Hello
The piece of code has false behavior. When click the button, the relief changes to tk.SUNKEN. I think this is a wrong behavior.
Thanks

Sadly, there is no `activerelief` option. The Tk man pages note the following:
> A button's relief is changed to sunken whenever mouse button 1 is pressed over the button, and the relief is restored to its original value when button 1 is later released. [https://www.tcl.tk/man/tcl8.6/TkCmd/button.html#M18]

You can also see in the source code that sunken is hard-coded:
https://github.com/tcltk/tk/blob/1802b8a5d6807bdab6ac703f48e6e6bf07970266/library/button.tcl#L227

Personally, I think changing the relief to 'sunken' on click is an important feature, since a user needs feedback on when they've clicked the button. Thank you for reporting this issue, but I think it should be closed as either 'not a bug' or 'third party'.

Thanks for your response