if in onButton() handler I switch the pressed button state to disabled, the button turns disabled but remains highlighted, even if mouse leaves buttons area. Therefore there can be several highlighted buttons.
Can I remove the highlighting somehow? Or the only way is to completely disable highlighting via CSS?
yep - it is not a very nice thing. Unfortunately there is no workaround. We are just preparing Update Packages for version 2.2/2.3 - available by soon (begin of next week).