17.7 Controlling the server

• positioning the plotting area in the page

  By default there is a single plotting area in the page (although in principle one can try and xasplot the viewport environment variable), which occupies a region controlled xassetting the plotcomment environment variable, as follows
  • the top half in default mode
  • almost all the window if plotcomment short
  • all the window if plotcomment none
  The remainder of the plot area is used for standard annotations.

• changing plot axes

  One can let the plot set the extrema of the axes automatically, or set them explicitly xasplotting the xaxis and yaxis environment variables. One may also explicitly xasset the xscale and yscale environment variable to lin or log.

• changing plot colours

  There are several environment variables which control the colour of various pens (for the X-11 and colour PostScript servers). There are 8 fundamental "plot" colours always available for plotting , in addition, by using a negative colour number, one may refer to "image" colours in the colour lookup table described below. The fundamental colours are :
  • 0 black
  • 1 white
  • 2 red
  • 3 green
  • 4 blue
  • 5 cyan
  • 6 magenta
  • 7 yellow

• handling colour tables

  There are commands to load the RGB colour tables used for image displays. The graphics servers use two sets of colours, the above listed fundamental colours for vector plotting, and a colour table (Look-Up Table, LUT) for image display.

  The size and content of the LUT are (partially or fully) under user control.

  • The black-and-white PostScript server default LUT is a 256-level gray table (and of course it does not much sense to edit it).
  • The colour PostScript server default LUT is also a 256-level table, initialized to gray, but is under complete user control (which may use and redefine up to 256 colours).
  • The X-11 server LUT could in principle be as long as 256 colours, but in practice it is limited by the number of colours already allocated by the workstation X server (on a Motif session this is usually about 30). One may allocate n colours from a start location j in the workstation default colourmap, provided that there are n consecutive locations free. One possibility is to allocate a small (n=16,32) number of colours to each server instance. Exclusive allocation is needed only if one wants to redefine colours. Otherwise one can share the LUT of another, non-XAS application, and just tell XAS to "start from j" guessing where the other application's LUT starts.

  The following two commands represent a PROVISIONAL interface.

  readlut [ startc ncol

  prints on the terminal screen the RGB values of the ncol colours starting at location startc. If ncol is positive, it is assumed that startc is relative to the current server instance start "j", if ncol is negative, one conventionally assumes that startc is absolute in the workstation X colourmap.

  writelut [ startc ncol rgb ...

  usually loads into the graphics server LUT ncol colours, each one specified as an RGB triplet rgb, from given location startc. However this command can be used to perform different tasks :
  • writelut 0 0 prints on the terminal screen the current start "j" as the particular graphics server instance thinks it is.
  • writelut j 0 redefine the current start to the absolute location "j".
  • writelut 0 n loads n colours in a new XAS LUT from beginning.
  • writelut k n loads n colours from the k-th location in the current LUT.
  This command is practical only to edit the content of one or a few colours. IT IS PLANNED to have a dedicated command to load entire LUTs. In the meanwhile a command file can be used in conjunction with writelut to load long tables.

• resizing the plot window

  In principle the screen window used by the X11 graphics server can be resized using the mouse. The way this is done is dependent on the particular window manager. The graphics server will do its best to cope with this at the next plot, but, since it is not ICCCM compliant, unpredictable results are possible.
  We remind also that the backing store of an already plotted window when obscured (partially or totally) is demanded to the window manager, which may cease to mantain it at any time.

• changing page size and orientation

  Currently the PostScript server uses only portrait orientation on A4 paper. It is planned to have a controlserver program in the future for the handling of page (or window) size and orientation changes.

• disposing of print files

  Currently the PostScript server opens a new file each time a new page is plotted upon. At the same time the previous file is properly closed. The last file is closed when terminating the server. There are currently no actions to dispose of (e.g. print) the files ; this is left to the care of the user. It is planned to have a controlserver program in the future capable of disposing of plot files.

• choice of fonts

  All graphics servers choose the font in which text is plotted using a conventional font number (default is number 1). The mapping between font numbers and actual fonts can be customized by copying the files xwfont.list (for the X-window server) and psfont.list (for the PostScript server) from the $XASTOP/include directory to one of the following directories (they will be consulted in this order of precedence) :
  • the current working directory (for customization done personally by each user for a particular purpose)
  • the user home directory (for customization done personally by each user for all of hir sessions)
  • $XASTOP/local (for customization done by the XAS installer for all users on a given system)
  • $XASTOP/include will be used if no customization was applied. The files in this directory shall NEVER be modified.

  Note that the choice of the font size in points is kept separate from the choice of the typeface for the PostScript server, while standard X11 names must be used for the X-window server.

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