Same thing for the window previews in the Alt+Tab list.

without having actually investigated this at all, i'm going to guess that it's probably a mutter bug; mutter has special code to not "really" hide minimized windows, so we can continue to create clones of them for the overview, and it's probably failing to apply that logic to shaded windows as well

Yes, this would require Mutter changes to accomplish, in addition to gnome-shell changes.

But it's quite difficult, since unlike the minimized case the shaded window isn't just hidden, it's modified. So we can't just keep it around behind the scenes and show the user what it looks like.

Fixing this would probably mean using keeping around two separate "frame windows" in Mutter - the frame window for the normal case and the frame window for the shaded window, and switching between them.

Another possibility would be to have the kept-around-for-cloning window be the actual application window, not the frame window. That would work equally well for minimized or shaded windows, and it would let us make the thumbnail windows a few pixels larger in the overview and app switcher because we wouldn't be thumbnailing the titlebar (which is really just noise in the thumbnail case anyway)

Reassigning. Sorry for the noise.

We don't expose the option to shade windows any more. It's also made more complicated by the existence of CSD - GTK+ won't support it.

That said, I'm fairly sure that we don't care enough about this issue to fix it.