[gnome-photos/wip/rishi/collection: 3/43] tracker-controller: React to Source changes only if a Query is active

[Debarshi Ray <debarshir src gnome org>]

commit dd204a28332d1577da8c3ff641e3b93c8067a5d6
Author: Debarshi Ray <debarshir gnome org>
Date:   Fri Feb 2 03:15:45 2018 +0100

    tracker-controller: React to Source changes only if a Query is active
    
    TrackerControllers with a delayed start might not have issued a Query
    until its mode is used. eg., SEARCH. If the Sources change before the
    mode is used, which can happen during startup, the TrackerController
    will queue a refresh even though there isn't a current Query. This is
    a problem because without a current Query it's not possible to check
    if the refresh is actually necessary or not.
    
    So far, this has been working purely by accident because
    TrackerSearchController detects the changes in search criteria before
    Embed. This means that TrackerSearchController is able to slip in a
    Query before Embed switches the mode and causes TrackerController to
    process the queued refresh.
    
    Relying on the order in which signal handlers get invoked is fragile.
    It can change if things are moved around and the order in which they
    are connected to the signal gets altered. It's better to remove the
    possibility of breakage due to such reasons.

 src/photos-tracker-controller.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)
---
diff --git a/src/photos-tracker-controller.c b/src/photos-tracker-controller.c
index ccf81aba..a8109158 100644
--- a/src/photos-tracker-controller.c
+++ b/src/photos-tracker-controller.c
@@ -382,18 +382,22 @@ static void
 photos_tracker_controller_refresh_for_source (PhotosTrackerController *self)
 {
   PhotosTrackerControllerPrivate *priv;
-  PhotosSource *source;
 
   priv = photos_tracker_controller_get_instance_private (self);
 
-  source = photos_query_get_source (priv->current_query);
-  if (source != NULL)
+  if (priv->current_query != NULL)
     {
-      const gchar *id;
+      PhotosSource *source;
 
-      id = photos_filterable_get_id (PHOTOS_FILTERABLE (source));
-      if (g_strcmp0 (id, PHOTOS_SOURCE_STOCK_ALL) == 0)
-        photos_tracker_controller_refresh_internal (self, PHOTOS_TRACKER_REFRESH_FLAGS_NONE);
+      source = photos_query_get_source (priv->current_query);
+      if (source != NULL)
+        {
+          const gchar *id;
+
+          id = photos_filterable_get_id (PHOTOS_FILTERABLE (source));
+          if (g_strcmp0 (id, PHOTOS_SOURCE_STOCK_ALL) == 0)
+            photos_tracker_controller_refresh_internal (self, PHOTOS_TRACKER_REFRESH_FLAGS_NONE);
+        }
     }
 
   priv->refresh_pending = FALSE;