'rgl.bringtotop' brings the current RGL window to the front of the window stack (and gives it focus).
rgl.bringtotop(stay = FALSE)
whether to make the window stay on top.
TRUE, then the window will stay on top
of normal windows.
not completely implemented for X11 graphics (stay not implemented; window managers such as KDE may block this action (set "Focus stealing prevention level" to None in Control Center/Window Behavior/Advanced)). Not currently implemented under OS/X.