In my plugin, I want to notify the admin of wrong settings or problems. So for example, if the admin submits the settings form, I check the input and want to inform him about values being wrong. However, it seems I have to come up with some custom code to keep track of the error message while processing the form.
This is a bit surprising, because e.g. in Drupal you have a simple set_message() function allowing to set a message, which is shown in a certain div on the page.
Am I just missing something or does something simple really not exist in WordPress?