Ok, I just checked. I was wrong in my earlier comment. From help(x11)
where a lot of detail is available -- the new Cairo-based devices do have anti-aliasing available:
x11 package:grDevices
R Documentation
X Window System Graphics
Description:
‘X11’ starts a graphics device driver for the X Window System
(version 11). This can only be done on machines/accounts that
have access to an X server.
‘x11’ is recognized as a synonym for ‘X11’.
Usage:
X11(display = "", width, height, pointsize, gamma, bg, canvas,
fonts, xpos, ypos, title, type, antialias)
X11.options(..., reset = FALSE)
Arguments:
[...]
fonts: X11 font description strings into which weight, slant and
size will be substituted. There are two, the first for fonts
1 to 4 and the second for font 5, the symbol font. See
section ‘Fonts’.
[...]
antialias: for cairo types, the typeof anti-aliasing (if any) to be
used. One of ‘c("default", "none", "gray", "subpixel")’.
[...]
Details:
The defaults for all of the arguments of ‘X11’ are set by
‘X11.options’: the ‘Arguments’ section gives the ‘factory-fresh’
defaults.
The initial size and position are only hints, and may not be acted
on by the window manager. Also, some systems (especially laptops)
are set up to appear to have a screen of a different size to the
physical screen.
Option ‘type’ selects between two separate devices: R can be built
with support for neither, ‘type = "Xlib"’ or both. Where both are
available, types ‘"cairo"’ and ‘"nbcairo"’ offer
* antialiasing of text and lines.
* translucent colours.
* scalable text, including to sizes like 4.5 pt.
* full support for UTF-8, so on systems with suitable fonts you
can plot in many languages on a single figure (and this will
work even in non-UTF-8 locales). The output should be
locale-independent.
‘type = "nbcairo"’ is the same device as ‘type="cairo"’ without
buffering: which is faster will depend on the X11 connection.
Both will be slower than ‘type = "Xlib"’, especially on a slow X11
connection as all the rendering is done on the machine running R
rather than in the X server.
All devices which use an X11 server (including the ‘type = "Xlib"’
versions of bitmap devices such as ‘png’) share internal
structures, which means that they must use the same ‘display’ and
visual. If you want to change display, first close all such
devices.
[...and more...]