How to make particular custom buttons/command enabled in rea

I noticed that when you make the editor readonly some of the command buttons (such as copy, preview, full screen) stay enabled. I have two questions:

What class/property do I need to set for my user-defined, custom buttons/commands (plugins) to have them behave this way?
How can I override this behavior. In other words, make copy, preview, full screen disabled when the editor is readonly.
I had some partial success. I tried adding a class called "alwaysEnabled" when creating the button (editor.ui.addButton). Then after I made the editor readonly, I executed this command:

$(".alwaysEnabled").removeClass("cke_disabled");

This made it "appear" enabled, but the command still din not fire.

thanks for help.