Give better feedback when required fields are missing

[doup]

When the user clicks on "Update" and there are errors we should give some feedback, otherwise the user might miss the errors, especially when the forms are down outside the visible area.

A notice just below the "Update" box would be ideal.

[m1r0]

Another option would be to scroll the user to the first invalid field if its not in the viewport.

More ideas/opinions are welcomed.

[boquiabierto]

An admin_notices including anchor links (with scroll) to the failed required field(s) would be nice because you point to the issue(s) without doing something the user is not expecting (an automatic page scroll). The admin notice can also contain customizable error notices for each required field with hints on what went wrong.

[atanas-dev]

Required fields missing values are already highlighted and the window is scrolled down with the field in view.
This ticket is now complete with 84635dc addressing some issues with the validation notice not appearing for all container types.