R devel - Aug 2008 - Cairo bitmap output should work without X11 dependency (PR#12218)

Full_Name: Craig Ruff
Version: 2.7.1
OS: Irix 6.5.30
Submission from: (NULL) (128.117.8.145)


Cairo based bitmap graphics output should work if cairo and R have been compiled
without xlib support.  2.7.1 gives the "X11 is not available" message
in this
case when run interactively, and from my reading the png documentation, calling
png(filename=..., type="cairo") should work.  Cairo itself is happy
without
xlib.

On Thu, 7 Aug 2008, cruff at ucar.edu wrote:
> Full_Name: Craig Ruff
> Version: 2.7.1
> OS: Irix 6.5.30
> Submission from: (NULL) (128.117.8.145)
>
>
> Cairo based bitmap graphics output should work if cairo and R have been
compiled
> without xlib support.  2.7.1 gives the "X11 is not available"
message in this
> case when run interactively, and from my reading the png documentation,
calling
> png(filename=..., type="cairo") should work.  Cairo itself is
happy without
> xlib.
The help for png() actually says

   \R can be compiled without support for each of these devices: this
   will be reported if you attempt to use them on a system where they are
   not supported.  For \code{type = "Xlib"} they may not be usable
unless
   the X11 display is available to the owner of the \R process.
   \code{type = "cairo"} requires cairo 1.2 or later.

You have apparently compiled R without support for the cairo device. 
Systems with cairo but not X11 libraries are rarer than hens' teeth and 
systems on which X11 could not be installed yet cairo/pango etc have been 
are even rarer (and the chances that they have an adequate set of fonts 
are miniscule).  It is not credible that Irix is such an OS.

Note that X11 support is under 'Essential programs', whereas cairo is 
under 'Useful libraries'.  If you choose to omit something
'essential'
expect not to be able to use something merely 'useful'.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595