Re: master cc29fab3a6: Redisplay "invisible" frames that are actually visible on modern X

[Stefan Monnier]

> +** Emacs will now redisplay frames that are made visible by a compositor.
> +This means even if `frame-visible-p' returns nil or `icon', the frame
> +will be redisplayed if it is being displayed to the user by the
> +compositing manager, which can happenas part of a preview for
> +iconified windows.

FWIW, while this sounds about right for `icon`ified frames, for those
frames that are marked as actually invisible, I think we should try and
keep them as invisible as possible.  IOW if they appear as
preview/thumbnails somewhere it should itself be considered as a bug
(either in our code or in the compositing manager or ...).
Keeping the preview's appearance up-to-date is wasted efforts in
this respect.


        Stefan


PS: In case you need to see concrete uses of invisible frames, you can
    find one in `server.el` and another in GNU ELPA's `xclip.el`.
    There are probably others, but these are the one I know of because
    I coded them :-)