3 files changed, 88 insertions, 3 deletions

diff --git a/components/script/dom/htmlmediaelement.rs b/components/script/dom/htmlmediaelement.rs
index 651084cfb84..91acd4b97e7 100644
--- a/components/script/dom/htmlmediaelement.rs
+++ b/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::{MediaSessionEvent, MediaSessionPlaybackState};
+use embedder_traits::{MediaPositionState, MediaSessionEvent, MediaSessionPlaybackState};
 use euclid::default::Size2D;
 use headers::{ContentLength, ContentRange, HeaderMapExt};
 use html5ever::{LocalName, Prefix};
@@ -1780,6 +1780,15 @@ impl HTMLMediaElement {
                     .add(self.playback_position.get(), position);
                 self.playback_position.set(position);
                 self.time_marches_on();
+                let media_position_state =
+                    MediaPositionState::new(self.duration.get(), self.playbackRate.get(), position);
+                debug!(
+                    "Sending media session event set position state {:?}",
+                    media_position_state
+                );
+                self.send_media_session_event(MediaSessionEvent::SetPositionState(
+                    media_position_state,
+                ));
             },
             PlayerEvent::SeekData(p, ref seek_lock) => {
                 self.fetch_request(Some(p), Some(seek_lock.clone()));
@@ -1925,6 +1934,18 @@ impl HTMLMediaElement {
 
         media_session.send_event(event);
     }
+
+    pub fn set_duration(&self, duration: f64) {
+        self.duration.set(duration);
+    }
+
+    pub fn reset(&self) {
+        if let Some(ref player) = *self.player.borrow() {
+            if let Err(e) = player.lock().unwrap().stop() {
+                eprintln!("Could not stop player {:?}", e);
+            }
+        }
+    }
 }
 
 // XXX Placeholder for [https://github.com/servo/servo/issues/22293]
diff --git a/components/script/dom/mediasession.rs b/components/script/dom/mediasession.rs
index 1523e9a0ae6..8dfc88a1c04 100644
--- a/components/script/dom/mediasession.rs
+++ b/components/script/dom/mediasession.rs
@@ -9,10 +9,13 @@ use crate::dom::bindings::codegen::Bindings::HTMLMediaElementBinding::HTMLMediaE
 use crate::dom::bindings::codegen::Bindings::MediaMetadataBinding::MediaMetadataInit;
 use crate::dom::bindings::codegen::Bindings::MediaMetadataBinding::MediaMetadataMethods;
 use crate::dom::bindings::codegen::Bindings::MediaSessionBinding;
+use crate::dom::bindings::codegen::Bindings::MediaSessionBinding::MediaPositionState;
 use crate::dom::bindings::codegen::Bindings::MediaSessionBinding::MediaSessionAction;
 use crate::dom::bindings::codegen::Bindings::MediaSessionBinding::MediaSessionActionHandler;
 use crate::dom::bindings::codegen::Bindings::MediaSessionBinding::MediaSessionMethods;
 use crate::dom::bindings::codegen::Bindings::MediaSessionBinding::MediaSessionPlaybackState;
+use crate::dom::bindings::error::{Error, Fallible};
+use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::reflector::{reflect_dom_object, DomObject, Reflector};
 use crate::dom::bindings::root::{DomRoot, MutNullableDom};
 use crate::dom::bindings::str::DOMString;
@@ -194,6 +197,62 @@ impl MediaSessionMethods for MediaSession {
             None => self.action_handlers.borrow_mut().remove(&action.into()),
         };
     }
+
+    /// https://w3c.github.io/mediasession/#dom-mediasession-setpositionstate
+    fn SetPositionState(&self, state: &MediaPositionState) -> Fallible<()> {
+        // If the state is an empty dictionary then clear the position state.
+        if state.duration.is_none() && state.position.is_none() && state.playbackRate.is_none() {
+            if let Some(media_instance) = self.media_instance.get() {
+                media_instance.reset();
+            }
+            return Ok(());
+        }
+
+        // If the duration is not present or its value is null, throw a TypeError.
+        if state.duration.is_none() {
+            return Err(Error::Type(
+                "duration is not present or its value is null".to_owned(),
+            ));
+        }
+
+        // If the duration is negative, throw a TypeError.
+        if let Some(state_duration) = state.duration {
+            if *state_duration < 0.0 {
+                return Err(Error::Type("duration is negative".to_owned()));
+            }
+        }
+
+        // If the position is negative or greater than duration, throw a TypeError.
+        if let Some(state_position) = state.position {
+            if *state_position < 0.0 {
+                return Err(Error::Type("position is negative".to_owned()));
+            }
+            if let Some(state_duration) = state.duration {
+                if *state_position > *state_duration {
+                    return Err(Error::Type("position is greater than duration".to_owned()));
+                }
+            }
+        }
+
+        // If the playbackRate is zero throw a TypeError.
+        if let Some(state_playback_rate) = state.playbackRate {
+            if *state_playback_rate <= 0.0 {
+                return Err(Error::Type("playbackRate is zero".to_owned()));
+            }
+        }
+
+        // Update the position state and last position updated time.
+        if let Some(media_instance) = self.media_instance.get() {
+            media_instance.set_duration(state.duration.map(|v| *v).unwrap());
+            // If the playbackRate is not present or its value is null, set it to 1.0.
+            let _ =
+                media_instance.SetPlaybackRate(state.playbackRate.unwrap_or(Finite::wrap(1.0)))?;
+            // If the position is not present or its value is null, set it to zero.
+            media_instance.SetCurrentTime(state.position.unwrap_or(Finite::wrap(0.0)));
+        }
+
+        Ok(())
+    }
 }
 
 impl From<MediaSessionAction> for MediaSessionActionType {
diff --git a/components/script/dom/webidls/MediaSession.webidl b/components/script/dom/webidls/MediaSession.webidl
index 12b3fe062ba..2680ea0c40b 100644
--- a/components/script/dom/webidls/MediaSession.webidl
+++ b/components/script/dom/webidls/MediaSession.webidl
@@ -42,6 +42,12 @@ dictionary MediaSessionSeekToActionDetails : MediaSessionActionDetails {
   boolean? fastSeek;
 };
 
+dictionary MediaPositionState {
+  double duration;
+  double playbackRate;
+  double position;
+};
+
 callback MediaSessionActionHandler = void(/*MediaSessionActionDetails details*/);
 
 [Exposed=Window]
@@ -52,6 +58,5 @@ interface MediaSession {
 
   void setActionHandler(MediaSessionAction action, MediaSessionActionHandler? handler);
 
-  //void setPositionState(optional MediaPositionState? state);
+  [Throws] void setPositionState(optional MediaPositionState state = {});
 };
-