You can find the list of available devices and their names with task GDNAMES. Names can be abbreviated provided they remain unambiguous. Two alternative naming schemes are supported, and the list produced by GDNAMES will include both.
In either scheme, either the device type or the file name or the entire device specification may be replaced by a logical name, in which case the value of the logical name will be used instead.
There is a global parameter for the graphics device. The purpose of this global parameter is ostensibly to prevent unnecessary prompting. However, there is an ulterior motive as well. The selection of devices outside of the graphics applications enables us to perform other necessary actions just once.
There is a command for selecting the current graphics device: GDSET. For example,
A selection remains in force until you change it using GDSET again, use NOGLOBALS, or delete the globals file. The current choice can be inspected via the GLOBALS command. If the global parameter is undefined you will be prompted for the device if an application requires it.
You can override the global parameter for the duration of a single application by specifying it by
DEVICE=), or in some applications, by position. Here is an example.
The most commonly used devices are X-windows. These can require a little preparation
before you select a device. Starlink graphics use GWM to manage windows. It enables a
window to persist between separate applications; or to be shared by different applications,
potentially even running on different machines. See SUN/130 for details of GWM and
how to change your X-defaults file (
$HOME/.Xdefaults), but the salient points are given
If the window appears on a terminal or workstation other than the one running the Kappa executables
you will need to redirect output to your screen, if you have not already done so for some other
software. You either use the
or set the
DISPLAY environment variable to point to the address of your screen.
You substitute your machine’s address or IP number. (Ask your computer manager.)
If you do not create the window before running Kappa, the first graphics application to open an X-windows device will create the window, using certain defaults. The defaults control amongst others the foreground and background colours, the number of colours allocated, the size and location of the window. These defaults may be altered with an X-defaults file, or a window created with the GWM xmake command.
This example makes a window of dimension 600-by-450 pixels, the background colour is black and colour for the line graphics is yellow.
The following set up to place in your X-defaults file is a reasonable compromise, as it maximises the number of colour indices for the graphics window (xwindows), and has a second graphics window (x2windows). In the defaults file there are the following lines
and you can also set the sizes of the windows too. Notice that the second device name is x2windows, but the window name is xwindows2. Don’t ask why. This confusing name rule applies also to all but the first window of the maximum of four windows allowed.
The device names can be abbreviated, to give unambiguous names. Thus you can enter
xw for the
x2w for the x2windows device; and so on. This is the reason for having device
names as they are.
The following tells Kappa that this is the current device. This remains as a global parameter, so you probably will not need to issue this command that often.
Kappa applications are modular so that you can build up more-complicated plots, and possibly add annotations with other packages especially PONGO. This is fine if the device is some sort of screen. However, care needs to be taken when using other types of device. For instance, some PGPLOT PostScript devices put the output from each command into a separate disk file. So how do you get the composite plot out on paper? There are two solutions:
If you use one of these devices, each subsequent graphics application will merge its PostScript
output automatically into any existing
pgplot.ps file. If you display
pgplot.ps using a
modern PDF/PostScript viewer such OKULAR or EVINCE, the display will update
automatically as each subsequent graphics application modifies the file. Once the final
graphics application has been run, you can rename the
pgplot.ps file to something more
To give an example, suppose we wanted to overlay a contour plot on an image.
/star/bin) to combine the plots.
To use the same example as above:
to form the merged graphic. You then print
myplot.ps to the colour PostScript printer. PSMERGE
also has options for scaling and rotating plots.
4You could alternatively include the required final file name in the device name before running the graphics applications.