[gnome-control-center] background: always pass a cancellable down to I/O operations

[Cosimo Cecchi <cosimoc src gnome org>]

commit 761f5f0b8bc9c6794f5df51041bfa404abec6b4c
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Mon Jun 11 08:59:09 2012 -0400

    background: always pass a cancellable down to I/O operations
    
    So they will be properly cancelled when the panel is disposed.
    Also, check early if the operation was cancelled, since it's not safe to
    assume the data of the callback is valid anymore before that point.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=672572

 panels/background/bg-pictures-source.c |   50 +++++++++++++++++++------------
 1 files changed, 31 insertions(+), 19 deletions(-)
---
diff --git a/panels/background/bg-pictures-source.c b/panels/background/bg-pictures-source.c
index 2c04695..34ac849 100644
--- a/panels/background/bg-pictures-source.c
+++ b/panels/background/bg-pictures-source.c
@@ -171,16 +171,29 @@ picture_scaled (GObject *source_object,
                 GAsyncResult *res,
                 gpointer user_data)
 {
-  BgPicturesSource *bg_source = BG_PICTURES_SOURCE (user_data);
+  BgPicturesSource *bg_source;
   CcBackgroundItem *item;
   GError *error = NULL;
   GdkPixbuf *pixbuf;
   const char *source_url;
   const char *software;
-
   GtkTreeIter iter;
   GtkListStore *store;
 
+  pixbuf = gdk_pixbuf_new_from_stream_finish (res, &error);
+  if (pixbuf == NULL)
+    {
+      if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+        g_warning ("Failed to load image: %s", error->message);
+
+      g_error_free (error);
+      return;
+    }
+
+  /* since we were not cancelled, we can now cast user_data
+   * back to BgPicturesSource.
+   */
+  bg_source = BG_PICTURES_SOURCE (user_data);
   store = bg_source_get_liststore (BG_SOURCE (bg_source));
   item = g_object_get_data (source_object, "item");
 
@@ -194,15 +207,6 @@ picture_scaled (GObject *source_object,
                                         1,
                                         GTK_SORT_ASCENDING);
 
-  pixbuf = gdk_pixbuf_new_from_stream_finish (res, &error);
-  if (pixbuf == NULL)
-    {
-      g_warning ("Failed to load image: %s", error->message);
-      g_error_free (error);
-      g_object_unref (item);
-      return;
-    }
-
   /* Ignore screenshots */
   software = gdk_pixbuf_get_option (pixbuf, "tEXt::Software");
   if (software != NULL &&
@@ -259,7 +263,7 @@ picture_opened_for_read (GObject *source_object,
                          GAsyncResult *res,
                          gpointer user_data)
 {
-  BgPicturesSource *bg_source = BG_PICTURES_SOURCE (user_data);
+  BgPicturesSource *bg_source;
   CcBackgroundItem *item;
   GFileInputStream *stream;
   GError *error = NULL;
@@ -268,22 +272,28 @@ picture_opened_for_read (GObject *source_object,
   stream = g_file_read_finish (G_FILE (source_object), res, &error);
   if (stream == NULL)
     {
-      char *filename;
+      if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+        {
+          char *filename = g_file_get_path (G_FILE (source_object));
+          g_warning ("Failed to load picture '%s': %s", filename, error->message);
+          g_free (filename);
+        }
 
-      filename = g_file_get_path (G_FILE (source_object));
-      g_warning ("Failed to load picture '%s': %s", filename, error->message);
-      g_free (filename);
       g_error_free (error);
       g_object_unref (item);
       return;
     }
 
-  g_object_set_data (G_OBJECT (stream), "item", item);
+  /* since we were not cancelled, we can now cast user_data
+   * back to BgPicturesSource.
+   */
+  bg_source = BG_PICTURES_SOURCE (user_data);
 
+  g_object_set_data (G_OBJECT (stream), "item", item);
   gdk_pixbuf_new_from_stream_at_scale_async (G_INPUT_STREAM (stream),
                                              THUMBNAIL_WIDTH, THUMBNAIL_HEIGHT,
                                              TRUE,
-                                             NULL,
+                                             bg_source->priv->cancellable,
                                              picture_scaled, bg_source);
   g_object_unref (stream);
 }
@@ -329,7 +339,9 @@ add_single_file (BgPicturesSource *bg_source,
     g_object_set (G_OBJECT (item), "source-url", source_uri, NULL);
 
   g_object_set_data (G_OBJECT (file), "item", item);
-  g_file_read_async (file, 0, NULL, picture_opened_for_read, bg_source);
+  g_file_read_async (file, G_PRIORITY_DEFAULT,
+                     bg_source->priv->cancellable,
+                     picture_opened_for_read, bg_source);
   g_object_unref (file);
   return TRUE;
 }