[R] pch="." plots much faster

[Karl Ove Hufthammer]

Prof Brian Ripley:

>> matrices, especially given that X11 redraws the plot whenever its window
>> is covered/uncovered by another window, or when I switch virtual
>> desktops.
> 
> That is a function of your X setup.  R does ask for backing store to be
> used, and so it seeems your setup is not doing so.

I believe this is a common problem. I have observed it on all systems and R
versions I've used.

On my Fedora 8 system with R 2.7.0 Patched, the following causes complete
repainting every time you I slightly move a window in front of the graphics
window:

X11(type="Xlib"); n=10^5; plot(rnorm(n),rnorm(n))

Using cairo, the backing pixmap is used (but cairo is extremely slow in
plotting 10^5 points, so that doesn't help much :-/ ).

-- 
Karl Ove Hufthammer