constellation: Remove BrowsingContext::throttled

This is now longer necessary now that `WebView`s track visibility.

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

components/compositing/webview_renderer.rs

@@ -173,8 +173,10 @@ impl WebViewRenderer {
             .any(PipelineDetails::animation_callbacks_running)
     }
 
+    /// Whether this [`WebViewRenderer`] is animating. Note that hidden `WebView`s
+    /// are never considered to be animating.
     pub(crate) fn animating(&self) -> bool {
-        self.animating
+        self.animating && !self.hidden()
     }
 
     pub(crate) fn hidden(&self) -> bool {
@@ -185,7 +187,14 @@ impl WebViewRenderer {
     /// value changed or `false` otherwise.
     pub(crate) fn set_hidden(&mut self, new_value: bool) -> bool {
         let old_value = std::mem::replace(&mut self.hidden, new_value);
-        new_value != old_value
+        if new_value == old_value {
+            return false;
+        }
+
+        let _ = self.embedder_to_constellation_sender.send(
+            EmbedderToConstellationMessage::SetWebViewHidden(self.id, new_value),
+        );
+        true
     }
 
     /// Returns the [`PipelineDetails`] for the given [`PipelineId`], creating it if needed.

components/constellation/browsingcontext.rs

@@ -26,10 +26,6 @@ pub struct NewBrowsingContextInfo {
 
     /// Whether this browsing context inherits a secure context.
     pub inherited_secure_context: Option<bool>,
-
-    /// Whether this browsing context should be throttled, using less resources
-    /// by stopping animations and running timers at a heavily limited rate.
-    pub throttled: bool,
 }
 
 /// The constellation's view of a browsing context.
@@ -57,10 +53,6 @@ pub struct BrowsingContext {
     /// Whether this browsing context inherits a secure context.
     pub inherited_secure_context: Option<bool>,
 
-    /// Whether this browsing context should be throttled, using less resources
-    /// by stopping animations and running timers at a heavily limited rate.
-    pub throttled: bool,
-
     /// The pipeline for the current session history entry.
     pub pipeline_id: PipelineId,
 
@@ -86,7 +78,6 @@ impl BrowsingContext {
         viewport_details: ViewportDetails,
         is_private: bool,
         inherited_secure_context: Option<bool>,
-        throttled: bool,
     ) -> BrowsingContext {
         let mut pipelines = FxHashSet::default();
         pipelines.insert(pipeline_id);
@@ -97,7 +88,6 @@ impl BrowsingContext {
             viewport_details,
             is_private,
             inherited_secure_context,
-            throttled,
             pipeline_id,
             parent_pipeline_id,
             pipelines,

components/constellation/constellation.rs

@@ -1030,20 +1030,18 @@ where
         // https://github.com/servo/ipc-channel/issues/138
         load_data: LoadData,
         is_private: bool,
-        throttled: bool,
     ) {
         if self.shutting_down {
             return;
         }
 
         debug!("Creating new pipeline ({new_pipeline_id:?}) in {browsing_context_id}");
-        let Some(theme) = self
-            .webviews
-            .get(&webview_id)
-            .map(ConstellationWebView::theme)
-        else {
-            warn!("Tried to create Pipeline for uknown WebViewId: {webview_id:?}");
-            return;
+        let (webview_hidden, theme) = {
+            let Some(webview) = self.webviews.get(&webview_id) else {
+                warn!("Tried to create Pipeline for uknown WebViewId: {webview_id:?}");
+                return;
+            };
+            (webview.hidden(), webview.theme())
         };
 
         let event_loop = match self.get_or_create_event_loop_for_new_pipeline(
@@ -1073,7 +1071,7 @@ where
             user_content_manager_id,
             theme,
         };
-        let pipeline = match Pipeline::spawn(new_pipeline_info, event_loop, self, throttled) {
+        let pipeline = match Pipeline::spawn(new_pipeline_info, event_loop, self, webview_hidden) {
             Ok(pipeline) => pipeline,
             Err(error) => return self.handle_send_error(new_pipeline_id, error),
         };
@@ -1163,7 +1161,6 @@ where
         viewport_details: ViewportDetails,
         is_private: bool,
         inherited_secure_context: Option<bool>,
-        throttled: bool,
     ) {
         debug!("{}: Creating new browsing context", browsing_context_id);
         let bc_group_id = match self
@@ -1202,7 +1199,6 @@ where
             viewport_details,
             is_private,
             inherited_secure_context,
-            throttled,
         );
         self.browsing_contexts
             .insert(browsing_context_id, browsing_context);
@@ -1503,8 +1499,8 @@ where
             EmbedderToConstellationMessage::MediaSessionAction(action) => {
                 self.handle_media_session_action_msg(action);
             },
-            EmbedderToConstellationMessage::SetWebViewThrottled(webview_id, throttled) => {
-                self.set_webview_throttled(webview_id, throttled);
+            EmbedderToConstellationMessage::SetWebViewHidden(webview_id, hidden) => {
+                self.set_webview_hidden(webview_id, hidden);
             },
             EmbedderToConstellationMessage::SetScrollStates(pipeline_id, scroll_states) => {
                 self.handle_set_scroll_states(pipeline_id, scroll_states)
@@ -2855,7 +2851,6 @@ where
         };
         let viewport_details = browsing_context.viewport_details;
         let pipeline_id = browsing_context.pipeline_id;
-        let throttled = browsing_context.throttled;
 
         let Some(pipeline) = self.pipelines.get(&pipeline_id) else {
             return warn!("failed pipeline is missing");
@@ -2900,7 +2895,6 @@ where
             viewport_details,
             new_load_data,
             is_private,
-            throttled,
         );
         self.add_pending_change(SessionHistoryChange {
             webview_id,
@@ -3062,7 +3056,6 @@ where
         let browsing_context_id = BrowsingContextId::from(webview_id);
         let load_data = LoadData::new_for_new_unrelated_webview(url);
         let is_private = false;
-        let throttled = false;
 
         // Register this new top-level browsing context id as a webview and set
         // its focused browsing context to be itself.
@@ -3089,7 +3082,6 @@ where
             viewport_details,
             load_data,
             is_private,
-            throttled,
         );
         self.add_pending_change(SessionHistoryChange {
             webview_id,
@@ -3100,7 +3092,6 @@ where
                 parent_pipeline_id: None,
                 is_private,
                 inherited_secure_context: None,
-                throttled,
             }),
             viewport_details,
         });
@@ -3290,7 +3281,6 @@ where
         };
 
         let browsing_context_size = browsing_context.viewport_details;
-        let browsing_context_throttled = browsing_context.throttled;
         // TODO(servo#30571) revert to debug_assert_eq!() once underlying bug is fixed
         #[cfg(debug_assertions)]
         if !(browsing_context_size == load_info.viewport_details) {
@@ -3309,7 +3299,6 @@ where
             browsing_context_size,
             load_info.load_data,
             is_private,
-            browsing_context_throttled,
         );
         self.add_pending_change(SessionHistoryChange {
             webview_id,
@@ -3343,9 +3332,9 @@ where
                     );
                 },
             };
-        let (is_parent_private, is_parent_throttled, is_parent_secure) =
+        let (is_parent_private, is_parent_secure) =
             match self.browsing_contexts.get(&parent_browsing_context_id) {
-                Some(ctx) => (ctx.is_private, ctx.throttled, ctx.inherited_secure_context),
+                Some(ctx) => (ctx.is_private, ctx.inherited_secure_context),
                 None => {
                     return warn!(
                         "{}: New iframe {} loaded in closed parent browsing context",
@@ -3353,6 +3342,11 @@ where
                     );
                 },
             };
+
+        let webview_hidden = self
+            .webviews
+            .get(&webview_id)
+            .is_none_or(|webview| webview.hidden());
         let is_private = is_private || is_parent_private;
         let pipeline = Pipeline::new_already_spawned(
             new_pipeline_id,
@@ -3361,7 +3355,7 @@ where
             None,
             script_sender,
             self.paint_proxy.clone(),
-            is_parent_throttled,
+            webview_hidden,
             load_info.load_data,
         );
 
@@ -3377,7 +3371,6 @@ where
                 parent_pipeline_id: Some(parent_pipeline_id),
                 is_private,
                 inherited_secure_context: is_parent_secure,
-                throttled: is_parent_throttled,
             }),
             viewport_details: load_info.viewport_details,
         });
@@ -3424,9 +3417,9 @@ where
                     );
                 },
             };
-        let (is_opener_private, is_opener_throttled, is_opener_secure) =
+        let (is_opener_private, is_opener_secure) =
             match self.browsing_contexts.get(&opener_browsing_context_id) {
-                Some(ctx) => (ctx.is_private, ctx.throttled, ctx.inherited_secure_context),
+                Some(ctx) => (ctx.is_private, ctx.inherited_secure_context),
                 None => {
                     return warn!(
                         "{}: New auxiliary {} loaded in closed opener browsing context",
@@ -3442,7 +3435,9 @@ where
             Some(opener_browsing_context_id),
             script_sender,
             self.paint_proxy.clone(),
-            is_opener_throttled,
+            // This means that the WebView isn't hidden. If it does become hidden
+            // at a later time, a followup message will arrive to the Constellation.
+            false,
             load_data,
         );
         let _ = response_sender.send(Some(AuxiliaryWebViewCreationResponse {
@@ -3483,7 +3478,6 @@ where
                 parent_pipeline_id: None,
                 is_private: is_opener_private,
                 inherited_secure_context: is_opener_secure,
-                throttled: is_opener_throttled,
             }),
             viewport_details,
         });
@@ -3622,14 +3616,13 @@ where
                 return None;
             },
         };
-        let (viewport_details, pipeline_id, parent_pipeline_id, is_private, is_throttled) =
+        let (viewport_details, pipeline_id, parent_pipeline_id, is_private) =
             match self.browsing_contexts.get(&browsing_context_id) {
                 Some(ctx) => (
                     ctx.viewport_details,
                     ctx.pipeline_id,
                     ctx.parent_pipeline_id,
                     ctx.is_private,
-                    ctx.throttled,
                 ),
                 None => {
                     // This should technically never happen (since `load_url` is
@@ -3716,7 +3709,6 @@ where
                     viewport_details,
                     load_data,
                     is_private,
-                    is_throttled,
                 );
                 self.add_pending_change(SessionHistoryChange {
                     webview_id,
@@ -3962,24 +3954,17 @@ where
                     browsing_context_id, pipeline_id,
                 );
 
-                let (
-                    webview_id,
-                    old_pipeline_id,
-                    parent_pipeline_id,
-                    viewport_details,
-                    is_private,
-                    throttled,
-                ) = match self.browsing_contexts.get(&browsing_context_id) {
-                    Some(ctx) => (
-                        ctx.webview_id,
-                        ctx.pipeline_id,
-                        ctx.parent_pipeline_id,
-                        ctx.viewport_details,
-                        ctx.is_private,
-                        ctx.throttled,
-                    ),
-                    None => return warn!("No browsing context to traverse!"),
-                };
+                let (webview_id, old_pipeline_id, parent_pipeline_id, viewport_details, is_private) =
+                    match self.browsing_contexts.get(&browsing_context_id) {
+                        Some(ctx) => (
+                            ctx.webview_id,
+                            ctx.pipeline_id,
+                            ctx.parent_pipeline_id,
+                            ctx.viewport_details,
+                            ctx.is_private,
+                        ),
+                        None => return warn!("No browsing context to traverse!"),
+                    };
                 let opener = match self.pipelines.get(&old_pipeline_id) {
                     Some(pipeline) => pipeline.opener,
                     None => None,
@@ -3994,7 +3979,6 @@ where
                     viewport_details,
                     load_data.clone(),
                     is_private,
-                    throttled,
                 );
                 self.add_pending_change(SessionHistoryChange {
                     webview_id,
@@ -4027,7 +4011,7 @@ where
 
         self.unload_document(old_pipeline_id);
 
-        if let Some(new_pipeline) = self.pipelines.get(&new_pipeline_id) {
+        if let Some(new_pipeline) = self.pipelines.get_mut(&new_pipeline_id) {
             if let Some(ref chan) = self.devtools_sender {
                 let state = NavigationState::Start(new_pipeline.url.clone());
                 let _ = chan.send(DevtoolsControlMsg::FromScript(
@@ -4044,7 +4028,7 @@ where
                 ));
             }
 
-            new_pipeline.set_throttled(false);
+            new_pipeline.set_has_active_document(true);
             self.notify_focus_state(new_pipeline_id);
         }
 
@@ -4572,19 +4556,29 @@ where
         }
     }
 
-    #[servo_tracing::instrument(skip_all)]
-    fn set_webview_throttled(&mut self, webview_id: WebViewId, throttled: bool) {
+    fn root_pipeline_for_webview(&mut self, webview_id: WebViewId) -> Option<&Pipeline> {
         let browsing_context_id = BrowsingContextId::from(webview_id);
-        let pipeline_id = match self.browsing_contexts.get(&browsing_context_id) {
-            Some(browsing_context) => browsing_context.pipeline_id,
-            None => {
-                return warn!("{browsing_context_id}: Tried to SetWebViewThrottled after closure");
-            },
-        };
-        match self.pipelines.get(&pipeline_id) {
-            None => warn!("{pipeline_id}: Tried to SetWebViewThrottled after closure"),
-            Some(pipeline) => pipeline.set_throttled(throttled),
+        let browsing_context = self.browsing_contexts.get(&browsing_context_id)?;
+        self.pipelines.get(&browsing_context.pipeline_id)
+    }
+
+    #[servo_tracing::instrument(skip_all)]
+    fn set_webview_hidden(&mut self, webview_id: WebViewId, hidden: bool) {
+        if self
+            .webviews
+            .get_mut(&webview_id)
+            .is_none_or(|webview| !webview.set_hidden(hidden))
+        {
+            return;
         }
+
+        let Some(root_pipeline) = self.root_pipeline_for_webview(webview_id) else {
+            warn!("Tried to send SetThrottled to WebView ({webview_id:?} after closure");
+            return;
+        };
+
+        // Throttle the root pipeline, recursively throttling descendant pipelines as well.
+        root_pipeline.send_throttle_messages(hidden);
     }
 
     #[servo_tracing::instrument(skip_all)]
@@ -4743,7 +4737,6 @@ where
                     change.viewport_details,
                     new_context_info.is_private,
                     new_context_info.inherited_secure_context,
-                    new_context_info.throttled,
                 );
                 self.update_activity(change.new_pipeline_id);
             },
@@ -5396,11 +5389,12 @@ where
 
     /// Send a message to script requesting the document associated with this pipeline runs the 'unload' algorithm.
     #[servo_tracing::instrument(skip_all)]
-    fn unload_document(&self, pipeline_id: PipelineId) {
-        if let Some(pipeline) = self.pipelines.get(&pipeline_id) {
-            pipeline.set_throttled(true);
-            let msg = ScriptThreadMessage::UnloadDocument(pipeline_id);
-            let _ = pipeline.event_loop.send(msg);
+    fn unload_document(&mut self, pipeline_id: PipelineId) {
+        if let Some(pipeline) = self.pipelines.get_mut(&pipeline_id) {
+            pipeline.set_has_active_document(false);
+            let _ = pipeline
+                .event_loop
+                .send(ScriptThreadMessage::UnloadDocument(pipeline_id));
         }
     }
 

components/constellation/constellation_webview.rs

@@ -45,6 +45,10 @@ pub(crate) struct ConstellationWebView {
     /// The [`Theme`] that this [`ConstellationWebView`] uses. This is communicated to all
     /// `ScriptThread`s so that they know how to render the contents of a particular `WebView.
     theme: Theme,
+
+    /// Whether or not this entire [`ConstellationWebView`] is hiden. `WebView`s that
+    /// are hidden will be throttled.
+    hidden: bool,
 }
 
 impl ConstellationWebView {
@@ -61,6 +65,7 @@ impl ConstellationWebView {
             last_mouse_move_point: Default::default(),
             session_history: JointSessionHistory::new(),
             theme: Theme::Light,
+            hidden: false,
         }
     }
 
@@ -75,6 +80,17 @@ impl ConstellationWebView {
         self.theme
     }
 
+    /// Whether or not the WebView is hidden.
+    pub(crate) fn hidden(&self) -> bool {
+        self.hidden
+    }
+
+    /// Set whether or not this [`ConstellationWebView`] is hidden, returning true if the value changed.
+    pub(crate) fn set_hidden(&mut self, hidden: bool) -> bool {
+        let old_hidden = std::mem::replace(&mut self.hidden, hidden);
+        old_hidden != self.hidden
+    }
+
     fn target_pipeline_id_for_input_event(
         &self,
         event: &ConstellationInputEvent,

components/constellation/pipeline.rs

@@ -67,7 +67,13 @@ pub struct Pipeline {
     /// The title of this pipeline's document.
     pub title: String,
 
+    /// The [`FocusSequenceNumber`] of this [`Pipeline`].
     pub focus_sequence: FocusSequenceNumber,
+
+    /// Whether or not this [`Pipeline`] has an actively loading/loaded. When there is no
+    /// active document, the [`Pipeline`] will never be unthrottled. Throttled pipelines
+    /// do not update animations and their timers are slowed.
+    has_active_document: bool,
 }
 
 impl Pipeline {
@@ -76,7 +82,7 @@ impl Pipeline {
         new_pipeline_info: NewPipelineInfo,
         event_loop: Rc<EventLoop>,
         constellation: &Constellation<STF, SWF>,
-        throttled: bool,
+        webview_hidden: bool,
     ) -> Result<Self, Error> {
         if let Err(error) = event_loop.send(ScriptThreadMessage::SpawnPipeline(
             new_pipeline_info.clone(),
@@ -92,7 +98,7 @@ impl Pipeline {
             new_pipeline_info.opener,
             event_loop,
             constellation.paint_proxy.clone(),
-            throttled,
+            webview_hidden,
             new_pipeline_info.load_data,
         ))
     }
@@ -106,7 +112,7 @@ impl Pipeline {
         opener: Option<BrowsingContextId>,
         event_loop: Rc<EventLoop>,
         paint_proxy: PaintProxy,
-        throttled: bool,
+        webview_hidden: bool,
         load_data: LoadData,
     ) -> Self {
         let pipeline = Self {
@@ -125,8 +131,14 @@ impl Pipeline {
             completely_loaded: false,
             title: String::new(),
             focus_sequence: FocusSequenceNumber::default(),
+            // Assume that every new Pipeline has an active document until told otherwise.
+            has_active_document: true,
         };
-        pipeline.set_throttled(throttled);
+
+        if webview_hidden {
+            pipeline.send_throttle_messages(true);
+        }
+
         pipeline
     }
 
@@ -187,15 +199,37 @@ impl Pipeline {
         }
     }
 
-    /// Set whether to make pipeline use less resources, by stopping animations and
-    /// running timers at a heavily limited rate.
-    pub fn set_throttled(&self, throttled: bool) {
-        let script_msg = ScriptThreadMessage::SetThrottled(self.webview_id, self.id, throttled);
-        let paint_message = PaintMessage::SetThrottled(self.webview_id, self.id, throttled);
-        let err = self.event_loop.send(script_msg);
-        if let Err(e) = err {
-            warn!("Sending SetThrottled to script failed ({}).", e);
+    /// Set whether or not this Pipeline has an active document.
+    pub(crate) fn set_has_active_document(&mut self, has_active_document: bool) {
+        if self.has_active_document == has_active_document {
+            return;
         }
-        self.paint_proxy.send(paint_message);
+
+        self.has_active_document = has_active_document;
+
+        // If the active document has gone away, throttle the WebView.
+        if !self.has_active_document {
+            self.send_throttle_messages(true);
+        }
+    }
+
+    /// Set whether this Pipeline is throttled or unthrottled. If the Pipeline
+    /// does not have an active Document, it will not be unthrottled until it does.
+    pub(crate) fn send_throttle_messages(&self, throttled: bool) {
+        // Never unthrottled Pipelines that do not have an active Document.
+        let throttled = !self.has_active_document || throttled;
+
+        if let Err(error) = self.event_loop.send(ScriptThreadMessage::SetThrottled(
+            self.webview_id,
+            self.id,
+            throttled,
+        )) {
+            warn!("Sending SetThrottled to script failed ({error}).");
+        }
+        self.paint_proxy.send(PaintMessage::SetThrottled(
+            self.webview_id,
+            self.id,
+            throttled,
+        ));
     }
 }

components/constellation/tracing.rs

@@ -69,7 +69,7 @@ mod from_embedder {
                 Self::ToggleProfiler(..) => target!("EnableProfiler"),
                 Self::ExitFullScreen(_) => target!("ExitFullScreen"),
                 Self::MediaSessionAction(_) => target!("MediaSessionAction"),
-                Self::SetWebViewThrottled(_, _) => target!("SetWebViewThrottled"),
+                Self::SetWebViewHidden(_, _) => target!("SetWebViewHidden"),
                 Self::SetScrollStates(..) => target!("SetScrollStates"),
                 Self::PaintMetric(..) => target!("PaintMetric"),
                 Self::EvaluateJavaScript(..) => target!("EvaluateJavaScript"),

components/script/dom/window.rs

@@ -430,6 +430,9 @@ pub(crate) struct Window {
     #[no_trace]
     player_context: WindowGLContext,
 
+    /// Whether or no this [`Window`] is "throttled." When this is true animations will not run
+    /// and timers will be slowed down. [`Window`]s become throttled when their [`Document`] is
+    /// no longer active or when the `WebView` that contains them is hidden.
     throttled: Cell<bool>,
 
     /// A shared marker for the validity of any cached layout values. A value of true

components/script/script_thread.rs

@@ -1169,21 +1169,24 @@ impl ScriptThread {
                 document.react_to_environment_changes()
             }
 
-            // > 11. For each doc of docs, update animations and send events for doc, passing
-            // > in relative high resolution time given frameTimestamp and doc's relevant
-            // > global object as the timestamp [WEBANIMATIONS]
-            document.update_animations_and_send_events(can_gc);
+            // Do not update animations or run rAFs if a Document is throttled.
+            if !document.window().throttled() {
+                // > 11. For each doc of docs, update animations and send events for doc, passing
+                // > in relative high resolution time given frameTimestamp and doc's relevant
+                // > global object as the timestamp [WEBANIMATIONS]
+                document.update_animations_and_send_events(can_gc);
 
-            // TODO(#31866): Implement "run the fullscreen steps" from
-            // https://fullscreen.spec.whatwg.org/multipage/#run-the-fullscreen-steps.
+                // TODO(#31866): Implement "run the fullscreen steps" from
+                // https://fullscreen.spec.whatwg.org/multipage/#run-the-fullscreen-steps.
 
-            // TODO(#31868): Implement the "context lost steps" from
-            // https://html.spec.whatwg.org/multipage/#context-lost-steps.
+                // TODO(#31868): Implement the "context lost steps" from
+                // https://html.spec.whatwg.org/multipage/#context-lost-steps.
 
-            // > 14. For each doc of docs, run the animation frame callbacks for doc, passing
-            // > in the relative high resolution time given frameTimestamp and doc's
-            // > relevant global object as the timestamp.
-            document.run_the_animation_frame_callbacks(can_gc);
+                // > 14. For each doc of docs, run the animation frame callbacks for doc, passing
+                // > in the relative high resolution time given frameTimestamp and doc's
+                // > relevant global object as the timestamp.
+                document.run_the_animation_frame_callbacks(can_gc);
+            }
 
             // Run the resize observer steps.
             let _realm = enter_realm(&*document);

components/servo/webview.rs

@@ -567,12 +567,6 @@ impl WebView {
             .send(EmbedderToConstellationMessage::ExitFullScreen(self.id()));
     }
 
-    pub fn set_throttled(&self, throttled: bool) {
-        self.inner().servo.constellation_proxy().send(
-            EmbedderToConstellationMessage::SetWebViewThrottled(self.id(), throttled),
-        );
-    }
-
     pub fn toggle_webrender_debugging(&self, debugging: WebRenderDebugOption) {
         self.inner().servo.paint().toggle_webrender_debug(debugging);
     }

components/shared/constellation/lib.rs

@@ -90,7 +90,7 @@ pub enum EmbedderToConstellationMessage {
     /// Media session action.
     MediaSessionAction(MediaSessionActionType),
     /// Set whether to use less resources, by stopping animations and running timers at a heavily limited rate.
-    SetWebViewThrottled(WebViewId, bool),
+    SetWebViewHidden(WebViewId, bool),
     /// The Servo renderer scrolled and is updating the scroll states of the nodes in the
     /// given pipeline via the constellation.
     SetScrollStates(PipelineId, FxHashMap<ExternalScrollId, LayoutVector2D>),