For a couple of days I've been developing an general validation library:

https://bitbucket.org/walczak_it/prodoko-base/src/HEAD/prodoko-fx/src/main/java/com/prodoko/fx/scene/validation?at=master

It's role is not just to decorate fields that didn't pass validation. But also Tabs and other containers that might hold those fields - in my app one form will have fields scattered around many tabs.

I thought it would be an great idea to use pseudo classes like :error, :warning, :ok on various scenegraph elements (Controls, Nodes Tabs in a TabPane) but after a couple of hours of coding I noticed that:
* I cannot modify the pseudo classes by just having a Styleable argument in my method
* only Node has the pseudoClassStateChanged method but for example Tab is not an node

So I changed my implementation to use normal style class.

First question is: was my intended approach to use pseudo classes for this case a good one ?

If the answer is no - pseudo classes should only be changed by a class that actually implements/extends some kind of new Node or Control and not by any external class - then I would suggest to make pseudoClassStateChanged protected and mention this in the documentation.

If the answer is yes - then I think we should add this method to the Styleable interface.