So I am overriding the login form and want to have unique state of the form for the first load screen, when user hasn't entered anything yet. What do I do, I tried to get what is the difference with form vars when submitted and when never submitted. I found out you can do this by form ID as it changes each time (which is not so good for theming of the forms). Somehow more convenient was to look at $vars['form']['#validated']) that is not present on the first load, so if it is not there I just do some custom actions
function my_theme_preprocess_user_login(&$vars) {
if (!$vars['form']['#validated']) {