GPS(4)                   DOMAIN/IX SYS5                    GPS(4)



NAME
     gps - graphical primitive string, format of graphical files

DESCRIPTION
     GPS is a format used to store graphical data.  Several rou-
     tines have been developed to edit and display GPS files on
     various devices.  Also, higher level graphics programs such
     as plot (in stat(1G)) and vtoc (in toc(1G)) produce GPS for-
     mat output files.

     A GPS is composed of five types of graphical data or primi-
     tives.

     GPS PRIMITIVES

     lines     The lines primitive has a variable number of
               points from which zero or more connected line seg-
               ments are produced.  The first point given pro-
               duces a move to that location.  (A move is a relo-
               cation of the graphic cursor without drawing.)
               Successive points produce line segments from the
               previous point.  Parameters are available to set
               color, weight, and style (see below).

     arc       The arc primitive has a variable number of points
               to which a curve is fitted.  The first point pro-
               duces a move to that point.  If only two points
               are included, a line connecting the points will
               result; if three points, a circular arc is drawn
               through the points; and if more than three points,
               lines connect the points.  (In the future, a
               spline will be fit to the points if they number
               greater than three.) Parameters are available to
               set color, weight, and style.

     text      The text primitive draws characters.  It requires
               a single point which locates the center of the
               first character to be drawn.  Parameters are
               color, font, textsize, and textangle.

     hardware  The hardware primitive draws hardware characters
               or gives control commands to a hardware device.  A
               single point locates the beginning location of the
               hardware string.

     comment   A comment is an integer string that is included in
               a GPS file but causes nothing to be displayed.
               All GPS files begin with a comment of zero length.





Printed 12/4/86                                             GPS-1

GPS(4)                   DOMAIN/IX SYS5                    GPS(4)



     GPS PARAMETERS

     color     Color is an integer value set for arc, lines, and
               text primitives.

     weight    Weight is an integer value set for arc and lines
               primitives to indicate line thickness.  The value
               0 is narrow weight, 1 is bold, and 2 is medium
               weight.

     style     Style is an integer value set for lines and arc
               primitives to give one of the five different line
               styles that can be drawn on TEKTRONIX 4010 series
               storage tubes.  They are:

                 0     solid
                 1     dotted
                 2     dot dashed
                 3     dashed
                 4     long dashed


     font      An integer value set for text primitives to desig-
               nate the text font to be used in drawing a charac-
               ter string.  (Currently font is expressed as a
               four-bit weight value followed by a four-bit style
               value.)

     textsize  Textsize is an integer value used in text primi-
               tives to express the size of the characters to be
               drawn.  Textsize represents the height of charac-
               ters in absolute "universe-units" and is stored at
               one-fifth this value in the size-orientation (so)
               word (see below).

     textangle Textangle is a signed integer value used in text
               primitives to express rotation of the character
               string around the beginning point.  Textangle is
               expressed in degrees from the positive x-axis and
               can be a positive or negative value.  It is stored
               in the size-orientation (so) word as a value
               256/360 of its absolute value.

     ORGANIZATION
     GPS primitives are organized internally as follows:

       lines          cw  points  sw
       arc            cw  points  sw
       text           cw  point  sw  so  [string]
       hardware       cw  point  [string]



GPS-2                                             Printed 12/4/86

GPS(4)                   DOMAIN/IX SYS5                    GPS(4)



       comment        cw  [string]


     cw        the control word.  This word begins all primi-
               tives, and consists of four bits that contain a
               primitive-type code and twelve bits that contain
               the word-count for that primitive.

     point(s)  one or more pairs of integer coordinates.  Text
               and hardware primitives only require a single
               point.  Point(s) are values within a Cartesian
               plane or "universe" having 64K (-32K to +32K)
               points on each axis.

     sw        the style-word, used in lines, arc, and text prim-
               itives.  For all three, eight bits contain color
               information.  In arc and lines, eight bits are
               divided as four bits of weight and four bits of
               style.  In the text primitive eight bits of sw
               contain the font.

     so        the size-orientation word used in text primitives.
               Eight bits contain text size and eight bits con-
               tain text rotation.

     string    a null-terminated character string.  If the string
               does not end on a word boundary, an additional
               null is added to the GPS file to insure word-
               boundary alignment.

RELATED INFORMATION
     graphics(1G), stat(1G), toc(1G).





















Printed 12/4/86                                             GPS-3