Fix metadata update

components/embedder_traits/lib.rs

@@ -213,9 +213,19 @@ pub struct MediaMetadata {
     /// Title
     pub title: String,
     /// Artist
-    pub artist: Option<String>,
+    pub artist: String,
     /// Album
-    pub album: Option<String>,
+    pub album: String,
+}
+
+impl MediaMetadata {
+    pub fn new(title: String) -> Self {
+        Self {
+            title,
+            artist: "".to_owned(),
+            album: "".to_owned(),
+        }
+    }
 }
 
 /// https://w3c.github.io/mediasession/#enumdef-mediasessionplaybackstate

components/script/dom/htmlmediaelement.rs

@@ -67,7 +67,7 @@ use crate::script_thread::ScriptThread;
 use crate::task_source::TaskSource;
 use dom_struct::dom_struct;
 use embedder_traits::resources::{self, Resource as EmbedderResource};
-use embedder_traits::{MediaMetadata, MediaSessionEvent, MediaSessionPlaybackState};
+use embedder_traits::{MediaSessionEvent, MediaSessionPlaybackState};
 use euclid::default::Size2D;
 use headers::{ContentLength, ContentRange, HeaderMapExt};
 use html5ever::{LocalName, Prefix};
@@ -1731,15 +1731,13 @@ impl HTMLMediaElement {
                 let global = self.global();
                 let window = global.as_window();
 
-                // Send a media session event with the obtained metadata.
-                self.send_media_session_event(MediaSessionEvent::SetMetadata(MediaMetadata {
-                    title: metadata
+                // Update the media session metadata title with the obtained metadata.
+                window.Navigator().MediaSession().update_title(
+                    metadata
                         .title
                         .clone()
                         .unwrap_or(window.get_url().into_string()),
-                    artist: None,
-                    album: None,
-                }));
+                );
             },
             PlayerEvent::NeedData => {
                 // The player needs more data.

components/script/dom/mediametadata.rs

@@ -68,7 +68,7 @@ impl MediaMetadataMethods for MediaMetadata {
     }
 
     /// https://w3c.github.io/mediasession/#dom-mediametadata-title
-    fn SetTitle(&self, value: DOMString) -> () {
+    fn SetTitle(&self, value: DOMString) {
         *self.title.borrow_mut() = value;
         self.queue_update_metadata_algorithm();
     }
@@ -79,7 +79,7 @@ impl MediaMetadataMethods for MediaMetadata {
     }
 
     /// https://w3c.github.io/mediasession/#dom-mediametadata-artist
-    fn SetArtist(&self, value: DOMString) -> () {
+    fn SetArtist(&self, value: DOMString) {
         *self.artist.borrow_mut() = value;
         self.queue_update_metadata_algorithm();
     }
@@ -90,7 +90,7 @@ impl MediaMetadataMethods for MediaMetadata {
     }
 
     /// https://w3c.github.io/mediasession/#dom-mediametadata-album
-    fn SetAlbum(&self, value: DOMString) -> () {
+    fn SetAlbum(&self, value: DOMString) {
         *self.album.borrow_mut() = value;
         self.queue_update_metadata_algorithm();
     }

components/script/dom/mediasession.rs

@@ -100,13 +100,6 @@ impl MediaSession {
     }
 
     pub fn send_event(&self, event: MediaSessionEvent) {
-        match event {
-            MediaSessionEvent::SetMetadata(ref metadata) => {
-                *self.metadata.borrow_mut() = Some(metadata.clone());
-            },
-            _ => (),
-        }
-
         let global = self.global();
         let window = global.as_window();
         let pipeline_id = window
@@ -114,6 +107,23 @@ impl MediaSession {
             .expect("Cannot send media session event outside of a pipeline");
         window.send_to_constellation(ScriptMsg::MediaSessionEvent(pipeline_id, event));
     }
+
+    pub fn update_title(&self, title: String) {
+        let mut metadata = self.metadata.borrow_mut();
+        if let Some(ref mut metadata) = *metadata {
+            // We only update the title with the data provided by the media
+            // player and iff the user did not provide a title.
+            if !metadata.title.is_empty() {
+                return;
+            }
+            metadata.title = title;
+        } else {
+            *metadata = Some(EmbedderMediaMetadata::new(title));
+        }
+        self.send_event(MediaSessionEvent::SetMetadata(
+            metadata.as_ref().unwrap().clone(),
+        ));
+    }
 }
 
 impl MediaSessionMethods for MediaSession {
@@ -122,8 +132,8 @@ impl MediaSessionMethods for MediaSession {
         if let Some(ref metadata) = *self.metadata.borrow() {
             let mut init = MediaMetadataInit::empty();
             init.title = DOMString::from_string(metadata.title.clone());
-            init.artist = DOMString::from_string(metadata.artist.clone().unwrap_or("".to_owned()));
-            init.album = DOMString::from_string(metadata.album.clone().unwrap_or("".to_owned()));
+            init.artist = DOMString::from_string(metadata.artist.clone());
+            init.album = DOMString::from_string(metadata.album.clone());
             let global = self.global();
             Some(MediaMetadata::new(&global.as_window(), &init))
         } else {
@@ -137,12 +147,27 @@ impl MediaSessionMethods for MediaSession {
             metadata.set_session(self);
         }
 
-        let _metadata = metadata.map(|m| EmbedderMediaMetadata {
-            title: m.Title().into(),
-            artist: Some(m.Artist().into()),
-            album: Some(m.Album().into()),
-        });
-        *self.metadata.borrow_mut() = _metadata;
+        let global = self.global();
+        let window = global.as_window();
+        let _metadata = match metadata {
+            Some(m) => {
+                let title = if m.Title().is_empty() {
+                    window.get_url().into_string()
+                } else {
+                    m.Title().into()
+                };
+                EmbedderMediaMetadata {
+                    title,
+                    artist: m.Artist().into(),
+                    album: m.Album().into(),
+                }
+            },
+            None => EmbedderMediaMetadata::new(window.get_url().into_string()),
+        };
+
+        *self.metadata.borrow_mut() = Some(_metadata.clone());
+
+        self.send_event(MediaSessionEvent::SetMetadata(_metadata));
     }
 
     /// https://w3c.github.io/mediasession/#dom-mediasession-playbackstate

ports/libsimpleservo/api/src/lib.rs

@@ -586,8 +586,8 @@ impl ServoGlue {
                         MediaSessionEvent::SetMetadata(metadata) => {
                             self.callbacks.host_callbacks.on_media_session_metadata(
                                 metadata.title,
-                                metadata.artist.unwrap_or("".to_owned()),
-                                metadata.album.unwrap_or("".to_owned()),
+                                metadata.artist,
+                                metadata.album,
                             )
                         },
                         MediaSessionEvent::PlaybackStateChange(state) => self