Try all available thumbnailers before declaring failure

The request thumbnailer array no longer contains one thumbnailer per
URI, but the list of available thumbnailers for this URI (after applying
the filters of the configuration file), sorted by priority.

For a given URI, we browse the thumbnailer list until we succeed in
generating a thumbnail. An error signal is only issued if the last
thumbnailer has failed. Intermediate errors are only displayed if debug
logging is enabled.

Closes #50.

7 files changed, 113 insertions, 56 deletions

diff --git a/tumblerd/tumbler-group-scheduler.c b/tumblerd/tumbler-group-scheduler.c
index f756f7a..a266542 100644
--- a/tumblerd/tumbler-group-scheduler.c
+++ b/tumblerd/tumbler-group-scheduler.c
@@ -423,7 +423,7 @@ tumbler_group_scheduler_thread (gpointer data,
   GList                   *ready_uris;
   GList                   *cached_uris = NULL;
   GList                   *missing_uris = NULL;
-  GList                   *lp;
+  GList                   *lp, *lq;
   guint                    n;
   gint                     error_code = 0;
   GQuark                   error_domain = 0;
@@ -550,25 +550,33 @@ tumbler_group_scheduler_thread (gpointer data,
         }
       tumbler_mutex_unlock (scheduler->mutex);
 
-      /* connect to the error signal of the thumbnailer */
-      g_signal_connect (request->thumbnailers[n], "error", 
-                        G_CALLBACK (tumbler_group_scheduler_thumbnailer_error),
-                        &uri_errors);
-
-      /* connect to the ready signal of the thumbnailer */
-      g_signal_connect (request->thumbnailers[n], "ready",
-                        G_CALLBACK (tumbler_group_scheduler_thumbnailer_ready),
-                        &ready_uris);
-
-      /* tell the thumbnailer to generate the thumbnail */
-      tumbler_thumbnailer_create (request->thumbnailers[n], 
-                                  request->cancellables[n],
-                                  request->infos[n]);
-
-      /* disconnect from all signals when we're finished */
-      g_signal_handlers_disconnect_matched (request->thumbnailers[n],
-                                            G_SIGNAL_MATCH_DATA,
-                                            0, 0, NULL, NULL, request);
+      for (lq = request->thumbnailers[n]; lq != NULL; lq = lq->next)
+        {
+          /* forward only the error signal of the last thumbnailer */
+          if (lq->next == NULL)
+            g_signal_connect (lq->data, "error",
+                              G_CALLBACK (tumbler_group_scheduler_thumbnailer_error), &uri_errors);
+          else if (tumbler_util_is_debug_logging_enabled (G_LOG_DOMAIN))
+            g_signal_connect (lq->data, "error",
+                              G_CALLBACK (tumbler_scheduler_thumberr_debuglog), request);
+
+          /* connect to the ready signal of the thumbnailer */
+          g_signal_connect (lq->data, "ready",
+                            G_CALLBACK (tumbler_group_scheduler_thumbnailer_ready), &ready_uris);
+
+          /* cancel lower priority thumbnailers for this uri on ready signal */
+          g_signal_connect_swapped (lq->data, "ready", G_CALLBACK (g_cancellable_cancel),
+                                    request->cancellables[n]);
+
+          /* tell the thumbnailer to generate the thumbnail */
+          tumbler_thumbnailer_create (lq->data, request->cancellables[n], request->infos[n]);
+
+          /* disconnect from all signals when we're finished */
+          g_signal_handlers_disconnect_by_data (lq->data, &uri_errors);
+          g_signal_handlers_disconnect_by_data (lq->data, &ready_uris);
+          g_signal_handlers_disconnect_by_data (lq->data, request);
+          g_signal_handlers_disconnect_by_data (lq->data, request->cancellables[n]);
+        }
     }
 
   tumbler_mutex_lock (scheduler->mutex);
diff --git a/tumblerd/tumbler-lifo-scheduler.c b/tumblerd/tumbler-lifo-scheduler.c
index e19d811..f1ff821 100644
--- a/tumblerd/tumbler-lifo-scheduler.c
+++ b/tumblerd/tumbler-lifo-scheduler.c
@@ -362,7 +362,7 @@ tumbler_lifo_scheduler_thread (gpointer data,
   GError                  *error = NULL;
   GList                   *cached_uris = NULL;
   GList                   *missing_uris = NULL;
-  GList                   *lp;
+  GList                   *lp, *lq;
   guint                    n;
 
   g_return_if_fail (TUMBLER_IS_LIFO_SCHEDULER (scheduler));
@@ -475,29 +475,35 @@ tumbler_lifo_scheduler_thread (gpointer data,
           return;
         }
 
-      /* We immediately forward error and ready so that clients rapidly know
-       * when individual thumbnails are ready. It's a LIFO for better inter-
-       * activity with the clients, so we assume this behaviour to be desired. */
-
-      /* connect to the error signal of the thumbnailer */
-      g_signal_connect (request->thumbnailers[n], "error", 
-                        G_CALLBACK (tumbler_lifo_scheduler_thumbnailer_error),
-                        request);
-
-      /* connect to the ready signal of the thumbnailer */
-      g_signal_connect (request->thumbnailers[n], "ready",
-                        G_CALLBACK (tumbler_lifo_scheduler_thumbnailer_ready),
-                        request);
-
-      /* tell the thumbnailer to generate the thumbnail */
-      tumbler_thumbnailer_create (request->thumbnailers[n], 
-                                  request->cancellables[n],
-                                  request->infos[n]);
-
-      /* disconnect from all signals when we're finished */
-      g_signal_handlers_disconnect_matched (request->thumbnailers[n],
-                                            G_SIGNAL_MATCH_DATA,
-                                            0, 0, NULL, NULL, request);
+      for (lq = request->thumbnailers[n]; lq != NULL; lq = lq->next)
+        {
+          /* We immediately forward error and ready so that clients rapidly know
+           * when individual thumbnails are ready. It's a LIFO for better inter-
+           * activity with the clients, so we assume this behaviour to be desired. */
+
+          /* forward only the error signal of the last thumbnailer */
+          if (lq->next == NULL)
+            g_signal_connect (lq->data, "error",
+                              G_CALLBACK (tumbler_lifo_scheduler_thumbnailer_error), request);
+          else if (tumbler_util_is_debug_logging_enabled (G_LOG_DOMAIN))
+            g_signal_connect (lq->data, "error",
+                              G_CALLBACK (tumbler_scheduler_thumberr_debuglog), request);
+
+          /* connect to the ready signal of the thumbnailer */
+          g_signal_connect (lq->data, "ready",
+                            G_CALLBACK (tumbler_lifo_scheduler_thumbnailer_ready), request);
+
+          /* cancel lower priority thumbnailers for this uri on ready signal */
+          g_signal_connect_swapped (lq->data, "ready", G_CALLBACK (g_cancellable_cancel),
+                                    request->cancellables[n]);
+
+          /* tell the thumbnailer to generate the thumbnail */
+          tumbler_thumbnailer_create (lq->data, request->cancellables[n], request->infos[n]);
+
+          /* disconnect from all signals when we're finished */
+          g_signal_handlers_disconnect_by_data (lq->data, request);
+          g_signal_handlers_disconnect_by_data (lq->data, request->cancellables[n]);
+        }
     }
 
   /* free list */
diff --git a/tumblerd/tumbler-registry.c b/tumblerd/tumbler-registry.c
index 32cdbfc..6f75654 100644
--- a/tumblerd/tumbler-registry.c
+++ b/tumblerd/tumbler-registry.c
@@ -411,12 +411,12 @@ tumbler_registry_get_thumbnailers (TumblerRegistry *registry)
 
 
 
-TumblerThumbnailer **
+GList **
 tumbler_registry_get_thumbnailer_array (TumblerRegistry    *registry,
                                         TumblerFileInfo   **infos,
                                         guint               length)
 {
-  TumblerThumbnailer **thumbnailers = NULL;
+  GList              **thumbnailers = NULL;
   gchar               *hash_key;
   gchar               *scheme;
   guint                n;
@@ -432,7 +432,7 @@ tumbler_registry_get_thumbnailer_array (TumblerRegistry    *registry,
   tumbler_mutex_lock (registry->mutex);
 
   /* allocate the thumbnailer array */
-  thumbnailers = g_new0 (TumblerThumbnailer *, length + 1);
+  thumbnailers = g_new0 (GList *, length + 1);
 
   /* iterate over all URIs */
   for (n = 0; n < length; ++n)
@@ -475,11 +475,12 @@ tumbler_registry_get_thumbnailer_array (TumblerRegistry    *registry,
             }
 
           /* found a usable thumbnailer */
-          thumbnailers[n] = g_object_ref (lp->data);
-
-          break;
+          thumbnailers[n] = g_list_prepend (thumbnailers[n], g_object_ref (lp->data));
         }
 
+      /* restore thumbnailer priority */
+      thumbnailers[n] = g_list_reverse (thumbnailers[n]);
+
       /* cleanup */
       g_free (hash_key);
       g_free (scheme);
diff --git a/tumblerd/tumbler-registry.h b/tumblerd/tumbler-registry.h
index c58a0e0..9714250 100644
--- a/tumblerd/tumbler-registry.h
+++ b/tumblerd/tumbler-registry.h
@@ -45,7 +45,7 @@ void                 tumbler_registry_add                   (TumblerRegistry
 void                 tumbler_registry_remove                (TumblerRegistry     *registry,
                                                              TumblerThumbnailer  *thumbnailer);
 GList               *tumbler_registry_get_thumbnailers      (TumblerRegistry     *registry) G_GNUC_MALLOC G_GNUC_WARN_UNUSED_RESULT;
-TumblerThumbnailer **tumbler_registry_get_thumbnailer_array (TumblerRegistry     *registry,
+GList              **tumbler_registry_get_thumbnailer_array (TumblerRegistry     *registry,
                                                              TumblerFileInfo    **infos,
                                                              guint                length) G_GNUC_MALLOC G_GNUC_WARN_UNUSED_RESULT;
 void                 tumbler_registry_update_supported      (TumblerRegistry     *registry);
diff --git a/tumblerd/tumbler-scheduler.c b/tumblerd/tumbler-scheduler.c
index 2110bc2..8ad820a 100644
--- a/tumblerd/tumbler-scheduler.c
+++ b/tumblerd/tumbler-scheduler.c
@@ -234,7 +234,7 @@ tumbler_scheduler_emit_uri_error (TumblerScheduler        *scheduler,
 
 TumblerSchedulerRequest *
 tumbler_scheduler_request_new (TumblerFileInfo    **infos,
-                               TumblerThumbnailer **thumbnailers,
+                               GList              **thumbnailers,
                                guint                length,
                                const gchar         *origin)
 {
@@ -335,3 +335,37 @@ tumbler_scheduler_thread_use_lower_priority (void)
     sched_setscheduler (0, SCHED_IDLE, &sp);
 #endif
 }
+
+
+
+void
+tumbler_scheduler_thumberr_debuglog (TumblerThumbnailer      *thumbnailer,
+                                     const gchar             *failed_uri,
+                                     GQuark                   error_domain,
+                                     gint                     error_code,
+                                     const gchar             *message,
+                                     TumblerSchedulerRequest *request)
+{
+  gchar *text;
+
+  g_return_if_fail (TUMBLER_IS_THUMBNAILER (thumbnailer));
+  g_return_if_fail (failed_uri != NULL);
+  g_return_if_fail (request != NULL);
+  g_return_if_fail (TUMBLER_IS_SCHEDULER (request->scheduler));
+
+  if (error_domain == G_IO_ERROR && error_code == G_IO_ERROR_CANCELLED)
+    return;
+
+  if (error_domain == TUMBLER_ERROR)
+    text = g_strdup (message);
+  else
+    {
+      error_code = TUMBLER_ERROR_OTHER_ERROR_DOMAIN;
+      text = g_strdup_printf ("(domain %s, code %d) %s",
+                              g_quark_to_string (error_domain), error_code, message);
+    }
+
+  g_debug ("Failed attempt for job %d, URI '%s': Code %d, message: %s",
+           request->handle, failed_uri, error_code, text);
+  g_free (text);
+}
diff --git a/tumblerd/tumbler-scheduler.h b/tumblerd/tumbler-scheduler.h
index 6423166..a317d66 100644
--- a/tumblerd/tumbler-scheduler.h
+++ b/tumblerd/tumbler-scheduler.h
@@ -81,7 +81,7 @@ void                     tumbler_scheduler_emit_uri_error        (TumblerSchedul
                                                                   const gchar             *uri,
                                                                   GError                  *error);
 TumblerSchedulerRequest *tumbler_scheduler_request_new           (TumblerFileInfo        **infos,
-                                                                  TumblerThumbnailer     **thumbnailers,
+                                                                  GList                  **thumbnailers,
                                                                   guint                    length,
                                                                   const gchar             *origin);
 void                     tumbler_scheduler_request_free          (gpointer                 data);
@@ -91,9 +91,17 @@ gint                     tumbler_scheduler_request_compare       (gconstpointer
 
 void                     tumbler_scheduler_thread_use_lower_priority (void);
 
+/* debug */
+void                     tumbler_scheduler_thumberr_debuglog     (TumblerThumbnailer      *thumbnailer,
+                                                                  const gchar             *failed_uri,
+                                                                  GQuark                   error_domain,
+                                                                  gint                     error_code,
+                                                                  const gchar             *message,
+                                                                  TumblerSchedulerRequest *request);
+
 struct _TumblerSchedulerRequest
 {
-  TumblerThumbnailer **thumbnailers;
+  GList              **thumbnailers;
   TumblerScheduler    *scheduler;
   TumblerFileInfo    **infos;
   GCancellable       **cancellables;
diff --git a/tumblerd/tumbler-service.c b/tumblerd/tumbler-service.c
index 8e6fbf1..a60858e 100644
--- a/tumblerd/tumbler-service.c
+++ b/tumblerd/tumbler-service.c
@@ -460,7 +460,7 @@ tumbler_service_scheduler_error (TumblerScheduler   *scheduler,
   else
     {
       info->error_code = TUMBLER_ERROR_OTHER_ERROR_DOMAIN;
-      info->message = g_strdup_printf ("(%s error, code %d) %s",
+      info->message = g_strdup_printf ("(domain %s, code %d) %s",
                                        g_quark_to_string (error_domain), error_code, message);
     }
 
@@ -716,10 +716,10 @@ tumbler_service_queue_cb (TumblerExportedService  *skeleton,
 {
   TumblerSchedulerRequest *scheduler_request;
   TumblerThumbnailFlavor  *flavor;
-  TumblerThumbnailer     **thumbnailers;
   TumblerScheduler        *scheduler = NULL;
   TumblerFileInfo        **infos;
   TumblerCache            *cache;
+  GList                  **thumbnailers;
   GList                   *iter;
   gchar                   *name;
   const gchar             *origin;