Using UpdateLayeredWindow() on iconic windows brings them *back* from
their iconic (minimized) state. That is bad.
As a precaution, also don't use SetWindowPos() on iconic windows.
This means that iconic windows can't be moved. That is fixable
by using SetWindowPlacement(), but there is no pressing need to do so,
as there are very few cases when windows need to be moved while minimized.
https://bugzilla.gnome.org/show_bug.cgi?id=763835