tag: convert GstTagDemux's sometimes source pad to an always source pad

Originally decodebin couldn't deal with that in 0.10, but now simply
setting the caps when we know them should be enough. Pad activation
mode switching might need some more testing/tweaking with the new
arrangement.

gst-libs/gst/tag/gsttagdemux.c

@@ -128,7 +128,7 @@ GST_DEBUG_CATEGORY_STATIC (tagdemux_debug);
 
 static GstStaticPadTemplate src_factory = GST_STATIC_PAD_TEMPLATE ("src",
     GST_PAD_SRC,
-    GST_PAD_SOMETIMES,
+    GST_PAD_ALWAYS,
     GST_STATIC_CAPS ("ANY")
     );
 
@@ -144,9 +144,8 @@ static GstFlowReturn gst_tag_demux_read_range (GstTagDemux * tagdemux,
 static GstFlowReturn gst_tag_demux_src_getrange (GstPad * srcpad,
     guint64 offset, guint length, GstBuffer ** buffer);
 
-static gboolean gst_tag_demux_add_srcpad (GstTagDemux * tagdemux,
+static void gst_tag_demux_set_src_caps (GstTagDemux * tagdemux,
     GstCaps * new_caps);
-static gboolean gst_tag_demux_remove_srcpad (GstTagDemux * tagdemux);
 
 static gboolean gst_tag_demux_srcpad_event (GstPad * pad, GstEvent * event);
 static gboolean gst_tag_demux_sink_activate (GstPad * sinkpad);
@@ -255,8 +254,6 @@ gst_tag_demux_reset (GstTagDemux * tagdemux)
   tagdemux->priv->collect_size = 0;
   gst_caps_replace (caps_p, NULL);
 
-  gst_tag_demux_remove_srcpad (tagdemux);
-
   if (tagdemux->priv->event_tags) {
     gst_tag_list_free (tagdemux->priv->event_tags);
     tagdemux->priv->event_tags = NULL;
@@ -284,6 +281,7 @@ gst_tag_demux_init (GstTagDemux * demux, GstTagDemuxClass * gclass)
   demux->priv = g_type_instance_get_private ((GTypeInstance *) demux,
       GST_TYPE_TAG_DEMUX);
 
+  /* sink pad */
   tmpl = gst_element_class_get_pad_template (element_klass, "sink");
   if (tmpl) {
     demux->priv->sinkpad = gst_pad_new_from_template (tmpl, "sink");
@@ -295,8 +293,25 @@ gst_tag_demux_init (GstTagDemux * demux, GstTagDemuxClass * gclass)
     gst_pad_set_chain_function (demux->priv->sinkpad,
         GST_DEBUG_FUNCPTR (gst_tag_demux_chain));
     gst_element_add_pad (GST_ELEMENT (demux), demux->priv->sinkpad);
+  } else {
+    g_warning ("GstTagDemux subclass %s must provide a sink pad template",
+        G_OBJECT_TYPE_NAME (demux));
   }
 
+  /* source pad */
+  tmpl = gst_element_class_get_pad_template (element_klass, "src");
+  demux->priv->srcpad = gst_pad_new_from_template (tmpl, "src");
+  gst_pad_set_query_function (demux->priv->srcpad,
+      GST_DEBUG_FUNCPTR (gst_tag_demux_pad_query));
+  gst_pad_set_event_function (demux->priv->srcpad,
+      GST_DEBUG_FUNCPTR (gst_tag_demux_srcpad_event));
+  gst_pad_set_activatepull_function (demux->priv->srcpad,
+      GST_DEBUG_FUNCPTR (gst_tag_demux_src_activate_pull));
+  gst_pad_set_getrange_function (demux->priv->srcpad,
+      GST_DEBUG_FUNCPTR (gst_tag_demux_src_getrange));
+  gst_pad_use_fixed_caps (demux->priv->srcpad);
+  gst_element_add_pad (GST_ELEMENT (demux), demux->priv->srcpad);
+
   gst_tag_demux_reset (demux);
 }
 
@@ -310,73 +325,25 @@ gst_tag_demux_dispose (GObject * object)
   G_OBJECT_CLASS (parent_class)->dispose (object);
 }
 
-static gboolean
+// FIXME: convert to set_caps / sending a caps event
-gst_tag_demux_add_srcpad (GstTagDemux * tagdemux, GstCaps * new_caps)
+static void
+gst_tag_demux_set_src_caps (GstTagDemux * tagdemux, GstCaps * new_caps)
 {
-  if (tagdemux->priv->src_caps == NULL ||
+  GstCaps *old_caps = tagdemux->priv->src_caps;
-      !gst_caps_is_equal (new_caps, tagdemux->priv->src_caps)) {
+
+  if (old_caps == NULL || !gst_caps_is_equal (new_caps, old_caps)) {
 
     gst_caps_replace (&tagdemux->priv->src_caps, new_caps);
 
-    if (tagdemux->priv->srcpad != NULL) {
     GST_DEBUG_OBJECT (tagdemux, "Changing src pad caps to %" GST_PTR_FORMAT,
         tagdemux->priv->src_caps);
 
     gst_pad_set_caps (tagdemux->priv->srcpad, tagdemux->priv->src_caps);
-    }
   } else {
     /* Caps never changed */
   }
-
-  if (tagdemux->priv->srcpad == NULL) {
-    tagdemux->priv->srcpad =
-        gst_pad_new_from_template (gst_element_class_get_pad_template
-        (GST_ELEMENT_GET_CLASS (tagdemux), "src"), "src");
-    g_return_val_if_fail (tagdemux->priv->srcpad != NULL, FALSE);
-
-    gst_pad_set_query_function (tagdemux->priv->srcpad,
-        GST_DEBUG_FUNCPTR (gst_tag_demux_pad_query));
-    gst_pad_set_event_function (tagdemux->priv->srcpad,
-        GST_DEBUG_FUNCPTR (gst_tag_demux_srcpad_event));
-    gst_pad_set_activatepull_function (tagdemux->priv->srcpad,
-        GST_DEBUG_FUNCPTR (gst_tag_demux_src_activate_pull));
-    gst_pad_set_getrange_function (tagdemux->priv->srcpad,
-        GST_DEBUG_FUNCPTR (gst_tag_demux_src_getrange));
-
-    gst_pad_use_fixed_caps (tagdemux->priv->srcpad);
-
-    if (tagdemux->priv->src_caps)
-      gst_pad_set_caps (tagdemux->priv->srcpad, tagdemux->priv->src_caps);
-
-    GST_DEBUG_OBJECT (tagdemux, "Adding src pad with caps %" GST_PTR_FORMAT,
-        tagdemux->priv->src_caps);
-
-    gst_object_ref (tagdemux->priv->srcpad);
-    gst_pad_set_active (tagdemux->priv->srcpad, TRUE);
-    if (!gst_element_add_pad (GST_ELEMENT (tagdemux), tagdemux->priv->srcpad))
-      return FALSE;
-    gst_element_no_more_pads (GST_ELEMENT (tagdemux));
-  }
-
-  return TRUE;
 }
 
-static gboolean
-gst_tag_demux_remove_srcpad (GstTagDemux * demux)
-{
-  gboolean res = TRUE;
-
-  if (demux->priv->srcpad != NULL) {
-    GST_DEBUG_OBJECT (demux, "Removing src pad");
-    res = gst_element_remove_pad (GST_ELEMENT (demux), demux->priv->srcpad);
-    g_return_val_if_fail (res != FALSE, FALSE);
-    gst_object_unref (demux->priv->srcpad);
-    demux->priv->srcpad = NULL;
-  }
-
-  return res;
-};
-
 /* will return FALSE if buffer is beyond end of data; will return TRUE
  * if buffer was trimmed successfully or didn't need trimming, but may
  * also return TRUE and set *buf_ref to NULL if the buffer was before
@@ -652,11 +619,7 @@ gst_tag_demux_chain (GstPad * pad, GstBuffer * buf)
       GST_DEBUG_OBJECT (demux, "Found type %" GST_PTR_FORMAT " with a "
           "probability of %u", caps, probability);
 
-      if (!gst_tag_demux_add_srcpad (demux, caps)) {
+      gst_tag_demux_set_src_caps (demux, caps);
-        GST_DEBUG_OBJECT (demux, "Failed to add srcpad");
-        gst_caps_unref (caps);
-        goto error;
-      }
       gst_caps_unref (caps);
 
       /* Move onto streaming and fall-through to push out existing
@@ -707,11 +670,6 @@ gst_tag_demux_chain (GstPad * pad, GstBuffer * buf)
     }
   }
   return GST_FLOW_OK;
-
-error:
-  GST_DEBUG_OBJECT (demux, "error in chain function");
-
-  return GST_FLOW_ERROR;
 }
 
 static gboolean
@@ -1239,11 +1197,8 @@ gst_tag_demux_sink_activate (GstPad * sinkpad)
    * the chain function if we end up in push mode */
   demux->priv->state = GST_TAG_DEMUX_STREAMING;
 
-  /* 6 Add the srcpad for output now we know caps. */
+  /* 6 Set the srcpad caps now we know them */
-  if (!gst_tag_demux_add_srcpad (demux, caps)) {
+  gst_tag_demux_set_src_caps (demux, caps);
-    GST_DEBUG_OBJECT (demux, "Could not add source pad");
-    goto done_activate;
-  }
 
   /* 7 - if the sinkpad is active, it was done by downstream so we're 
    * done, otherwise switch to push */