USP Pro makes it easy to display a simple login/register form anywhere on your site. That way visitors can log in via the sidebar or on any post or page. By default, the login/register form does not include any options for customizing things. So this quick tutorial is for anyone who may need to modify the default form with custom markup, styles, or anything else.
How it works normally
As explained here, to display the login/register form, add the following shortcode to any post or page:
Once added, it displays a login form, with tabs for registering and resetting password. Check out this post for more information and screenshots.
How to customize the form
The default login/register form is self-contained in its own function, with no required assets or dependencies to worry about. That means we can customize the function by simply replacing it. To make this as easy as possible, here is a simple plugin that replaces the default login/register form. So you can customize things as much as needed.
Install as usual, customize as desired. No dependencies, it’s all self-contained. As written, everything in the above plugin works exactly the same as the default login/register form. It’s an exact copy, ready for you to customize however you wish.
Once the plugin is activated on your site, WordPress will ignore the default login form and use the custom plugin version instead. This is an example of a pluggable function, which WordPress uses for a number of interesting things.