Error handling: Fit to the spec and complete message if needed

A parameter is added to Tumbler's internal error signals to account for
the error domain, and the error code `TUMBLER_ERROR_OTHER_ERROR_DOMAIN`
is added to indicate that the error originated from a third-party API.

When sending the error signal via D-Bus, cancelling errors are filtered
out, and when the error originates from a third-party API, the error
message is prefixed with the domain and code of that error, in a
possibly parsable format.

Fixes #49.

21 files changed, 116 insertions, 59 deletions

diff --git a/plugins/cover-thumbnailer/cover-thumbnailer.c b/plugins/cover-thumbnailer/cover-thumbnailer.c
index 4758dee..e1448b0 100644
--- a/plugins/cover-thumbnailer/cover-thumbnailer.c
+++ b/plugins/cover-thumbnailer/cover-thumbnailer.c
@@ -673,7 +673,7 @@ cover_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
   if (error != NULL)
     {
       g_signal_emit_by_name (thumbnailer, "error", uri,
-                             error->code, error->message);
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
   else
diff --git a/plugins/desktop-thumbnailer/desktop-thumbnailer.c b/plugins/desktop-thumbnailer/desktop-thumbnailer.c
index 7304ea6..96e357e 100644
--- a/plugins/desktop-thumbnailer/desktop-thumbnailer.c
+++ b/plugins/desktop-thumbnailer/desktop-thumbnailer.c
@@ -393,7 +393,8 @@ desktop_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
   if (error != NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
   else
diff --git a/plugins/ffmpeg-thumbnailer/ffmpeg-thumbnailer.c b/plugins/ffmpeg-thumbnailer/ffmpeg-thumbnailer.c
index f2edf1e..3b3494e 100644
--- a/plugins/ffmpeg-thumbnailer/ffmpeg-thumbnailer.c
+++ b/plugins/ffmpeg-thumbnailer/ffmpeg-thumbnailer.c
@@ -163,7 +163,8 @@ ffmpeg_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
     /* there was an error, emit error signal */
     g_set_error (&error, TUMBLER_ERROR, TUMBLER_ERROR_NO_CONTENT,
                  TUMBLER_ERROR_MESSAGE_CREATION_FAILED);
-    g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+    g_signal_emit_by_name (thumbnailer, "error", uri,
+                           error->domain, error->code, error->message);
     g_error_free (error);
 
     return;
@@ -194,7 +195,8 @@ ffmpeg_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       /* there was an error, emit error signal */
       g_set_error (&error, TUMBLER_ERROR, TUMBLER_ERROR_INVALID_FORMAT,
                    TUMBLER_ERROR_MESSAGE_CREATION_FAILED);
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
                              g_error_free (error);
 
       /* clean up */
@@ -209,7 +211,8 @@ ffmpeg_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       /* there was an error, emit error signal */
       g_set_error (&error, TUMBLER_ERROR, TUMBLER_ERROR_INVALID_FORMAT,
                    TUMBLER_ERROR_MESSAGE_CREATION_FAILED);
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
 
       /* clean up */
@@ -228,7 +231,8 @@ ffmpeg_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       /* there was an error, emit error signal */
       g_set_error (&error, TUMBLER_ERROR, TUMBLER_ERROR_INVALID_FORMAT,
                    TUMBLER_ERROR_MESSAGE_CREATION_FAILED);
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
 
       /* clean up */
@@ -245,7 +249,8 @@ ffmpeg_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
   if (v_pixbuf == NULL)
     {
       /* emit an error signal */
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
 
       /* clean up */
@@ -277,7 +282,8 @@ ffmpeg_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
   if (error != NULL)
     {
       /* emit an error signal */
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
   else
diff --git a/plugins/font-thumbnailer/font-thumbnailer.c b/plugins/font-thumbnailer/font-thumbnailer.c
index f9ed136..a816cdf 100644
--- a/plugins/font-thumbnailer/font-thumbnailer.c
+++ b/plugins/font-thumbnailer/font-thumbnailer.c
@@ -429,7 +429,8 @@ font_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       /* there was an error in the freetype initialization, abort */
       error_msg = g_strdup_printf (_("Could not initialize freetype: %s"),
                                    ft_strerror (font_thumbnailer->library_error));
-      g_signal_emit_by_name (thumbnailer, "error", uri, TUMBLER_ERROR_UNSUPPORTED, error_msg);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             TUMBLER_ERROR, TUMBLER_ERROR_UNSUPPORTED, error_msg);
       g_free (error_msg);
       return;
     }
@@ -441,7 +442,8 @@ font_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       /* there was an error, emit error signal */
       error_msg = g_strdup_printf (_("Could not load file contents: %s"), 
                                    error->message);
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error_msg);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error_msg);
       g_free (error_msg);
 
       /* clean up */
@@ -460,7 +462,8 @@ font_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       /* the font file could not be loaded, emit an error signal */
       error_msg = g_strdup_printf (_("Could not open font file: %s"),
                                    ft_strerror (ft_error));
-      g_signal_emit_by_name (thumbnailer, "error", uri, TUMBLER_ERROR_NO_CONTENT, error_msg);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             TUMBLER_ERROR, TUMBLER_ERROR_NO_CONTENT, error_msg);
       g_free (error_msg);
 
       /* clean up */
@@ -485,7 +488,7 @@ font_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
               error_msg = g_strdup_printf (_("Could not set the character map: %s"),
                                            ft_strerror (ft_error));
               g_signal_emit_by_name (thumbnailer, "error", uri,
-                                     TUMBLER_ERROR_INVALID_FORMAT, error_msg);
+                                     TUMBLER_ERROR, TUMBLER_ERROR_INVALID_FORMAT, error_msg);
               g_free (error_msg);
 
               /* clean up */
@@ -512,7 +515,8 @@ font_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       /* emit an error signal */
       error_msg = g_strdup_printf (_("Could not render glyphs: %s"),
                                    ft_strerror (ft_error));
-      g_signal_emit_by_name (thumbnailer, "error", uri, TUMBLER_ERROR_INVALID_FORMAT, error_msg);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             TUMBLER_ERROR, TUMBLER_ERROR_INVALID_FORMAT, error_msg);
       g_free (error_msg);
 
       /* clean up */
@@ -543,7 +547,8 @@ font_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
   if (error != NULL)
     {
       /* emit an error signal */
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
   else
diff --git a/plugins/gepub-thumbnailer/gepub-thumbnailer.c b/plugins/gepub-thumbnailer/gepub-thumbnailer.c
index 98062c7..9b65762 100644
--- a/plugins/gepub-thumbnailer/gepub-thumbnailer.c
+++ b/plugins/gepub-thumbnailer/gepub-thumbnailer.c
@@ -170,7 +170,7 @@ gepub_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       if (error != NULL)
         {
           g_signal_emit_by_name (thumbnailer, "error", uri,
-                                 error->code, error->message);
+                                 error->domain, error->code, error->message);
           g_error_free (error);
 
           g_object_unref (file);
@@ -184,7 +184,7 @@ gepub_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       if (cover_mime == NULL)
         {
           g_signal_emit_by_name (thumbnailer, "error", uri,
-                                 TUMBLER_ERROR_NO_CONTENT,
+                                 TUMBLER_ERROR, TUMBLER_ERROR_NO_CONTENT,
                                  "Cover not found");
 
           g_free (cover);
@@ -228,8 +228,8 @@ gepub_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
   if (error != NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code,
-                             error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
   else
diff --git a/plugins/gst-thumbnailer/gst-thumbnailer.c b/plugins/gst-thumbnailer/gst-thumbnailer.c
index d68a3cb..461471b 100644
--- a/plugins/gst-thumbnailer/gst-thumbnailer.c
+++ b/plugins/gst-thumbnailer/gst-thumbnailer.c
@@ -546,7 +546,8 @@ gst_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
     /* there was an error, emit error signal */
     g_set_error (&error, TUMBLER_ERROR, TUMBLER_ERROR_NO_CONTENT,
                  TUMBLER_ERROR_MESSAGE_CREATION_FAILED);
-    g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+    g_signal_emit_by_name (thumbnailer, "error", uri,
+                           error->domain, error->code, error->message);
     g_error_free (error);
 
     return;
@@ -607,7 +608,8 @@ gst_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
       if (error != NULL)
         {
-          g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+          g_signal_emit_by_name (thumbnailer, "error", uri,
+                                 error->domain, error->code, error->message);
           g_error_free (error);
         }
       else
@@ -622,7 +624,8 @@ gst_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
         g_set_error (&error, TUMBLER_ERROR, TUMBLER_ERROR_NO_CONTENT,
                      TUMBLER_ERROR_MESSAGE_CREATION_FAILED);
 
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
 
diff --git a/plugins/jpeg-thumbnailer/jpeg-thumbnailer.c b/plugins/jpeg-thumbnailer/jpeg-thumbnailer.c
index bf5c0d3..9df8224 100644
--- a/plugins/jpeg-thumbnailer/jpeg-thumbnailer.c
+++ b/plugins/jpeg-thumbnailer/jpeg-thumbnailer.c
@@ -928,7 +928,8 @@ jpeg_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
   if (error != NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
   else
diff --git a/plugins/odf-thumbnailer/odf-thumbnailer.c b/plugins/odf-thumbnailer/odf-thumbnailer.c
index ff47bfc..7e62d1d 100644
--- a/plugins/odf-thumbnailer/odf-thumbnailer.c
+++ b/plugins/odf-thumbnailer/odf-thumbnailer.c
@@ -300,7 +300,8 @@ odf_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       input = gsf_input_gio_new (file, &error);
       if (G_UNLIKELY (input == NULL))
         {
-          g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+          g_signal_emit_by_name (thumbnailer, "error", uri,
+                                 error->domain, error->code, error->message);
           g_error_free (error);
           g_object_unref (file);
           return;
@@ -353,7 +354,8 @@ odf_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
   if (error != NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
   else
diff --git a/plugins/pixbuf-thumbnailer/pixbuf-thumbnailer.c b/plugins/pixbuf-thumbnailer/pixbuf-thumbnailer.c
index 6395d7f..8ee8364 100644
--- a/plugins/pixbuf-thumbnailer/pixbuf-thumbnailer.c
+++ b/plugins/pixbuf-thumbnailer/pixbuf-thumbnailer.c
@@ -218,8 +218,8 @@ pixbuf_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
   if (stream == NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code,
-                             error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
 
       return;
@@ -239,8 +239,8 @@ pixbuf_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
   if (pixbuf == NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code,
-                             error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
       g_object_unref (thumbnail);
 
@@ -263,7 +263,8 @@ pixbuf_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
   if (error != NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
   else
diff --git a/plugins/poppler-thumbnailer/poppler-thumbnailer.c b/plugins/poppler-thumbnailer/poppler-thumbnailer.c
index 8ee1083..e8aee20 100644
--- a/plugins/poppler-thumbnailer/poppler-thumbnailer.c
+++ b/plugins/poppler-thumbnailer/poppler-thumbnailer.c
@@ -259,7 +259,8 @@ poppler_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
       /* try to load the file contents using GIO */
       if (!g_file_load_contents (file, cancellable, &contents, &length, NULL, &error))
         {
-          g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+          g_signal_emit_by_name (thumbnailer, "error", uri,
+                                 error->domain, error->code, error->message);
           g_error_free (error);
           g_object_unref (file);
           return;
@@ -281,7 +282,8 @@ poppler_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
   /* emit an error if both ways to load the document failed */
   if (document == NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
       poppler_thumbnailer_free (contents);
       return;
@@ -290,7 +292,8 @@ poppler_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
   /* check if the document has content (= at least one page) */
   if (poppler_document_get_n_pages (document) <= 0)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, TUMBLER_ERROR_NO_CONTENT,
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             TUMBLER_ERROR, TUMBLER_ERROR_NO_CONTENT,
                              _("The document is empty"));
       g_object_unref (document);
       poppler_thumbnailer_free (contents);
@@ -302,7 +305,8 @@ poppler_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
   if (page == NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, TUMBLER_ERROR_NO_CONTENT,
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             TUMBLER_ERROR, TUMBLER_ERROR_NO_CONTENT,
                              _("First page of the document could not be read"));
       g_object_unref (document);
       poppler_thumbnailer_free (contents);
@@ -353,7 +357,8 @@ poppler_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
   if (error != NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
   else
diff --git a/plugins/raw-thumbnailer/raw-thumbnailer.c b/plugins/raw-thumbnailer/raw-thumbnailer.c
index 92ac01d..962736a 100644
--- a/plugins/raw-thumbnailer/raw-thumbnailer.c
+++ b/plugins/raw-thumbnailer/raw-thumbnailer.c
@@ -178,7 +178,8 @@ raw_thumbnailer_create (TumblerAbstractThumbnailer *thumbnailer,
 
   if (error != NULL)
     {
-      g_signal_emit_by_name (thumbnailer, "error", uri, error->code, error->message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             error->domain, error->code, error->message);
       g_error_free (error);
     }
   else
diff --git a/tumbler/tumbler-error.h b/tumbler/tumbler-error.h
index 036a7b8..938c67c 100644
--- a/tumbler/tumbler-error.h
+++ b/tumbler/tumbler-error.h
@@ -63,6 +63,7 @@ typedef enum /*< enum >*/
   TUMBLER_ERROR_UNSUPPORTED_FLAVOR,
   TUMBLER_ERROR_NO_CONTENT,
   TUMBLER_ERROR_SHUTTING_DOWN,
+  TUMBLER_ERROR_OTHER_ERROR_DOMAIN,
 } TumblerErrorEnum;
 
 G_END_DECLS
diff --git a/tumbler/tumbler-marshal.list b/tumbler/tumbler-marshal.list
index 4a83ff1..acacac6 100644
--- a/tumbler/tumbler-marshal.list
+++ b/tumbler/tumbler-marshal.list
@@ -1,7 +1,4 @@
-VOID:STRING,INT,STRING
-VOID:UINT,STRING,INT,STRING
-VOID:UINT,BOXED,INT,STRING,STRING
-VOID:STRING,INT,STRING
+VOID:STRING,UINT,INT,STRING
+VOID:UINT,BOXED,UINT,INT,STRING,STRING
 VOID:UINT,BOXED,STRING
 VOID:UINT,STRING
-VOID:UINT,POINTER,INT,STRING
diff --git a/tumbler/tumbler-thumbnailer.c b/tumbler/tumbler-thumbnailer.c
index 67f0fc8..27d3177 100644
--- a/tumbler/tumbler-thumbnailer.c
+++ b/tumbler/tumbler-thumbnailer.c
@@ -114,10 +114,11 @@ tumbler_thumbnailer_default_init (TumblerThumbnailerIface *klass)
                   G_STRUCT_OFFSET (TumblerThumbnailerIface, error),
                   NULL,
                   NULL,
-                  tumbler_marshal_VOID__STRING_INT_STRING,
+                  tumbler_marshal_VOID__STRING_UINT_INT_STRING,
                   G_TYPE_NONE,
-                  3,
+                  4,
                   G_TYPE_STRING,
+                  G_TYPE_UINT,
                   G_TYPE_INT,
                   G_TYPE_STRING);
 
diff --git a/tumbler/tumbler-thumbnailer.h b/tumbler/tumbler-thumbnailer.h
index 285626e..b983d4e 100644
--- a/tumbler/tumbler-thumbnailer.h
+++ b/tumbler/tumbler-thumbnailer.h
@@ -50,6 +50,7 @@ struct _TumblerThumbnailerIface
                       const gchar        *uri);
   void (*error)      (TumblerThumbnailer *thumbnailer,
                       const gchar        *failed_uri,
+                      GQuark              error_domain,
                       gint                error_code,
                       const gchar        *message);
   void (*unregister) (TumblerThumbnailer *thumbnailer);
diff --git a/tumblerd/tumbler-group-scheduler.c b/tumblerd/tumbler-group-scheduler.c
index ad6bda5..f756f7a 100644
--- a/tumblerd/tumbler-group-scheduler.c
+++ b/tumblerd/tumbler-group-scheduler.c
@@ -75,6 +75,7 @@ static void tumbler_group_scheduler_thread            (gpointer
                                                        gpointer                   user_data);
 static void tumbler_group_scheduler_thumbnailer_error (TumblerThumbnailer        *thumbnailer,
                                                        const gchar               *failed_uri,
+                                                       GQuark                     error_domain,
                                                        gint                       error_code,
                                                        const gchar               *message,
                                                        GList                    **uri_errors);
@@ -105,6 +106,7 @@ struct _TumblerGroupScheduler
 struct _UriError
 {
   guint  error_code;
+  GQuark error_domain;
   gchar *message;
   gchar *failed_uri;
 };
@@ -373,12 +375,14 @@ tumbler_group_scheduler_dequeue_request (TumblerSchedulerRequest *request,
 
 static UriError *
 uri_error_new (gint         code,
+               GQuark       domain,
                const gchar *uri,
                const gchar *message)
 {
   UriError *error;
 
   error = g_slice_new0 (UriError);
+  error->error_domain = domain;
   error->error_code = code;
   error->failed_uri = g_strdup (uri);
   error->message = g_strdup (message);
@@ -422,6 +426,7 @@ tumbler_group_scheduler_thread (gpointer data,
   GList                   *lp;
   guint                    n;
   gint                     error_code = 0;
+  GQuark                   error_domain = 0;
 
   g_return_if_fail (TUMBLER_IS_GROUP_SCHEDULER (scheduler));
   g_return_if_fail (request != NULL);
@@ -585,8 +590,11 @@ tumbler_group_scheduler_thread (gpointer data,
           uri_error = iter->data;
 
           /* we use the error code of the first failed URI */
-          if (iter == uri_errors) 
-            error_code = uri_error->error_code;
+          if (iter == uri_errors)
+            {
+              error_domain = uri_error->error_domain;
+              error_code = uri_error->error_code;
+            }
 
           if (uri_error->message != NULL)
             {
@@ -607,7 +615,7 @@ tumbler_group_scheduler_thread (gpointer data,
 
       /* forward the error signal */
       g_signal_emit_by_name (request->scheduler, "error", request->handle, 
-                             failed_uris, error_code, message->str, 
+                             failed_uris, error_domain, error_code, message->str,
                              request->origin);
 
       /* free the failed URIs array. Its contents are owned by the URI errors */
@@ -655,6 +663,7 @@ tumbler_group_scheduler_thread (gpointer data,
 static void
 tumbler_group_scheduler_thumbnailer_error (TumblerThumbnailer *thumbnailer,
                                            const gchar        *failed_uri,
+                                           GQuark              error_domain,
                                            gint                error_code,
                                            const gchar        *message,
                                            GList             **uri_errors)
@@ -667,7 +676,7 @@ tumbler_group_scheduler_thumbnailer_error (TumblerThumbnailer *thumbnailer,
   g_return_if_fail (uri_errors != NULL);
 
   /* allocate a new URI error */
-  error = uri_error_new (error_code, failed_uri, message);
+  error = uri_error_new (error_code, error_domain, failed_uri, message);
 
   /* add the error to the list */
   *uri_errors = g_list_prepend (*uri_errors, error);
diff --git a/tumblerd/tumbler-lifo-scheduler.c b/tumblerd/tumbler-lifo-scheduler.c
index ce09930..e19d811 100644
--- a/tumblerd/tumbler-lifo-scheduler.c
+++ b/tumblerd/tumbler-lifo-scheduler.c
@@ -71,6 +71,7 @@ static void tumbler_lifo_scheduler_thread            (gpointer
                                                       gpointer                   user_data);
 static void tumbler_lifo_scheduler_thumbnailer_error (TumblerThumbnailer        *thumbnailer,
                                                       const gchar               *failed_uri,
+                                                      GQuark                     error_domain,
                                                       gint                       error_code,
                                                       const gchar               *message,
                                                       TumblerSchedulerRequest   *request);
@@ -515,6 +516,7 @@ tumbler_lifo_scheduler_thread (gpointer data,
 static void
 tumbler_lifo_scheduler_thumbnailer_error (TumblerThumbnailer      *thumbnailer,
                                           const gchar             *failed_uri,
+                                          GQuark                   error_domain,
                                           gint                     error_code,
                                           const gchar             *message,
                                           TumblerSchedulerRequest *request)
@@ -528,7 +530,7 @@ tumbler_lifo_scheduler_thumbnailer_error (TumblerThumbnailer      *thumbnailer,
 
   /* forward the error signal */
   g_signal_emit_by_name (request->scheduler, "error", request->handle, failed_uris, 
-                         error_code, message, request->origin);
+                         error_domain, error_code, message, request->origin);
 }
 
 
diff --git a/tumblerd/tumbler-scheduler.c b/tumblerd/tumbler-scheduler.c
index d15dfa1..2110bc2 100644
--- a/tumblerd/tumbler-scheduler.c
+++ b/tumblerd/tumbler-scheduler.c
@@ -99,11 +99,12 @@ tumbler_scheduler_default_init (TumblerSchedulerIface *klass)
                   G_STRUCT_OFFSET (TumblerSchedulerIface, error),
                   NULL,
                   NULL,
-                  tumbler_marshal_VOID__UINT_BOXED_INT_STRING_STRING,
+                  tumbler_marshal_VOID__UINT_BOXED_UINT_INT_STRING_STRING,
                   G_TYPE_NONE,
-                  5,
+                  6,
                   G_TYPE_UINT,
                   G_TYPE_STRV,
+                  G_TYPE_UINT,
                   G_TYPE_INT,
                   G_TYPE_STRING,
                   G_TYPE_STRING);
diff --git a/tumblerd/tumbler-scheduler.h b/tumblerd/tumbler-scheduler.h
index 6f50a00..6423166 100644
--- a/tumblerd/tumbler-scheduler.h
+++ b/tumblerd/tumbler-scheduler.h
@@ -46,6 +46,7 @@ struct _TumblerSchedulerIface
   void (*error)    (TumblerScheduler        *scheduler,
                     guint32                  handle,
                     const gchar *const      *failed_uris,
+                    GQuark                   error_domain,
                     gint                     error_code,
                     const gchar             *message);
   void (*finished) (TumblerScheduler        *scheduler,
diff --git a/tumblerd/tumbler-service.c b/tumblerd/tumbler-service.c
index 94f06b5..8e6fbf1 100644
--- a/tumblerd/tumbler-service.c
+++ b/tumblerd/tumbler-service.c
@@ -95,6 +95,7 @@ static gboolean tumbler_service_get_flavors_cb  (TumblerExportedService  *skelet
 static void tumbler_service_scheduler_error    (TumblerScheduler   *scheduler,
                                                 guint32             handle,
                                                 const gchar *const *failed_uris,
+                                                GQuark              error_domain,
                                                 gint                error_code,
                                                 const gchar        *message,
                                                 const gchar        *origin,
@@ -425,6 +426,7 @@ static void
 tumbler_service_scheduler_error (TumblerScheduler   *scheduler,
                                  guint32             handle,
                                  const gchar *const *failed_uris,
+                                 GQuark              error_domain,
                                  gint                error_code,
                                  const gchar        *message,
                                  const gchar        *origin,
@@ -437,20 +439,34 @@ tumbler_service_scheduler_error (TumblerScheduler   *scheduler,
   g_return_if_fail (message != NULL && *message != '\0');
   g_return_if_fail (origin != NULL && *origin != '\0');
   g_return_if_fail (TUMBLER_IS_SERVICE (service));
-  
-  g_debug ("Error signal for job %d: Code %d, message: %s",
-           handle, error_code, message);
-  tumbler_util_dump_strv (G_LOG_DOMAIN, "URIs", failed_uris);
+
+  /* request cancelled at some level after being handled by the thumbnailer: no signal,
+   * just as if it had been cancelled before */
+  if (error_domain == G_IO_ERROR && error_code == G_IO_ERROR_CANCELLED)
+    return;
 
   info = g_slice_new0 (SchedulerIdleInfo);
 
   info->scheduler = g_object_ref (scheduler);
   info->handle = handle;
   info->uris = g_strdupv ((gchar **)failed_uris);
-  info->error_code = error_code;
-  info->message = g_strdup (message);
   info->origin = g_strdup (origin);
   info->service = g_object_ref (service);
+  if (error_domain == TUMBLER_ERROR)
+    {
+      info->error_code = error_code;
+      info->message = g_strdup (message);
+    }
+  else
+    {
+      info->error_code = TUMBLER_ERROR_OTHER_ERROR_DOMAIN;
+      info->message = g_strdup_printf ("(%s error, code %d) %s",
+                                       g_quark_to_string (error_domain), error_code, message);
+    }
+
+  g_debug ("Error signal for job %d: Code %d, message: %s",
+           handle, info->error_code, info->message);
+  tumbler_util_dump_strv (G_LOG_DOMAIN, "URIs", failed_uris);
 
   g_idle_add (tumbler_service_error_idle, info);
 }
@@ -783,7 +799,7 @@ tumbler_service_queue_cb (TumblerExportedService  *skeleton,
                                          service);
 
       /* emit an error signal */
-      tumbler_service_scheduler_error (scheduler, handle, uris, 
+      tumbler_service_scheduler_error (scheduler, handle, uris, TUMBLER_ERROR,
                                        TUMBLER_ERROR_UNSUPPORTED_FLAVOR, 
                                        TUMBLER_ERROR_MESSAGE_UNSUPPORTED_FLAVOR,
                                        scheduler_request->origin,
diff --git a/tumblerd/tumbler-specialized-thumbnailer.c b/tumblerd/tumbler-specialized-thumbnailer.c
index 01d9cee..85d18dd 100644
--- a/tumblerd/tumbler-specialized-thumbnailer.c
+++ b/tumblerd/tumbler-specialized-thumbnailer.c
@@ -361,7 +361,8 @@ thumbnailer_proxy_g_signal_cb (GDBusProxy *proxy,
           g_variant_get (parameters, "(u&si&s)", &handle, &uri, &error_code, &error_msg);
           if (info->handle == handle) 
             {
-              g_signal_emit_by_name (info->thumbnailer, "error", uri, error_code, error_msg);
+              g_signal_emit_by_name (info->thumbnailer, "error", uri,
+                                     TUMBLER_ERROR, error_code, error_msg);
             }
         }
     }
@@ -436,7 +437,8 @@ tumbler_specialized_thumbnailer_create (TumblerThumbnailer *thumbnailer,
           if (!g_cond_wait_until (&sinfo.condition, &sinfo.mutex, end_time))
             {
               message = g_strdup (_("Failed to call the specialized thumbnailer: timeout"));
-              g_signal_emit_by_name (thumbnailer, "error", uri, 1, message);
+              g_signal_emit_by_name (thumbnailer, "error", uri,
+                                     TUMBLER_ERROR, TUMBLER_ERROR_CONNECTION_ERROR, message);
               g_free (message);
             }
         }
@@ -446,7 +448,8 @@ tumbler_specialized_thumbnailer_create (TumblerThumbnailer *thumbnailer,
     {
       message = g_strdup_printf (_("Failed to call the specialized thumbnailer: %s"),
                                  error->message);
-      g_signal_emit_by_name (thumbnailer, "error", uri, 1, message);
+      g_signal_emit_by_name (thumbnailer, "error", uri,
+                             TUMBLER_ERROR, TUMBLER_ERROR_CONNECTION_ERROR, message);
       g_free (message);
       g_clear_error (&error);
     }