Set is_screencast on NativeVideoSource creation

.nanpa/properly_set_is_screencast.kdl

@@ -0,0 +1,4 @@
+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"

libwebrtc/src/native/video_source.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.
@@ -113,4 +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

@@ -1,4 +1,4 @@
-// Copyright 2024 LiveKit, Inc.
+// Copyright 2024-2025 LiveKit, Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -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"))]
@@ -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-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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 LiveKit
+ * Copyright 2023-2025 LiveKit
  *
  * Licensed under the Apache License, Version 2.0 (the “License”);
  * you may not use this file except in compliance with the License.
@@ -87,10 +87,11 @@ std::shared_ptr<NativeVideoSink> new_native_video_sink(
 class VideoTrackSource {
   class InternalSource : public rtc::AdaptedVideoTrackSource {
    public:
-    InternalSource(const VideoResolution&
-                       resolution);  // (0, 0) means no resolution/optional, the
-                                     // source will guess the resolution at the
-                                     // first captured frame
+    /*
+     * resolution set to (0, 0) means no resolution/optional, the source will
+     * guess the resolution at the first captured frame.
+     */
+    InternalSource(const VideoResolution& resolution);
     ~InternalSource() override;
 
     bool is_screencast() const override;
@@ -99,11 +100,13 @@ 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_;
     rtc::TimestampAligner timestamp_aligner_;
     VideoResolution resolution_;
+    bool is_screencast_;
   };
 
  public:
@@ -116,6 +119,8 @@ class VideoTrackSource {
 
   rtc::scoped_refptr<InternalSource> get() const;
 
+  void set_is_screencast(bool is_screencast) const;
+
  private:
   rtc::scoped_refptr<InternalSource> source_;
 };

webrtc-sys/src/video_track.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 LiveKit
+ * Copyright 2023-2025 LiveKit
  *
  * Licensed under the Apache License, Version 2.0 (the “License”);
  * you may not use this file except in compliance with the License.
@@ -111,7 +111,13 @@ VideoTrackSource::InternalSource::InternalSource(
 VideoTrackSource::InternalSource::~InternalSource() {}
 
 bool VideoTrackSource::InternalSource::is_screencast() const {
-  return false;
+  webrtc::MutexLock lock(&mutex_);
+  return is_screencast_;
+}
+
+void VideoTrackSource::InternalSource::set_is_screencast(bool is_screencast) {
+  webrtc::MutexLock lock(&mutex_);
+  is_screencast_ = is_screencast;
 }
 
 absl::optional<bool> VideoTrackSource::InternalSource::needs_denoising() const {
@@ -189,6 +195,10 @@ bool VideoTrackSource::on_captured_frame(
   return source_->on_captured_frame(rtc_frame);
 }
 
+void VideoTrackSource::set_is_screencast(bool is_screencast) const {
+  source_->set_is_screencast(is_screencast);
+}
+
 rtc::scoped_refptr<VideoTrackSource::InternalSource> VideoTrackSource::get()
     const {
   return source_;

webrtc-sys/src/video_track.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.
@@ -67,6 +67,7 @@ pub mod ffi {
 
         fn video_resolution(self: &VideoTrackSource) -> VideoResolution;
         fn on_captured_frame(self: &VideoTrackSource, frame: &UniquePtr<VideoFrame>) -> bool;
+        fn set_is_screencast(self: &VideoTrackSource, is_screencast: bool);
         fn new_video_track_source(resolution: &VideoResolution) -> SharedPtr<VideoTrackSource>;
         fn video_to_media(track: SharedPtr<VideoTrack>) -> SharedPtr<MediaStreamTrack>;
         unsafe fn media_to_video(track: SharedPtr<MediaStreamTrack>) -> SharedPtr<VideoTrack>;