(texdraw)PostScript Commands

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Appendix A PostScript Commands
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This appendix describes a set of macros for accessing some of the
PostScript builtin functions.  Each of these macros issues a single
PostScript command.  The extra services provided by TeXdraw are the
interpretation of coordinates in user units relative to the current
drawing segment and the writing of a pending TeXdraw move to the
PostScript file.  This last operation establishes the current point in
PostScript.  The user of these commands should be familiar with the
concepts of path construction and filling in PostScript.  Further
details on the PostScript functions used can found in the 'PostScript
Language Reference Manual, Second Edition', Adobe Systems,
Addison-Wesley, 1990.

   These macros are distributed in file 'txdps.tex'.

   The '\PSsetlinecap' and '\PSsetlinejoin' commands control the way
line ends and line joins are rendered.  The default values set by
TeXdraw (round caps and round join) are appropriate for most drawings.
Changes to these parameters apply to the current and subsequent paths.

'\PSsetlinecap TYPE'
     Set the line cap parameter.  The value '0' gives a butt cap; '1'
     gives a round cap; and '2' gives a projecting square cap.  The
     initial value is corresponds to a round cap.
'\PSsetlinejoin TYPE'
     Set the line join parameter.  The value '0' gives a miter join; '1'
     gives a round join; and '2' gives a bevel join.  The initial value
     corresponds to a round join.

   PostScript paths and fill operations can be controlled by a number of
functions.  By design, TeXdraw always maintains a defined PostScript
current point.  Some of the following macros cause the PostScript
current point to become undefined.  The PostScript current point must be
set again (say with a '\PSmoveto' command) before invoking basic TeXdraw
commands.
'\PSstroke'
     Stroke a PostScript path.  The current path is stroked with the
     current gray level (set with '\setgray') and the current line
     pattern (set with '\lpatt').  The PostScript current point becomes
     undefined.
'\PSnewpath'
     Establish a new path.  The PostScript current point becomes
     undefined.
'\PSclosepath'
     Close a subpath.  A new subpath is started.
'\PSfill'
     Fill a region defined by a path.  Each subpath is closed and the
     enclosed regions painted with the current gray level.  The
     PostScript current point becomes undefined.  The gray level can be
     set with the TeXdraw command '\setgray'.

   The following line commands interpret coordinates relative to the
current TeXdraw scaling and drawing segment.  The specified coordinate
affects the drawing size as determined by TeXdraw.
'\PSlineto (X Y)'
     Add a line segment to the current path.  This command is identical
     to the TeXdraw command '\lvec'.  The PostScript current point must
     be defined before this command is issued.
'\PSmoveto (X Y)'
     Move to the coordinate specified by '(X Y)'.  The PostScript
     current point becomes defined.

   The following macros provide access to the general arc commands in
PostScript.  The coordinates are interpreted relative to the current
TeXdraw scaling and drawing segment.  The specified coordinate affects
the drawing size as determined by TeXdraw.
'\PSarc r:RADIUS sd:START-ANGLE ed:END-ANGLE (X Y)'
     Draw a counterclockwise arc.  The center of the arc is at the given
     position.  The radius is specified by RADIUS.  The start and end
     angles (in degrees) are specified by START-ANGLE and END-ANGLE.  If
     the PostScript current point is defined, this command also draws
     the line from the current point to the beginning of the arc.  The
     line and arc become part of the current path.  The current point
     becomes defined.
'\PSarcn r:RADIUS sd:START-ANGLE ed:END-ANGLE (X Y)'
     Draw a clockwise arc.  The center of the arc is at the given
     position.  The radius is specified by RADIUS.  The start and end
     angles (in degrees) are specified by START-ANGLE and END-ANGLE.  If
     the PostScript current point is defined, this command also draws
     the line from the current point to the beginning of the arc.  The
     line and arc become part of the current path.  The current point
     becomes defined.

   The macro '\writeps' provides the general facility to write arbitrary
PostScript commands to the PostScript file.  This macro is used by the
preceding commands and by the TeXdraw commands themselves.  This
facility has to be used with care since changes in position or scaling
resulting from the PostScript commands are not known to TeXdraw.
'\writeps {<PS-COMMANDS>}'
     Write PostScript commands to the intermediate PostScript file.
     Before the commands are inserted, any pending TeXdraw move is
     written to the PostScript file.  The PostScript scaling gives 300
     units/inch.