constellation: Pass system theme to new Pipelines (#37132)

Previously, when the theme was set it was only set on currently active
`Window`s. This change makes setting the `Theme` stateful. Now the
`Constellation` tracks what theme is applied to a `WebView` and properly
passes that value to new `Pipeline`s when they are constructed. In
addition, the value is passed to layout when that is constructed as
well.

Testing: this change adds a unit test.

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

components/script/dom/htmliframeelement.rs

@@ -223,6 +223,7 @@ impl HTMLIFrameElement {
                     old_pipeline_id,
                     sandbox: sandboxed,
                     viewport_details,
+                    theme: window.theme(),
                 };
                 window
                     .as_global_scope()
@@ -238,6 +239,7 @@ impl HTMLIFrameElement {
                     opener: None,
                     load_data,
                     viewport_details,
+                    theme: window.theme(),
                 };
 
                 self.pipeline_id.set(Some(new_pipeline_id));
@@ -250,6 +252,7 @@ impl HTMLIFrameElement {
                     old_pipeline_id,
                     sandbox: sandboxed,
                     viewport_details,
+                    theme: window.theme(),
                 };
                 window
                     .as_global_scope()

components/script/dom/window.rs

@@ -80,7 +80,6 @@ use style::dom::OpaqueNode;
 use style::error_reporting::{ContextualParseError, ParseErrorReporter};
 use style::properties::PropertyId;
 use style::properties::style_structs::Font;
-use style::queries::values::PrefersColorScheme;
 use style::selector_parser::PseudoElement;
 use style::str::HTML_SPACE_CHARACTERS;
 use style::stylesheets::UrlExtraData;
@@ -269,7 +268,7 @@ pub(crate) struct Window {
 
     /// Platform theme.
     #[no_trace]
-    theme: Cell<PrefersColorScheme>,
+    theme: Cell<Theme>,
 
     /// Parent id associated with this page, if any.
     #[no_trace]
@@ -2739,13 +2738,13 @@ impl Window {
         self.viewport_details.get()
     }
 
+    /// Get the theme of this [`Window`].
+    pub(crate) fn theme(&self) -> Theme {
+        self.theme.get()
+    }
+
     /// Handle a theme change request, triggering a reflow is any actual change occured.
     pub(crate) fn handle_theme_change(&self, new_theme: Theme) {
-        let new_theme = match new_theme {
-            Theme::Light => PrefersColorScheme::Light,
-            Theme::Dark => PrefersColorScheme::Dark,
-        };
-
         if self.theme.get() == new_theme {
             return;
         }
@@ -3033,6 +3032,7 @@ impl Window {
         player_context: WindowGLContext,
         #[cfg(feature = "webgpu")] gpu_id_hub: Arc<IdentityHub>,
         inherited_secure_context: Option<bool>,
+        theme: Theme,
     ) -> DomRoot<Self> {
         let error_reporter = CSSErrorReporter {
             pipelineid: pipeline_id,
@@ -3118,7 +3118,7 @@ impl Window {
             throttled: Cell::new(false),
             layout_marker: DomRefCell::new(Rc::new(Cell::new(true))),
             current_event: DomRefCell::new(None),
-            theme: Cell::new(PrefersColorScheme::Light),
+            theme: Cell::new(theme),
             trusted_types: Default::default(),
         });
 

components/script/dom/windowproxy.rs

@@ -329,6 +329,9 @@ impl WindowProxy {
             opener: Some(self.browsing_context_id),
             load_data,
             viewport_details: window.viewport_details(),
+            // Use the current `WebView`'s theme initially, but the embedder may
+            // change this later.
+            theme: window.theme(),
         };
         ScriptThread::process_attach_layout(new_layout_info, document.origin().clone());
         // TODO: if noopener is false, copy the sessionStorage storage area of the creator origin.

components/script/navigation.rs

@@ -12,7 +12,7 @@ use base::cross_process_instant::CrossProcessInstant;
 use base::id::{BrowsingContextId, PipelineId, WebViewId};
 use constellation_traits::LoadData;
 use crossbeam_channel::Sender;
-use embedder_traits::ViewportDetails;
+use embedder_traits::{Theme, ViewportDetails};
 use http::header;
 use net_traits::request::{
     CredentialsMode, InsecureRequestsPolicy, RedirectMode, RequestBuilder, RequestMode,
@@ -159,6 +159,9 @@ pub(crate) struct InProgressLoad {
     /// this load.
     #[no_trace]
     pub(crate) url_list: Vec<ServoUrl>,
+    /// The [`Theme`] to use for this page, once it loads.
+    #[no_trace]
+    pub(crate) theme: Theme,
 }
 
 impl InProgressLoad {
@@ -171,6 +174,7 @@ impl InProgressLoad {
         parent_info: Option<PipelineId>,
         opener: Option<BrowsingContextId>,
         viewport_details: ViewportDetails,
+        theme: Theme,
         origin: MutableOrigin,
         load_data: LoadData,
     ) -> InProgressLoad {
@@ -189,6 +193,7 @@ impl InProgressLoad {
             canceller: Default::default(),
             load_data,
             url_list: vec![url],
+            theme,
         }
     }
 

components/script/script_thread.rs

@@ -403,14 +403,20 @@ impl ScriptThreadFactory for ScriptThread {
                 WebViewId::install(state.webview_id);
                 let roots = RootCollection::new();
                 let _stack_roots = ThreadLocalStackRoots::new(&roots);
-                let id = state.id;
-                let browsing_context_id = state.browsing_context_id;
-                let webview_id = state.webview_id;
-                let parent_info = state.parent_info;
-                let opener = state.opener;
                 let memory_profiler_sender = state.memory_profiler_sender.clone();
-                let viewport_details = state.viewport_details;
 
+                let in_progress_load = InProgressLoad::new(
+                    state.id,
+                    state.browsing_context_id,
+                    state.webview_id,
+                    state.parent_info,
+                    state.opener,
+                    state.viewport_details,
+                    state.theme,
+                    MutableOrigin::new(load_data.url.origin()),
+                    load_data,
+                );
+                let reporter_name = format!("script-reporter-{:?}", state.id);
                 let script_thread = ScriptThread::new(state, layout_factory, system_font_service);
 
                 SCRIPT_THREAD_ROOT.with(|root| {
@@ -419,19 +425,8 @@ impl ScriptThreadFactory for ScriptThread {
 
                 let mut failsafe = ScriptMemoryFailsafe::new(&script_thread);
 
-                let origin = MutableOrigin::new(load_data.url.origin());
-                script_thread.pre_page_load(InProgressLoad::new(
-                    id,
-                    browsing_context_id,
-                    webview_id,
-                    parent_info,
-                    opener,
-                    viewport_details,
-                    origin,
-                    load_data,
-                ));
+                script_thread.pre_page_load(in_progress_load);
 
-                let reporter_name = format!("script-reporter-{:?}", id);
                 memory_profiler_sender.run_with_memory_reporting(
                     || {
                         script_thread.start(CanGc::note());
@@ -2435,6 +2430,7 @@ impl ScriptThread {
             opener,
             load_data,
             viewport_details,
+            theme,
         } = new_layout_info;
 
         // Kick off the fetch for the new resource.
@@ -2446,6 +2442,7 @@ impl ScriptThread {
             parent_info,
             opener,
             viewport_details,
+            theme,
             origin,
             load_data,
         );
@@ -3189,6 +3186,7 @@ impl ScriptThread {
             time_profiler_chan: self.senders.time_profiler_sender.clone(),
             compositor_api: self.compositor_api.clone(),
             viewport_details: incomplete.viewport_details,
+            theme: incomplete.theme,
         };
 
         // Create the window and document objects.
@@ -3228,6 +3226,7 @@ impl ScriptThread {
             #[cfg(feature = "webgpu")]
             self.gpu_id_hub.clone(),
             incomplete.load_data.inherited_secure_context,
+            incomplete.theme,
         );
 
         let _realm = enter_realm(&*window);