thumbnailer: Always prefer the backend provided preview

If a preview exists for a particular file, in particular a preview icon
for videos and images on external devices, prefer those to running a
script.

https://bugzilla.gnome.org/show_bug.cgi?id=738503
origin commit:
https://gitlab.gnome.org/GNOME/gnome-desktop/commit/370b985
https://gitlab.gnome.org/GNOME/gnome-desktop/commit/e629e46
https://gitlab.gnome.org/GNOME/gnome-desktop/commit/a15db1d
https://gitlab.gnome.org/GNOME/gnome-desktop/commit/fc19c94

1 files changed, 64 insertions, 2 deletions

diff --git a/libmate-desktop/mate-desktop-thumbnail.c b/libmate-desktop/mate-desktop-thumbnail.c
index 7802684..b00f155 100644
--- a/libmate-desktop/mate-desktop-thumbnail.c
+++ b/libmate-desktop/mate-desktop-thumbnail.c
@@ -948,6 +948,64 @@ expand_thumbnailing_script (const char *script,
   return NULL;
 }
 
+static GdkPixbuf *
+get_preview_thumbnail (const char *uri,
+                       int         size)
+{
+    GdkPixbuf *pixbuf;
+    GFile *file;
+    GFileInfo *file_info;
+    GInputStream *input_stream;
+    GObject *object;
+
+    g_return_val_if_fail (uri != NULL, NULL);
+
+    input_stream = NULL;
+
+    file = g_file_new_for_uri (uri);
+
+    /* First see if we can get an input stream via preview::icon  */
+    file_info = g_file_query_info (file,
+                                   G_FILE_ATTRIBUTE_PREVIEW_ICON,
+                                   G_FILE_QUERY_INFO_NONE,
+                                   NULL,  /* GCancellable */
+                                   NULL); /* return location for GError */
+    g_object_unref (file);
+
+    if (file_info == NULL)
+      return NULL;
+
+    object = g_file_info_get_attribute_object (file_info,
+                                               G_FILE_ATTRIBUTE_PREVIEW_ICON);
+    if (object)
+        g_object_ref (object);
+    g_object_unref (file_info);
+
+    if (!object)
+      return NULL;
+    if (!G_IS_LOADABLE_ICON (object)) {
+      g_object_unref (object);
+      return NULL;
+    }
+
+    input_stream = g_loadable_icon_load (G_LOADABLE_ICON (object),
+                                         0,     /* size */
+                                         NULL,  /* return location for type */
+                                         NULL,  /* GCancellable */
+                                         NULL); /* return location for GError */
+    g_object_unref (object);
+
+    if (!input_stream)
+      return NULL;
+
+    pixbuf = gdk_pixbuf_new_from_stream_at_scale (input_stream,
+                                                  size, size,
+                                                  TRUE, NULL, NULL);
+    g_object_unref (input_stream);
+
+    return pixbuf;
+}
+
 /**
  * mate_desktop_thumbnail_factory_generate_thumbnail:
  * @factory: a #MateDesktopThumbnailFactory
@@ -965,8 +1023,8 @@ expand_thumbnailing_script (const char *script,
  **/
 GdkPixbuf *
 mate_desktop_thumbnail_factory_generate_thumbnail (MateDesktopThumbnailFactory *factory,
-						    const char            *uri,
-						    const char            *mime_type)
+                                                   const char                  *uri,
+                                                   const char                  *mime_type)
 {
   GdkPixbuf *pixbuf;
   char *script, *expanded_script;
@@ -985,6 +1043,10 @@ mate_desktop_thumbnail_factory_generate_thumbnail (MateDesktopThumbnailFactory *
 
   pixbuf = NULL;
 
+  pixbuf = get_preview_thumbnail (uri, size);
+  if (pixbuf != NULL)
+    return pixbuf;
+
   script = NULL;
   g_mutex_lock (&factory->priv->lock);
   if (!mate_desktop_thumbnail_factory_is_disabled (factory, mime_type))