Support specialized thumbnailers and overrides files properly.

This required some major changes, most of which are documented in the
source code. It still needs to be tested but it should be fine. The
mutex locks in TumblerManager could probably be optimized and some other
parts are not optimal with regards to speed and memory usage yet.

All in all, what's done now is:
  - overrides files are parsed into override info structs and kept in
    a (hashkey -> override info list) hash table
  - each of these override info lists is sorted in the order of the
    directories the overrides files are located in (with higher priority
    directories coming first)
  - the first override info in each list determines which specialized
    thumbnailer is set as preferred for the corresponding hash key in
    the registry
  - thumbnailer service files are parsed into thumbnailer info structs
    and kept in a (basename -> thumbnailer info list) hash table
  - each of these thumbnailer info lists is sorted in the order of
    the directories the thumbnailer service infos come from
  - the first thumbnailers in each list are added to the registry
  - whenever something changes on the disk, this internal representation
    is updated

1 files changed, 23 insertions, 1 deletions

diff --git a/tumbler/tumbler-thumbnailer.c b/tumbler/tumbler-thumbnailer.c
index 588cfa2..d40c1b8 100644
--- a/tumbler/tumbler-thumbnailer.c
+++ b/tumbler/tumbler-thumbnailer.c
@@ -125,7 +125,7 @@ tumbler_thumbnailer_class_init (TumblerThumbnailerIface *klass)
   tumbler_thumbnailer_signals[SIGNAL_UNREGISTER] =
     g_signal_new ("unregister",
                   TUMBLER_TYPE_THUMBNAILER,
-                  G_SIGNAL_RUN_LAST,
+                  G_SIGNAL_RUN_LAST | G_SIGNAL_NO_HOOKS,
                   G_STRUCT_OFFSET (TumblerThumbnailerIface, unregister),
                   NULL,
                   NULL,
@@ -191,6 +191,28 @@ tumbler_thumbnailer_get_uri_schemes (TumblerThumbnailer *thumbnailer)
 
 
 
+gboolean
+tumbler_thumbnailer_supports_hash_key (TumblerThumbnailer *thumbnailer,
+                                       const gchar        *hash_key)
+{
+  gboolean supported = FALSE;
+  GStrv    hash_keys;
+  guint    n;
+
+  g_return_val_if_fail (TUMBLER_IS_THUMBNAILER (thumbnailer), FALSE);
+  g_return_val_if_fail (hash_key != NULL && *hash_key != '\0', FALSE);
+
+  hash_keys = tumbler_thumbnailer_get_hash_keys (thumbnailer);
+
+  for (n = 0; !supported && hash_keys != NULL && hash_keys[n] != NULL; ++n)
+    if (g_strcmp0 (hash_keys[n], hash_key) == 0)
+      supported = TRUE;
+
+  return supported;
+}
+
+
+
 TumblerThumbnailer **
 tumbler_thumbnailer_array_copy (TumblerThumbnailer **thumbnailers,
                                 guint                length)