Apparently this works using SetLayeredWindowAttributes on Windows and we seem to offer support for this in Wine. sync_window_opacity in winex11.drv explicitly has such code for the systray. That's perhaps a place to look.
Apparently this works using SetLayeredWindo wAttributes on Windows and we seem to offer support for this in Wine. sync_window_opacity in winex11.drv explicitly has such code for the systray. That's perhaps a place to look.