[grilo] core: Make grl_media_source_metadata() cancelable

[Juan A. Suarez Romero <jasuarez src gnome org>]

commit 2317ad79021fca088dd46486c088ea247d65f2c4
Author: Juan A. Suarez Romero <jasuarez igalia com>
Date:   Mon Jul 12 10:58:15 2010 +0200

    core: Make grl_media_source_metadata() cancelable
    
    Asynchronous functions should be cancelable.

 src/grl-media-source.c |   28 +++++++++++++++++++++-------
 src/grl-media-source.h |   14 ++++++++------
 2 files changed, 29 insertions(+), 13 deletions(-)
---
diff --git a/src/grl-media-source.c b/src/grl-media-source.c
index 0d6b887..5aaa483 100644
--- a/src/grl-media-source.c
+++ b/src/grl-media-source.c
@@ -492,7 +492,12 @@ metadata_idle (gpointer user_data)
 {
   g_debug ("metadata_idle");
   GrlMediaSourceMetadataSpec *ms = (GrlMediaSourceMetadataSpec *) user_data;
-  GRL_MEDIA_SOURCE_GET_CLASS (ms->source)->metadata (ms->source, ms);
+  if (!operation_is_cancelled (ms->source, ms->metadata_id)) {
+    GRL_MEDIA_SOURCE_GET_CLASS (ms->source)->metadata (ms->source, ms);
+  } else {
+    g_debug ("  operation was cancelled");
+    ms->callback (ms->source, ms->media, ms->user_data, NULL);
+  }
   return FALSE;
 }
 
@@ -1495,8 +1500,10 @@ grl_media_source_query (GrlMediaSource *source,
  * a given @media to the media source.
  *
  * This method is asynchronous.
+ *
+ * Returns: the operation identifier
  */
-void
+guint
 grl_media_source_metadata (GrlMediaSource *source,
                            GrlMedia *media,
                            const GList *keys,
@@ -1510,14 +1517,15 @@ grl_media_source_metadata (GrlMediaSource *source,
   struct SourceKeyMapList key_mapping;
   GrlMediaSourceMetadataSpec *ms;
   struct MetadataRelayCb *mrc;
+  guint metadata_id;
 
   g_debug ("grl_media_source_metadata");
 
-  g_return_if_fail (GRL_IS_MEDIA_SOURCE (source));
-  g_return_if_fail (keys != NULL);
-  g_return_if_fail (callback != NULL);
-  g_return_if_fail (grl_metadata_source_supported_operations (GRL_METADATA_SOURCE (source)) &
-		    GRL_OP_METADATA);
+  g_return_val_if_fail (GRL_IS_MEDIA_SOURCE (source), 0);
+  g_return_val_if_fail (keys != NULL, 0);
+  g_return_val_if_fail (callback != NULL, 0);
+  g_return_val_if_fail (grl_metadata_source_supported_operations (GRL_METADATA_SOURCE (source)) &
+                        GRL_OP_METADATA, 0);
 
   /* By default assume we will use the parameters specified by the user */
   _callback = callback;
@@ -1551,6 +1559,8 @@ grl_media_source_metadata (GrlMediaSource *source,
     }
   }
 
+  metadata_id = grl_media_source_gen_operation_id (source);
+
   /* Always hook an own relay callback so we can do some
      post-processing before handing out the results
      to the user */
@@ -1562,6 +1572,7 @@ grl_media_source_metadata (GrlMediaSource *source,
 
   ms = g_new0 (GrlMediaSourceMetadataSpec, 1);
   ms->source = g_object_ref (source);
+  ms->metadata_id = metadata_id;
   ms->keys = _keys; /* It is already a copy */
   ms->flags = flags;
   ms->callback = _callback;
@@ -1579,7 +1590,10 @@ grl_media_source_metadata (GrlMediaSource *source,
      user_data so that we can free the spec there */
   mrc->spec = ms;
 
+  set_operation_ongoing (source, metadata_id);
   g_idle_add (metadata_idle, ms);
+
+  return metadata_id;
 }
 
 static GrlSupportedOps
diff --git a/src/grl-media-source.h b/src/grl-media-source.h
index ba24950..cb8e886 100644
--- a/src/grl-media-source.h
+++ b/src/grl-media-source.h
@@ -226,6 +226,7 @@ typedef struct {
 /**
  * GrlMediaSourceMetadataSpec:
  * @source: a media source
+ * @metadata_id: operation identifier
  * @media: a data transfer object
  * @keys: the list of #GrlKeyID to request
  * @flags: the resolution mode
@@ -237,6 +238,7 @@ typedef struct {
  */
 typedef struct {
   GrlMediaSource *source;
+  guint metadata_id;
   GrlMedia *media;
   GList *keys;
   GrlMetadataResolutionFlags flags;
@@ -353,12 +355,12 @@ guint grl_media_source_query (GrlMediaSource *source,
                               GrlMediaSourceResultCb callback,
                               gpointer user_data);
 
-void grl_media_source_metadata (GrlMediaSource *source,
-                                GrlMedia *media,
-                                const GList *keys,
-                                GrlMetadataResolutionFlags flags,
-                                GrlMediaSourceMetadataCb callback,
-                                gpointer user_data);
+guint grl_media_source_metadata (GrlMediaSource *source,
+                                 GrlMedia *media,
+                                 const GList *keys,
+                                 GrlMetadataResolutionFlags flags,
+                                 GrlMediaSourceMetadataCb callback,
+                                 gpointer user_data);
 
 void grl_media_source_store (GrlMediaSource *source,
                              GrlMediaBox *parent,