the I/O priority of the request. E.g. G_PRIORITY_LOW, G_PRIORITY_DEFAULT or G_PRIORITY_HIGH.
optional gio.Cancellable 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 gsv.SourceBuffer See the GAsyncResult documentation to know how to use this function.