Stop animations when window is hidden (API + UWP)

components/compositing/lib.rs

@@ -110,6 +110,8 @@ pub enum ConstellationMsg {
     ExitFullScreen(TopLevelBrowsingContextId),
     /// Media session action.
     MediaSessionAction(MediaSessionActionType),
+    /// Toggle browser visibility.
+    ChangeBrowserVisibility(TopLevelBrowsingContextId, bool),
 }
 
 impl fmt::Debug for ConstellationMsg {
@@ -141,6 +143,7 @@ impl fmt::Debug for ConstellationMsg {
             DisableProfiler => "DisableProfiler",
             ExitFullScreen(..) => "ExitFullScreen",
             MediaSessionAction(..) => "MediaSessionAction",
+            ChangeBrowserVisibility(..) => "ChangeBrowserVisibility",
         };
         write!(formatter, "ConstellationMsg::{}", variant)
     }

components/compositing/windowing.rs

@@ -105,6 +105,8 @@ pub enum WindowEvent {
     /// Sent when the user triggers a media action through the UA exposed media UI
     /// (play, pause, seek, etc.).
     MediaSessionAction(MediaSessionActionType),
+    /// Set browser visibility. A hidden browser will not tick the animations.
+    ChangeBrowserVisibility(TopLevelBrowsingContextId, bool),
 }
 
 impl Debug for WindowEvent {
@@ -136,6 +138,7 @@ impl Debug for WindowEvent {
             WindowEvent::ToggleSamplingProfiler(..) => write!(f, "ToggleSamplingProfiler"),
             WindowEvent::ExitFullScreen(..) => write!(f, "ExitFullScreen"),
             WindowEvent::MediaSessionAction(..) => write!(f, "MediaSessionAction"),
+            WindowEvent::ChangeBrowserVisibility(..) => write!(f, "ChangeBrowserVisibility"),
         }
     }
 }

components/constellation/constellation.rs

@@ -1681,6 +1681,9 @@ where
             FromCompositorMsg::MediaSessionAction(action) => {
                 self.handle_media_session_action_msg(action);
             },
+            FromCompositorMsg::ChangeBrowserVisibility(top_level_browsing_context_id, visible) => {
+                self.handle_change_browser_visibility(top_level_browsing_context_id, visible);
+            },
         }
     }
 
@@ -4276,6 +4279,32 @@ where
         }
     }
 
+    fn handle_change_browser_visibility(
+        &mut self,
+        top_level_browsing_context_id: TopLevelBrowsingContextId,
+        visible: bool,
+    ) {
+        let browsing_context_id = BrowsingContextId::from(top_level_browsing_context_id);
+        let pipeline_id = match self.browsing_contexts.get(&browsing_context_id) {
+            Some(browsing_context) => browsing_context.pipeline_id,
+            None => {
+                return warn!(
+                    "Browsing context {} got visibility change event after closure.",
+                    browsing_context_id
+                );
+            },
+        };
+        match self.pipelines.get(&pipeline_id) {
+            None => {
+                return warn!(
+                    "Pipeline {} got visibility change event after closure.",
+                    pipeline_id
+                )
+            },
+            Some(pipeline) => pipeline.notify_visibility(visible),
+        };
+    }
+
     fn notify_history_changed(&self, top_level_browsing_context_id: TopLevelBrowsingContextId) {
         // Send a flat projection of the history to embedder.
         // The final vector is a concatenation of the LoadData of the past

components/servo/lib.rs

@@ -735,6 +735,19 @@ where
                     );
                 }
             },
+
+            WindowEvent::ChangeBrowserVisibility(top_level_browsing_context_id, visible) => {
+                let msg = ConstellationMsg::ChangeBrowserVisibility(
+                    top_level_browsing_context_id,
+                    visible,
+                );
+                if let Err(e) = self.constellation_chan.send(msg) {
+                    warn!(
+                        "Sending ChangeBrowserVisibility to constellation failed ({:?}).",
+                        e
+                    );
+                }
+            },
         }
     }