With two, three, or four, all but the newest are blank until resized, so
far as I can tell with just a few tests.
Mod-n to refresh and focus changes do nothing, but any xmonad operation
that resizes triggers redrawing.
Another weird symptom is that with 3 plots, the third plotted and the
first two blank... changing to an empty workspace and then back to the
plot workspace draws two of the plots but not consistently. Sometimes 1
and 3 get drawn, and other times 2 and 3. :/
Toggling plots to and from full-screen also give unpredictable behavior.
Somehow I'm thinking R is waiting until some negotiation is complete, that xmonad thinks is already complete. I'm curious as to whether it relies on libX11/xcb/whatever toolkit it's using handling ConfigureRequest or tries to do so itself; that's the most obvious difference between the various cases *and* where xmonad is likely to differ from other window managers.
I'd be curious as to whether any problems have been reported with R in other nonreparenting or tiling window managers. (Note, the two are not the same thing.)