[grilo-plugins] local-metadata: consolidate code for allocating a cancellable

[Simon McVittie <smcv src gnome org>]

commit 60417240a6464d5f640f5bba35d453f22cb12967
Author: Simon McVittie <simon mcvittie collabora co uk>
Date:   Thu Jul 16 14:55:05 2015 +0100

    local-metadata: consolidate code for allocating a cancellable
    
    If the operation_id already has a cancellable attached to it, which
    might be in use by parallel asynchronous operations, we don't want
    to allocate another one.
    
    This allows chains of async operations to call into each other
    without error.
    
    Bug: https://bugzilla.gnome.org/show_bug.cgi?id=752437

 src/local-metadata/grl-local-metadata.c |   33 ++++++++++++++++++++----------
 1 files changed, 22 insertions(+), 11 deletions(-)
---
diff --git a/src/local-metadata/grl-local-metadata.c b/src/local-metadata/grl-local-metadata.c
index 632aa7f..bcba507 100644
--- a/src/local-metadata/grl-local-metadata.c
+++ b/src/local-metadata/grl-local-metadata.c
@@ -526,6 +526,25 @@ video_guess_values_from_display_name (const gchar *display_name,
   }
 }
 
+/* Returns: (transfer none) */
+static GCancellable *
+resolve_data_ensure_cancellable (ResolveData *resolve_data)
+{
+  GCancellable *cancellable;
+
+  cancellable = grl_operation_get_data (resolve_data->rs->operation_id);
+
+  if (cancellable)
+    return cancellable;
+
+  cancellable = g_cancellable_new ();
+  /* The operation owns the cancellable */
+  grl_operation_set_data_full (resolve_data->rs->operation_id,
+                               cancellable,
+                               (GDestroyNotify) g_object_unref);
+  return cancellable;
+}
+
 static void
 extract_gibest_hash_done (GObject      *source_object,
                           GAsyncResult *res,
@@ -631,7 +650,7 @@ got_file_info (GFile *file,
 
   priv = GRL_LOCAL_METADATA_SOURCE_GET_PRIVATE (resolve_data->source);
 
-  cancellable = grl_operation_get_data (rs->operation_id);
+  cancellable = resolve_data_ensure_cancellable (resolve_data);
 
   info = g_file_query_info_finish (file, result, &error);
   if (error)
@@ -815,11 +834,7 @@ resolve_image (ResolveData         *resolve_data,
 
     file = g_file_new_for_uri (grl_media_get_url (resolve_data->rs->media));
 
-    cancellable = g_cancellable_new ();
-    /* The operation owns the cancellable */
-    grl_operation_set_data_full (resolve_data->rs->operation_id,
-                                 cancellable,
-                                 (GDestroyNotify) g_object_unref);
+    cancellable = resolve_data_ensure_cancellable (resolve_data);
 
 #if GLIB_CHECK_VERSION (2, 39, 0)
     attributes = G_FILE_ATTRIBUTE_THUMBNAIL_PATH "," \
@@ -884,10 +899,7 @@ resolve_album_art (ResolveData         *resolve_data,
   if (!artist || !album)
     goto done;
 
-  cancellable = g_cancellable_new ();
-  grl_operation_set_data_full (resolve_data->rs->operation_id,
-                               g_object_ref (cancellable),
-                               (GDestroyNotify) g_object_unref);
+  cancellable = resolve_data_ensure_cancellable (resolve_data);
 
   media_art_get_file (artist, album, "album", &cache_file);
 
@@ -905,7 +917,6 @@ done:
   resolve_data_finish_operation (resolve_data, "album-art", NULL);
 
   g_clear_object (&cache_file);
-  g_clear_object (&cancellable);
 }
 
 static gboolean