fix(rtp_transceiver): trigger renegotiation on set_direction (closes #51)

rtc/src/peer_connection/internal.rs

@@ -847,7 +847,7 @@ where
     }
 
     /// Helper to trigger a negotiation needed.
-    pub(super) fn trigger_negotiation_needed(&mut self) {
+    pub(crate) fn trigger_negotiation_needed(&mut self) {
         if !self.do_negotiation_needed() {
             return;
         }

rtc/src/rtp_transceiver/internal.rs

@@ -155,9 +155,6 @@ where
 
         if direction != previous_direction {
             trace!("Changing direction of transceiver from {previous_direction} to {direction}");
-
-            //TODO: https://www.w3.org/TR/webrtc/#dom-rtcrtptransceiver-direction
-            // Update the negotiation-needed flag for connection.
         }
     }
 

rtc/src/rtp_transceiver/mod.rs

@@ -289,7 +289,12 @@ where
     pub fn set_direction(&mut self, direction: RTCRtpTransceiverDirection) {
         // peer_connection is mutable borrow, its rtp_transceivers won't be resized,
         // so, [self.id] here is safe.
+        let previous = self.peer_connection.rtp_transceivers[self.id].direction();
         self.peer_connection.rtp_transceivers[self.id].set_direction(direction);
+        // Per W3C WebRTC §5.5: changing direction must trigger renegotiation.
+        if direction != previous {
+            self.peer_connection.trigger_negotiation_needed();
+        }
     }
 
     /// Returns the negotiated direction of the transceiver.