[rhythmbox] xfade: always attribute tags to the right stream

[Jonathan Matthew <jmatthew src gnome org>]

commit b624cc6d03eaf1954d21b5c215d92288fda2ba41
Author: Jonathan Matthew <jonathan d14n org>
Date:   Fri Mar 13 20:43:08 2015 +1000

    xfade: always attribute tags to the right stream
    
    Tag messages are emitted by the sink, which makes it difficult to
    associate them with the originating stream.  Previously we've just
    assumed the stream that is currently in PLAYING state owns any tags
    that come out, which isn't good enough.  Tag updates now include
    the full tags from the stream, which means embedded cover art too.
    Attributing this to the wrong stream means we get the wrong cover art
    image.
    
    To fix this, we inject a tag into each stream containing the stream uri,
    which we use to locate the stream instance.  Injecting a tag into the
    stream is a bit ugly but it effectively fixes the problem.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=743493

 backends/gstreamer/rb-player-gst-xfade.c |   60 +++++++++++++++++++++++++++++-
 1 files changed, 58 insertions(+), 2 deletions(-)
---
diff --git a/backends/gstreamer/rb-player-gst-xfade.c b/backends/gstreamer/rb-player-gst-xfade.c
index ff1ea99..a30b9cb 100644
--- a/backends/gstreamer/rb-player-gst-xfade.c
+++ b/backends/gstreamer/rb-player-gst-xfade.c
@@ -210,6 +210,8 @@ G_DEFINE_TYPE_WITH_CODE(RBPlayerGstXFade, rb_player_gst_xfade, G_TYPE_OBJECT,
 #define FADE_IN_DONE_MESSAGE   "rb-fade-in-done"
 #define STREAM_EOS_MESSAGE     "rb-stream-eos"
 
+#define STREAM_URI_TAG         "rb-stream-uri"
+
 #define PAUSE_FADE_LENGTH      (GST_SECOND / 2)
 
 enum
@@ -598,10 +600,20 @@ find_stream_for_message (RBPlayerGstXFade *player, GstMessage *message)
                return stream;
 
        /* tag messages are emitted by the sink, so we can't find the message
-        * source in a stream bin.  attribute them to the first playing stream.
+        * source in a stream bin.  instead, we add a tag to the stream containing
+        * the stream uri and use that to locate the stream.
         */
        if (GST_MESSAGE_TYPE (message) == GST_MESSAGE_TAG) {
-               return find_stream_by_state (player, FADING_IN | PLAYING | FADING_OUT_PAUSED | PAUSED | 
PENDING_REMOVE | REUSING);
+               GstTagList *tags;
+               char *loc;
+               gst_message_parse_tag (message, &tags);
+
+               if (gst_tag_list_get_string (tags, STREAM_URI_TAG, &loc)) {
+                       stream = find_stream_by_uri (player, loc);
+                       g_free (loc);
+                       if (stream)
+                               return stream;
+               }
        }
 
        return NULL;
@@ -715,6 +727,8 @@ rb_player_gst_xfade_class_init (RBPlayerGstXFadeClass *klass)
                              G_TYPE_STRING);
 
        g_type_class_add_private (klass, sizeof (RBPlayerGstXFadePrivate));
+
+       gst_tag_register_static (STREAM_URI_TAG, GST_TAG_FLAG_META, G_TYPE_STRING, "rb stream uri", "rb 
stream uri", gst_tag_merge_use_first);
 }
 
 static void
@@ -2017,6 +2031,45 @@ stream_source_setup_cb (GstElement *decoder, GstElement *source, RBXFadeStream *
        g_signal_emit (stream->player, signals[PREPARE_SOURCE], 0, stream->uri, source);
 }
 
+static GstPadProbeReturn
+drop_events (GstPad *pad, GstPadProbeInfo *info, gpointer data)
+{
+       return GST_PAD_PROBE_DROP;
+}
+
+static void
+add_stream_uri_tag (GstPad *pad, RBXFadeStream *stream)
+{
+       GstTagList *t;
+       GstElement *e;
+       GstPad *target;
+       GstPad *t2;
+       GstPad *sink;
+       gulong probe_id;
+
+       t = gst_tag_list_new (STREAM_URI_TAG, stream->uri, NULL);
+       gst_tag_list_set_scope (t, GST_TAG_SCOPE_STREAM);
+
+       /* uridecodebin src -> decodebin src */
+       t2 = gst_ghost_pad_get_target (GST_GHOST_PAD (pad));
+
+       /* decodebin src -> actual decoder src */
+       target = gst_ghost_pad_get_target (GST_GHOST_PAD (t2));
+       probe_id = gst_pad_add_probe (target, GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM, drop_events, NULL, NULL);
+
+       /* get the decoder sink pad and push the tags through it */
+       e = GST_ELEMENT (gst_pad_get_parent (target));
+       sink = gst_element_get_static_pad (e, "sink");
+       gst_pad_send_event (sink, gst_event_new_tag (t));
+       gst_object_unref (sink);
+       gst_object_unref (e);
+
+       gst_pad_remove_probe (target, probe_id);
+
+       gst_object_unref (target);
+       gst_object_unref (t2);
+}
+
 /* links uridecodebin src pads to the rest of the output pipeline */
 static void
 stream_pad_added_cb (GstElement *decoder, GstPad *pad, RBXFadeStream *stream)
@@ -2046,6 +2099,9 @@ stream_pad_added_cb (GstElement *decoder, GstPad *pad, RBXFadeStream *stream)
                /* probably should never happen */
                rb_debug ("hmm, decoder is already linked");
        } else {
+               /* push a location tag through the decoder so we can use it to identify the stream later */
+               add_stream_uri_tag (pad, stream);
+
                rb_debug ("got decoded audio pad for stream %s", stream->uri);
                vpad = gst_element_get_static_pad (stream->identity, "sink");
                gst_pad_link (pad, vpad);