptors.borrow().clone();
+        new_descriptors.unicodeRange = value;
+        self.validate_and_set_descriptors(new_descriptors)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-featuresettings>
+    fn FeatureSettings(&self) -> DOMString {
+        self.descriptors.borrow().featureSettings.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-featuresettings>
+    fn SetFeatureSettings(&self, value: DOMString) -> ErrorResult {
+        let mut new_descriptors = self.descriptors.borrow().clone();
+        new_descriptors.featureSettings = value;
+        self.validate_and_set_descriptors(new_descriptors)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-variationsettings>
+    fn VariationSettings(&self) -> DOMString {
+        self.descriptors.borrow().variationSettings.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-variationsettings>
+    fn SetVariationSettings(&self, value: DOMString) -> ErrorResult {
+        let mut new_descriptors = self.descriptors.borrow().clone();
+        new_descriptors.variationSettings = value;
+        self.validate_and_set_descriptors(new_descriptors)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-display>
+    fn Display(&self) -> DOMString {
+        self.descriptors.borrow().display.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-display>
+    fn SetDisplay(&self, value: DOMString) -> ErrorResult {
+        let mut new_descriptors = self.descriptors.borrow().clone();
+        new_descriptors.display = value;
+        self.validate_and_set_descriptors(new_descriptors)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-ascentoverride>
+    fn AscentOverride(&self) -> DOMString {
+        self.descriptors.borrow().ascentOverride.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-ascentoverride>
+    fn SetAscentOverride(&self, value: DOMString) -> ErrorResult {
+        let mut new_descriptors = self.descriptors.borrow().clone();
+        new_descriptors.ascentOverride = value;
+        self.validate_and_set_descriptors(new_descriptors)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-descentoverride>
+    fn DescentOverride(&self) -> DOMString {
+        self.descriptors.borrow().descentOverride.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-descentoverride>
+    fn SetDescentOverride(&self, value: DOMString) -> ErrorResult {
+        let mut new_descriptors = self.descriptors.borrow().clone();
+        new_descriptors.descentOverride = value;
+        self.validate_and_set_descriptors(new_descriptors)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-linegapoverride>
+    fn LineGapOverride(&self) -> DOMString {
+        self.descriptors.borrow().lineGapOverride.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-linegapoverride>
+    fn SetLineGapOverride(&self, value: DOMString) -> ErrorResult {
+        let mut new_descriptors = self.descriptors.borrow().clone();
+        new_descriptors.lineGapOverride = value;
+        self.validate_and_set_descriptors(new_descriptors)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-status>
+    fn Status(&self) -> FontFaceLoadStatus {
+        self.status.get()
+    }
+
+    /// The load() method of FontFace forces a url-based font face to request its font data and
+    /// load. For fonts constructed from a buffer source, or fonts that are already loading or
+    /// loaded, it does nothing.
+    /// <https://drafts.csswg.org/css-font-loading/#font-face-load>
+    fn Load(&self) -> Rc<Promise> {
+        let Some(sources) = self.urls.borrow_mut().take() else {
+            // Step 2. If font face’s [[Urls]] slot is null, or its status attribute is anything
+            // other than "unloaded", return font face’s [[FontStatusPromise]] and abort these
+            // steps.
+            return self.font_status_promise.clone();
+        };
+
+        // FontFace must not be loaded at this point as `self.urls` is not None, implying `Load`
+        // wasn't called already. In our implementation, `urls` is set after parsing, so it
+        // cannot be `Some` if the status is `Error`.
+        debug_assert_eq!(self.status.get(), FontFaceLoadStatus::Unloaded);
+
+        let global = self.global();
+        let trusted = Trusted::new(self);
+        let task_source = global
+            .task_manager()
+            .font_loading_task_source()
+            .to_sendable();
+
+        let finished_callback = Box::new(
+            move |family_name: LowercaseFontFamilyName, load_result: Option<_>| {
+                let trusted = trusted.clone();
+
+                // Step 5. When the load operation completes, successfully or not, queue a task to
+                // run the following steps synchronously:
+                task_source.queue(task!(resolve_font_face_load_task: move || {
+                    let font_face = trusted.root();
+
+                    match load_result {
+                        None => {
+                            // Step 5.1. If the attempt to load fails, reject font face’s
+                            // [[FontStatusPromise]] with a DOMException whose name is "NetworkError"
+                            // and set font face’s status attribute to "error".
+                            font_face.status.set(FontFaceLoadStatus::Error);
+                            font_face.font_status_promise.reject_error(Error::Network);
+                        }
+                        Some(template) => {
+                            // Step 5.2. Otherwise, font face now represents the loaded font;
+                            // fulfill font face’s [[FontStatusPromise]] with font face and set
+                            // font face’s status attribute to "loaded".
+                            font_face.status.set(FontFaceLoadStatus::Loaded);
+                            let old_template = font_face.template.borrow_mut().replace((family_name, template));
+                            debug_assert!(old_template.is_none(), "FontFace's template must be intialized only once");
+                            font_face.font_status_promise.resolve_native(&font_face);
+                        }
+                    }
+
+                    if let Some(font_face_set) = font_face.font_face_set.get() {
+                        // For each FontFaceSet font face is in: ...
+                        //
+                        // This implements steps 5.1.1, 5.1.2, 5.2.1 and 5.2.2 - these
+                        // take care of changing the status of the `FontFaceSet` in which this
+                        // `FontFace` is a member, for both failed and successful load.
+                        font_face_set.handle_font_face_status_changed(&font_face);
+                    }
+                }));
+            },
+        );
+
+        // We parse the descriptors again because they are stored as `DOMString`s in this `FontFace`
+        // but the `load_web_font_for_script` API needs parsed values.
+        let parsed_font_face_rule = parse_font_face_descriptors(
+            &global,
+            &self.family_name.borrow(),
+            None,
+            &self.descriptors.borrow(),
+        )
+        .expect("Parsing shouldn't fail as descriptors are valid by construction");
+
+        // Step 4. Using the value of font face’s [[Urls]] slot, attempt to load a font as defined
+        // in [CSS-FONTS-3], as if it was the value of a @font-face rule’s src descriptor.
+        // TODO: FontFaceSet is not supported on Workers yet. The `as_window` call below should be
+        // replaced when we do support it.
+        global.as_window().font_context().load_web_font_for_script(
+            global.webview_id(),
+            sources,
+            (&parsed_font_face_rule).into(),
+            finished_callback,
+        );
+
+        // Step 3. Set font face’s status attribute to "loading", return font face’s
+        // [[FontStatusPromise]], and continue executing the rest of this algorithm asynchronously.
+        self.status.set(FontFaceLoadStatus::Loading);
+        self.font_status_promise.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontface-loaded>
+    fn Loaded(&self) -> Rc<Promise> {
+        self.font_status_promise.clone()
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#font-face-constructor>
+    fn Constructor(
+        window: &Window,
+        proto: Option<HandleObject>,
+        can_gc: CanGc,
+        family: DOMString,
+        source: UnionTypes::StringOrArrayBufferViewOrArrayBuffer,
+        descriptors: &FontFaceDescriptors,
+    ) -> DomRoot<FontFace> {
+        let global = window.as_global_scope();
+        FontFace::new(global, proto, family, source, descriptors, can_gc)
+    }
+}
diff --git a/components/script/dom/fontfaceset.rs b/components/script/dom/fontfaceset.rs
index dfaaf553b10..497da30680d 100644
--- a/components/script/dom/fontfaceset.rs
+++ b/components/script/dom/fontfaceset.rs
@@ -5,26 +5,35 @@
 use std::rc::Rc;
 
 use dom_struct::dom_struct;
+use fonts::FontContextWebFontMethods;
 use js::rust::HandleObject;
 
+use super::bindings::reflector::DomGlobal;
+use super::types::Window;
 use crate::dom::bindings::codegen::Bindings::FontFaceSetBinding::FontFaceSetMethods;
+use crate::dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
+use crate::dom::bindings::refcounted::TrustedPromise;
 use crate::dom::bindings::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::fontface::FontFace;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::promise::Promise;
-use crate::realms::enter_realm;
 use crate::script_runtime::CanGc;
 
+/// <https://drafts.csswg.org/css-font-loading/#FontFaceSet-interface>
 #[dom_struct]
 pub(crate) struct FontFaceSet {
     target: EventTarget,
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-readypromise-slot>
     #[ignore_malloc_size_of = "Rc"]
     promise: Rc<Promise>,
 }
 
 impl FontFaceSet {
-    pub(crate) fn new_inherited(global: &GlobalScope, can_gc: CanGc) -> Self {
+    fn new_inherited(global: &GlobalScope, can_gc: CanGc) -> Self {
         FontFaceSet {
             target: EventTarget::new_inherited(),
             promise: Promise::new(global, can_gc),
@@ -44,9 +53,24 @@ impl FontFaceSet {
         )
     }
 
+    pub(super) fn handle_font_face_status_changed(&self, font_face: &FontFace) {
+        if font_face.loaded() {
+            let Some(window) = DomRoot::downcast::<Window>(self.global()) else {
+                return;
+            };
+
+            let (family_name, template) = font_face
+                .template()
+                .expect("A loaded web font should have a template");
+            window
+                .font_context()
+                .add_template_to_font_context(family_name, template);
+            window.Document().dirty_all_nodes();
+        }
+    }
+
     pub(crate) fn fulfill_ready_promise_if_needed(&self) {
         if !self.promise.is_fulfilled() {
-            let _ac = enter_realm(&*self.promise);
             self.promise.resolve_native(self);
         }
     }
@@ -57,4 +81,43 @@ impl FontFaceSetMethods<crate::DomTypeHolder> for FontFaceSet {
     fn Ready(&self) -> Rc<Promise> {
         self.promise.clone()
     }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-add>
+    fn Add(&self, font_face: &FontFace) -> DomRoot<FontFaceSet> {
+        font_face.set_associated_font_face_set(self);
+        self.handle_font_face_status_changed(font_face);
+        DomRoot::from_ref(self)
+    }
+
+    /// <https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-load>
+    fn Load(&self, _font: DOMString, _text: DOMString, can_gc: CanGc) -> Rc<Promise> {
+        // Step 1. Let font face set be the FontFaceSet object this method was called on. Let
+        // promise be a newly-created promise object.
+        let promise = Promise::new(&self.global(), can_gc);
+
+        // TODO: Step 3. Find the matching font faces from font face set using the font and text
+        // arguments passed to the function, and let font face list be the return value (ignoring
+        // the found faces flag). If a syntax error was returned, reject promise with a SyntaxError
+        // exception and terminate these steps.
+
+        let trusted = TrustedPromise::new(promise.clone());
+        // Step 4. Queue a task to run the following steps synchronously:
+        self.global()
+            .task_manager()
+            .font_loading_task_source()
+            .queue(task!(resolve_font_face_set_load_task: move || {
+                let promise = trusted.root();
+
+                // TODO: Step 4.1. For all of the font faces in the font face list, call their load()
+                // method.
+
+                // TODO: Step 4.2. Resolve promise with the result of waiting for all of the
+                // [[FontStatusPromise]]s of each font face in the font face list, in order.
+                let matched_fonts = Vec::<&FontFace>::new();
+                promise.resolve_native(&matched_fonts);
+            }));
+
+        // Step 2. Return promise. Complete the rest of these steps asynchronously.
+        promise
+    }
 }
diff --git a/components/script/dom/mod.rs b/components/script/dom/mod.rs
index b0ea5d3aeb6..7127828224e 100644
--- a/components/script/dom/mod.rs
+++ b/components/script/dom/mod.rs
@@ -321,6 +321,7 @@ pub(crate) mod filelist;
 pub(crate) mod filereader;
 pub(crate) mod filereadersync;
 pub(crate) mod focusevent;
+pub(crate) mod fontface;
 pub(crate) mod fontfaceset;
 pub(crate) mod formdata;
 pub(crate) mod formdataevent;
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 375e6621992..f0b4b430ed6 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -634,6 +634,10 @@ impl Window {
     ) -> EventStatus {
         event.dispatch(self.upcast(), true, can_gc)
     }
+
+    pub(crate) fn font_context(&self) -> &Arc<FontContext> {
+        &self.font_context
+    }
 }
 
 // https://html.spec.whatwg.org/multipage/#atob
diff --git a/components/script/network_listener.rs b/components/script/network_listener.rs
index 5e662b8ef76..0e18af5dd16 100644
--- a/components/script/network_listener.rs
+++ b/components/script/network_listener.rs
@@ -73,7 +73,7 @@ pub(crate) fn submit_timing_data(
 }
 
 impl<Listener: PreInvoke + Send + 'static> NetworkListener<Listener> {
-    pub(crate) fn notify<A: Action<Listener> + Send + 'static>(&self, action: A) {
+    pub(crate) fn notify<A: Action<Listener> + Send + 'static>(&mut self, action: A) {
         self.task_source.queue(ListenerTask {
             context: self.context.clone(),
             action,
@@ -83,11 +83,11 @@ impl<Listener: PreInvoke + Send + 'static> NetworkListener<Listener> {
 
 // helps type inference
 impl<Listener: FetchResponseListener + PreInvoke + Send + 'static> NetworkListener<Listener> {
-    pub(crate) fn notify_fetch(&self, action: FetchResponseMsg) {
+    pub(crate) fn notify_fetch(&mut self, action: FetchResponseMsg) {
         self.notify(action);
     }
 
-    pub(crate) fn into_callback(self) -> BoxedFetchCallback {
+    pub(crate) fn into_callback(mut self) -> BoxedFetchCallback {
         Box::new(move |response_msg| self.notify_fetch(response_msg))
     }
 }
diff --git a/components/script/script_runtime.rs b/components/script/script_runtime.rs
index a51871eadf4..71e93671f47 100644
--- a/components/script/script_runtime.rs
+++ b/components/script/script_runtime.rs
@@ -104,6 +104,7 @@ pub(crate) enum ScriptThreadEventCategory {
     DevtoolsMsg,
     DocumentEvent,
     FileRead,
+    FontLoading,
     FormPlannedNavigation,
     HistoryEvent,
     ImageCacheMsg,
@@ -139,6 +140,7 @@ impl From<ScriptThreadEventCategory> for ProfilerCategory {
             ScriptThreadEventCategory::EnterFullscreen => ProfilerCategory::ScriptEnterFullscreen,
             ScriptThreadEventCategory::ExitFullscreen => ProfilerCategory::ScriptExitFullscreen,
             ScriptThreadEventCategory::FileRead => ProfilerCategory::ScriptFileRead,
+            ScriptThreadEventCategory::FontLoading => ProfilerCategory::ScriptFontLoading,
             ScriptThreadEventCategory::FormPlannedNavigation => {
                 ProfilerCategory::ScriptPlannedNavigation
             },
@@ -181,6 +183,7 @@ impl From<ScriptThreadEventCategory> for ScriptHangAnnotation {
             ScriptThreadEventCategory::DocumentEvent => ScriptHangAnnotation::DocumentEvent,
             ScriptThreadEventCategory::InputEvent => ScriptHangAnnotation::InputEvent,
             ScriptThreadEventCategory::FileRead => ScriptHangAnnotation::FileRead,
+            ScriptThreadEventCategory::FontLoading => ScriptHangAnnotation::FontLoading,
             ScriptThreadEventCategory::FormPlannedNavigation => {
                 ScriptHangAnnotation::FormPlannedNavigation
             },
diff --git a/components/script/script_thread.rs b/components/script/script_thread.rs
index b0066c88768..22a4e2e9e9b 100644
--- a/components/script/script_thread.rs
+++ b/components/script/script_thread.rs
@@ -1614,6 +1614,9 @@ impl ScriptThread {
                 ScriptThreadEventCategory::FileRead => {
                     time_profile!(ProfilerCategory::ScriptFileRead, None, profiler_chan, f)
                 },
+                ScriptThreadEventCategory::FontLoading => {
+                    time_profile!(ProfilerCategory::ScriptFontLoading, None, profiler_chan, f)
+                },
                 ScriptThreadEventCategory::FormPlannedNavigation => time_profile!(
                     ProfilerCategory::ScriptPlannedNavigation,
                     None,
diff --git a/components/script/task_manager.rs b/components/script/task_manager.rs
index eeae042b6ee..4854ef7cd56 100644
--- a/components/script/task_manager.rs
+++ b/components/script/task_manager.rs
@@ -134,6 +134,7 @@ impl TaskManager {
     task_source_functions!(self, canvas_blob_task_source, Canvas);
     task_source_functions!(self, dom_manipulation_task_source, DOMManipulation);
     task_source_functions!(self, file_reading_task_source, FileReading);
+    task_source_functions!(self, font_loading_task_source, FontLoading);
     task_source_functions!(self, gamepad_task_source, Gamepad);
     task_source_functions!(self, media_element_task_source, MediaElement);
     task_source_functions!(self, networking_task_source, Networking);
diff --git a/components/script/task_source.rs b/components/script/task_source.rs
index 0030dcb8c30..3d9993f6082 100644
--- a/components/script/task_source.rs
+++ b/components/script/task_source.rs
@@ -27,6 +27,8 @@ pub(crate) enum TaskSourceName {
     Canvas,
     DOMManipulation,
     FileReading,
+    /// <https://drafts.csswg.org/css-font-loading/#task-source>
+    FontLoading,
     HistoryTraversal,
     Networking,
     PerformanceTimeline,
@@ -48,6 +50,7 @@ impl From<TaskSourceName> for ScriptThreadEventCategory {
             TaskSourceName::Canvas => ScriptThreadEventCategory::ScriptEvent,
             TaskSourceName::DOMManipulation => ScriptThreadEventCategory::ScriptEvent,
             TaskSourceName::FileReading => ScriptThreadEventCategory::FileRead,
+            TaskSourceName::FontLoading => ScriptThreadEventCategory::FontLoading,
             TaskSourceName::HistoryTraversal => ScriptThreadEventCategory::HistoryEvent,
             TaskSourceName::Networking => ScriptThreadEventCategory::NetworkEvent,
             TaskSourceName::PerformanceTimeline => {
@@ -71,6 +74,7 @@ impl TaskSourceName {
             TaskSourceName::Canvas,
             TaskSourceName::DOMManipulation,
             TaskSourceName::FileReading,
+            TaskSourceName::FontLoading,
             TaskSourceName::HistoryTraversal,
             TaskSourceName::Networking,
             TaskSourceName::PerformanceTimeline,
diff --git a/components/script_bindings/codegen/Bindings.conf b/components/script_bindings/codegen/Bindings.conf
index bdc57b39746..57e268c9f10 100644
--- a/components/script_bindings/codegen/Bindings.conf
+++ b/components/script_bindings/codegen/Bindings.conf
@@ -175,6 +175,10 @@ DOMInterfaces = {
     'canGc': ['Abort'],
 },
 
+'FontFaceSet': {
+    'canGc': ['Load'],
+},
+
 'GamepadHapticActuator': {
     'inRealms': ['PlayEffect', 'Reset'],
     'canGc': ['PlayEffect', 'Reset'],
@@ -577,6 +581,10 @@ DOMInterfaces = {
 }
 
 Dictionaries = {
+'FontFaceDescriptors': {
+    'derives': ['Clone', 'MallocSizeOf']
+},
+
 'GPUCanvasConfiguration': {
     'derives': ['Clone']
 },
diff --git a/components/script_bindings/webidls/FontFace.webidl b/components/script_bindings/webidls/FontFace.webidl
new file mode 100644
index 00000000000..e2b1cc7f02c
--- /dev/null
+++ b/components/script_bindings/webidls/FontFace.webidl
@@ -0,0 +1,54 @@
+/* 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/. */
+
+typedef DOMString CSSOMString;
+
+dictionary FontFaceDescriptors {
+  CSSOMString style = "normal";
+  CSSOMString weight = "normal";
+  CSSOMString stretch = "normal";
+  CSSOMString unicodeRange = "U+0-10FFFF";
+  CSSOMString featureSettings = "normal";
+  CSSOMString variationSettings = "normal";
+  CSSOMString display = "auto";
+  CSSOMString ascentOverride = "normal";
+  CSSOMString descentOverride = "normal";
+  CSSOMString lineGapOverride = "normal";
+};
+
+enum FontFaceLoadStatus { "unloaded", "loading", "loaded", "error" };
+
+// https://drafts.csswg.org/css-font-loading/#fontface-interface
+[Exposed=(Window /*, Worker */), Pref="dom_fontface_enabled"] // TODO: Add support for FontFace in Workers.
+interface FontFace {
+  constructor(CSSOMString family, (CSSOMString or BufferSource) source,
+                optional FontFaceDescriptors descriptors = {});
+  [SetterThrows]
+  attribute CSSOMString family;
+  [SetterThrows]
+  attribute CSSOMString style;
+  [SetterThrows]
+  attribute CSSOMString weight;
+  [SetterThrows]
+  attribute CSSOMString stretch;
+  [SetterThrows]
+  attribute CSSOMString unicodeRange;
+  [SetterThrows]
+  attribute CSSOMString featureSettings;
+  [SetterThrows]
+  attribute CSSOMString variationSettings;
+  [SetterThrows]
+  attribute CSSOMString display;
+  [SetterThrows]
+  attribute CSSOMString ascentOverride;
+  [SetterThrows]
+  attribute CSSOMString descentOverride;
+  [SetterThrows]
+  attribute CSSOMString lineGapOverride;
+
+  readonly attribute FontFaceLoadStatus status;
+
+  Promise<FontFace> load();
+  readonly attribute Promise<FontFace> loaded;
+};
diff --git a/components/script_bindings/webidls/FontFaceSet.webidl b/components/script_bindings/webidls/FontFaceSet.webidl
index f114b2ac9b4..1bac3489ef6 100644
--- a/components/script_bindings/webidls/FontFaceSet.webidl
+++ b/components/script_bindings/webidls/FontFaceSet.webidl
@@ -19,12 +19,13 @@ enum FontFaceSetLoadStatus { "loading" , "loaded" };
 */
 
 // https://drafts.csswg.org/css-font-loading/#FontFaceSet-interface
-[Exposed=(Window,Worker)]
+[Exposed=(Window /*, Worker */)]
 interface FontFaceSet : EventTarget {
   // constructor(sequence<FontFace> initialFaces);
 
   // setlike<FontFace>;
-  // FontFaceSet add(FontFace font);
+  [Pref="dom_fontface_enabled"]
+  FontFaceSet add(FontFace font);
   // boolean delete(FontFace font);
   // undefined clear();
 
@@ -35,7 +36,8 @@ interface FontFaceSet : EventTarget {
 
   // check and start loads if appropriate
   // and fulfill promise when all loads complete
-  // Promise<sequence<FontFace>> load(DOMString font, optional DOMString text = " ");
+  [Pref="dom_fontface_enabled"]
+  Promise<sequence<FontFace>> load(DOMString font, optional DOMString text = " ");
 
   // return whether all fonts in the fontlist are loaded
   // (does not initiate load if not available)
diff --git a/components/shared/background_hang_monitor/lib.rs b/components/shared/background_hang_monitor/lib.rs
index ae7e587226a..223ace39c4b 100644
--- a/components/shared/background_hang_monitor/lib.rs
+++ b/components/shared/background_hang_monitor/lib.rs
@@ -21,6 +21,7 @@ pub enum ScriptHangAnnotation {
     DevtoolsMsg,
     DocumentEvent,
     FileRead,
+    FontLoading,
     FormPlannedNavigation,
     ImageCacheMsg,
     InputEvent,
diff --git a/components/shared/fonts/lib.rs b/components/shared/fonts/lib.rs
index 032dcfd19e0..9ba8d9425ee 100644
--- a/components/shared/fonts/lib.rs
+++ b/components/shared/fonts/lib.rs
@@ -17,4 +17,4 @@ int_range_index! {
     struct ByteIndex(isize)
 }
 
-pub type WebFontLoadFinishedCallback = Arc<dyn Fn(bool) + Send + Sync + 'static>;
+pub type StylesheetWebFontLoadFinishedCallback = Arc<dyn Fn(bool) + Send + Sync + 'static>;
diff --git a/components/shared/net/lib.rs b/components/shared/net/lib.rs
index bbdad23fa6f..b6c44cad75f 100644
--- a/components/shared/net/lib.rs
+++ b/components/shared/net/lib.rs
@@ -524,7 +524,7 @@ enum ToFetchThreadMessage {
     FetchResponse(FetchResponseMsg),
 }
 
-pub type BoxedFetchCallback = Box<dyn Fn(FetchResponseMsg) + Send + 'static>;
+pub type BoxedFetchCallback = Box<dyn FnMut(FetchResponseMsg) + Send + 'static>;
 
 /// A thread to handle fetches in a Servo process. This thread is responsible for
 /// listening for new fetch requests as well as updates on those operations and forwarding
@@ -601,7 +601,7 @@ impl FetchThread {
                         matches!(fetch_response_msg, FetchResponseMsg::ProcessResponseEOF(..));
 
                     self.active_fetches
-                        .get(&request_id)
+                        .get_mut(&request_id)
                         .expect("Got fetch response for unknown fetch")(
                         fetch_response_msg
                     );
diff --git a/components/shared/profile/time.rs b/components/shared/profile/time.rs
index ccb842a2224..78c380b70dc 100644
--- a/components/shared/profile/time.rs
+++ b/components/shared/profile/time.rs
@@ -90,43 +90,44 @@ pub enum ProfilerCategory {
 
     ScriptEvent = 0x66,
     ScriptFileRead = 0x67,
-    ScriptImageCacheMsg = 0x68,
-    ScriptInputEvent = 0x69,
-    ScriptNetworkEvent = 0x6a,
+    ScriptFontLoading = 0x68,
+    ScriptImageCacheMsg = 0x69,
+    ScriptInputEvent = 0x6a,
+    ScriptNetworkEvent = 0x6b,
 
     /// The script thread is parsing HTML, rather than doing other work like evaluating scripts or doing layout.
-    ScriptParseHTML = 0x6b,
-
-    ScriptPlannedNavigation = 0x6c,
-    ScriptResize = 0x6d,
-    ScriptRendering = 0x6e,
-    ScriptSetScrollState = 0x6f,
-    ScriptSetViewport = 0x70,
-    ScriptTimerEvent = 0x71,
-    ScriptStylesheetLoad = 0x72,
-    ScriptUpdateReplacedElement = 0x73,
-    ScriptWebSocketEvent = 0x74,
-    ScriptWorkerEvent = 0x75,
-    ScriptServiceWorkerEvent = 0x76,
+    ScriptParseHTML = 0x6c,
+
+    ScriptPlannedNavigation = 0x6d,
+    ScriptResize = 0x6e,
+    ScriptRendering = 0x6f,
+    ScriptSetScrollState = 0x70,
+    ScriptSetViewport = 0x71,
+    ScriptTimerEvent = 0x72,
+    ScriptStylesheetLoad = 0x73,
+    ScriptUpdateReplacedElement = 0x74,
+    ScriptWebSocketEvent = 0x75,
+    ScriptWorkerEvent = 0x76,
+    ScriptServiceWorkerEvent = 0x77,
 
     /// The script thread is parsing XML, rather than doing other work like evaluating scripts or doing layout.
-    ScriptParseXML = 0x77,
+    ScriptParseXML = 0x78,
 
-    ScriptEnterFullscreen = 0x78,
-    ScriptExitFullscreen = 0x79,
-    ScriptWorkletEvent = 0x7a,
-    ScriptPerformanceEvent = 0x7b,
-    ScriptHistoryEvent = 0x7c,
-    ScriptPortMessage = 0x7d,
-    ScriptWebGPUMsg = 0x7e,
+    ScriptEnterFullscreen = 0x79,
+    ScriptExitFullscreen = 0x7a,
+    ScriptWorkletEvent = 0x7b,
+    ScriptPerformanceEvent = 0x7c,
+    ScriptHistoryEvent = 0x7d,
+    ScriptPortMessage = 0x7e,
+    ScriptWebGPUMsg = 0x7f,
 
     /// Web performance metrics.
-    TimeToFirstPaint = 0x80,
-    TimeToFirstContentfulPaint = 0x81,
-    TimeToInteractive = 0x82,
+    TimeToFirstPaint = 0x90,
+    TimeToFirstContentfulPaint = 0x91,
+    TimeToInteractive = 0x92,
 
-    IpcReceiver = 0x83,
-    IpcBytesReceiver = 0x84,
+    IpcReceiver = 0x93,
+    IpcBytesReceiver = 0x94,
 }
 
 impl ProfilerCategory {
@@ -151,6 +152,7 @@ impl ProfilerCategory {
             ProfilerCategory::ScriptEvaluate => "ScriptEvaluate",
             ProfilerCategory::ScriptEvent => "ScriptEvent",
             ProfilerCategory::ScriptFileRead => "ScriptFileRead",
+            ProfilerCategory::ScriptFontLoading => "ScriptFontLoading",
             ProfilerCategory::ScriptImageCacheMsg => "ScriptImageCacheMsg",
             ProfilerCategory::ScriptInputEvent => "ScriptInputEvent",
             ProfilerCategory::ScriptNetworkEvent => "ScriptNetworkEvent",
diff --git a/tests/wpt/meta/__dir__.ini b/tests/wpt/meta/__dir__.ini
index b5b2db98287..f69cd94922b 100644
--- a/tests/wpt/meta/__dir__.ini
+++ b/tests/wpt/meta/__dir__.ini
@@ -1 +1 @@
-prefs: ["dom_imagebitmap_enabled:true", "dom_offscreen_canvas_enabled:true", "dom_shadowdom_enabled:true", "dom_xpath_enabled:true", "dom_intersection_observer_enabled:true", "dom_resize_observer_enabled:true", "dom_notification_enabled:true"]
+prefs: ["dom_imagebitmap_enabled:true", "dom_offscreen_canvas_enabled:true", "dom_shadowdom_enabled:true", "dom_xpath_enabled:true", "dom_intersection_observer_enabled:true", "dom_resize_observer_enabled:true", "dom_notification_enabled:true", "dom_fontface_enabled:true"]
diff --git a/tests/wpt/meta/css/css-cascade/layer-cssom-order-reverse.html.ini b/tests/wpt/meta/css/css-cascade/layer-cssom-order-reverse.html.ini
index 9bfa3e73791..6694f4405f2 100644
--- a/tests/wpt/meta/css/css-cascade/layer-cssom-order-reverse.html.ini
+++ b/tests/wpt/meta/css/css-cascade/layer-cssom-order-reverse.html.ini
@@ -1,6 +1,3 @@
 [layer-cssom-order-reverse.html]
-  [Insert layer invalidates @font-face]
-    expected: FAIL
-
   [Delete layer invalidates @font-face]
     expected: FAIL
diff --git a/tests/wpt/meta/css/css-cascade/layer-font-face-override.html.ini b/tests/wpt/meta/css/css-cascade/layer-font-face-override.html.ini
index b453839c49f..6195b20bcec 100644
--- a/tests/wpt/meta/css/css-cascade/layer-font-face-override.html.ini
+++ b/tests/wpt/meta/css/css-cascade/layer-font-face-override.html.ini
@@ -1,9 +1,11 @@
 [layer-font-face-override.html]
+  bug: https://github.com/servo/servo/issues/35520
+
   [@font-face unlayered overrides layered]
-    expected: FAIL
+    expected: [FAIL, PASS]
 
   [@font-face override between layers]
-    expected: FAIL
+    expected: [FAIL, PASS]
 
   [@font-face override update with appended sheet 1]
     expected: FAIL
diff --git a/tests/wpt/meta/css/css-fonts/fallback-remote-to-data-url.html.ini b/tests/wpt/meta/css/css-fonts/fallback-remote-to-data-url.html.ini
index 08229124c2f..28cbce9fd3a 100644
--- a/tests/wpt/meta/css/css-fonts/fallback-remote-to-data-url.html.ini
+++ b/tests/wpt/meta/css/css-fonts/fallback-remote-to-data-url.html.ini
@@ -1,2 +1,3 @@
 [fallback-remote-to-data-url.html]
-  expected: ERROR
+  [We should use the inline custom font to render the page when the primary remote font is loading]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-fonts/font-display/font-display-change.html.ini b/tests/wpt/meta/css/css-fonts/font-display/font-display-change.html.ini
index 8643675f6b3..5e3c6fc0042 100644
--- a/tests/wpt/meta/css/css-fonts/font-display/font-display-change.html.ini
+++ b/tests/wpt/meta/css/css-fonts/font-display/font-display-change.html.ini
@@ -1,2 +1,3 @@
 [font-display-change.html]
-  expected: TIMEOUT
+  bug: https://github.com/servo/servo/issues/35521
+  expected: [FAIL, TIMEOUT, PASS]
diff --git a/tests/wpt/meta/css/css-fonts/format-specifiers-variations.html.ini b/tests/wpt/meta/css/css-fonts/format-specifiers-variations.html.ini
index 041f8eb820b..4cd865a3c24 100644
--- a/tests/wpt/meta/css/css-fonts/format-specifiers-variations.html.ini
+++ b/tests/wpt/meta/css/css-fonts/format-specifiers-variations.html.ini
@@ -1,16 +1,4 @@
 [format-specifiers-variations.html]
-  [Load Ahem with format woff]
-    expected: FAIL
-
-  [Load Ahem with format truetype]
-    expected: FAIL
-
-  [Load Ahem with format opentype]
-    expected: FAIL
-
-  [Load Ahem with format woff2]
-    expected: FAIL
-
   [Load Ahem with format woff-variations]
     expected: FAIL
 
@@ -22,123 +10,3 @@
 
   [Load Ahem with format woff2-variations]
     expected: FAIL
-
-  [Do not load Ahem with format xyzwoff]
-    expected: FAIL
-
-  [Do not load Ahem with format xyztruetype]
-    expected: FAIL
-
-  [Do not load Ahem with format xyzopentype]
-    expected: FAIL
-
-  [Do not load Ahem with format xyzwoff2]
-    expected: FAIL
-
-  [Do not load Ahem with format xyzwoff-variations]
-    expected: FAIL
-
-  [Do not load Ahem with format xyztruetype-variations]
-    expected: FAIL
-
-  [Do not load Ahem with format xyzopentype-variations]
-    expected: FAIL
-
-  [Do not load Ahem with format xyzwoff2-variations]
-    expected: FAIL
-
-  [Do not load Ahem with format woffxyz]
-    expected: FAIL
-
-  [Do not load Ahem with format truetypexyz]
-    expected: FAIL
-
-  [Do not load Ahem with format opentypexyz]
-    expected: FAIL
-
-  [Do not load Ahem with format woff2xyz]
-    expected: FAIL
-
-  [Do not load Ahem with format woff-variationsxyz]
-    expected: FAIL
-
-  [Do not load Ahem with format truetype-variationsxyz]
-    expected: FAIL
-
-  [Do not load Ahem with format opentype-variationsxyz]
-    expected: FAIL
-
-  [Do not load Ahem with format woff2-variationsxyz]
-    expected: FAIL
-
-  [Do not load Ahem with format wo]
-    expected: FAIL
-
-  [Do not load Ahem with format truety]
-    expected: FAIL
-
-  [Do not load Ahem with format openty]
-    expected: FAIL
-
-  [Do not load Ahem with format wof]
-    expected: FAIL
-
-  [Do not load Ahem with format woff-variatio]
-    expected: FAIL
-
-  [Do not load Ahem with format truetype-variatio]
-    expected: FAIL
-
-  [Do not load Ahem with format opentype-variatio]
-    expected: FAIL
-
-  [Do not load Ahem with format woff2-variatio]
-    expected: FAIL
-
-  [Do not load Ahem with format ff]
-    expected: FAIL
-
-  [Do not load Ahem with format uetype]
-    expected: FAIL
-
-  [Do not load Ahem with format entype]
-    expected: FAIL
-
-  [Do not load Ahem with format ff2]
-    expected: FAIL
-
-  [Do not load Ahem with format ff-variations]
-    expected: FAIL
-
-  [Do not load Ahem with format uetype-variations]
-    expected: FAIL
-
-  [Do not load Ahem with format entype-variations]
-    expected: FAIL
-
-  [Do not load Ahem with format ff2-variations]
-    expected: FAIL
-
-  [Do not load Ahem with format wff]
-    expected: FAIL
-
-  [Do not load Ahem with format tretype]
-    expected: FAIL
-
-  [Do not load Ahem with format opntype]
-    expected: FAIL
-
-  [Do not load Ahem with format wff2]
-    expected: FAIL
-
-  [Do not load Ahem with format woff-ariations]
-    expected: FAIL
-
-  [Do not load Ahem with format truetye-variations]
-    expected: FAIL
-
-  [Do not load Ahem with format opentye-variations]
-    expected: FAIL
-
-  [Do not load Ahem with format woff2variations]
-    expected: FAIL
diff --git a/tests/wpt/meta/css/css-fonts/parsing/font-size-adjust-computed.html.ini b/tests/wpt/meta/css/css-fonts/parsing/font-size-adjust-computed.html.ini
index be39e77c50d..7236e490ccf 100644
--- a/tests/wpt/meta/css/css-fonts/parsing/font-size-adjust-computed.html.ini
+++ b/tests/wpt/meta/css/css-fonts/parsing/font-size-adjust-computed.html.ini
@@ -38,5 +38,20 @@
   [Property font-size-adjust value 'ic-height from-font']
     expected: FAIL
 
-  [CSS Fonts Module Level 5: getComputedStyle().fontSizeAdjust]
+  [Property font-size-adjust value 'calc(0.5)']
+    expected: FAIL
+
+  [Property font-size-adjust value 'ex-height calc(0.5)']
+    expected: FAIL
+
+  [Property font-size-adjust value 'cap-height calc(0.5)']
+    expected: FAIL
+
+  [Property font-size-adjust value 'cap-height calc(0.5 + 1)']
+    expected: FAIL
+
+  [Property font-size-adjust value 'cap-height calc(-0.5)']
+    expected: FAIL
+
+  [Property font-size-adjust value 'cap-height calc(10 + (sign(20cqw - 10px) * 5))']
     expected: FAIL
diff --git a/tests/wpt/meta/css/css-fonts/variations/font-parse-numeric-stretch-style-weight.html.ini b/tests/wpt/meta/css/css-fonts/variations/font-parse-numeric-stretch-style-weight.html.ini
deleted file mode 100644
index 13ae17b2eb2..00000000000
--- a/tests/wpt/meta/css/css-fonts/variations/font-parse-numeric-stretch-style-weight.html.ini
+++ /dev/null
@@ -1,156 +0,0 @@
-[font-parse-numeric-stretch-style-weight.html]
-  [Valid value 100 matches 100 for weight in @font-face.]
-    expected: FAIL
-
-  [Valid value 700 matches 700 for weight in @font-face.]
-    expected: FAIL
-
-  [Valid value 900 matches 900 for weight in @font-face.]
-    expected: FAIL
-
-  [Valid value bold matches bold for weight in @font-face.]
-    expected: FAIL
-
-  [Valid value normal matches normal for weight in @font-face.]
-    expected: FAIL
-
-  [Valid value 100 400 matches 100 400 for weight in @font-face.]
-    expected: FAIL
-
-  [Valid value 100 101.5 matches 100 101.5 for weight in @font-face.]
-    expected: FAIL
-
-  [Valid value 999.8 999.9 matches 999.8 999.9 for weight in @font-face.]
-    expected: FAIL
-
-  [Valid value 500 400 matches 500 400 for weight in @font-face.]
-    expected: FAIL
-
-  [Valid value 0% matches 0% for stretch in @font-face.]
-    expected: FAIL
-
-  [Valid value calc(0% - 10%) matches calc(-10%) for stretch in @font-face.]
-    expected: FAIL
-
-  [Valid value 100% matches 100% for stretch in @font-face.]
-    expected: FAIL
-
-  [Valid value 110% matches 110% for stretch in @font-face.]
-    expected: FAIL
-
-  [Valid value 111.5% matches 111.5% for stretch in @font-face.]
-    expected: FAIL
-
-  [Valid value 50% 200% matches 50% 200% for stretch in @font-face.]
-    expected: FAIL
-
-  [Valid value 0.1% 1% matches 0.1% 1% for stretch in @font-face.]
-    expected: FAIL
-
-  [Valid value 900% 901% matches 900% 901% for stretch in @font-face.]
-    expected: FAIL
-
-  [Valid value ultra-condensed matches ultra-condensed for stretch in @font-face.]
-    expected: FAIL
-
-  [Valid value ultra-expanded matches ultra-expanded for stretch in @font-face.]
-    expected: FAIL
-
-  [Valid value normal matches normal for style in @font-face.]
-    expected: FAIL
-
-  [Valid value italic matches italic for style in @font-face.]
-    expected: FAIL
-
-  [Valid value oblique matches oblique for style in @font-face.]
-    expected: FAIL
-
-  [Valid value oblique 10deg matches oblique 10deg for style in @font-face.]
-    expected: FAIL
-
-  [Valid value oblique 10deg 20deg matches oblique 10deg 20deg for style in @font-face.]
-    expected: FAIL
-
-  [Value 0 must not be accepted as weight in @font-face.]
-    expected: FAIL
-
-  [Value 0.9 must not be accepted as weight in @font-face.]
-    expected: FAIL
-
-  [Value -100 200 must not be accepted as weight in @font-face.]
-    expected: FAIL
-
-  [Value 100 -200 must not be accepted as weight in @font-face.]
-    expected: FAIL
-
-  [Value 100 1001 must not be accepted as weight in @font-face.]
-    expected: FAIL
-
-  [Value 1001 must not be accepted as weight in @font-face.]
-    expected: FAIL
-
-  [Value 1000.5 must not be accepted as weight in @font-face.]
-    expected: FAIL
-
-  [Value 100 200 300 must not be accepted as weight in @font-face.]
-    expected: FAIL
-
-  [Value a must not be accepted as weight in @font-face.]
-    expected: FAIL
-
-  [Value a b c must not be accepted as weight in @font-face.]
-    expected: FAIL
-
-  [Value -0.5% must not be accepted as stretch in @font-face.]
-    expected: FAIL
-
-  [Value -1% must not be accepted as stretch in @font-face.]
-    expected: FAIL
-
-  [Value 60% 70% 80% must not be accepted as stretch in @font-face.]
-    expected: FAIL
-
-  [Value a% must not be accepted as stretch in @font-face.]
-    expected: FAIL
-
-  [Value a b c must not be accepted as stretch in @font-face.]
-    expected: FAIL
-
-  [Value 0.1 must not be accepted as stretch in @font-face.]
-    expected: FAIL
-
-  [Value -60% 80% must not be accepted as stretch in @font-face.]
-    expected: FAIL
-
-  [Value ultra-expannnned must not be accepted as stretch in @font-face.]
-    expected: FAIL
-
-  [Value 50% 0 must not be accepted as stretch in @font-face.]
-    expected: FAIL
-
-  [Value oblique 100deg must not be accepted as style in @font-face.]
-    expected: FAIL
-
-  [Value oblique italic must not be accepted as style in @font-face.]
-    expected: FAIL
-
-  [Value oblique -91deg must not be accepted as style in @font-face.]
-    expected: FAIL
-
-  [Value oblique 0 must not be accepted as style in @font-face.]
-    expected: FAIL
-
-  [Value oblique 10 must not be accepted as style in @font-face.]
-    expected: FAIL
-
-  [Value iiitalic must not be accepted as style in @font-face.]
-    expected: FAIL
-
-  [Value 90deg must not be accepted as style in @font-face.]
-    expected: FAIL
-
-  [Value 11 must not be accepted as style in @font-face.]
-    expected: FAIL
-
-  [Value italic 90deg must not be accepted as style in @font-face.]
-    expected: FAIL
diff --git a/tests/wpt/meta/css/css-masking/clip-path/clip-path-svg-text-font-loading.html.ini b/tests/wpt/meta/css/css-masking/clip-path/clip-path-svg-text-font-loading.html.ini
index 103381380a3..3ea1cb4f41d 100644
--- a/tests/wpt/meta/css/css-masking/clip-path/clip-path-svg-text-font-loading.html.ini
+++ b/tests/wpt/meta/css/css-masking/clip-path/clip-path-svg-text-font-loading.html.ini
@@ -1,2 +1,2 @@
 [clip-path-svg-text-font-loading.html]
-  expected: TIMEOUT
+  expected: FAIL
diff --git a/tests/wpt/meta/css/css-values/ch-empty-pseudo-recalc-on-font-load.html.ini b/tests/wpt/meta/css/css-values/ch-empty-pseudo-recalc-on-font-load.html.ini
index e9b278c3ee8..64b77b15066 100644
--- a/tests/wpt/meta/css/css-values/ch-empty-pseudo-recalc-on-font-load.html.ini
+++ b/tests/wpt/meta/css/css-values/ch-empty-pseudo-recalc-on-font-load.html.ini
@@ -1,5 +1,4 @@
 [ch-empty-pseudo-recalc-on-font-load.html]
-  expected: ERROR
   [ch in pseudo-element ::before should be recalculated after loading a web font]
     expected: FAIL
 
diff --git a/tests/wpt/meta/css/css-values/ch-pseudo-recalc-on-font-load.html.ini b/tests/wpt/meta/css/css-values/ch-pseudo-recalc-on-font-load.html.ini
index 8bb7ac740bb..53b82763175 100644
--- a/tests/wpt/meta/css/css-values/ch-pseudo-recalc-on-font-load.html.ini
+++ b/tests/wpt/meta/css/css-values/ch-pseudo-recalc-on-font-load.html.ini
@@ -1,5 +1,4 @@
 [ch-pseudo-recalc-on-font-load.html]
-  expected: ERROR
   [ch in pseudo-element ::before should be recalculated after loading a web font]
     expected: FAIL
 
diff --git a/tests/wpt/meta/css/css-values/ch-recalc-on-font-load.html.ini b/tests/wpt/meta/css/css-values/ch-recalc-on-font-load.html.ini
deleted file mode 100644
index 507454f0afa..00000000000
--- a/tests/wpt/meta/css/css-values/ch-recalc-on-font-load.html.ini
+++ /dev/null
@@ -1,10 +0,0 @@
-[ch-recalc-on-font-load.html]
-  expected: ERROR
-  [ch in a normal div should be recalculated after loading a web font]
-    expected: TIMEOUT
-
-  [ch in display:contents should be recalculated after loading a web font]
-    expected: TIMEOUT
-
-  [ch in display:none should be recalculated after loading a web font]
-    expected: TIMEOUT
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/2d.text.draw.fill.maxWidth.fontface.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/2d.text.draw.fill.maxWidth.fontface.html.ini
deleted file mode 100644
index 3e7da9f9a61..00000000000
--- a/tests/wpt/meta/html/canvas/offscreen/text/2d.text.draw.fill.maxWidth.fontface.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[2d.text.draw.fill.maxWidth.fontface.html]
-  [fillText works on @font-face fonts]
-    expected: FAIL
-
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/2d.text.measure.width.empty.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/2d.text.measure.width.empty.html.ini
index e7133922d3d..2d3a3958f5c 100644
--- a/tests/wpt/meta/html/canvas/offscreen/text/2d.text.measure.width.empty.html.ini
+++ b/tests/wpt/meta/html/canvas/offscreen/text/2d.text.measure.width.empty.html.ini
@@ -1,6 +1,3 @@
 [2d.text.measure.width.empty.html]
   [The empty string has zero width for OffscreenCanvas]
     expected: FAIL
-
-  [The empty string has zero width]
-    expected: FAIL
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.condensed.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.condensed.html.ini
new file mode 100644
index 00000000000..f1389317ba4
--- /dev/null
+++ b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.condensed.html.ini
@@ -0,0 +1,2 @@
+[canvas.2d.fontStretch.condensed.html]
+  expected: FAIL
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.expanded.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.expanded.html.ini
new file mode 100644
index 00000000000..dc035a8d7a6
--- /dev/null
+++ b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.expanded.html.ini
@@ -0,0 +1,2 @@
+[canvas.2d.fontStretch.expanded.html]
+  expected: FAIL
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.extra-condensed.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.extra-condensed.html.ini
new file mode 100644
index 00000000000..b21e1ff7942
--- /dev/null
+++ b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.extra-condensed.html.ini
@@ -0,0 +1,2 @@
+[canvas.2d.fontStretch.extra-condensed.html]
+  expected: FAIL
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.extra-expanded.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.extra-expanded.html.ini
new file mode 100644
index 00000000000..2a3dae38d26
--- /dev/null
+++ b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.extra-expanded.html.ini
@@ -0,0 +1,2 @@
+[canvas.2d.fontStretch.extra-expanded.html]
+  expected: FAIL
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.normal.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.normal.html.ini
new file mode 100644
index 00000000000..06249acdefc
--- /dev/null
+++ b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.normal.html.ini
@@ -0,0 +1,2 @@
+[canvas.2d.fontStretch.normal.html]
+  expected: FAIL
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.semi-condensed.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.semi-condensed.html.ini
new file mode 100644
index 00000000000..82112139c28
--- /dev/null
+++ b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.semi-condensed.html.ini
@@ -0,0 +1,2 @@
+[canvas.2d.fontStretch.semi-condensed.html]
+  expected: FAIL
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.semi-expanded.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.semi-expanded.html.ini
new file mode 100644
index 00000000000..5d96cf42cd9
--- /dev/null
+++ b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.semi-expanded.html.ini
@@ -0,0 +1,2 @@
+[canvas.2d.fontStretch.semi-expanded.html]
+  expected: FAIL
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.ultra-condensed.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.ultra-condensed.html.ini
new file mode 100644
index 00000000000..4655dc92135
--- /dev/null
+++ b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.ultra-condensed.html.ini
@@ -0,0 +1,2 @@
+[canvas.2d.fontStretch.ultra-condensed.html]
+  expected: FAIL
diff --git a/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.ultra-expanded.html.ini b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.ultra-expanded.html.ini
new file mode 100644
index 00000000000..118ea5fd38c
--- /dev/null
+++ b/tests/wpt/meta/html/canvas/offscreen/text/canvas.2d.fontStretch.ultra-expanded.html.ini
@@ -0,0 +1,2 @@
+[canvas.2d.fontStretch.ultra-expanded.html]
+  expected: FAIL
diff --git a/tests/wpt/meta/webidl/current-realm.html.ini b/tests/wpt/meta/webidl/current-realm.html.ini
index a2c668873b7..f8e0202efb1 100644
--- a/tests/wpt/meta/webidl/current-realm.html.ini
+++ b/tests/wpt/meta/webidl/current-realm.html.ini
@@ -4,6 +4,3 @@
 
   [getImageData]
     expected: FAIL
-
-  [FontFace's load()]
-    expected: FAIL
diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index e1671aa476a..63bd8acee17 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -13513,7 +13513,7 @@
      ]
     ],
     "interfaces.worker.js": [
-     "fc621bbafeec167942f802caae43b9f2ef23b29b",
+     "f708bfb25594a239be31671e9fd15d6771309a12",
      [
       "mozilla/interfaces.worker.html",
       {}
diff --git a/tests/wpt/mozilla/tests/mozilla/interfaces.worker.js b/tests/wpt/mozilla/tests/mozilla/interfaces.worker.js
index fc621bbafee..f708bfb2559 100644
--- a/tests/wpt/mozilla/tests/mozilla/interfaces.worker.js
+++ b/tests/wpt/mozilla/tests/mozilla/interfaces.worker.js
@@ -34,7 +34,6 @@ test_interfaces([
   "FileReader",
   "FileReaderSync",
   "FinalizationRegistry",
-  "FontFaceSet",
   "FormData",
   "Headers",
   "History",