The login widget included with XenWord allows webmasters to integrate Twitter, Facebook, and Google. Unfortunately the code is terrible and I've been wanting to fix it.
Currently, the widget file must be opened and the Google code and secret must be modified. I'll try to pull this information from the XenForo options.
Here is some easy code to pull the information from the XenForo options.
PHP:
$options = XenForo_Application::get('options');
$googleClientId = $options->googleClientId;
$googleClientSecret = $options->googleClientSecret;
At this moment, I'm uncertain about the replacement of this information: code=__CODE__&csrf=7TMaP5TirQ9UhUh0
I believe the information will have to be sanitized, too. So I'm looking into it.