Forward tag events to consumers in StreamProducer

Fix #386

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1045>

gstreamer-utils/src/streamproducer.rs

@@ -235,9 +235,9 @@ impl StreamProducer {
         }
     }
 
-    /// configure if EOS from appsrc should be forwarded to all the consumers (default: `true`)
-    pub fn set_forward_eos(&self, forward_eos: bool) {
-        self.consumers.lock().unwrap().forward_eos = forward_eos;
+    /// configure event types the appsrc should forward to all consumers (default: `Eos`).
+    pub fn set_forward_events(&self, events_to_forward: impl IntoIterator<Item = gst::EventType>) {
+        self.consumers.lock().unwrap().events_to_forward = events_to_forward.into_iter().collect();
     }
 
     /// Get the GStreamer `appsink` wrapped by this producer
@@ -272,7 +272,9 @@ impl<'a> From<&'a gst_app::AppSink> for StreamProducer {
             current_latency: None,
             latency_updated: false,
             consumers: HashMap::new(),
-            forward_eos: true,
+            // it would make sense to automatically forward more events such as Tag but that would break
+            // with older GStreamer, see https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4297
+            events_to_forward: vec![gst::EventType::Eos],
         }));
 
         appsink.set_callbacks(
@@ -375,12 +377,36 @@ impl<'a> From<&'a gst_app::AppSink> for StreamProducer {
 
                     Ok(gst::FlowSuccess::Ok)
                 }))
+                .new_event(glib::clone!(@strong consumers => move |appsink| {
+                    match appsink.pull_object().map(|obj| obj.downcast::<gst::Event>()) {
+                        Ok(Ok(event)) => {
+                            let (events_to_forward, appsrcs) = {
+                                // clone so we don't keep the lock while pushing events
+                                let consumers = consumers.lock().unwrap();
+                                let events = consumers.events_to_forward.clone();
+                                let appsrcs = consumers.consumers.keys().cloned().collect::<Vec<_>>();
+
+                                (events, appsrcs)
+                            };
+
+                            if events_to_forward.contains(&event.type_()){
+                                for appsrc in appsrcs {
+                                    appsrc.send_event(event.clone());
+                                }
+                            }
+                        }
+                        Ok(Err(_)) => {}, // pulled another unsupported object type, ignore
+                        Err(_err) => gst::warning!(CAT, obj: appsink, "Failed to pull event"),
+                    }
+
+                    false
+                }))
                 .eos(glib::clone!(@strong consumers => move |appsink| {
                     let stream_consumers = consumers
                         .lock()
                         .unwrap();
 
-                    if stream_consumers.forward_eos {
+                    if stream_consumers.events_to_forward.contains(&gst::EventType::Eos) {
                         let current_consumers = stream_consumers
                             .consumers
                             .values()
@@ -432,8 +458,8 @@ struct StreamConsumers {
     latency_updated: bool,
     /// The consumers, AppSrc pointer value -> consumer
     consumers: HashMap<gst_app::AppSrc, StreamConsumer>,
-    /// Whether appsrc EOS should be forwarded to consumers
-    forward_eos: bool,
+    /// What events should be forwarded to consumers
+    events_to_forward: Vec<gst::EventType>,
 }
 
 /// Wrapper around a consumer's `appsrc`