effect: Create ghost pads ourself

As we can have effects with several pads and the default ghosting
doesn't allow that.

This way we also filter the pads to ghost to match our track type.

ges/ges-effect.c

@@ -239,11 +239,45 @@ ges_effect_finalize (GObject * object)
   G_OBJECT_CLASS (ges_effect_parent_class)->finalize (object);
 }
 
+static void
+ghost_compatible_pads (GstElement * bin, GstElement * child,
+    GstCaps * valid_caps, gint * n_src, gint * n_sink)
+{
+  GList *tmp;
+
+  for (tmp = child->pads; tmp; tmp = tmp->next) {
+    GstCaps *caps;
+    GstPad *pad = tmp->data;
+
+    if (GST_PAD_PEER (pad))
+      continue;
+
+    caps = gst_pad_query_caps (pad, NULL);
+
+    if (gst_caps_can_intersect (caps, valid_caps)) {
+      gchar *name =
+          g_strdup_printf ("%s_%d", GST_PAD_IS_SINK (pad) ? "sink" : "src",
+          GST_PAD_IS_SINK (pad) ? *n_sink++ : *n_src++);
+
+      GST_DEBUG_OBJECT (bin, "Ghosting pad: %" GST_PTR_FORMAT, pad);
+      gst_element_add_pad (GST_ELEMENT (bin), gst_ghost_pad_new (name, pad));
+      g_free (name);
+    } else {
+      GST_DEBUG_OBJECT (pad, "Can't ghost pad %" GST_PTR_FORMAT, caps);
+    }
+
+    gst_caps_unref (caps);
+  }
+}
+
 static GstElement *
 ges_effect_create_element (GESTrackElement * object)
 {
+  GList *tmp;
   GstElement *effect;
   gchar *bin_desc;
+  GstCaps *valid_caps;
+  gint n_src = 0, n_sink = 0;
 
   GError *error = NULL;
   GESEffect *self = GES_EFFECT (object);
@@ -256,29 +290,47 @@ ges_effect_create_element (GESTrackElement * object)
     bin_desc = g_strconcat ("videoconvert name=pre_video_convert ! ",
         self->priv->bin_description, " ! videoconvert name=post_video_convert",
         NULL);
+    valid_caps = gst_caps_from_string ("video/x-raw(ANY)");
   } else if (type == GES_TRACK_TYPE_AUDIO) {
     bin_desc =
         g_strconcat ("audioconvert ! audioresample !",
         self->priv->bin_description, NULL);
+    valid_caps = gst_caps_from_string ("audio/x-raw(ANY)");
   } else {
     g_assert_not_reached ();
   }
 
-  effect = gst_parse_bin_from_description (bin_desc, TRUE, &error);
-
+  effect = gst_parse_bin_from_description (bin_desc, FALSE, &error);
   g_free (bin_desc);
-
   if (error != NULL) {
     GST_ERROR ("An error occured while creating the GstElement: %s",
         error->message);
     g_error_free (error);
-    return NULL;
+    goto fail;
+  }
+
+  for (tmp = GST_BIN_CHILDREN (effect); tmp; tmp = tmp->next) {
+    ghost_compatible_pads (effect, tmp->data, valid_caps, &n_src, &n_sink);
+
+    if (n_src > 1) {
+      GST_ERROR ("More than 1 source pad in the effect, that is not possible");
+
+      goto fail;
+    }
   }
 
   ges_track_element_add_children_props (object, effect, NULL,
       blacklisted_factories, NULL);
 
+done:
+  gst_clear_caps (&valid_caps);
+
   return effect;
+
+fail:
+  gst_clear_object (&effect);
+
+  goto done;
 }
 
 /**