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.

11 files changed, 60 insertions, 35 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