testtreelistmodel: Make the directory loading async

This is way more complicated than it should be, because it requires
manually limiting the number of open file enumerators.

On the other hand, it exhaustively tests the items-changed emission of
all involved listmodels because those signals come in pretty much
randomly.

It's also 50% slower than the sync version, with the caeat that the sync
version only shows the UI after it's done loading, while this version
shows it right away.

1 files changed, 100 insertions, 19 deletions

diff --git a/tests/testtreelistmodel.c b/tests/testtreelistmodel.c
index 6b3fa7a9c9..42ec20a3b2 100644
--- a/tests/testtreelistmodel.c
+++ b/tests/testtreelistmodel.c
@@ -2,42 +2,123 @@
 
 #define ROWS 30
 
-static GListModel *
-create_list_model_for_directory (gpointer file,
-                                 gpointer unused)
+GSList *pending;
+guint active = 0;
+
+static void
+got_files (GObject      *enumerate,
+           GAsyncResult *res,
+           gpointer      store);
+
+static gboolean
+start_enumerate (GListStore *store)
 {
   GFileEnumerator *enumerate;
-  GListStore *store;
-  GFile *child;
-  GFileInfo *info;
-
-  if (g_file_query_file_type (file, G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS, NULL) != G_FILE_TYPE_DIRECTORY)
-    return NULL;
+  GFile *file = g_object_get_data (G_OBJECT (store), "file");
+  GError *error = NULL;
 
   enumerate = g_file_enumerate_children (file,
                                          G_FILE_ATTRIBUTE_STANDARD_TYPE
                                          "," G_FILE_ATTRIBUTE_STANDARD_NAME,
                                          0,
                                          NULL,
-                                         NULL);
+                                         &error);
+
   if (enumerate == NULL)
-    return NULL;
+    {
+      if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_TOO_MANY_OPEN_FILES))
+        {
+          g_clear_error (&error);
+          pending = g_slist_prepend (pending, g_object_ref (store));
+          return TRUE;
+        }
+
+      g_clear_error (&error);
+      g_object_unref (store);
+      return FALSE;
+    }
 
-  store = g_list_store_new (G_TYPE_FILE);
+  if (active > 20)
+    {
+      g_object_unref (enumerate);
+      pending = g_slist_prepend (pending, g_object_ref (store));
+      return TRUE;
+    }
 
-  while (g_file_enumerator_iterate (enumerate, &info, NULL, NULL, NULL))
+  active++;
+  g_file_enumerator_next_files_async (enumerate,
+                                      g_file_is_native (file) ? 5000 : 100,
+                                      G_PRIORITY_DEFAULT_IDLE,
+                                      NULL,
+                                      got_files,
+                                      g_object_ref (store));
+
+  g_object_unref (enumerate);
+  return TRUE;
+}
+
+static void
+got_files (GObject      *enumerate,
+           GAsyncResult *res,
+           gpointer      store)
+{
+  GList *l, *files;
+  GFile *file = g_object_get_data (store, "file");
+  GPtrArray *array;
+
+  files = g_file_enumerator_next_files_finish (G_FILE_ENUMERATOR (enumerate), res, NULL);
+  if (files == NULL)
+    {
+      g_object_unref (store);
+      if (pending)
+        {
+          GListStore *store = pending->data;
+          pending = g_slist_remove (pending, store);
+          start_enumerate (store);
+        }
+      active--;
+      return;
+    }
+
+  array = g_ptr_array_new ();
+  g_ptr_array_new_with_free_func (g_object_unref);
+  for (l = files; l; l = l->next)
     {
-      if (info == NULL)
-        break;
+      GFileInfo *info = l->data;
+      GFile *child;
 
       child = g_file_get_child (file, g_file_info_get_name (info));
-      g_list_store_append (store, child);
-      g_object_unref (child);
+      g_ptr_array_add (array, child);
     }
+  g_list_free_full (files, g_object_unref);
 
-  g_object_unref (enumerate);
+  g_list_store_splice (store, g_list_model_get_n_items (store), 0, array->pdata, array->len);
+  g_ptr_array_unref (array);
 
-  return G_LIST_MODEL (store);
+  g_file_enumerator_next_files_async (G_FILE_ENUMERATOR (enumerate),
+                                      g_file_is_native (file) ? 5000 : 100,
+                                      G_PRIORITY_DEFAULT_IDLE,
+                                      NULL,
+                                      got_files,
+                                      store);
+}
+
+static GListModel *
+create_list_model_for_directory (gpointer file,
+                                 gpointer unused)
+{
+  GListStore *store;
+
+  if (g_file_query_file_type (file, G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS, NULL) != G_FILE_TYPE_DIRECTORY)
+    return NULL;
+
+  store = g_list_store_new (G_TYPE_FILE);
+  g_object_set_data_full (G_OBJECT (store), "file", g_object_ref (file), g_object_unref);
+
+  if (start_enumerate (store))
+    return G_LIST_MODEL (store);
+  else
+    return NULL;
 }
 
 static GtkWidget *