pbutils: Move DiscovererStreamInfo iterators to an extension trait

This way it can also be called directly on subclasses.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1273>

gstreamer-pbutils/src/discoverer_stream_info.rs

@@ -28,20 +28,25 @@ impl Iterator for Iter {
     }
 }
 
-impl DiscovererStreamInfo {
-    pub fn next_iter(&self) -> Iter {
+impl std::iter::FusedIterator for Iter {}
+
+pub trait DiscovererStreamInfoExtManual: 'static {
+    fn next_iter(&self) -> Iter;
+    fn previous_iter(&self) -> Iter;
+}
+
+impl<O: IsA<DiscovererStreamInfo>> DiscovererStreamInfoExtManual for O {
+    fn next_iter(&self) -> Iter {
         Iter {
             stream_info: self.next(),
             direction_forward: true,
         }
     }
 
-    pub fn previous_iter(&self) -> Iter {
+    fn previous_iter(&self) -> Iter {
         Iter {
             stream_info: self.previous(),
             direction_forward: false,
         }
     }
 }
-
-impl std::iter::FusedIterator for Iter {}

gstreamer-pbutils/src/lib.rs

@@ -62,6 +62,7 @@ pub mod prelude {
     pub use crate::{
         audio_visualizer::*,
         auto::traits::*,
+        discoverer_stream_info::DiscovererStreamInfoExtManual,
         encoding_profile::{
             EncodingProfileBuilder, EncodingProfileExtManual, EncodingProfileHasRestrictionGetter,
         },