isWritable
Checks if @stream can be written.
Note that some stream types may not be able to implement this 100% reliably, and it is possible that a call to g_output_stream_write() after this returns true would still block. To guarantee non-blocking behavior, you should always use g_pollable_output_stream_write_nonblocking(), which will return a %G_IO_ERROR_WOULD_BLOCK error rather than blocking.
Return
true if @stream is writable, false if not. If an error has occurred on @stream, this will result in g_pollable_output_stream_is_writable() returning true, and the next attempt to write will return the error.
Since
2.28