[gnome-photos/wip/rishi/import-8: 3/5] item-manager: Do not create an item if one already exists

[Debarshi Ray <debarshir src gnome org>]

commit a0bd89a0919177af81c7b0d7eaba32f0348b7df9
Author: Debarshi Ray <debarshir gnome org>
Date:   Tue Feb 6 00:34:16 2018 +0100

    item-manager: Do not create an item if one already exists
    
    The goal is to have only one BaseItem instance per Tracker URN per
    SearchContext. However, that's not the case right now because
    CollectionIconWatcher creates its own BaseItems to keep a collection's
    thumbnail synchronized with its contents.
    
    A subsequent commit will add a dialog to add items that are going to
    be imported from an attached device to a collection. This dialog will
    need a list of all collection BaseItems, which might exceed those that
    are currently present in ItemManager and being rendered by the various
    ViewContainers.
    
    This is a good time to take a step towards the end goal of having only
    one BaseItem instance per Tracker URN.
    
    The easiest thing to do is to not create a new BaseItem if one already
    exists in ItemManager. This also doesn't involve any complication
    around whether to initiate thumbnailing or not because the dialog
    doesn't require thumbnails anyway and would just re-use whatever is
    already available.
    
    In the future, BaseItems that are created out-of-band should be
    cached. However, that would require carefully deciding whether and
    when to initiate thumbnailing or not.
    
    https://gitlab.gnome.org/GNOME/gnome-photos/issues/29

 src/photos-item-manager.c | 84 +++++++++++++++++++++++++++--------------------
 1 file changed, 49 insertions(+), 35 deletions(-)
---
diff --git a/src/photos-item-manager.c b/src/photos-item-manager.c
index db97a19a..4dea5800 100644
--- a/src/photos-item-manager.c
+++ b/src/photos-item-manager.c
@@ -1287,8 +1287,9 @@ photos_item_manager_create_item (PhotosItemManager *self,
                                  TrackerSparqlCursor *cursor,
                                  gboolean create_thumbnails)
 {
-  GType type;
+  PhotosBaseItem *item;
   PhotosBaseItem *ret_val = NULL;
+  const gchar *id;
 
   g_return_val_if_fail (PHOTOS_IS_ITEM_MANAGER (self), NULL);
   g_return_val_if_fail (base_item_type == G_TYPE_NONE
@@ -1296,52 +1297,65 @@ photos_item_manager_create_item (PhotosItemManager *self,
                             && g_type_is_a (base_item_type, PHOTOS_TYPE_BASE_ITEM)), NULL);
   g_return_val_if_fail (TRACKER_SPARQL_IS_CURSOR (cursor), NULL);
 
-  if (base_item_type == G_TYPE_NONE)
+  id = tracker_sparql_cursor_get_string (cursor, PHOTOS_QUERY_COLUMNS_URN, NULL);
+  item = PHOTOS_BASE_ITEM (photos_base_manager_get_object_by_id (PHOTOS_BASE_MANAGER (self), id));
+  if (item != NULL)
     {
-      GIOExtension *extension;
-      g_auto (GStrv) split_identifier = NULL;
-      const gchar *extension_name = "local";
-      g_autofree gchar *identifier = NULL;
+      ret_val = g_object_ref (item);
+    }
+  else
+    {
+      GType type;
 
-      identifier = g_strdup (tracker_sparql_cursor_get_string (cursor, PHOTOS_QUERY_COLUMNS_IDENTIFIER, 
NULL));
-      if (identifier != NULL)
+      if (base_item_type == G_TYPE_NONE)
         {
-          split_identifier = g_strsplit (identifier, ":", 4);
-
-          if (photos_item_manager_cursor_is_collection (cursor))
+          GIOExtension *extension;
+          g_auto (GStrv) split_identifier = NULL;
+          const gchar *extension_name = "local";
+          g_autofree gchar *identifier = NULL;
+
+          identifier = g_strdup (tracker_sparql_cursor_get_string (cursor,
+                                                                   PHOTOS_QUERY_COLUMNS_IDENTIFIER,
+                                                                   NULL));
+          if (identifier != NULL)
             {
-              /* Its a collection. */
-              extension_name = split_identifier[2];
+              split_identifier = g_strsplit (identifier, ":", 4);
+
+              if (photos_item_manager_cursor_is_collection (cursor))
+                {
+                  /* Its a collection. */
+                  extension_name = split_identifier[2];
+                }
+              else
+                {
+                  /* Its a normal photo item. */
+                  if (g_strv_length (split_identifier) > 1)
+                    extension_name = split_identifier[0];
+                }
             }
-          else
+
+          extension = g_io_extension_point_get_extension_by_name (self->extension_point, extension_name);
+          if (G_UNLIKELY (extension == NULL))
             {
-              /* Its a normal photo item. */
-              if (g_strv_length (split_identifier) > 1)
-                extension_name = split_identifier[0];
+              g_warning ("Unable to find extension %s for identifier: %s", extension_name, identifier);
+              goto out;
             }
-        }
 
-      extension = g_io_extension_point_get_extension_by_name (self->extension_point, extension_name);
-      if (G_UNLIKELY (extension == NULL))
+          type = g_io_extension_get_type (extension);
+        }
+      else
         {
-          g_warning ("Unable to find extension %s for identifier: %s", extension_name, identifier);
-          goto out;
+          type = base_item_type;
         }
 
-      type = g_io_extension_get_type (extension);
-    }
-  else
-    {
-      type = base_item_type;
-    }
+      g_return_val_if_fail (type != G_TYPE_NONE, NULL);
+      g_return_val_if_fail (type != PHOTOS_TYPE_BASE_ITEM && g_type_is_a (type, PHOTOS_TYPE_BASE_ITEM), 
NULL);
 
-  g_return_val_if_fail (type != G_TYPE_NONE, NULL);
-  g_return_val_if_fail (type != PHOTOS_TYPE_BASE_ITEM && g_type_is_a (type, PHOTOS_TYPE_BASE_ITEM), NULL);
-
-  ret_val = PHOTOS_BASE_ITEM (g_object_new (type,
-                                            "cursor", cursor,
-                                            "failed-thumbnailing", !create_thumbnails,
-                                            NULL));
+      ret_val = PHOTOS_BASE_ITEM (g_object_new (type,
+                                                "cursor", cursor,
+                                                "failed-thumbnailing", !create_thumbnails,
+                                                NULL));
+    }
 
  out:
   return ret_val;