2.4 Configuring

In interactive mode, or when given the -V option (the default when running Asymptote on a single file under MSDOS), Asymptote will automatically invoke the PostScript viewer gv (under UNIX) or gsview (under MSDOS; available from http://www.cs.wisc.edu/~ghost/gsview/) to display graphical output. These defaults may be overridden with the configuration variable psviewer.

Configuration variables are most easily set as Asymptote variables in the configuration file (by default, .asy/config.asy in the user's home directory or %USERPROFILE%\.asy\config.asy under MSDOS); see configuration file. Here are the default values of several important configuration variables.

Under UNIX:

import settings;
psviewer="gv";
pdfviewer="xpdf";
gs="gs";
python="";

Under MSDOS:

import settings;
psviewer="c:\Program Files\Ghostgum\gsview\gsview32.exe";
pdfviewer="c:\Program Files\Adobe\Acrobat 7.0\Reader\AcroRd32.exe";
gs="c:\Program Files\gs\gs8.54\bin\gswin32c.exe";
python="c:\Python24\python.exe";

For PDF format output, the gs setting specifies the location of the PostScript-to-PDF processor gs and pdfviewer specifies the location of the PDF viewer. The graphical user interface may also require setting the variable python if Python is installed in a nonstandard location.

The configuration variable dir can be used to adjust the search path (see Search paths).

By default, Asymptote attempts to center the figure on the page, assuming that the paper type is letter. The default paper type may be changed to a4 with the configuration variable papertype. Alignment to other paper sizes can be obtained by setting the configuration variables paperwidth and paperheight.

The following configuration variables normally do not require adjustment:

latex
dvips
convert
display
animate
xasy

Configuration variables may also be set or overwritten with a command line option:

asy -psviewer=gsview -V venn

Alternatively, system environment versions of these configuration variables may be set in the conventional way. The corresponding environment variable name is obtained by converting the configuration variable name to upper case and prepending ASYMPTOTE_: For example, to set the environment variable

ASYMPTOTE_PSVIEWER="c:\Program Files\Ghostgum\gsview\gsview32.exe";

1. Click on the Start button;
2. Right-click on My Computer;
3. Choose Properties from the popup menu;
4. Click the Advanced tab;
5. Click the Environment Variables button.

To properly support interactive mode, the PostScript viewer should be capable of automatically redrawing whenever the output file is updated. The default UNIX PostScript viewer gv supports this (via a SIGHUP signal). Users of ggv will need to enable Watch file under Edit/Postscript Viewer Preferences and gsview users will need to enable Options/Auto Redisplay (however, under MSDOS it is still necessary to click on the gsview window; under UNIX one must manually redisplay by pressing the r key).

The patches supplied in the patches directory fix known bugs in the UNIX PostScript viewer gv-3.5.8 and gv-3.6.1. In particular, a bug in gv-3.6.1 requires it to be explicitly configured with ./configure --enable-signal-handle for it to work properly with Asymptote's interactive mode (these patches will be in the next release of gv).

After downloading gv-3.6.1 from http://ftp.gnu.org/gnu/gv/ and denoting the location of the Asymptote source directory by SOURCE, here are the steps to install a properly working gv (as the UNIX root user):

tar -zxf gv-3.6.1.tar.gz
cd gv-3.6.1
cat SOURCE/patches/gv-3.6.1-*.patch | patch -p1
./configure --enable-signal-handle
make install