Set is_screencast in publish_track

Author: iparaskev

.nanpa/properly_set_is_screencast.kdl

@@ -1,4 +1,4 @@
-patch type="added" "Set is_screencast on VideoTrackSource creation" package="webrtc-sys"
-patch type="added" "Set is_screencast on NativeVideoSource creation" package="libwebrtc"
-patch type="added" "Extend NewVideoSourceRequest with is_screencast" package="livekit-ffi"
-patch type="changed" "Use new NativeVideoSource constructor in examples" package="examples"
+patch type="added" "Add a setter for is_screencast in InternalSource" package="webrtc-sys"
+patch type="added" "Expose set_is_screencast in NativeVideoSource" package="libwebrtc"
+patch type="added" "Extend enum_dispatch to create functions that don't have a return type" package="livekit-protocol"
+patch type="added" "Set is_screencast in publish_track when the source is Screenshare" package="livekit"

examples/wgpu_room/src/logo_track.rs

@@ -47,10 +47,10 @@ pub struct LogoTrack {
 impl LogoTrack {
     pub fn new(room: Arc<Room>) -> Self {
         Self {
-            rtc_source: NativeVideoSource::new(
-                VideoResolution { width: FB_WIDTH as u32, height: FB_HEIGHT as u32 },
-                false,
-            ),
+            rtc_source: NativeVideoSource::new(VideoResolution {
+                width: FB_WIDTH as u32,
+                height: FB_HEIGHT as u32,
+            }),
             room,
             handle: None,
         }

libwebrtc/src/native/video_source.rs

@@ -50,12 +50,11 @@ struct VideoSourceInner {
 }
 
 impl NativeVideoSource {
-    pub fn new(resolution: VideoResolution, is_screencast: bool) -> NativeVideoSource {
+    pub fn new(resolution: VideoResolution) -> NativeVideoSource {
         let source = Self {
-            sys_handle: vt_sys::ffi::new_video_track_source(
-                &vt_sys::ffi::VideoResolution::from(resolution.clone()),
-                is_screencast,
-            ),
+            sys_handle: vt_sys::ffi::new_video_track_source(&vt_sys::ffi::VideoResolution::from(
+                resolution.clone(),
+            )),
             inner: Arc::new(Mutex::new(VideoSourceInner { captured_frames: 0 })),
         };
 
@@ -114,4 +113,8 @@ impl NativeVideoSource {
     pub fn video_resolution(&self) -> VideoResolution {
         self.sys_handle.video_resolution().into()
     }
+
+    pub fn set_is_screencast(&self, is_screencast: bool) {
+        self.sys_handle.set_is_screencast(is_screencast);
+    }
 }

libwebrtc/src/video_source.rs

@@ -36,6 +36,10 @@ impl RtcVideoSource {
         [Native];
         pub fn video_resolution(self: &Self) -> VideoResolution;
     );
+    enum_dispatch!(
+        [Native];
+        pub fn set_is_screencast(self: &Self, is_screencast: bool);
+    );
 }
 
 #[cfg(not(target_arch = "wasm32"))]
@@ -58,13 +62,13 @@ pub mod native {
 
     impl Default for NativeVideoSource {
         fn default() -> Self {
-            Self::new(VideoResolution::default(), false)
+            Self::new(VideoResolution::default())
         }
     }
 
     impl NativeVideoSource {
-        pub fn new(resolution: VideoResolution, is_screencast: bool) -> Self {
-            Self { handle: vs_imp::NativeVideoSource::new(resolution, is_screencast) }
+        pub fn new(resolution: VideoResolution) -> Self {
+            Self { handle: vs_imp::NativeVideoSource::new(resolution) }
         }
 
         pub fn capture_frame<T: AsRef<dyn VideoBuffer>>(&self, frame: &VideoFrame<T>) {
@@ -74,6 +78,10 @@ pub mod native {
         pub fn video_resolution(&self) -> VideoResolution {
             self.handle.video_resolution()
         }
+
+        pub fn set_is_screencast(&self, is_screencast: bool) {
+            self.handle.set_is_screencast(is_screencast)
+        }
     }
 }
 

livekit-ffi/protocol/video_frame.proto

@@ -49,7 +49,6 @@ message NewVideoSourceRequest {
   // Used to determine which encodings to use + simulcast layers
   // Most of the time it corresponds to the source resolution
   required VideoSourceResolution resolution = 2;
-  optional bool is_screencast = 3;
 }
 message NewVideoSourceResponse { required OwnedVideoSource source = 1; }
 

livekit-ffi/src/livekit.proto.rs

@@ -1,4 +1,5 @@
 // @generated
+// This file is @generated by prost-build.
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct FrameCryptor {
@@ -302,11 +303,11 @@ impl EncryptionState {
 /// # Safety
 /// The foreign language is responsable for disposing handles
 /// Forgetting to dispose the handle may lead to memory leaks
-///
+/// 
 /// Dropping a handle doesn't necessarily mean that the object is destroyed if it is still used
 /// on the FfiServer (Atomic reference counting)
-///
-/// When refering to a handle without owning it, we just use a uint32 without this message.
+/// 
+/// When refering to a handle without owning it, we just use a uint32 without this message. 
 /// (the variable name is suffixed with "_handle")
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
@@ -1765,8 +1766,6 @@ pub struct NewVideoSourceRequest {
     /// Most of the time it corresponds to the source resolution
     #[prost(message, required, tag="2")]
     pub resolution: VideoSourceResolution,
-    #[prost(bool, optional, tag="3")]
-    pub is_screencast: ::core::option::Option<bool>,
 }
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
@@ -3455,7 +3454,7 @@ pub struct NewAudioSourceResponse {
     #[prost(message, required, tag="1")]
     pub source: OwnedAudioSource,
 }
-/// Push a frame to an AudioSource
+/// Push a frame to an AudioSource 
 /// The data provided must be available as long as the client receive the callback.
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
@@ -4009,7 +4008,7 @@ pub struct RpcMethodInvocationEvent {
 //    that it receives from the server.
 //
 // Therefore, the ffi client is easier to implement if there is less handles to manage.
-//
+// 
 // - We are mainly using FfiHandle on info messages (e.g: RoomInfo, TrackInfo, etc...)
 //    For this reason, info are only sent once, at creation (We're not using them for updates, we can infer them from
 //    events on the client implementation).

livekit-ffi/src/server/video_source.rs

@@ -37,7 +37,6 @@ impl FfiVideoSource {
                 use livekit::webrtc::video_source::native::NativeVideoSource;
                 let video_source = NativeVideoSource::new(
                     new_source.resolution.into(),
-                    new_source.is_screencast(),
                 );
                 RtcVideoSource::Native(video_source)
             }

livekit-protocol/src/enum_dispatch.rs

@@ -1,4 +1,4 @@
-// Copyright 2023 LiveKit, Inc.
+// Copyright 2023-2025 LiveKit, Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -33,9 +33,23 @@ macro_rules! enum_dispatch {
         }
     };
 
+    // Handle functions without a return type
+    (@fnc [$($variant:ident),+]: $vis:vis fn $fnc:ident($self:ident: $sty:ty $(, $arg:ident: $t:ty)*)) => {
+        #[inline]
+        $vis fn $fnc($self: $sty, $($arg: $t),*) {
+            enum_dispatch!(@match [$($variant),+]: $fnc, $self, ($($arg,)*))
+        }
+    };
+
     ($variants:tt; $($vis:vis fn $fnc:ident$args:tt -> $ret:ty;)+) => {
         $(
             enum_dispatch!(@fnc $variants: $vis fn $fnc$args -> $ret);
         )+
     };
+
+    ($variants:tt; $($vis:vis fn $fnc:ident$args:tt;)+) => {
+        $(
+            enum_dispatch!(@fnc $variants: $vis fn $fnc$args);
+        )+
+    };
 }

livekit/src/room/participant/local_participant.rs

@@ -1,4 +1,4 @@
-// Copyright 2023 LiveKit, Inc.
+// Copyright 2023-2025 LiveKit, Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -232,6 +232,13 @@ impl LocalParticipant {
 
                 encodings = compute_video_encodings(req.width, req.height, &options);
                 req.layers = video_layers_from_encodings(req.width, req.height, &encodings);
+
+                match options.source {
+                    TrackSource::Screenshare => {
+                        video_track.rtc_source().set_is_screencast(true);
+                    }
+                    _ => {}
+                }
             }
             LocalTrack::Audio(_audio_track) => {
                 // Setup audio encoding

webrtc-sys/include/livekit/video_track.h

@@ -91,7 +91,7 @@ class VideoTrackSource {
      * resolution set to (0, 0) means no resolution/optional, the source will
      * guess the resolution at the first captured frame.
      */
-    InternalSource(const VideoResolution& resolution, bool is_screencast);
+    InternalSource(const VideoResolution& resolution);
     ~InternalSource() override;
 
     bool is_screencast() const override;
@@ -100,6 +100,7 @@ class VideoTrackSource {
     bool remote() const override;
     VideoResolution video_resolution() const;
     bool on_captured_frame(const webrtc::VideoFrame& frame);
+    void set_is_screencast(bool is_screencast);
 
    private:
     mutable webrtc::Mutex mutex_;
@@ -109,7 +110,7 @@ class VideoTrackSource {
   };
 
  public:
-  VideoTrackSource(const VideoResolution& resolution, bool is_screencast);
+  VideoTrackSource(const VideoResolution& resolution);
 
   VideoResolution video_resolution() const;
 
@@ -118,13 +119,14 @@ class VideoTrackSource {
 
   rtc::scoped_refptr<InternalSource> get() const;
 
+  void set_is_screencast(bool is_screencast) const;
+
  private:
   rtc::scoped_refptr<InternalSource> source_;
 };
 
 std::shared_ptr<VideoTrackSource> new_video_track_source(
-    const VideoResolution& resolution,
-    bool is_screencast);
+    const VideoResolution& resolution);
 
 static std::shared_ptr<MediaStreamTrack> video_to_media(
     std::shared_ptr<VideoTrack> track) {