script: Move the FontContext to Window (#34845)

This will allow using layout's `FontContext` in `Window` letting script
manage font selection and download.

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

components/script/dom/window.rs

@@ -28,6 +28,7 @@ use dom_struct::dom_struct;
 use embedder_traits::{EmbedderMsg, PromptDefinition, PromptOrigin, PromptResult};
 use euclid::default::{Point2D as UntypedPoint2D, Rect as UntypedRect};
 use euclid::{Point2D, Rect, Scale, Size2D, Vector2D};
+use fonts::FontContext;
 use ipc_channel::ipc::{self, IpcSender};
 use ipc_channel::router::ROUTER;
 use js::conversions::ToJSValConvertible;
@@ -207,6 +208,11 @@ pub struct Window {
     #[no_trace]
     #[ignore_malloc_size_of = "TODO: Add MallocSizeOf support to layout"]
     layout: RefCell<Box<dyn Layout>>,
+    /// A [`FontContext`] which is used to store and match against fonts for this `Window` and to
+    /// trigger the download of web fonts.
+    #[no_trace]
+    #[conditional_malloc_size_of]
+    font_context: Arc<FontContext>,
     navigator: MutNullableDom<Navigator>,
     #[ignore_malloc_size_of = "Arc"]
     #[no_trace]
@@ -1942,9 +1948,8 @@ impl Window {
     /// should happen as part of the HTML event loop via *update the rendering*. Currerntly, the
     /// only exceptions are script queries and scroll requests.
     pub(crate) fn reflow(&self, reflow_goal: ReflowGoal, can_gc: CanGc) -> bool {
-        // Fetch the pending web fonts before layout, in case a font loads during
-        // the layout.
-        let pending_web_fonts = self.layout.borrow().waiting_for_web_fonts_to_load();
+        // Count the pending web fonts before layout, in case a font loads during the layout.
+        let waiting_for_web_fonts_to_load = self.font_context.web_fonts_still_loading() != 0;
 
         self.Document().ensure_safe_to_run_script_or_layout();
 
@@ -1988,7 +1993,7 @@ impl Window {
         // Thus, we are queueing promise resolution here. This reflow should have been triggered by
         // a "rendering opportunity" in `ScriptThread::handle_web_font_loaded, which should also
         // make sure a microtask checkpoint happens, triggering the promise callback.
-        if !pending_web_fonts && is_ready_state_complete {
+        if !waiting_for_web_fonts_to_load && is_ready_state_complete {
             font_face_set.fulfill_ready_promise_if_needed();
         }
 
@@ -2017,7 +2022,7 @@ impl Window {
                 is_ready_state_complete &&
                 !reftest_wait &&
                 !pending_images &&
-                !pending_web_fonts
+                !waiting_for_web_fonts_to_load
             {
                 debug!(
                     "{:?}: Sending DocumentState::Idle to Constellation",
@@ -2674,6 +2679,7 @@ impl Window {
         runtime: Rc<Runtime>,
         script_chan: MainThreadScriptChan,
         layout: Box<dyn Layout>,
+        font_context: Arc<FontContext>,
         image_cache_chan: Sender<ImageCacheMsg>,
         image_cache: Arc<dyn ImageCache>,
         resource_threads: ResourceThreads,
@@ -2737,6 +2743,7 @@ impl Window {
             ),
             script_chan,
             layout: RefCell::new(layout),
+            font_context,
             image_cache_chan,
             image_cache,
             navigator: Default::default(),

components/script/script_thread.rs

@@ -47,7 +47,7 @@ use devtools_traits::{
 };
 use embedder_traits::EmbedderMsg;
 use euclid::default::{Point2D, Rect};
-use fonts::SystemFontServiceProxy;
+use fonts::{FontContext, SystemFontServiceProxy};
 use headers::{HeaderMapExt, LastModified, ReferrerPolicy as ReferrerPolicyHeader};
 use html5ever::{local_name, namespace_url, ns};
 use hyper_serde::Serde;
@@ -3142,6 +3142,12 @@ impl ScriptThread {
             incomplete.navigation_start,
         );
 
+        let font_context = Arc::new(FontContext::new(
+            self.system_font_service.clone(),
+            self.compositor_api.clone(),
+            self.resource_threads.clone(),
+        ));
+
         let layout_config = LayoutConfig {
             id: incomplete.pipeline_id,
             url: final_url.clone(),
@@ -3149,8 +3155,7 @@ impl ScriptThread {
             constellation_chan: self.senders.layout_to_constellation_ipc_sender.clone(),
             script_chan: self.senders.constellation_sender.clone(),
             image_cache: self.image_cache.clone(),
-            system_font_service: self.system_font_service.clone(),
-            resource_threads: self.resource_threads.clone(),
+            font_context: font_context.clone(),
             time_profiler_chan: self.senders.time_profiler_sender.clone(),
             compositor_api: self.compositor_api.clone(),
             paint_time_metrics,
@@ -3162,6 +3167,7 @@ impl ScriptThread {
             self.js_runtime.clone(),
             self.senders.self_sender.clone(),
             self.layout_factory.create(layout_config),
+            font_context,
             self.senders.image_cache_sender.clone(),
             self.image_cache.clone(),
             self.resource_threads.clone(),