clapper: Wait with flush after streams are selected

Instead flushing right after select streams request, wait until
they are selected before doing a flush.

This fixes a hang when changing audio language with hlsdemux2.

src/lib/clapper/clapper-playbin-bus.c

@@ -755,7 +755,7 @@ _handle_stream_change_msg (GstMessage *msg,
           && player->current_state >= GST_STATE_PAUSED) {
         /* XXX: I am not sure if we "officially" need to flush seek after select
          * streams, but as of GStreamer 1.22 it doesn't work otherwise. */
-        _perform_flush_seek (player);
+        player->pending_flush = TRUE;
       }
       g_list_free (list);
     }
@@ -1021,6 +1021,13 @@ _handle_streams_selected_msg (GstMessage *msg, ClapperPlayer *player)
      * we iterate in search for all active ones */
     clapper_player_playbin_update_current_decoders (player);
   }
+
+  if (player->pending_flush) {
+    player->pending_flush = FALSE;
+
+    if (player->current_state >= GST_STATE_PAUSED)
+      _perform_flush_seek (player);
+  }
 }
 
 static inline void

src/lib/clapper/clapper-player-private.h

@@ -85,6 +85,7 @@ struct _ClapperPlayer
   gboolean seeking; // during seek operation
   gboolean speed_changing; // during rate change operation
   gboolean pending_eos; // when pausing due to EOS
+  gboolean pending_flush; // after another stream selection
   gint eos; // atomic integer
 
   /* Set adaptive props immediately */

src/lib/clapper/clapper-player.c

@@ -751,6 +751,7 @@ clapper_player_reset (ClapperPlayer *self, gboolean pending_dispose)
   GST_DEBUG_OBJECT (self, "Reset");
 
   self->had_error = FALSE;
+  self->pending_flush = FALSE;
   gst_clear_object (&self->played_item);
 
   if (pending_dispose) {