Eliminate usage of GVolumeMonitor if no FmFolder object was created.

If libfm is used without FmFolder usage then there is no reason to run
the volume monitor. Therefore it should be activated when some folder
was opened and deactivated when all of them were closed.
This may be a culprit of external green drives been waked up (see the
http://sourceforge.net/p/lxde/bugs/751/ bugreport against lxpanel).

NEWS

@@ -27,6 +27,8 @@
 
 * Rewritten broken rubberband rendering in icon view for GTK3.
 
+* Eliminated usage of GVolumeMonitor if no FmFolder object was created.
+
 
 Changes on 1.2.3 since 1.2.2:
 

src/base/fm-folder.c

@@ -91,6 +91,7 @@ struct _FmFolder
 };
 
 static void fm_folder_dispose(GObject *object);
+static void fm_folder_finalize(GObject *object);
 static void fm_folder_content_changed(FmFolder* folder);
 
 static GList* _fm_folder_get_file_by_path(FmFolder* folder, FmPath *path);
@@ -99,9 +100,13 @@ G_DEFINE_TYPE(FmFolder, fm_folder, G_TYPE_OBJECT);
 
 static guint signals[N_SIGNALS];
 static GHashTable* hash = NULL;
+static int hash_uses = 0;
 
 static GVolumeMonitor* volume_monitor = NULL;
 
+static void on_mount_added(GVolumeMonitor* vm, GMount* mount, gpointer user_data);
+static void on_mount_removed(GVolumeMonitor* vm, GMount* mount, gpointer user_data);
+
 /* used for on_query_filesystem_info_finished() to lock folder */
 G_LOCK_DEFINE_STATIC(query);
 /* protects hash access */
@@ -115,6 +120,7 @@ static void fm_folder_class_init(FmFolderClass *klass)
     FmFolderClass* folder_class;
     g_object_class = G_OBJECT_CLASS(klass);
     g_object_class->dispose = fm_folder_dispose;
+    g_object_class->finalize = fm_folder_finalize;
     fm_folder_parent_class = (GObjectClass*)g_type_class_peek(G_TYPE_OBJECT);
 
     folder_class = FM_FOLDER_CLASS(klass);
@@ -336,6 +342,19 @@ static void fm_folder_class_init(FmFolderClass *klass)
 static void fm_folder_init(FmFolder *folder)
 {
     folder->files = fm_file_info_list_new();
+    G_LOCK(hash);
+    if (G_UNLIKELY(hash_uses == 0))
+    {
+        hash = g_hash_table_new((GHashFunc)fm_path_hash, (GEqualFunc)fm_path_equal);
+        volume_monitor = g_volume_monitor_get();
+        if (G_LIKELY(volume_monitor))
+        {
+            g_signal_connect(volume_monitor, "mount-added", G_CALLBACK(on_mount_added), NULL);
+            g_signal_connect(volume_monitor, "mount-removed", G_CALLBACK(on_mount_removed), NULL);
+        }
+    }
+    hash_uses++;
+    G_UNLOCK(hash);
 }
 
 static gboolean on_idle_reload(FmFolder* folder)
@@ -831,7 +850,7 @@ static FmFolder* fm_folder_get_internal(FmPath* path, GFile* gf)
      * to associate all kinds of data structures with FmPaths? */
 
     G_LOCK(hash);
-    folder = (FmFolder*)g_hash_table_lookup(hash, path);
+    folder = hash ? (FmFolder*)g_hash_table_lookup(hash, path) : NULL;
 
     if( G_UNLIKELY(!folder) )
     {
@@ -966,6 +985,27 @@ static void fm_folder_dispose(GObject *object)
     (* G_OBJECT_CLASS(fm_folder_parent_class)->dispose)(object);
 }
 
+static void fm_folder_finalize(GObject *object)
+{
+    G_LOCK(hash);
+    hash_uses--;
+    if (G_UNLIKELY(hash_uses == 0))
+    {
+        g_hash_table_destroy(hash);
+        hash = NULL;
+        if(volume_monitor)
+        {
+            g_signal_handlers_disconnect_by_func(volume_monitor, on_mount_added, NULL);
+            g_signal_handlers_disconnect_by_func(volume_monitor, on_mount_removed, NULL);
+            g_object_unref(volume_monitor);
+            volume_monitor = NULL;
+        }
+    }
+    G_UNLOCK(hash);
+
+    (* G_OBJECT_CLASS(fm_folder_parent_class)->finalize)(object);
+}
+
 /**
  * fm_folder_from_gfile
  * @gf: #GFile file descriptor
@@ -1423,8 +1463,11 @@ void fm_folder_query_filesystem_info(FmFolder* folder)
  */
 FmFolder *fm_folder_find_by_path(FmPath *path)
 {
-    FmFolder *folder = (FmFolder*)g_hash_table_lookup(hash, path);
+    FmFolder *folder;
 
+    G_LOCK(hash);
+    folder = hash ? (FmFolder*)g_hash_table_lookup(hash, path) : NULL;
+    G_UNLOCK(hash);
     return folder ? g_object_ref(folder) : NULL;
 }
 
@@ -1611,24 +1654,8 @@ static void on_mount_removed(GVolumeMonitor* vm, GMount* mount, gpointer user_da
 
 void _fm_folder_init()
 {
-    hash = g_hash_table_new((GHashFunc)fm_path_hash, (GEqualFunc)fm_path_equal);
-    volume_monitor = g_volume_monitor_get();
-    if(G_LIKELY(volume_monitor))
-    {
-        g_signal_connect(volume_monitor, "mount-added", G_CALLBACK(on_mount_added), NULL);
-        g_signal_connect(volume_monitor, "mount-removed", G_CALLBACK(on_mount_removed), NULL);
-    }
 }
 
 void _fm_folder_finalize()
 {
-    g_hash_table_destroy(hash);
-    hash = NULL;
-    if(volume_monitor)
-    {
-        g_signal_handlers_disconnect_by_func(volume_monitor, on_mount_added, NULL);
-        g_signal_handlers_disconnect_by_func(volume_monitor, on_mount_removed, NULL);
-        g_object_unref(volume_monitor);
-        volume_monitor = NULL;
-    }
 }