How to decrypt signatures with gpgme?

[Florian Schwind]

Hello List,

when I create a signature with "gpg --sign", I'm able to use "gpg 
--decrypt" to get the plaintext from the signature.

When I'm try to to this using gpgme resp.

gpgme_op_decrypt (gpgme_ctx_t ctx, gpgme_data_t cipher, gpgme_data_t plain)

I'm getting a GPG_ERR_NO_DATA error if cipher does not contain any data 
to decrypt.

So is there a way to get the plaintext from the signature using gpgme?

Thanks
  Florian