fonts: Remove synchronous web font loading functionality (#35000)

Synchronous web font loading is not specification compliant and was
added in #8341 to work around issues that do not exist any longer. This
change removes the functionality and ensures that WPT tests are run with
the spec compliant loader.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/config/opts.rs

@@ -177,9 +177,6 @@ pub struct DebugOptions {
     /// Log GC passes and their durations.
     pub gc_profile: bool,
 
-    /// Load web fonts synchronously to avoid non-deterministic network-driven reflows.
-    pub load_webfonts_synchronously: bool,
-
     /// Show webrender profiling stats on screen.
     pub webrender_stats: bool,
 
@@ -209,7 +206,6 @@ impl DebugOptions {
                 "dump-rule-tree" => self.dump_rule_tree = true,
                 "dump-style-tree" => self.dump_style_tree = true,
                 "gc-profile" => self.gc_profile = true,
-                "load-webfonts-synchronously" => self.load_webfonts_synchronously = true,
                 "precache-shaders" => self.precache_shaders = true,
                 "profile-script-events" => self.profile_script_events = true,
                 "relayout-event" => self.relayout_event = true,

components/fonts/font_context.rs

@@ -9,7 +9,6 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
 
 use app_units::Au;
-use crossbeam_channel::unbounded;
 use fnv::FnvHasher;
 use fonts_traits::WebFontLoadFinishedCallback;
 use log::{debug, trace};
@@ -374,7 +373,6 @@ pub trait FontContextWebFontMethods {
         guard: &SharedRwLockReadGuard,
         device: &Device,
         finished_callback: WebFontLoadFinishedCallback,
-        synchronous: bool,
     ) -> usize;
     fn remove_all_web_fonts_from_stylesheet(&self, stylesheet: &DocumentStyleSheet);
     fn collect_unused_webrender_resources(&self, all: bool)
@@ -388,21 +386,7 @@ impl FontContextWebFontMethods for Arc<FontContext> {
         guard: &SharedRwLockReadGuard,
         device: &Device,
         finished_callback: WebFontLoadFinishedCallback,
-        synchronous: bool,
     ) -> usize {
-        let (finished_callback, synchronous_receiver) = if synchronous {
-            let (sender, receiver) = unbounded();
-            let finished_callback = move |_succeeded: bool| {
-                let _ = sender.send(());
-            };
-            (
-                Arc::new(finished_callback) as WebFontLoadFinishedCallback,
-                Some(receiver),
-            )
-        } else {
-            (finished_callback, None)
-        };
-
         let mut number_loading = 0;
         for rule in stylesheet.effective_rules(device, guard) {
             let CssRule::FontFace(ref lock) = *rule else {
@@ -464,11 +448,6 @@ impl FontContextWebFontMethods for Arc<FontContext> {
                 local_fonts: Arc::new(local_fonts),
                 stylesheet: stylesheet.clone(),
             });
-
-            // If the load is synchronous wait for it to be signalled.
-            if let Some(ref synchronous_receiver) = synchronous_receiver {
-                synchronous_receiver.recv().unwrap();
-            }
         }
 
         number_loading

components/layout_thread/lib.rs

@@ -639,22 +639,12 @@ impl LayoutThread {
                 );
             };
 
-        // Find all font-face rules and notify the FontContext of them.
-        // GWTODO: Need to handle unloading web fonts.
-        let newly_loading_font_count = self.font_context.add_all_web_fonts_from_stylesheet(
+        self.font_context.add_all_web_fonts_from_stylesheet(
             stylesheet,
             guard,
             self.stylist.device(),
             Arc::new(web_font_finished_loading_callback) as WebFontLoadFinishedCallback,
-            self.debug.load_webfonts_synchronously,
         );
-
-        if self.debug.load_webfonts_synchronously && newly_loading_font_count > 0 {
-            // TODO: Handle failure in web font loading
-            let _ = self
-                .script_chan
-                .send(ConstellationControlMsg::WebFontLoaded(self.id, true));
-        }
     }
 
     fn try_get_layout_root<'dom>(&self, node: impl LayoutNode<'dom>) -> Option<FlowRef> {

components/layout_thread_2020/lib.rs

@@ -618,22 +618,12 @@ impl LayoutThread {
                 ));
         };
 
-        // Find all font-face rules and notify the font cache of them.
-        // GWTODO: Need to handle unloading web fonts.
-        let newly_loading_font_count = self.font_context.add_all_web_fonts_from_stylesheet(
+        self.font_context.add_all_web_fonts_from_stylesheet(
             stylesheet,
             guard,
             self.stylist.device(),
             Arc::new(web_font_finished_loading_callback) as WebFontLoadFinishedCallback,
-            self.debug.load_webfonts_synchronously,
         );
-
-        if self.debug.load_webfonts_synchronously && newly_loading_font_count > 0 {
-            // TODO: Handle failure in web font loading
-            let _ = self
-                .script_chan
-                .send(ConstellationControlMsg::WebFontLoaded(self.id, true));
-        }
     }
 
     /// The high-level routine that performs layout.

tests/wpt/meta/MANIFEST.json

@@ -503873,7 +503873,7 @@
         []
        ],
        "executorservo.py": [
-        "1d96ffa41da33c9b3c2650ee68c27174bf3081a6",
+        "8b6db6091a84e9e83ec8d161fc86b1d0387f41e6",
         []
        ],
        "executorservodriver.py": [

tests/wpt/tests/tools/wptrunner/wptrunner/executors/executorservo.py

@@ -231,7 +231,7 @@ class ServoRefTestExecutor(ServoExecutor):
             extra_args = ["--exit",
                           "--output=%s" % output_path,
                           "--window-size", viewport_size or "800x600"]
-            debug_opts = "disable-text-aa,load-webfonts-synchronously,replace-surrogates"
+            debug_opts = "disable-text-aa,replace-surrogates"
 
             if dpi:
                 extra_args += ["--device-pixel-ratio", dpi]