On 2016-10-02 14:10, martin rudalics wrote:
>> That we’re doing it from within Emacs, so it’s an Emacs feature, and
>> therefore needs to be available on a Free platform first.
> 
> I hope I answered this one.  You can create a borderless frame without
> titlebar on GNU/Linux - it's the native Emacs tooltip frame.

Can you really?  More precisely, can you create and display more than one at a time?

Cheers,
Clément.