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<TITLE>TeXdraw - A. PostScript Commands</TITLE>
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<P><HR><P>
<H1><A NAME="SEC30" HREF="texdraw_toc.html#TOC30">A. PostScript Commands</A></H1>
<P>
<A NAME="IDX137"></A>
<P>
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
<CITE>PostScript Language Reference Manual, Second Edition</CITE>, Adobe
Systems, Addison-Wesley, 1990.
<P>
These macros are distributed in file <TT>`txdps.tex'</TT>.
<P>
The <CODE>\PSsetlinecap</CODE> and <CODE>\PSsetlinejoin</CODE> 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.
<P>
<A NAME="IDX138"></A>
<A NAME="IDX139"></A>
<DL COMPACT>
<DT><CODE>\PSsetlinecap <VAR>type</VAR></CODE>
<DD>
<A NAME="IDX140"></A>
<A NAME="IDX141"></A>
Set the line cap parameter. The value <CODE>0</CODE> gives a butt cap;
<CODE>1</CODE> gives a round cap; and <CODE>2</CODE> gives a projecting square cap.
The initial value is corresponds to a round cap.
<A NAME="IDX142"></A>
<A NAME="IDX143"></A>
<DT><CODE>\PSsetlinejoin <VAR>type</VAR></CODE>
<DD>
Set the line join parameter. The value <CODE>0</CODE> gives a miter join;
<CODE>1</CODE> gives a round join; and <CODE>2</CODE> gives a bevel join. The
initial value corresponds to a round join.
</DL>
<P>
<A NAME="IDX144"></A>
<A NAME="IDX145"></A>
<A NAME="IDX146"></A>
<A NAME="IDX147"></A>
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 <CODE>\PSmoveto</CODE> command) before invoking basic
TeXdraw commands.
<DL COMPACT>
<DT><CODE>\PSstroke</CODE>
<DD>
<A NAME="IDX148"></A>
<A NAME="IDX149"></A>
Stroke a PostScript path. The current path is stroked with the current
gray level (set with <CODE>\setgray</CODE>) and the current line pattern (set
with <CODE>\lpatt</CODE>). The PostScript current point becomes undefined.
<A NAME="IDX150"></A>
<A NAME="IDX151"></A>
<DT><CODE>\PSnewpath</CODE>
<DD>
Establish a new path. The PostScript current point becomes undefined.
<A NAME="IDX152"></A>
<A NAME="IDX153"></A>
<DT><CODE>\PSclosepath</CODE>
<DD>
Close a subpath. A new subpath is started.
<A NAME="IDX154"></A>
<A NAME="IDX155"></A>
<DT><CODE>\PSfill</CODE>
<DD>
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 <CODE>\setgray</CODE>.
</DL>
<P>
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.
<A NAME="IDX156"></A>
<A NAME="IDX157"></A>
<DL COMPACT>
<DT><CODE>\PSlineto (<VAR>x</VAR> <VAR>y</VAR>)</CODE>
<DD>
<A NAME="IDX158"></A>
<A NAME="IDX159"></A>
Add a line segment to the current path. This command is identical to
the TeXdraw command <CODE>\lvec</CODE>. The PostScript current point must
be defined before this command is issued.
<A NAME="IDX160"></A>
<A NAME="IDX161"></A>
<DT><CODE>\PSmoveto (<VAR>x</VAR> <VAR>y</VAR>)</CODE>
<DD>
Move to the coordinate specified by <CODE>(<VAR>x</VAR> <VAR>y</VAR>)</CODE>. The
PostScript current point becomes defined.
</DL>
<P>
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.
<A NAME="IDX162"></A>
<DL COMPACT>
<DT><CODE>\PSarc r:<VAR>radius</VAR> sd:<VAR>start-angle</VAR> ed:<VAR>end-angle</VAR> (<VAR>x</VAR> <VAR>y</VAR>)</CODE>
<DD>
<A NAME="IDX163"></A>
<A NAME="IDX164"></A>
Draw a counterclockwise arc. The center of the arc is at the given
position. The radius is specified by <VAR>radius</VAR>. The start and end
angles (in degrees) are specified by <VAR>start-angle</VAR> and
<VAR>end-angle</VAR>. 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.
<A NAME="IDX165"></A>
<A NAME="IDX166"></A>
<DT><CODE>\PSarcn r:<VAR>radius</VAR> sd:<VAR>start-angle</VAR> ed:<VAR>end-angle</VAR> (<VAR>x</VAR> <VAR>y</VAR>)</CODE>
<DD>
Draw a clockwise arc. The center of the arc is at the given position.
The radius is specified by <VAR>radius</VAR>. The start and end angles (in
degrees) are specified by <VAR>start-angle</VAR> and <VAR>end-angle</VAR>. 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.
</DL>
<P>
The macro <CODE>\writeps</CODE> 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.
<DL COMPACT>
<DT><CODE>\writeps {<VAR><ps-commands></VAR>}</CODE>
<DD>
<A NAME="IDX167"></A>
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.
</DL>
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