Oh, it's worse: I installed `picom` which made the opacity slider work, but that affects the whole window, whereas I only want the background to be transparent.
Along the way I noticed another problem with the opacity compared to the
old code that relied on the "Shape" X11 extension: even if I can use the
"opacity" setting to let me see my windows underneath the clock,
clicking in the background of the clock sends the even to the clock
rather than to the underlying window :-(
Stefan
