Register media instance with session and prepare communication with embedder

components/script_traits/lib.rs

@@ -1087,3 +1087,34 @@ pub enum MediaSessionActionType {
     /// The action intent is to move the playback time to a specific time.
     SeekTo,
 }
+
+/// https://w3c.github.io/mediasession/#mediametadata
+#[derive(Clone, Debug, Deserialize, Serialize)]
+pub struct MediaMetadata {
+    /// Title
+    pub title: String,
+    /// Artist
+    pub artist: Option<String>,
+    /// Album
+    pub album: Option<String>,
+}
+
+/// https://w3c.github.io/mediasession/#enumdef-mediasessionplaybackstate
+#[derive(Clone, Debug, Deserialize, Serialize)]
+pub enum MediaSessionPlaybackState {
+    /// The browsing context does not specify whether it’s playing or paused.
+    None_,
+    /// The browsing context has paused media and it can be resumed.
+    Playing,
+    /// The browsing context is currently playing media and it can be paused.
+    Paused,
+}
+
+/// Type of events sent from script to the constellation about the media session.
+#[derive(Clone, Debug, Deserialize, Serialize)]
+pub enum MediaSessionEvent {
+    /// Indicates that the media metadata is available.
+    SetMetadata(MediaMetadata),
+    /// Indicates that the playback state has changed.
+    PlaybackStateChange(MediaSessionPlaybackState),
+}

components/script_traits/script_msg.rs

@@ -8,6 +8,7 @@ use crate::DocumentState;
 use crate::IFrameLoadInfoWithData;
 use crate::LayoutControlMsg;
 use crate::LoadData;
+use crate::MediaSessionEvent;
 use crate::MessagePortMsg;
 use crate::PortMessageTask;
 use crate::StructuredSerializedData;
@@ -254,6 +255,9 @@ pub enum ScriptMsg {
     GetScreenSize(IpcSender<DeviceIntSize>),
     /// Get the available screen size (pixel)
     GetScreenAvailSize(IpcSender<DeviceIntSize>),
+    /// Notifies the constellation about media session events
+    /// (i.e. when there is metadata for the active media session, playback state changes...).
+    MediaSessionEventMsg(TopLevelBrowsingContextId, MediaSessionEvent),
 }
 
 impl fmt::Debug for ScriptMsg {
@@ -305,6 +309,7 @@ impl fmt::Debug for ScriptMsg {
             GetClientWindow(..) => "GetClientWindow",
             GetScreenSize(..) => "GetScreenSize",
             GetScreenAvailSize(..) => "GetScreenAvailSize",
+            MediaSessionEventMsg(..) => "MediaSessionEventMsg",
         };
         write!(formatter, "ScriptMsg::{}", variant)
     }