Get the main Gtk struct
the main Gtk struct as a void*
Checks if stream can be written.
Attempts to write up to count bytes from buffer to stream, as with OutputStream.write. If stream is not currently writable, this will immediately return G_IO_ERROR_WOULD_BLOCK, and you can use g_pollable_output_stream_create_source() to create a glib.Source that will be triggered when stream is writable.