the I/O priority of the request. E.g. %G_PRIORITY_LOW, %G_PRIORITY_DEFAULT or %G_PRIORITY_HIGH.
optional #GCancellable object, %NULL to ignore.
function to call back with progress information, or %NULL if progress information is not needed.
user data to pass to @progress_callback.
function to call on @progress_callback_data when the @progress_callback is no longer needed, or %NULL.
a #GAsyncReadyCallback to call when the request is satisfied.
user data to pass to @callback.
3.14
Loads asynchronously the file or input stream contents into the #GtkSourceBuffer. See the #GAsyncResult documentation to know how to use this function.