Default value login form from URL argument

While I understand the interest in simplifying the registration experience, I would not recommend what you're trying. First and foremost, it implies that you're not using any sort of user activation. At first, that may be ok. When a spam bot finds your site, and they will, and detects that user accounts can be created without any sort of activation requirement, you will find your site flooded with bogus accounts. It happens to all sites.

If you choose to go forward with it, there is some PHP we could provide to get the email address out of the URL and pre-fill the username field. I do see how that could be nice.

For password though, there really isn't a good way to 'hand' off secret credentials like your asking and pre-populate a password field. Once an input field is marked as a type="password", there are a lot of limitations within the browser and Javascript on how you can manipulate that data.

I hope that helps explain, but again, for good site hygiene and maintenance, I'd recommend enabling some form of activation.

Thanks,
Alex

If there is a way of enable activation link, and the activation link get the user logged automatically, i'm for it
i'm sure there is a way to create a temporary token within the link non?
is there a feature like this ?

There's not anything that we know of like this. However, we agree it's a good idea to allow for login through a URL. If you find something, let us know and we may investigate it further as well.

But, how can I pass url parameter to the login url redirect ?
SClogin redirect to specific page but, i want to add redirect=xxx and catch it in backend to redirect to another page

Can you explain how you envision this working a bit more? A user comes to the site and:
* Clicks in the "Username" field of the SCLogin module
* Then, clicks the "Register New Account" link (not the Login button)
* User is brought to the Joomla registration page and their email is already filled in

Is that right? Since they won't be submitting the form, it makes it harder to fetch that value. You'd need some javascript to catch the link click, fetch the email address and then build up the proper url to go too. Doable, but just want to make sure I'm thinking through what you want correctly.

Thanks,
Alex